This study reveals the effects of Ca content (0.0002–0.0025 wt%) on the CGHAZ toughness of Al-Ca-Ti steels. Increasing the Ca content transforms inclusions from Ti2O3-MnS to CaO·6Al2O3-CaTiO3-MnS(-CaS), raising the effective inclusion density from 72.11 to 114.35 mm−2. First-principles and lattice mismatch calculations reveal the superior lattice matching between CaTiO3 and MnS, facilitating Mn-depleted zone formation around Ca-containing inclusions. Moreover, CaO·6Al2O3-CaTiO3-MnS(-CaS) exhibits lower lattice mismatch with ferrite (<6%) compared to Ti2O3-MnS, significantly promoting primary IAF nucleation. Consequently, with increasing Ca content, the primary IAF length grows from 7.7 to 11.3 μm, and the secondary IAF count increases from 2.1 to 3.7 per inclusion, enhancing CGHAZ impact toughness from 18 to 162 J.
ZouXSunJMatsuuraH, et al.Profiling microstructure evolution roadmap in heat-affected zones of EH36 shipbuilding steel under controlled thermal simulation. Metall Mater Trans A2020; 51: 3392–3397.
2.
SunLGLiHRZhuLG, et al.Research on the evolution mechanism of pinned particles in welding HAZ of Mg treated shipbuilding steel. Mater Des2020; 192: 108670.
3.
WanXLWeiRWuKM. Effect of acicular ferrite formation on grain refinement in the coarse-grained region of heat-affected zone. Mater Charact2010; 61: 726–731.
4.
SungHKShinSYChaW, et al.Effects of acicular ferrite on charpy impact properties in heat affected zones of oxide-containing API X80 linepipe steels. Mater Sci Eng A2011; 528: 3350–3357.
5.
TakamuraJMizoguchiS. Roles of oxides in steels performance. Metallurgy of oxides in steels. In Proceedings. 6th International Iron and Steel Congress. Japan. 1990: 591–597.
6.
ZhangDShintakuYSuzukiS, et al.In situ observation of phase transformation in low-carbon, boron-treated steels. Metall Mater Trans A2012; 43: 447–458.
7.
JiaXChenYPLiHK, et al.Study on the mechanism of AF nucleation induced by complex oxide inclusions after LF refining in oxide metallurgical steel. Mater Charact2023; 204: 113239.
8.
CostinWLLavigneOKotousovA. A study on the relationship between microstructure and mechanical properties of acicular ferrite and upper bainite. Mater Sci Eng A2016; 663: 193–203.
9.
ZouXSunJMatsuuraH, et al.In situ observation of the nucleation and growth of ferrite laths in the heat-affected zone of EH36-Mg shipbuilding steel subjected to different heat inputs. Metall Mater Trans B2018; 49: 2168–2173.
10.
EsmailianM. The effect of cooling rate and austenite grain size on the austenite to ferrite transformation temperature and different ferrite morphologies in microalloyed steels. Iran J Mater Sci Eng2010; 7: 7–14.
11.
YangZWangFWangS, et al.Intragranular ferrite formation mechanism and mechanical properties of non-quenched-and-tempered medium carbon steels. Steel Res Int2008; 79: 390–395.
12.
ZhangYHYangJXuLY, et al.The effect of Ca content on the formation behavior of inclusions in the heat affected zone of thick high-strength low-alloy steel plates after large heat input weldings. Metals (Basel)2019; 9: 1328.
13.
ZhangYHYangJLiuDK, et al.Improvement of impact toughness of the welding heat-affected zone in high-strength low-alloy steels through Ca deoxidation. Metall Mater Trans A2021; 52: 668–679.
14.
LiuZSongBMaoJH. Effect of Ca on the evolution of inclusions and the formation of acicular ferrite in Ti-Mg killed EH36 steel. Ironmak Steelmak2021; 48: 1115–1122.
15.
WangCWangXKangJ, et al.Effect of thermomechanical treatment on acicular ferrite formation in Ti–Ca deoxidized low carbon steel. Metals (Basel)2019; 9: 296.
16.
LinCKPanYCSuY-HF, et al.Effects of Mg-Al-O-Mn-S inclusion on the nucleation of acicular ferrite in magnesium-containing low-carbon steel. Mater Charact2018; 141: 318–327.
17.
ZhuLGWangYWangSM, et al.Research of microalloy elements to induce intragranular acicular ferrite in shipbuilding steel. Ironmak Steelmak2019; 46: 499–507.
18.
WangXChenYWangC, et al.Effect of heat input on microstructure and impact toughness of coarse-grained heat-affected zone in Al-Ca and Ti-Ca killed steels. Steel Res Int2020; 91: 2000133.
19.
