Engineering ductility in magnesium: A review of texture-driven challenges and opportunities

Abstract

Magnesium and its alloys are increasingly used in automotive and aerospace industries due to their low density, which supports lightweighting and reduces environmental impact. However, their broader application is limited by poor formability, largely resulting from strong textures formed during mechanical processing that reduce ductility. Extensive research has focused on mitigating this issue through alloying and optimised processing. While rare earth (RE) elements are highly effective in weakening texture, their scarcity drives interest in alternative approaches. This review discusses the mechanisms by which RE elements influence texture, explores the potential of non-RE elements, particularly calcium, and highlights promising results from multi-component alloying. It also examines key processing parameters for the AZ31 alloy, emphasising properties, industrial feasibility, and directions for alloy development.

Keywords

Magnesium texture rare earths deformation recrystallisation mechanical properties

Introduction

Advancements in the physical metallurgy of magnesium and its alloys empowers the pursuit of high-performance, sustainable materials that promise innovation through reduced emissions in industrial applications. This alloy class boasts properties that can match, or exceed, those of other commonly used metals such as steel, aluminium, and titanium alloys, ideally suited for use in aerospace, automotive, healthcare, electronic and sports sectors, primarily thanks to a low magnesium density of 1.74 g.cm⁻³.¹ Its advantage over competitor alloys is elicited by a high specific strength; components can potentially satisfy structural properties with a lower mass. In the aerospace and automotive industries, this is a key materials selection consideration where reduced vehicle or aircraft weight correlates to lower CO $_{2}$ emissions; this, for example, may be a direct benefit to combustion technology or an indirect gain for reduced battery energy consumption when charging from a carbon-producing energy supply. Lightweighting contributes to improved environmental sustainability, a necessary attribute for satisfying consumer expectations and to meet national legislation related to climate change.² Magnesium also boasts good castability, exceptional damping properties, and considerable thermal and electrical conductivity,³ underlying its broad applicability and potential for use in numerous applications.

Despite these promising applications, magnesium is still not widespread in industrial use. There are, inevitably, drawbacks to magnesium – notably its propensity to corrode, creep susceptibility, and considerable flammability due to a low ignition point,³ necessitating careful consideration during high-speed machining.⁴ Magnesium is also more costly in comparison to aluminium.⁵ An issue which cannot be overlooked is the formation of strong textures during wrought processing, resulting in a significant loss in ductility and formability.² The term ductility refers to the ability of the material to undergo plastic deformation under tensile loading, quantitatively measured by elongation, prior to fracture. Formability describes its ability to be plastically deformed into a desired shape without cracking, tearing, or failing, specific to manufacturing operations such as bending, stamping or drawing.⁶ For magnesium to fulfil its potential, the texture development must be understood and controlled, necessitating the interplay between different alloying additions and processing techniques to be understood. While the environmental benefit of magnesium use is attractive, to compete against well-established engineering alloys, new magnesium alloys must match or exceed their mechanical or physical properties without incurring prohibitive costs.

In this review, an overview of texture and its relevance to magnesium is firstly given, with subsequent sections discussing mechanisms for modifying this, through (i) alloying additions and (ii) processing methods. An outlook of this research area is provided with recommended opportunities for future exploration.

Texture and its prevalence in magnesium

Categorised based on when it develops, texture may comprise two types: deformation texture or recrystallisation texture. When a polycrystalline material with a HCP (hexagonal close packed) crystal structure experiences high stresses, for example during mechanically processing, plastic strains are accommodated through dislocation slip or deformation twinning. During deformation that comprises a particular strain path, certain crystal orientations exist for which these mechanisms can successfully accommodate the imposed strain, both macroscopically and at the grain scale through compatibility. The crystals will tend to rotate towards the orientations where these mechanisms can most easily accommodate the imposed strain. As a result, a polycrystal will develop a higher proportion of crystals aligned to a particular, stable direction compared to the original random arrangement; this is the deformation texture.⁷ For magnesium, the texture that develops is heavily influenced by its HCP crystal structure.

The deformation texture that is most prevalent in magnesium is basal texture. An example of this is evident during extrusion, where the basal planes align to be parallel to the extrusion direction (ED), denoted as ${0001} ∥$ (ED) and $⟨ 10 \bar{1} 0 ⟩ ∥$ (ED), respectively.^8–10 During rolling, crystals align with their $c$ -axis parallel to the normal direction of the sheet (ND) and the basal planes become parallel to the rolling direction (RD), described by $⟨ 10 \bar{1} 0 ⟩ ‖$ (RD).^7,9,10 Basal texture is thus commonly represented as ${0001} ‖ ⟨ 10 \bar{1} 0 ⟩$ .¹⁰ These relationships are depicted in Figure 1. It is noteworthy that these texture relationships have been established from studies of common processing or deformation routes that have inherently slow strain rates, however, high strain-rate processes such as machining are seldom explored.

Figure 1.

Schematic representation of HCP magnesium crystals (a) forming a basal texture, where basal planes are parallel to RD during rolling, or ED during extrusion, such that the $c$ -axis of the unit cell is parallel to ND, and (b) the possible slip systems of magnesium. In (c), the geometry of common tension and compression twins in magnesium are shown.

The formation of a ‘C-texture’ has also been shown to prevail in extruded and recrystallised Mg alloys, presenting as bands of similarly orientated grains that are aligned with their $c$ -axis parallel to the extrusion direction, given as $⟨ 0001 ⟩ ∥$ (ED). This has primarily been reported in rare-earth containing Mg alloys,^11–19 but has also been shown in binary Mg-6.5Zn.^8,20 This texture is shown to develop in Mg alloys that (i) are highly alloyed, and (ii) have been subjected to large extrusion ratios. The ability to promote such textures is highly attractive if mechanical properties are improved, where C-texture, for example, can be used in combination with other fiber textures to suppress yield asymmetry.²⁰

Any deformation texture developed will not necessarily persist in a material if recrystallisation occurs. During recrystallisation, deformed regions of the material will be replaced by new, relatively strain-free grains that do not necessarily inherit the orientation of the parent grain. The nucleation, and subsequent growth, of these new grains will therefore have a marked impact on the texture of a material – this is described by the recrystallisation texture. Recrystallisation commonly takes place under two distinct regimes: dynamic recrystallisation, which occurs during deformation, and static recrystallisation, which occurs during exposure to an elevated temperature heat treatment after deformation.²¹

Plastic strain will be accommodated by deformation modes, which are crystal structure dependent. These can be quantified by the critical resolved shear stress (CRSS) required to activate a particular deformation mode. Because of its lack of symmetry, the HCP crystal structure contains three types of potential slip systems: $⟨ a ⟩$ dislocations on basal planes, $⟨ a ⟩$ on prism planes, and $⟨ c + a ⟩$ on pyramidal planes. If there is a bias towards $⟨ c + a ⟩$ slip due to high concentration of solutes, for example, in combination with easy $⟨ a ⟩$ prismatic slip, lattice rotation is likely and will promote ‘C-texture’ formation over the more common basal texture.⁸ In addition to slip, deformation twinning is another accommodation method that has distinctive tension or compression modes.²² Specific to Mg, the temperature sensitivity of these parameters are shown in Figure 2, with the variation in CRSS between the deformation modes found to be significant.¹⁰ Here, $⟨ a ⟩$ basal slip occurs readily, with a CRSS of $< 1$ MPa at room temperature, whilst tension twinning is similarly easy, occurring at $< 10$ MPa. Other modes, however, are not readily activated at room temperature, with CRSS values of 40-45 MPa for the other slip systems, and even higher for compression twinning.²³ While magnesium does have sufficient slip systems to meet the von Mises criterion, that five independent slip systems are required to produce uniformity in deformation, the difficulty in activating many of the systems results in strong texture formation during mechanical processing, leading to anisotropic properties.^9,24 Additionally, deformation twinning has a loading direction dependence,²⁵ leading to a greater capacity to accommodate deformation in one direction over another. Consequently, deformation twinning is a contributing factor to yield asymmetry.^22,26

Figure 2.

