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Excellent strength-ductility synergy properties of Mg–Sn–Zn–Zr alloy mediated by a novel differential thermal ECAP (DT-ECAP).

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Title: Excellent strength-ductility synergy properties of Mg–Sn–Zn–Zr alloy mediated by a novel differential thermal ECAP (DT-ECAP).
Authors: Zhou, Tianshui1,2 (AUTHOR), Wang, Bing1,2 (AUTHOR), Zhang, Minjie1,2 (AUTHOR), Li, Yaqin1,2 (AUTHOR), Hu, Shiwen1,2 (AUTHOR), Li, Xiaoqiang1,2 (AUTHOR), Liu, Dexue1,2 (AUTHOR) dxliu@lut.edu.cn
Source: Materials Science & Engineering: A. May2024, Vol. 899, pN.PAG-N.PAG. 1p.
Subjects: Magnesium alloys, Tensile strength, Alloys, Grain refinement, Tensile tests, Dislocation density
Abstract: The application of structural magnesium (Mg) alloys in engineering industry is usually impeded by the challenge of strength-ductility synergy. In this study, a considerable ductility (elongation, ∼27–33 %) and high ultimate tensile strength (UTS, ∼340–370 MPa) Mg–Sn–Zn–Zr alloy was developed by a combination of aging, extrusion and novel differential thermal equal-channel angular pressing (DT-ECAP) process. Both dislocation slip and (double) cross-slip are primary deformation mechanisms of the alloy. Furthermore, jogs or kinks induced by the interaction between high density of dislocations were also observed in the alloy before and after tensile test, indicating good deformability. More importantly, based on the two-beam bright-filed TEM under three g conditions, multiple slip systems containing pyramidal , prismatic and basal dislocations were activated to accommodate both c-axis and a-axis strains of the alloy, leading to superior work-hardening effect and thus superb ductility. On the other hand, the DT-ECAP process was in favor of grain refinement and ultrafine second phases with ∼54–63 nm. Therefore, the principal strengthening mechanisms of the DT-ECAPed alloys were grain boundary strengthening, precipitation strengthening and dislocation strengthening. The contributions of the three strengthening mechanisms to TYSs of second pass (2P) and forth pass (4P) alloys are ∼77 MPa and ∼66 MPa, ∼30 MPa and ∼27 MPa, ∼34 MPa and ∼27 MPa, respectively. The current work develops a novel DT-ECAP process for preparing a new Mg–Sn–Zn–Zr alloy with strength-ductility synergy and provides a strategy to break the strength-ductility tradeoff dilemma of rare-earth-free Mg alloy. • The strength-ductility synergy in TZK alloy was achieved by a combination of aging, extrusion and novel DT-ECAP process. • The appearance of jogs or kinks highly contributed to the continued plastic straining during DT-ECAP process. • The high strength originated from the strengthening mechanisms of grain boundary, ultrafine second phase and dislocations. • The activation of pyramidal , prismatic and basal dislocations was responsible for the superb ductility. [ABSTRACT FROM AUTHOR]
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Abstract:The application of structural magnesium (Mg) alloys in engineering industry is usually impeded by the challenge of strength-ductility synergy. In this study, a considerable ductility (elongation, ∼27–33 %) and high ultimate tensile strength (UTS, ∼340–370 MPa) Mg–Sn–Zn–Zr alloy was developed by a combination of aging, extrusion and novel differential thermal equal-channel angular pressing (DT-ECAP) process. Both dislocation slip and (double) cross-slip are primary deformation mechanisms of the alloy. Furthermore, jogs or kinks induced by the interaction between high density of dislocations were also observed in the alloy before and after tensile test, indicating good deformability. More importantly, based on the two-beam bright-filed TEM under three g conditions, multiple slip systems containing pyramidal <c + a>, prismatic and basal <a> dislocations were activated to accommodate both c-axis and a-axis strains of the alloy, leading to superior work-hardening effect and thus superb ductility. On the other hand, the DT-ECAP process was in favor of grain refinement and ultrafine second phases with ∼54–63 nm. Therefore, the principal strengthening mechanisms of the DT-ECAPed alloys were grain boundary strengthening, precipitation strengthening and dislocation strengthening. The contributions of the three strengthening mechanisms to TYSs of second pass (2P) and forth pass (4P) alloys are ∼77 MPa and ∼66 MPa, ∼30 MPa and ∼27 MPa, ∼34 MPa and ∼27 MPa, respectively. The current work develops a novel DT-ECAP process for preparing a new Mg–Sn–Zn–Zr alloy with strength-ductility synergy and provides a strategy to break the strength-ductility tradeoff dilemma of rare-earth-free Mg alloy. • The strength-ductility synergy in TZK alloy was achieved by a combination of aging, extrusion and novel DT-ECAP process. • The appearance of jogs or kinks highly contributed to the continued plastic straining during DT-ECAP process. • The high strength originated from the strengthening mechanisms of grain boundary, ultrafine second phase and dislocations. • The activation of pyramidal <c + a>, prismatic and basal <a> dislocations was responsible for the superb ductility. [ABSTRACT FROM AUTHOR]
ISSN:09215093
DOI:10.1016/j.msea.2024.146469