MuWZJönssonPGNakajimaK. Recent aspects on the effect of inclusion characteristics on the intragranular ferrite formation in low alloy steels: a review. High Temp. Mater. Process.2017; 36: 309–325.
20.
ShimJHChoYWChungSH, et al.2Nucleation of intragranular ferrite at Ti2O3 particle in low carbon steel. Acta Metall1999; 47: 2751–2760.
21.
ShimJHOhYJSuhJY, et al.Ferrite nucleation potency of non-metallic inclusions in medium carbon steels. Acta Mater2001; 49: 2115–2122.
22.
ZhangSHHattoriNEnomotoM, et al.Ferrite nucleation at ceramic/austenite interfaces. ISIJ Int1996; 36: 1301–1309.
23.
AndrésCGDCapdevilaCCaballeroFG, et al.Effect of molybdenum on continuous cooling transformations in two medium carbon forging steels. J Mater Sci2001; 36: 565–571.
24.
GrongØKlukenAONylundHK, et al.Catalyst effects in heterogeneous nucleation of acicular ferrite. Metall Mater Trans A1995; 26: 525–534.
25.
MuWZShibataHHedströmP, et al.Ferrite formation dynamics and microstructure due to inclusion engineering in low-alloy steels by Ti2O3 and TiN addition. Metall Mater Trans B2016; 47: 2133–2147.
26.
ShimJHByunJSChoYW, et al.Mn absorption characteristics of Ti2O3 inclusions in low carbon steels. Scr Mater2001; 44: 49–54.
27.
LiYWanXLChengL, et al.First-principles calculation of the interaction of Mn with ZrO2 and its effect on the formation of ferrite in high-strength low-alloy steels. Scr Mater2014; 75: 78–81.
28.
TomitaYSaitoNTsuzukiT, et al.Improvement in HAZ toughness of steel by TiN-MnS addition. ISIJ Int1994; 34: 829–835.
29.
JiangMWangXHHuZY, et al.Microstructure refinement and mechanical properties improvement by developing IAF on inclusions in Ti-Al complex deoxidized HSLA steel. Mater Charact2015; 108: 58–67.
30.
LiTYangJZhangY, et al.Deterioration mechanism of impact toughness in the coarse-grained heat-affected zone of Ca-treated shipbuilding steel plate with high-Cr content. J Alloys Compd2025; 1024: 180194.
31.
MadariagaIGutierrezIBhadeshiaHKDH. Acicular ferrite morphologies in a medium-carbon micoalloyed steel. Metall Mater Trans A2001; 32A: 2187–2197.
32.
WangXWangCKangJ, et al.Improved toughness of double-pass welding heat affected zone by fine Ti–Ca oxide inclusions for high-strength low-alloy steel. Mater Sci Eng A2020; 780: 139198.
33.
SongFYinCHuF, et al.Effects of Mn-depleted zone formation on acicular ferrite transformation in weld metals under high heat input welding. Materials (Basel)2022; 15: 8477.
34.
KangYBLeeHG. Thermodynamic analysis of Mn-depleted zone near Ti oxide inclusions for intragranular nucleation of ferrite in steel. ISIJ Int2010; 50: 501–508.
35.
ZhangQKZhaoMQLiQH, et al.A DFT study on electronic and optical properties of La Ce–doped CaTiO3 perovskite[C]. in The Proceedings of the 5th International Conference on Energy Storage and Intelligent Vehicles. 2022. Singapore Springer.
36.
LiuPTXingWWChengXY, et al.Effects of dilute substitutional solutes on interstitial carbon in α-Fe: Interactions and associated carbon diffusion from first-principles calculations. Phys Rev B2014; 90: 024103.
37.
LiuEKWangQGuoZH, et al.Nucleation and growth mechanisms of ferrite on Mg–Ti–oxide surfaces: First-principles investigation. J Mater Res Technol2023; 24: 6968–6981.
38.
LiYWanXLChengL, et al.Effect of oxides on nucleation of ferrite: First principle modelling and experimental approach. Mater Sci Technol2016; 32: 88–93.
39.
WangDChangWShenY, et al.The role of lattice mismatch in heterogeneous nucleation of pure Al on Al2O3 single-crystal substrates with different termination planes. J Therm Anal Calorim2019; 137: 791–797.
40.
BramfittBL. The effect of carbide and nitride additions on the heterogeneous nucleation behavior of liquid iron. Metallurgical Transactions1970; 1: 1987–1995.
41.
MadariagaIGutiérrezI. Role of the particle-matrix interface on the nucleation of acicular ferrite in a medium carbon microalloyed steel. Acta Mater1999; 47: 951–960.
42.
MillsARThewlisGWhitemanJA. Nature of inclusions in steel weld metals and their influence on formation of acicular ferrite. Mater Sci Technol2013; 3: 1051–1061.
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