Critical resolved shear stress values as a function of temperature for different slip systems and twinning modes in pure magnesium. Replotted and adapted from Nie et al.¹⁰

The texture weakening desired in magnesium can be achieved either by suppressing the original deformation texture formation or subsequently conferring this texture through recrystallisation. One strategy for minimising deformation texture is by altering the CRSS values for different slip and twinning processes, for instance to suppress extension twinning, or to promote non-basal slip, which is achieved through various microstructural changes.²⁰ There are also various recrystallisation mechanisms relevant to magnesium, including grain boundary nucleation, subgrain boundary nucleation, shear band nucleation, deformation twinning nucleation and particle-stimulated nucleation. While the first two often form recrystallised grains of the same orientation to the parent, the last three promote new orientations that are different to the deformed grains, with particle-stimulated nucleation producing new grains that are randomly oriented.^24,27

New understanding of the role and impact of alloying additions that alter the deformation and recrystallisation mechanisms in Mg is highly desirable. Progress here would allow the refinement of alloy compositions to possess the best properties, however, any new alloy must also consider how economical the solution is. The following sections discuss the successes that have been achieved through various texture weakening strategies.

Alloying

To eradicate material property deficiencies, alloying is a clear starting point. The impact of various alloying additions on texture development in wrought magnesium has been investigated extensively, diverging into two main classes: rare earth and non-rare earth additions. Significant progress has been made in achieving texture weakened magnesium alloys using rare earth (RE) elements, particularly La, Ce, Nd, Eu, Gd, Yb and Y.⁵³ For non-RE alloying, aluminium is recognised to be a beneficial addition, with AZ31 (Mg-3wt%Al-1wt%Zn) being of notable commercial use.^10,54 Zinc and calcium are also common alloying additions; combinations of these are known to produce similar texture weakening affects to RE alloys.^27,54,55

Rare Earth Alloys and Proposed Mechanisms of Texture Weakening

There are several mechanisms through which RE alloying is theorised to impact texture, including particle-stimulated recrystallisation, promoting growth of non-basal orientated grains, tailored solute drag effects, changing the stacking fault energy, promoting shear banding, or modification of the $c / a$ lattice ratio.^24,56 For such RE elemental additions, no definitive conclusion of the most potent mechanism has been reached, making it difficult to transfer knowledge to non-RE containing Mg alloys. Potential mechanisms for RE-alloys will hence be examined in this section.

The addition of RE elements to Mg alloys has been shown to mainly affect recrystallisation texture, rather than deformation texture;²⁷ this observation is helpful for constraining the number of potential mechanisms by which this modification has been achieved. This is evidenced, for example, when comparing ZE100, a commercial RE containing alloy, to the non-RE AZ31 alloy. After cold rolling the two have been shown to possess similar deformation behaviour. These both exhibited strong basal texture, but after static recrystallisation the RE alloy loses this texture, returning to its pre-cold rolled state.⁵³ These textures can be seen in the pole figures in Figure 3(a). The data here implies that the nucleation and growth of recrystallised grains are most significantly impacted by RE additions, rather than any deformation mechanisms, although this is not a rule without exception.^24,57 In general, as well as weakening the basal texture, RE alloying can also introduce new texture components – so-called RE textures.^8,58 These include a $⟨ 11 \bar{2} 1 ⟩$ $‖$ (ED) extrusion texture, and a unique transverse direction (TD) spread observed on rolling, depicted in Figures 3(b) and 3(c). These textures tend to facilitate more basal slip, such that the ductility of the alloys is improved. A critical alloying concentration also exists for each element, below which no impact on texture occurs, but this tends to be low, between 0.01-0.1 at.%.²⁴ A pattern is seen, where the more soluble RE element in Mg correlates to a lower concentration required to promote a texture modification. The different RE elements are often split into two groups, the yttrium (Y) subgroup and the cerium (Ce) subgroup, based on their solubility in Mg at different temperatures; two distinct trends can be seen (Figure 4), with the Y group demonstrating superior solubility.^58,59

Figure 3.

(a) Textures evaluated for ZEK100 and AZ31 after different stages of thermomechanical processing. A strong basal texture is evident at all stages in AZ31, while ZEK100 displays a modified texture after hot rolling, develops basal texture on cold rolling, and then returns to the pre-rolled state on annealing. (b) Inverse pole figures depicting the characteristic grain orientation spread along the transverse direction (TD), after rolling Mg-RE alloys. The basal texture seen in pure Mg is also included for reference. (c) Pole figures showing a characteristic $⟨ 11 \bar{2} 1 ⟩ ∥$ (ED) extrusion texture seen in Mg-RE alloys, compared to pure Mg. Obtained and adapted from Griffiths⁵³, with permission from Elsevier.

Figure 4.

Sensitivity of the RE elements solubility for different temperatures, classified into two distinct subgroups, Ce and Y. Adapted from Rokhlin.⁵⁹

As the concentration of a RE addition is increased beyond a critical point, further texture weakening seems negligible, however, the ductility continues to increase, implying that RE additions improve ductility through methods other than texture weakening.⁵³ It has been established that a ductility improvement has been attributed to a decrease in CRSS for non-basal slip systems, such that these are favoured over twinning (which is inherently anisotropic).²⁴ Much research has focused, therefore, on methods that suppress twinning.^26,60 Additionally, success in reducing yield asymmetry has been attributed to modifying the CRSS magnitudes of tension and compression twinning such that they are equally favourable.²⁰ Exemplar CRSS values between different deformation modes for various Mg & Mg alloy compositions are shown in Table 1, illustrating the CRSS sensitivity and variability to the elemental additions that results in plastic anisotropy and, consequently, the prevailing texture.

Table 1.

Summary of critical resolved shear stress (CRSS) values for various Mg alloys, their deformation modes, and an indication of the texture characteristics for alloys in the polycrystalline form.

