TY - JOUR
T1 - Mechanistic investigation of a low-alloy Mg–Ca-based extrusion alloy with high strength–ductility synergy
AU - Pan, Hucheng
AU - Kang, Rui
AU - Li, Jingren
AU - Xie, Hongbo
AU - Zeng, Zhuoran
AU - Huang, Qiuyan
AU - Yang, Changlin
AU - Ren, Yuping
AU - Qin, Gaowu
PY - 2020/3
Y1 - 2020/3
N2 - High strength–ductility synergy is difficult to achieve in Mg alloys. Although high strength has been achieved through considerable alloying addition and low-temperature extrusion, these techniques result in low ductility (2%–5%). In this work, a novel low-alloy Mg–Ca-based alloy that overcomes this strength–ductility trade-off is designed. The alloy has an excellent tensile yield strength (∼425 MPa) and exhibits a reasonably high elongation capacity (∼11%). A microstructure examination reveals that a high density of submicron grains and nano-precipitates provides the alloy high strength, and the leaner alloy additions and higher extrusion temperatures initially improve ductility. As a result, the density of residual dislocations is reduced, and the formation of low-angle grain boundaries (LAGBs) is enhanced. With fewer residue dislocations, it becomes less probable for the newly activated mobile dislocations to be impeded and transformed into an immobile type during the subsequent tensile test. The LAGBs function as potential sites to emit new dislocations, thus enhancing the dislocation–multiplication capability. More importantly, they can induce evident sub-grain refinement hardening and guarantee that the alloy achieves high strength. The findings lead to a controllable Mg alloy design strategy that can simultaneously afford high strength and ductility.
AB - High strength–ductility synergy is difficult to achieve in Mg alloys. Although high strength has been achieved through considerable alloying addition and low-temperature extrusion, these techniques result in low ductility (2%–5%). In this work, a novel low-alloy Mg–Ca-based alloy that overcomes this strength–ductility trade-off is designed. The alloy has an excellent tensile yield strength (∼425 MPa) and exhibits a reasonably high elongation capacity (∼11%). A microstructure examination reveals that a high density of submicron grains and nano-precipitates provides the alloy high strength, and the leaner alloy additions and higher extrusion temperatures initially improve ductility. As a result, the density of residual dislocations is reduced, and the formation of low-angle grain boundaries (LAGBs) is enhanced. With fewer residue dislocations, it becomes less probable for the newly activated mobile dislocations to be impeded and transformed into an immobile type during the subsequent tensile test. The LAGBs function as potential sites to emit new dislocations, thus enhancing the dislocation–multiplication capability. More importantly, they can induce evident sub-grain refinement hardening and guarantee that the alloy achieves high strength. The findings lead to a controllable Mg alloy design strategy that can simultaneously afford high strength and ductility.
KW - Dynamic recrystallisation
KW - Low-angle grain boundary
KW - Mechanical property
KW - Mg wrought alloy
KW - Pyramidal dislocations
UR - http://www.scopus.com/inward/record.url?scp=85077943322&partnerID=8YFLogxK
U2 - 10.1016/j.actamat.2020.01.017
DO - 10.1016/j.actamat.2020.01.017
M3 - Article
AN - SCOPUS:85077943322
SN - 1359-6454
VL - 186
SP - 278
EP - 290
JO - Acta Materialia
JF - Acta Materialia
ER -