Simultaneously improving yield strength and formability potential of Mg alloy via introducing nano precipitates and texture-weakened heterogeneous grains

Abstract

Simultaneously improving the yield strength (YS) and formability at room temperature of magnesium (Mg) alloys is one of the key issues to broaden the application further. In this work, we report a new hot-extruded + annealed alloy (i.e., Mg–2Sm–0.8Mn–0.6Ca–0.5Zn) having good combination of yield strength (YS: 167 MPa) and formability potential (UTS−YS: 115 MPa and elongation: 25%), mainly due to formation of nano precipitates and texture-weakened heterogeneous grains. The results indicate that introduction of a certain amount of nano precipitates can enhance the strength of the alloy with little detrimental effect on ductility. The formation of heterogeneous-grained structure with a weak basal texture is mainly related to Sm/Zn/Ca elements grain boundary (GB) segregation. Geometrically necessary dislocations would nucleate at grain boundaries due to uneven deformation behavior caused by heterogeneous-grained structure, obtaining additional hetero-deformation induced hardening and large work-hardening capacity. Formation of heterogeneous-grained structure and solid solution of Sm/Zn/Ca promote the activation of considerable non-basal slips and the suppression of twinning during the deformation process. Meanwhile, GB segregation is conducive to dislocation nucleation from GBs and suppression of the GB cracking. All of these contribute to the high elongation. Thus, we put forwards a new strategy for improving the YS and formability potential via introducing nano precipitates and texture-weakened heterogeneous grains.

Keywords

• Magnesium alloy
• Ductility
• Work-hardening
• Deformation mechanism
• Grain boundary segregation