Composition (wt.%)	Texture Characteristics	Slip/Twinning System	CRSS (MPa)
Pure Mg	Very strong basal²⁸	Basal slip	$< 2$ ^29–33
		Prismatic slip	$10 - 43$ ^30,31,34,35
		Pyramidal slip	37-78^36–40
		Tension twin	2–3^41,42
		Compression twin	30–100^38,41,43
AZ31 (Mg-3Al-1Zn)	Strong basal²⁸	Basal slip	$15 \pm 4$ ⁴⁴
		Tensile twinning	27 $\pm$ 3⁴⁴
AZ31 (Mg-3Al-1Zn)-0.5Ca	Weak basal⁴⁵	Basal slip	50 (at 5% strain)⁴⁵
		Prismatic slip	95 (at 5% strain)⁴⁵
		Pyramidal slip	315 (at 5% strain)⁴⁵
		Tension twin	14 (at 5% strain)⁴⁵
Mg-0.2Ca-1.8Zn	Weak basal⁴⁶	Basal slip	$\sim$ 13.5⁴⁶
		Pyramidal slip	<85⁴⁶
		Twin	$\sim$ 37⁴⁶
Mg-1Mn-1Nd	Weak basal⁴⁷	Basal slip	12–37⁴⁷
		Prismatic slip	78–90⁴⁷
Mg-1Zn-0.7Nd	Weak basal⁴⁸	Prismatic slip	$\sim$ 20⁴⁸
		Prismatic slip	$\sim$ 60⁴⁸
		Prismatic slip	$\sim$ 70⁴⁸
		Prismatic slip	$\sim$ 40⁴⁸
Mg-1Zn	Strong basal⁴⁸	Basal slip	$\sim$ 20⁴⁸
		Prismatic slip	$\sim$ 50⁴⁸
		Pyramidal slip	$\sim$ 90⁴⁸
		Tension twins	$\sim$ 10⁴⁸
Mg-6Sn	Basal & split pole⁴⁹	Basal slip	114–149⁴⁹
		Pyramidal slip	446–1571⁴⁹
Mg-4.7Gd	Split pole; double	Basal slip	16 $\pm$ 2⁵⁰
	fibre $[11 \bar{2} 1]$ - $[20 \bar{2} 1]$ ⁵¹	Pyramidal slip	95 $\pm$ 6⁵⁰
		Twinning	63 $\pm$ 4⁵⁰
Mg-2.2Y	Basal but Y	Pyramidal (1 $^{st}$ order) slip	$\sim$ 57⁵²
Mg-3.2Y	additions weaken⁵²	Pyramidal (1 $^{st}$ order) slip	$\sim$ 70⁵²
Mg-3.9Y		Pyramidal (1 $^{st}$ order) slip	$\sim$ 90⁵²
Mg-3.9Y		Prismatic slip	$\sim$ 70⁵²
Mg-4.6Y		Prismatic slip	$\sim$ 80⁵²

As the RE texture effect is observed at very low elemental concentrations, this is indicative of RE atoms segregating to grain boundaries, giving a higher local concentration than in the bulk. This has been convincingly shown experimentally through energy dispersive X-ray spectroscopy.^61–63 It is also hypothesised that RE solute atoms will segregate to dislocations, inhibiting their motion and further contributing to the overall RE effect.⁵⁸ The tendency for RE elements to segregate is likely related to the large size misfit between RE atoms and the host Mg lattice. This gives rise to solute drag that is amplified by the low diffusivity of the RE atoms in Mg. Non-RE additions such as zinc tend to have an atomic radius more akin to Mg; when a Mg-Zn alloy was examined, no grain boundary segregation nor texture modification was observed,⁶¹ lending support to the correlation between segregation and texture.

Robson et al.⁵⁸ used a Cahn-Lücke-Stüwe impurity drag model⁶⁴ to investigate how the behaviour of Y in Mg differs to Al and Zn, ultimately concluding that Y incurs by far the greatest drag pressure. At temperatures typical to mechanical processing, Y has a strong drag effect that retards dynamic recrystallisation, while Al and Zn atoms exert a peak drag force at much lower temperatures than those used during processing. It was proposed that the texture weakening arises from more energy being stored during deformation, which then increases the rate of static recrystallisation during thermal exposure.⁵⁸ It is noted that Robson’s model implementation relied on an estimate of grain boundary diffusivity for Y due to a lack of experimental data, which has influenced the conclusions, however, they are arguably reliable given the agreement with experimental observations. An alternative explanation is that drag will affect basal dislocation nucleation more than non-basal during dynamic recrystallisation, such that non-basal slip is activated preferentially, hence weakening the basal texture.^24,27,65 These various drag effects are not mutually exclusive, so it is plausible that they occur simultaneously.

The stacking fault energy (SFE) is a key factor known to influence both twinning and slip, particularly in HCP structures.^24,66 Relevant to ductility, a wide stacking fault will form when the SFE is low, inhibiting cross-slip, hence this is a desirable attribute when formability is required, for example. Alloying additions can alter the SFE of various slip systems, ultimately culminating in greater $⟨ c + a ⟩$ slip, improving ductility.^24,54 In Mg-X alloys, a general trend is seen where the basal SFE⁶⁷ and the energy barrier to $⟨ c + a ⟩$ dislocations on pyramidal planes⁶⁸ are reduced with increasing size of a solute addition. This relationship is seen in Figure 5, indicating that RE elements promote $⟨ c + a ⟩$ slip in Mg alloys, while Al and Zn in alloys of comparable grain size do not.^66,68 The relationship between RE additions and SFE is not undisputed, however, Yin et al.⁶⁹ found from first-principle calculations that Y additions did not significantly affect the basal SFE, concluding that alternate mechanisms were more likely culpable. As atomic size is not the only factor affecting SFE (it is also dependent on bulk modulus, volume, binding and ionisation energy of the alloying element⁶⁷) asserting a definitive effect of a particular addition is difficult.

Figure 5.

The energy barrier to $⟨ c + a ⟩$ slip on pyramidal (type II) planes reduces with an increased atomic radius of the alloying addition. This indicates that larger solute atoms promote easy $⟨ c + a ⟩$ slip . Reproduced from Sun et al.⁶⁸ with permission from Elsevier.

Particle stimulated nucleation is where particles that do not deform during processing lead to the formation of a relaxed zone between themselves and the deformed matrix, creating a deformation zone by trapping dislocations. This region is a prime site for grain nucleation during recrystallisation.⁷⁰ However, this cannot be a contributing factor to the characteristic RE texture as the presence of such particles has been shown to nucleate grains with a random texture. Regardless, ductility and strain hardening behaviour both improve as the basal texture is weakened, as seen in Figure 6. Here, the stress-strain behaviour of ZK10, a Zn-Zr-Mg alloy, is compared to ZWEK1000, with the latter containing added Nd (a RE element), for which particle stimulated nucleation was observed, increasing ductility.⁷¹

Figure 6.

Tensile response of a non-RE alloy ZK10 and ZWEK100 (ZK10 with RE additions). Reproduced from Al-Samman,⁷¹ with permission from Elsevier.

Another mechanism through which texture weakening can occur is the creation of shear bands and through the nucleation of shear bands with annealing. Due to deformation heterogeneities in the shear bands, recrystallised grains favour growth in off-basal orientations over basal-orientations, and so when annealed, a fully recrystallised microstructure without basal texture can be achieved.⁷² In pure Mg, limited slip activity leads to regions of high localised strain, where concentrated shear bands are formed from the few twins present.⁷³ In contrast, RE additions promote non-basal slip and more twinning, so a more homogeneous distribution of shear bands results.^73,74 This can be seen when comparing the schematic microstructures of pure Mg and Mg-3wt%Y (illustrated in Figure 7). Mg-3Y displayed superior ductility, although Sandlöbes et al.⁷³ related this to the concentration of strain at the localised shear bands in pure Mg. This caused faster fracture than the more homogeneous shear band distribution in Mg-3Y. Evidently, a homogeneous spread of shear bands is desired. This can be enhanced, for example, through hot rolling in a single pass to high strains (e.g. 80% thickness reduction²⁷) as this forms a dense distribution of shear bands in RE alloys.

Figure 7.

