Materials Science and Technology

In this work, the microstructure of the WAAM-fabricated Mg-12.1Gd-1.6Ag-0.7Al (wt.%) alloy featured a distinct lamellar structure with alternating dendrites and equiaxed grains. The second phase contained MgAg, GdH_2, (Mg, Ag)₅Gd and Al₂Gd. After the solid solution treatment at 500°C for 2 h, coarse (Mg, Ag)₅Gd phase dissolved, followed by the formation of lamellar Al₂Gd phase. With additional aging treatment at 200°C for 24 h, dense γ″ and β′ nano-precipitates formed in the α-Mg matrix, resulting in remarkable precipitation strengthening, namely the improved UTS of 312 ± 7.9 MPa, YS of 224 ± 5.3 MPa and EL of 4.3 ± 0.5%. This work contributes to the development of high-performance, advanced magnesium alloy workpieces.

In response to the brittleness issues of 0.13C-7Mn TRIP steel welds, a heat treatment process with varying holding times was designed. This study investigates the effects of tempering on the microstructure and mechanical properties of the welds. After holding at 250 °C for 10, 20, and 30 min, the peak load in tensile shear tests increased by 89.6%, 104.8%, and 41.6%, respectively, compared to the samples that were not tempered. Furthermore, the failure mode transitioned from complete brittle interfacial fracture (IF) to more ductile modes, including partial interfacial fracture (PIF) and pull-out fracture (PF). After tempering, the martensite in the weld zone transforms into tempered martensite. The hardness of both the heat-affected zone and the fusion zone (FZ) decreased by approximately 20 HV, leading to a more uniform hardness distribution, leading to a more uniform hardness distribution. Additionally, the segregation of manganese (Mn) in the fusion zone is also mitigated.

In this work, the forming behavior of the High Strength Low Alloy (HSLA) 420 steel sheet during the Single Point Incremental Forming (SPIF) process was investigated. The formability is enhanced by increasing the spindle rotational speed, reducing the tool feed and reducing the incremental step-down. A numerical simulation was also performed and the results were compatible with experimental results. The studies are further extended to microstructural analyses. A large dislocation density was obtained due to a high swiveling effect. Therefore, the possibilities of high-angle grain boundaries were increased, which caused an increase in the percentage of ultra-fine grain formation. Hence, the strong texture was obtained by increasing the swiveling effect and the texture components were favored to enhance the formability.

The influence of anisotropy and the loading circumstances on the deformation and damage behaviour of Al6092/SiC particle composites is examined in this study at 2× 10⁻⁴ s⁻¹ strain rate and in three orientations with respect to the rolling directions (0, 45, 90) °. The influence of heat treatment (T6 and O-condition) on the microstructure, deformation, and damage behaviour of metal matrix composites under various loading conditions is investigated to obtain a fundamental understanding of the heat treatment effect on the fracture mechanism, the microstructural changes, and the interface between the Al-matrix and SiC particles, and to establish a correlation between heat treatment and anisotropy effect, it is necessary to examine the influence of heat treatment (T6 and O-condition) on the microstructure, deformation, and damage behaviour of metal matrix composites.

The effect of post-forging heat treatment on the microstructure and tensile properties of the heavily alloyed nickel-based superalloy SDZhS-15 (Ni-37(Co,Cr,Mo,W,Re)-12.5(Al,Ti,Nb,Ta)-0.17(B,C,La,Y,Ce), wt.%)) intended for disc applications at temperatures up to 850 °C was studied. The as-cast superalloy was subjected to homogenization, subsolvus hot forging, and various heat treatments, including either solution treatment at subsolvus temperature and ageing or direct ageing. The tensile tests showed that the strength/ductility combination at T = 20–850 °C was appreciably better in the fine-grained condition. SEM study revealed that the fraction of intergranular brittle cleavage fracture increased with increasing the test temperature and at transition from the fine-grained condition obtained via direct ageing to the coarse-grained one obtained via solution heat treatment and ageing.

The nanocrystalline ferrite samples of Fe_(3−x)Al_xO₄ with (x = 0.0, 0.1, 0.5, and 1.0) were synthesized by using auto-combustion technique. The spinel cubic structure with no impurity markings was determined by X-ray diffraction and the lattice constants ranged from 8.398 Å to 8.359 Å. The crystallite sizes, which range from 32.15 nm to 21.38 nm with aluminum, indicate nano-size formation. Micrographs obtained with a FESEM demonstrate that the particles are uniformly distributed and nanoscale in size. Energy dispersive spectral analysis identified the composition of all fundamental elements. Two fundamentally distinct absorption bands, ν₁ and ν₂, were seen in the FTIR spectra from 600 cm⁻¹ to 404 cm⁻¹. The VSM experiments were conducted at room temperature and noticed a decrease in saturation magnetization, coercivity and remanent magnetization with aluminum.

In this paper, to obtain high strength and plasticity titanium alloy, a (Ti₇₈Fe₂₂)₈₉Nb₉Y₂ alloy was synthesized and tailored by semi-solid isothermal processing (SSIP). The experiment revealed that during the semi-solid treatment process, the microstructure of the alloy progressively transformed from dendritic to spherical crystals as the temperature and holding time increased. This transformation was accompanied by the dissolution of fine precipitates into the matrix. As a result, the alloy was composed of bimodal micro-spherical/ultrafine lamellar structure. Compression tests show that the compressive strength remains at 2551 MPa after holding at 1100 °C for 60 min, the plasticity reaches reached 50.5%. The shape factor SF and average size D a well as their correlation with plastic strain ε was also calculated and analyzed in detail.

In the present study, Al-Cu WAAM deposits were fabricated under three conditions: powder free, with TiB₂ and TiC powder at the interlayer. After deposition, the deposits were solutionized at 530 °C for 90 min and artificially aged at 180 °C for 3 h. The effect of powder particle addition and post-processing heat treatment (PPHT) were investigated. Powder free specimens show non-uniform structures throughout the deposit. TiB₂ and TiC powders refined the non-uniform solidification structure and diminished it to an equiaxed structure. PPHT promotes precipitation of secondary phases, enhancing mechanical characteristics of the depsoits. As-deposited specimens had Ultimate Tensile Strength (UTS) values of 263 MPa (powder free), 322 MPa (TiB₂), and 314 MPa (TiC), whereas PPHT specimens had 465, 487, and 482 MPa.