Shear band patterning observed in (a) Mg and (b) Mg-3wt%Y after cold rolling. Concentrated shear bands are seen in pure Mg, while for the alloy they are comparably more dispersed and finer, as interpreted from misorientation data from EBSD obtained by Sandlöbes et al.⁷³

This mechanism, however, has not proved successful for all RE alloys. While Mg-1wt.%Gd exhibits a clear change in texture from the strong basal textures post rolling, Mg-1wt.%Ce does not exhibit significant texture modification post annealing (Figure 8), despite also developing dense shear banding like the Gd-containing alloy.⁷² Gd is part of the Y subgroup, and is much more soluble in Mg than Ce (4at.% vs 0.13at.%²⁷). As Gd is soluble in the Mg-1wt.%Gd alloy and Ce in Mg-1wt.%Ce leads to a dispersion of Mg₁₂Ce secondary precipitates, due to the differing atomic radius of the solute elements, the dissimilar microstructures affect texture. For the Mg-1wt.%Ce alloy, when rolled, the precipitates fragmented, leading to pinning that restricts grain growth following recrystallisation, such that its deformation texture was largely retained, but with a weakened intensity.⁷² The correlation between shear banding and texture weakening is not infallible; the RE texture has been observed in alloys with negligible shear banding, and equally some shear-banded alloys do not develop RE textures.⁵³

Figure 8.

Texture development of Mg-1wt.%Ce and Mg-1wt.%Gd from an as rolled condition and following different thermal exposures. Obtained from Basu et al.,⁷² with permission from Elsevier.

Texture weakening is also sometimes attributed to a change of Mg lattice parameters. The low symmetry of the HCP structure, with its large $c / a$ ratio, is a key reason for the strong texture of Mg as non-basal slip is unfavourable. It follows that if this ratio can be adjusted by alloying by judicious selection of solutes based on atomic size, then texture weakening may be achieved by lowering the energy barrier for $⟨ c + a ⟩$ slip.⁷⁵ RE atoms and Ca are bigger than Mg and thus are expected to decrease the $c / a$ ratio. Ding et al.⁵⁴ investigated this via X-ray diffraction and found that Mg-Ca and Mg-Ca-Zn alloys exhibited a reduced $c / a$ , while Mg-RE and Mg-RE-Zn showed $c / a$ ratios larger than pure Mg; all alloys had a favourable texture over pure Mg. This implies that modification of the $c / a$ ratio does not directly correlate to texture modification as has been theorised.

Non-Rare Earth Alloys and Multiple Additions

While the addition of rare earth elements clearly enhances the properties of magnesium alloys, through weakening the texture strength, they are not a perfect solution, largely due to the scarcity of these elements as natural resources as well as their environmental toxicity.²⁰ For magnesium alloys to be a truly viable commercial option, sustainability and economic efficiency must be optimised. To this end, the use of non-rare earth alloying additions is of much interest.

Calcium additions are attractive due to their high solubility in magnesium and as they possess an atomic size comparable to RE elements. From this, microstructures are likely to be similar. Binary Mg-Ca alloys demonstrate superior grain refinement over Mg-Zn and even Mg-RE (Figure 9(a)), attributed to significant dynamic recrystallisation due to undissolved secondary phases. This corresponds to a greater yield strength and ultimate tensile strength (UTS) for the Mg-Ca alloys.⁵⁴ Texture is also influenced: Mg-0.5wt.%Ca produces a similar texture to that observed in RE alloys, while alloys such as Mg-2wt.%Zn are often less effective at weakening texture (Figure 9(b)). Calcium additions have also been associated with a decreased SFE,⁷⁶ which may further contribute to texture weakening. Despite the similar textures, Mg-Re alloys still display superior ductility to Mg-Ca.⁵⁴ This is a key consideration as high ductility is, ultimately, the desired property that will be used to ascertain suitability for material selection.

Figure 9.

(a) EBSD maps for Mg and its alloys extruded at 320 $\circ$ C, with Mg-Ca alloy shown to possess the finest grain size. (b) The strength of {0001} texture (TD vertical) for several Mg binary alloys (Mg-2Zn; Mg–0.5RE and Mg–0.5Ca) following hot extrusion. While Mg-2Zn shows a strong basal texture, both Mg-0.5Ca and Mg-0.5RE show a basal tilt from ND to ED, resulting in the double peak seen. (c) Similarly the {0001} texture (TD vertical) is shown for hot extruded Mg-2Zn-0.5RE and Mg–2Zn-0.5Ca alloys. (d) A comparison of the ultimate tensile strength, yield strength and elongation of (i) Pure Mg, (ii) Mg-2Zn, (iii) Mg-0.5RE, (iv) Mg-0.5Ca, (v) Mg-2Zn-0.5RE and (vi) Mg-2Zn-0.5Ca, all in wt.%, after hot extrusion, all measured at 0 $\circ$ , 45 $\circ$ and 90 $\circ$ to the extrusion direction. Plastic anisotropy can be seen in all cases, but the ternary alloys display the best strength properties. Taken from Ding et al.⁵⁴ with permission from Elsevier.

Alloy systems combining zinc and calcium weaken the texture of Mg more successfully than either binary Mg-Zn or Mg-Ca alloys.^54,55 This reflects a general trend seen: ternary alloys exhibit a weaker final texture than their binary counterparts.^27,54,55 For example, in a series of Mg- $x$ Zn-0.2Ca wt.% alloys, the recrystallised grain fraction after annealing is much higher for a greater zinc fraction, benefitting both yield and ultimate tensile strengths.⁵⁵ Following hot rolling⁵⁵ or extrusion,⁵⁴ Mg-2Zn-0.5Ca wt.% sheets display modified texture, analogous to that seen in Mg-2Zn-0.5RE wt.% alloys after the same processing (Figure 9(c)). This effect has been attributed to the presence of nano-precipitates, which increases the energy required for deformation due to a high density of dislocations being retained. This encourages more static recrystallisation of randomly orientated grains, such that texture weakens.⁵⁵ Grain boundary segregation of nano particles also contributes to the texture weakening.⁶⁵ Figure 9(d) summarises these findings, comparing the mechanical properties in the binary alloys to their ternary counterparts. Importantly, unlike binary Mg-Ca, the texture refinement in Mg-Ca-Zn alloys is accompanied by improved ductility^54,65 – a result that is considered to be highly promising.

As well as multi-additions of non-RE elements, RE alloys also exhibit improved properties when further alloyed. For example, ductility has been shown to be significantly improved by the addition of Zn and Zr to Mg-Ce and Mg-Gd alloys, explained by the texture weakening (Figure 10). Shear band nucleation was determined to be the key texture weakening mechanism, but unlike the binary alloys, clusters of Zn and Zr with RE atoms intensified the solute-dislocation interactions. The addition of Zr and Zn influenced the Ce alloy by promoting particle-stimulated recrystallisation.²⁷ By combining lower concentrations of RE with non-RE additions, a compromise could be made between the improved mechanical properties of RE alloys and the environmental appeal of non-RE alloys. However, it is not guaranteed that concentrations below the critical concentrations of RE²⁴ would still initiate the RE effect even with the presence of non-RE additions; this is a research area that has great opportunities for further exploration.

Figure 10.

Tensile response of (a) Mg-1Ce, (b) Mg-1Gd, (c) Mg-1Zn-0.6Zr-1Ce and (d) Mg-1Zn-0.6Zr-1Gd, all in wt.%, in the as-rolled condition, and after annealing at a range of temperatures; the quaternary alloys exhibit superior ductility to their binary counterparts. (e) Pole figures of {0001} texture (RD vertical) for hot rolled and annealed Mg-1Ce, Mg-1Gd, Mg-1Zn-0.6Zr-1Ce and Mg-1Zn-0.6Zr-1Gd alloys. The quaternary alloys show a marked crystal orientation spread towards TD, unlike the binary counterparts, as well as a weaker basal texture. Taken from Basu and Al-Samman²⁷ with permission from Elsevier.

Processing

While alloying can be an effective method of weakening texture, benefits can only be realised when combined with appropriate processing routes. The choice of processing method and parameters will inevitably impact the microstructural properties and hence the texture developed. Some processing methods may be able to effectively suppress texture, but it is equally conceivable that other methods could only promote its formation. Additionally, while weakened texture is clearly desirable, the aim is to ultimately optimise the material properties - this could be achieved through processing refinement (either dependent or independent of texture). For Mg, rolling and extrusion, as previously introduced, are common materials processing routes. As discussed, specific alloying additions can be used to tailor the texture, but in commercial alloys, such as AZ31, this is not the case. Instead, the processing method itself must be adapted to weaken the texture; either through changing the thermomechanical processing parameters or performing post-processing treatments, such as annealing.

Irrespective of texture, it has been established that both strength and ductility improve from a fine grain size in magnesium and its alloys, a result often attributed to the decrease in twinning in favour of slip in smaller grains.^77,78 Carvalho et al.⁷⁸ compiled data from $\sim$ 300 papers to investigate these relationships in a range of Mg alloys, as shown in Figure 11. For flow stress as a function of grain size, a distinctive negative correlation can be seen. Except for pure Mg, which notably has low strength, there is no obvious distinction between the Mg alloys with similar levels of correlation between them. This result is encouraging as it suggests that similar grain refinement is possible for most Mg alloys, such that related processing to tailor the microstructure could be universally applicable.

Figure 11.

Yield stress (a) and elongation (b) as a function of grain size for Mg and various alloys with the data points representing measurements from which trends can be inferred. The yield stress increases for a smaller grain size, however, the effect is more effective above 1 µm where twinning dominates; below 1 µm slip dominates, and yield strength changes less rapidly. The relationship between elongation and grain size is less clear, although the greatest ductility is ground when the grain size is in the range 2–10 µm. Replotted and adapted from Carvalho and Figueiredo.⁷⁸

Two grain size dependent regimes are proposed:⁷⁸ when above 1 µm, the strength increase for a decreasing grain size is more significant than below 1 µm, where further strength improvement is more limited. Above 1 µm, twinning dominates over slip, accounting for the distinct regimes. The correlation between grain size and elongation is less clear, but still some conclusions can be drawn. An optimal grain size around 2–10 µm is proposed for best ductility, but other alloys achieve increasing elongation at even smaller grain sizes. Pure Mg, Mg-Li and Mg-Mn in particular can reach elongations greater than 100% when the grain size is $\sim$ 1 µm.⁷⁸ It is noted that while these results seem promising, the elongation achieved during laboratory tests, on non-standard miniaturised samples, may be an overestimate compared to properties that can be achieved on an industrial scale, as the sample ductility has been shown to be dependent on the specimen aspect ratio, i.e. a size effect exists.⁷⁹ Regardless, grain refinement is one of the most important considerations when choosing a processing route, commonly achieved through recrystallisation.

Recrystallisation can also contribute to texture modification. In pure Mg, both dynamic recrystallisation that occurs during mechanical deformation or static recrystallisation during subsequent heat treatments have proved ineffective at modifying texture, as the recrystallised grains adopt the same orientations as the deformed parent grains and hence exhibit strong basal texture.²⁴ However, in the presence of alloying additions, this is not necessarily the case: the type of recrystallisation that occurs will influence the resultant texture. Continuous dynamic recrystallisation produces grains that can have different orientations to the parent grain, such that relatively random textures can be achieved, as recrystallisation occurs via absorption of dislocations by subgrain boundaries. In contrast, during discontinuous dynamic recrystallisation, nucleation and growth arises from the migration of high angle grain boundaries, so the new grains have orientations that are inherited from parent grain, and importantly, from each other, resulting in a stronger texture.⁸⁰ Evidently, both in terms of grain refinement and texture modification, promoting the recrystallisation of fine grains is an important goal, but the specific methods for achieving this will undoubtedly lead to variations in properties.

Processing of AZ31

To isolate the effects of different processing routes from alloying additions, research pertaining specifically to the processing of AZ31, one of the most used magnesium alloys in industry,⁵ is discussed here.

As already described, the most desirable mechanical properties arise from well refined grains; a strategy to satisfy this is to maximise the recrystallisation fraction. When hot rolling, for AZ31, an optimised grain structure is achieved by using a small rolling reduction per pass (using multiple passes), rather than fewer passes at a higher strain rate, due to the prevalence of grain boundary nucleation during dynamic recrystallisation.⁸¹ This is at odds to processing costs, which are reduced by larger rolling reductions per pass, favouring single passes. In a bid to reduce costs without sacrificing formability, increasing rolling speed will give a larger reduction per pass while still maintaining reasonable rollability; ultrafast rolling shows promise, even at low temperatures.^10,82,83 It is recognised, however, that in an industrial setting, there will be limitations on the maximum rolling speed, which could limit the success of this interesting method.

To further refine the grain size, heat treatment after rolling is a common practice. This can, for certain temperatures, also impact texture. After hot rolling, the microstructure tends to be partially recrystallised, where strong basal texture, $(0001) ⟨ 10 \bar{1} 0 ⟩$ , is seen in the deformed grains, while the recrystallised grains show a pronounced $(0001) ⟨ 11 \bar{2} 0 ⟩$ .^10,84 Upon thermal exposure, a general trend appears; the recrystallisation fraction increases with increasing temperature, which results in a decreasing basal texture until the point of full recrystallisation. Sustaining the thermal exposure beyond this point leads to any beneficial texture weakening being lost as recrystallised grains grow. This suggests that there exists an optimal temperature, for which full recrystallisation but minimal grain coarsening occurs, but there is some discrepancy in the literature over which temperature this is. Some reports suggest close to 300 $\circ$ C,¹⁰ while others suggest increasing closer to 400-450 $\circ$ C is more beneficial.⁸⁴

Extrusion is the other industrially prevalent method for processing magnesium. The key parameters involved are extrusion temperature, ratio, and flow rate, as they determine the fraction and form of grain structure that results from dynamic recrystallisation. An increased extrusion temperature is known to increase the grain size, but this is accompanied by a decrease in basal texture intensity – these factors are contradictory such that a balance between them is desirable. A decrease in yield strength and ultimate tensile strength as temperature increases exists, which is correlated to an increased mean grain size.^85,86 However, basal texture intensity decreases at higher temperature processing, giving better ductility.⁸⁵ Clearly, a low extrusion temperature is not always beneficial; to achieve a reasonable balance between elongation and strength an intermediate temperature is likely best, and adaptations to the other extrusion parameters will be necessary.

The recrystallisation fraction becomes greater as the extrusion ratio increases; the grains become finer and more homogeneous at higher ratios^86,87 due to greater stored strain energy, which promotes more dynamic recrystallisation.^88,89 There exists a maximum extrusion ratio where mechanical properties (ultimate tensile strength, yield strength, elongation) no longer improved. For the ultimate tensile strength and yield strength, this occurs at a ratio of $\sim 25$ , whereas elongation improves further, up to $\sim 40$ (Figure 12).⁸⁷ Additionally, low-speed extrusion has been shown to be more beneficial than a fast rate; as deformation time increases, more dynamic recrystallisation occurs, leading to more refined grains and better mechanical properties.^85,90 Lower speed also results in less heat generated from internal friction, an effective means of eliminating problematic temperature inhomogeneity, favouring a uniform distribution of recrystallised grains.⁹⁰

Figure 12.

Variation in ultimate tensile strength (UTS), yield strength (YS) and elongation of AZ31 with changing extrusion ratio. Taken from Chen et al.⁸⁷ with permission from Elsevier .

An area that has garnered much interest for improved mechanical properties of magnesium alloys, including AZ31, is the use of severe plastic deformation methods, which are often reported to refine grains and thus improve the mechanical properties.⁹¹ An example of this is equal channel angle pressing (ECAP), specifically if performed after extrusion. ECAP subjects a bulk polycrystalline material to repeated intense pressing, through simple shear, without any change of cross-sectional dimensions, via passes through a die, rotating between passes.⁹² This can produce an ultra-fine grain size, with 0.7 µm reported to be achievable,⁹³ as well as the added benefit of a significantly reduced basal texture. Lower ECAP temperatures have been associated with a finer, more homogeneous resultant grain size.⁹⁴ Low temperature superplasticity has been observed, such that elongation is improved over extrusion processing, although a lower yield stress is also evident, as seen in Figure 13.^93–95 This is clearly a potential limitation to this method. It is suggested that if the post extrusion texture can be restored after ECAP, then a higher yield strength could be produced in addition to the improved ductility.⁹⁴ However, the ECAP procedure, while demonstrating promising results, is not favourably suited to commercial usage, which severely limits its applications.⁷⁷ It has been claimed that this could be attributed to a current lack of research into scale up potential,⁹⁶ such that with further research, this method could be implemented into industrial practice.

Figure 13.

Tensile behaviour for the Mg alloy AZ31 in the as-cast condition, post extrusion, and post ECAP. While elongation is improved by the ECAP process, the yield strength is inferior to values obtained following extrusion. Taken from Lin et al.⁹³ with permission from Elsevier.

Summary and Outlook

Various methods that refine or improve the mechanical properties of magnesium and its alloys have been considered, concerning both the use of alloying and processing routes, with a focus on weakening the strong texture conventionally formed during wrought processing. It is evident that rare earth (RE) additions have proved successful at modifying this texture, resulting in improved mechanical properties, but despite substantial research, a consensus on the underlying mechanisms that govern this remains elusive, with experimental evidence often presenting contradictory results. Grain boundary segregation seems a particularly convincing mechanism, but it is likely that texture modification can be achieved in numerous ways, even if the RE texture specifically is more evasive. In numerous studies, emphasis is placed on assigning the RE effect to a singular mechanism, however, it is suggested that consideration of multiple factors acting in conjunction is likely to prove more successful in future research.

Ultimately, it is improved mechanical properties of magnesium alloys that are necessary for their wider use in structural applications; studies have shown that this can be achieved separately to texture weakening. Much research has focused only on the weakening of basal texture, or the formation of RE texture, but without a direct relation to the mechanical properties. This is considered to be of limited benefit. While a desired texture found from RE alloying has not been successfully replicated, ternary Mg-Ca-Zn alloys demonstrate attractive yield strength, ultimate tensile strength, and ductility properties regardless, making them a promising choice of alloy for commercial use. Future research into the implementation of these alloys in industry would be beneficial, especially considering the issues associated with scarcity, cost and environmental impact related to using RE elements.

An examination of the processing of AZ31 demonstrated the possibility to reduce texture strength and refine properties without modifying the bulk alloy chemistry. For AZ31, industrial processing methods are well-established, so for another alloy to be introduced commercially, similar research regarding processing parameter optimisation would be required. For both rolling and extrusion, it has been seen that ductility and yield strength are often optimised by opposing conditions, such that a compromise must be found to achieve a reasonable range of mechanical properties. While processes such as equal channel angle pressing present promising results, adaptions must be made to ensure industrial viability. From the studies to date, there is enormous potential for utilising both alloying and processing to weaken the texture and improve mechanical properties of magnesium alloys. Undoubtedly, the exploitation of any new alloy will need to consider industrial scale up from the outset. If successful, Mg alloys may offer property gains over traditional engineering alloys for existing and future structural applications, particularly to capitalise on its lightweighting potential.

Footnotes

Acknowledgments

An acknowledgement section was need needed as no funding, nor editorial assistance was used in the preparation of this manuscript.

ORCID iDs

Emma L. Podd

David M. Collins

Ethical approval and informed consent statements

No ethical approval was needed for this work.

Author contribution(s)

Emma L. Podd: Data curation; Formal analysis; Investigation; Visualization; Writing – original draft.

David M. Collins: Conceptualization; Project administration; Supervision; Writing – review & editing.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability statement

All sources of data are available in the open literature; full references are provided through the manuscript.

Any other identifying information related to the authors and/or their institutions, funders, approval committees, etc, that might compromise anonymity. There are no aspects in the paper, nor references made to our own work that would compromise anonymity.

References

Polmear

StJohn

Nie

, et al. Light Alloys. Fifth ed. Boston: Butterworth-Heinemann, 2017.

Trzepieciński

Najm

. Current trends in metallic materials for body panels and structural members used in the automotive industry. Materials 2024; 17: 590.

Yang

Zhu

Han

, et al. Evolution, limitations, advantages, and future challenges of magnesium alloys as materials for aerospace applications. J Alloys Compd 2024; 1008: 176707.

Carou

Rubio

Davim

. Machinability of magnesium and its alloys: A review. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. pp.133–152.

Tan

Ramakrishna

. Applications of magnesium and its alloys: A review. Appl Sci 2021; 11: 6861.

Straffelini

. Ductility and formability of metals. Trento, Italy: Academic Press, 2023.

Wilkinson

. Deformation Textures. In: Buschow KHJ, Cahn RW, Flemings MC et al. (eds.) Encyclopedia of Materials: Science and Technology, 2001, pp.2022–2026. Oxford: Elsevier. 10.1016/B0-08-043152-6/00368-5.

Wang

Ferdowsi

MRG

Kada

, et al. Appearance of textures with a c-axis parallel to the extrusion direction in Mg alloys. Scr Mater 2022; 210: 114422.

Jin

Dong

, et al. The texture and its optimization in magnesium alloy. J Mater Sci Technol 2020; 42: 175–189.

10.

Nie

Shin

Zeng

. Microstructure, deformation, and property of wrought magnesium alloys. Metall Mater Trans A 2020; 51: 6045–6109.

11.

Robson

Twier

Lorimer

, et al. Effect of extrusion conditions on microstructure, texture, and yield asymmetry in Mg–6Y–7Gd–0.5wt%Zr alloy. Mater Sci Eng: A 2011; 528: 7247–7256.

12.

Tong

Zhang

. Effect of long period stacking ordered phase on the microstructure, texture and mechanical properties of extruded Mg–Y–Zn alloy. Mater Sci Eng: A 2013; 563: 177–183.

13.

Zhang

Deng

, et al. Effect of secondary extrusion on the microstructure and mechanical properties of a Mg–RE alloy. Mater Sci Eng: A 2014; 616: 148–154.

14.

Alizadeh

Mahmudi

Ngan

AHW

, et al. An unusual extrusion texture in Mg–Gd–Y–Zr alloys. Adv Eng Mater 2016; 18: 1044–1049.

15.

Kim

Jung

You

, et al. Microstructure and texture variation with Gd addition in extruded magnesium. J Alloys Compd 2017; 695: 344–350.

16.

Imandoust

Barrett

Al-Samman

, et al. Unraveling recrystallization mechanisms governing texture development from rare-earth element additions to magnesium. Metall Mater Trans A 2018; 49: 1809–1829.

17.

Zhang

, et al. An unusual texture evolution in extruded Mg–14Gd–based alloy during annealing. Adv Eng Mater 2018; 20: 1701129.

18.

Lyu

Xiao

, et al. Formation mechanism of the abnormal texture during extrusion in Mg-Y-Sm-Zn-Zr alloy. J Alloys Compd 2020; 821: 153477.

19.

Gao

Liu

Jiang

, et al. Analysis of abnormal texture and strengthening mechanisms of extruded Mg–Gd–Y–Nd–Zr alloy. Adv Eng Mater 2023; 25: 2201046.

20.

Yang

Wang

, et al. Deformation mechanisms of dual-textured Mg-6.5Zn alloy with limited tension-compression yield asymmetry. Acta Mater 2023; 248: 118766.

21.

Juul Jensen

. Annealing Textures. In: Buschow KHJ, Cahn RW, Flemings MC et al. (eds.) Encyclopedia of Materials: Science and Technology, 2001, pp.319–323. Oxford: Elsevier. 10.1016/B0-08-043152-6/00066-8.

22.

Zahiri

Ombogo

Lotfpour

, et al. Twinning in hexagonal close-packed materials: The role of phase transformation. Metals 2023; 13: 525.

23.

Chaudry

Tariq

HMR

Zubair

, et al. Implications of twinning on the microstructure development, crystallographic texture and mechanical performance of Mg alloys- a critical review. J Magnes Alloys 2023; 11: 4146–4165.

24.

Imandoust

Barrett

Al-Samman

, et al. A review on the effect of rare-earth elements on texture evolution during processing of magnesium alloys. J Mater Sci 2017; 52: 1–29.

25.

Mayama

Noda

Chiba

, et al. Crystal plasticity analysis of texture development in magnesium alloy during extrusion. Int J Plast 2011; 27: 1916–1935.

26.

Robson

Stanford

Barnett

. Effect of precipitate shape and habit on mechanical asymmetry in magnesium alloys. Metall Mater Trans A 2013; 44: 2984–2995.

27.

Basu

Al-Samman

. Triggering rare earth texture modification in magnesium alloys by addition of zinc and zirconium. Acta Mater 2014; 67: 116–133.

28.

Nie

Shin

Zeng

. Microstructure, deformation, and property of wrought magnesium alloys. Metall Mater Trans A 2020; 51: 6045–6109.

29.

Burke

Hibbard

. Plastic deformation of magnesium single crystals. JOM 1952; 4: 295–303.

30.

Yoshinaga

Horiuchi

. On the nonbasal slip in magnesium crystals. Trans Japan Inst Metals 1964; 5: 14–21.

31.

Akhtar

Teghtsoonian

. Solid solution strengthening of magnesium single crystals—I alloying behaviour in basal slip. Acta Metall 1969; 17: 1339–1349.

32.

Hirsch

Lally

. The deformation of magnesium single crystals. Philosop Magaz 1965; 12: 595–648.

33.

Schmid

Boas

. Plasticity of crystals with special reference to metals. London: F.A. Hughes, 1968.

34.

Stohr

Poirier

. Etude en microscopie electronique du glissement pyramidal

{11 \bar{2} 2} ⟨ 11 \bar{2} 3 ⟩

dans le magnesium. Philos Magaz 1972; 25: 1313–1329.

35.

Yoshinaga

Horiuchi

. Deformation mechanisms in magnesium single crystals compressed in the direction parallel to hexagonal axis. Trans Japan Inst Metals 1963; 4: 1–8.

36.

Ando

Harada

Tsushida

, et al. Temperature dependence of deformation behavior in magnesium and magnesium alloy single crystals. In: The mechanical behavior of materials X, Key Engineering Materials, Vol. 345, pp.101–104. Trans Tech Publications Ltd. 10.4028/www.scientific.net/KEM.345-346.101.

37.

Lilleodden

. Microcompression study of Mg (0001) single crystal. Scr Mater 2010; 62: 532–535.

38.

Kitahara

Ando

Tsushida

, et al. Deformation Behavior of Magnesium Single Crystals in C-Axis Compression. In: The Mechanical behavior of materials X, Key Engineering Materials, Vol. 345, pp.129–132. Trans Tech Publications Ltd. 10.4028/www.scientific.net/KEM.345-346.129.

39.

Obara

Yoshinga

Morozumi

{11 \bar{2} 2} ⟨ 1123 ⟩

slip system in magnesium. Acta Metall 1973; 21: 845–853.

40.

Byer

Cao

, et al. Microcompression of single-crystal magnesium. Scr Mater 2010; 62: 536–539.

41.

Kelley

Hosford

. Plane-strain compression of magnesium and magnesium alloy crystals. Trans Met Soc AIME 1968; 242: 5–13.

42.

Roberts

. Magnesium and its Alloys. New York: Wiley, 1960.

43.

Wonsiewicz

. Plasticity of Magnesium Crystals. PhD Thesis, Massachusetts Institute of Technology, 1966.

44.

Cao

Wang

, et al. In situ synchrotron X-ray microdiffraction study of basal slip and tensile twinning in AZ31 magnesium alloy. Metals 2025; 15: 675.

45.

Masood Chaudry

Hamad

JGK

Kim . Ca-induced plasticity in magnesium alloy: EBSD measurements and VPSC calculations. Crystals 2020; 10: 67.

46.

Wang

Chen

, et al. Deformation mechanisms of Mg-Ca-Zn alloys studied by means of micropillar compression tests. Acta Mater 2021; 217: 117151.

47.

Sánchez-Martín

Pérez-Prado

Segurado

, et al. Measuring the critical resolved shear stresses in Mg alloys by instrumented nanoindentation. Acta Mater 2014; 71: 283–292.

48.

Zhou

, et al. Texture and lattice strain evolution of hot-rolled Mg–Zn–Nd alloys investigated by in situ synchrotron diffraction. Metals 2020; 10: 124.

49.

Majchrowicz

Józwik

Chrominski

, et al. Microstructure, texture and mechanical properties of Mg-6Sn alloy processed by differential speed rolling. Materials (Basel) 2020; 14: 83.

50.

Ovri

. Mechanisms and anisotropy of serrated flow in Mg-Gd single crystals. J Magnes Alloys 2023; 11: 1643–1655.

51.

Zhao

Jiang

, et al. The influence of Gd on the recrystallisation, texture and mechanical properties of Mg alloy. Mater Sci Eng: A 2022; 839: 142867.

52.

Rikihisa

Mori

Tsushida

, et al. Influence of yttrium addition on plastic deformation of magnesium. Mater Trans 2017; 58: 1656–1663.

53.

Griffiths

. Explaining texture weakening and improved formability in magnesium rare earth alloys. Mater Sci Technol 2015; 31: 10–24.

54.

Ding

Shi

Wang

, et al. Texture weakening and ductility variation of Mg–2Zn alloy with Ca or RE addition. Mater Sci Eng: A 2015; 645: 196–204.

55.

Zhao

Wang

Chen

, et al. Development of weak-textured and high-performance Mg–Zn–Ca alloy sheets based on zn content optimization. J Alloys Compd 2020; 849: 156640.

56.

Guan

Liu

Gao

, et al. Exploring the mechanism of “rare earth” texture evolution in a lean Mg–Zn–Ca alloy. Sci Rep 2019; 9: 7152.

57.

Agnew

Yoo

Tomé

. Application of texture simulation to understanding mechanical behavior of Mg and solid solution alloys containing Li or Y. Acta Mater 2001; 49: 4277–4289.

58.

Robson

. Effect of rare-earth additions on the texture of wrought magnesium alloys: The role of grain boundary segregation. Metall Mater Trans A 2014; 45: 3205–3212.

59.

Rokhlin

. The regularities in the Mg-rich parts of the phase diagram, phase transformations and mechanical properties of magnesium alloys with individual rare earth metals. Arch Metall Mater 2007; 52: 5–11.

60.

Stanford

Geng

Chun

, et al. Effect of plate-shaped particle distributions on the deformation behaviour of magnesium alloy AZ91 in tension and compression. Acta Mater 2012; 60: 218–228.

61.

Hadorn

Hantzsche

, et al. Role of solute in the texture modification during hot deformation of Mg-rare earth alloys. Metall Mater Trans A 2012; 43: 1347–1362.

62.

Stanford

Sha

Xia

, et al. Solute segregation and texture modification in an extruded magnesium alloy containing gadolinium. Scr Mater 2011; 65: 919–921.

63.

Bugnet

Kula

Niewczas

, et al. Segregation and clustering of solutes at grain boundaries in Mg–rare earth solid solutions. Acta Mater 2014; 79: 66–73.

64.

Lc̈ke

Stüwe

. On the theory of impurity controlled grain boundary motion. Acta Metall 1971; 19: 1087–1099.

65.

Zhang

Xie

Zhang

, et al. Simultaneously improving yield strength and formability potential of Mg alloy via introducing nano precipitates and texture-weakened heterogeneous grains. J Mater Res Technol 2023; 24: 5486–5500.

66.

Basu

Chen

Wheeler

, et al. Stacking-fault mediated plasticity and strengthening in lean, rare-earth free magnesium alloys. Acta Mater 2021; 211: 116877.

67.

Dong

Luo

Zhu

, et al. Basal-plane stacking-fault energies of Mg alloys: A first-principles study of metallic alloying effects. J Mater Sci Technol 2018; 34: 1773–1780.

68.

Sun

Ding

Zhang

, et al. Predicting the formation of dislocations in magnesium alloys from multiple stacking fault energies. Materialia 2019; 7: 100352.

69.

Yin

Curtin

. First-principles calculations of stacking fault energies in Mg-Y, Mg-Al and Mg-Zn alloys and implications for

⟨ c + a ⟩

activity. Acta Mater 2017; 136: 249–261.

70.

Ball

Prangnell

. Tensile-compressive yield asymmetries in high strength wrought magnesium alloys. Scripta Metall et Mater 1994; 31: 111–116.

71.

Al-Samman

. Modification of texture and microstructure of magnesium alloy extrusions by particle-stimulated recrystallization. Mater Sci Eng: A 2013; 560: 561–566.

72.

Basu

Al-Samman

Gottstein

. Shear band-related recrystallization and grain growth in two rolled magnesium-rare earth alloys. Mater Sci Eng: A 2013; 579: 50–56.

73.

Sandlöbes

Schestakow

, et al. The relation between shear banding, microstructure and mechanical properties in Mg and Mg-Y alloys. Mater Sci Forum 2011; 690: 202–205.

74.

Shi

Wang

Shang

, et al. Microstructure evolution of twinning-induced shear bands and correlation with ‘RD-split’ texture during hot rolling in a Mg-1.1Zn-0.76Y-0.56Zr alloy. Mater Charact 2022; 187: 111853.

75.

Wang

Bao

Wang

, et al. Deformation mechanisms in hexagonal close-packed high-entropy alloys. J Appl Phys 2021; 129: 175104.

76.

Ganeshan

Shang

Wang

, et al. Effect of alloying elements on the elastic properties of Mg from first-principles calculations. Acta Mater 2009; 57: 3876–3884.

77.

Stanford

Barnett

. Fine grained AZ31 produced by conventional thermo-mechanical processing. J Alloys Compd 2008; 466: 182–188.

78.

Carvalho

Figueiredo

. An overview of the effect of grain size on mechanical properties of magnesium and its alloy. Mater Trans 2023; 64: 1272–1283.

79.

Kohno

Kohyama

Hamilton

, et al. Specimen size effects on the tensile properties of JPCA and JFMS. J Nuclear Mater 2000; 283-287: 1014–1017.

80.

Borkar

Gauvin

Pekguleryuz

. Effect of extrusion temperature on texture evolution and recrystallization in extruded Mg–1% Mn and Mg–1% Mn–1.6%Sr alloys. J Alloys Compd 2013; 555: 219–224.

81.

Barnett

Keshavarz

Nave

. Microstructural features of rolled Mg-3Al-1Zn. Metall Mater Trans A 2005; 36: 1697–1704.

82.

Bian

Zeng

, et al. Enhanced tensile properties of Mg sheets by a unique thermomechanical processing method. Metall Mater Trans A 2016; 47: 5709–5713.

83.

Sakai

Utsunomiya

Koh

, et al. Texture of AZ31 magnesium alloy sheet heavily rolled by high speed warm rolling. Mater Process Texture 2007; 539-543: 3359–3364.

84.

Bhattacharyya

Agnew

Muralidharan

. Texture enhancement during grain growth of magnesium alloy AZ31B. Acta Mater 2015; 86: 80–94.

85.

Zhang

Wang

, et al. Microstructure evolution and mechanical properties of AZ31 magnesium alloy sheets prepared by low-speed extrusion with different temperature. Crystals 2020; 10: 644.

86.

Zhang

Cong

, et al. Microstructures, mechanical and corrosion properties of the extruded AZ31-xCaO alloys. Materials 2018; 11: 1467.

87.

Chen

Wang

Peng

, et al. Effects of extrusion ratio on the microstructure and mechanical properties of AZ31 Mg alloy. J Mater Process Technol 2007; 182: 281–285.

88.

Xia

Dai

, et al. Effect of extrusion ratio on the microstructure and mechanical properties of Al-0.5Mg-0.4Si-0.1Cu alloy. Metals 2023; 13: 669.

89.

Wang

. Effect of extrusion ratio on the microstructure and texture evolution of AZ31 magnesium alloy by the staggered extrusion (SE). J Magnes Alloys 2020; 8: 1304–1313.

90.

Azpiazu

Egea

Letzig

, et al. Advanced direct extrusion process with real-time controllable extrusion parameters for microstructure optimization of magnesium alloys. Int J Mater Forming 2023; 16: 39.

91.

Fan

Liu

. Effect of deformation temperature on microstructure and texture of AZ31 magnesium alloy processed by new plastic deformation method. Trans Nonferrous Metals Soci China 2024; 34: 2138–2152.

92.

Krállics

Horváth

Nyiro

. Forming and machining of the nano-crystalline alloys. In: Menz W, Dimov S and Fillon B (eds.) 4M 2006 - Second International Conference on Multi-Material Micro Manufacture, 2006, pp.175–178. Oxford: Elsevier.

93.

Lin

Huang

Langdon

. Relationship between texture and low temperature superplasticity in an extruded AZ31 mg alloy processed by ECAP. Mater Sci Eng: A 2005; 402: 250–257.

94.

Kim

Jeong

. Grain-size strengthening in equal-channel-Angular-Pressing processed AZ31 Mg alloys with a constant texture. Mater Trans 2005; 46: 251–258.

95.

Mukai

Yamanoi

Higashi

. Processing of ductile magnesium alloy under dynamic tensile loading. Materials Trans 2001; 42: 2652–2654.

96.

Ferrasse

Segal

Alford

, et al. Scale up and application of equal-channel angular extrusion for the electronics and aerospace industries. Materials Sci Eng: A 2008; 493: 130–140.