Creep behaviors of Mg–6Zn-0.4Mn-0.3Al-0.2Ca (wt.%) alloy enhanced by icosahedral quasicrystal

Abstract

Magnesium (Mg) alloys are considered to be the lightest metal structural materials, however, their poor creep resistance considerably limits their applications. In this study, a novel Mg–6Zn-0.4Mn-0.3Al-0.2Ca (ZMAX6000) alloy with icosahedral quasicrystal phases (I-phases) distributed at almost all triangular grain boundaries was developed by hot extrusion and heat treatment. Tensile creep tests were systematically conducted on the alloy at temperatures of 398 K, 423 K, and 448 K under stresses of 50 MPa, 70 MPa, and 90 MPa, respectively. These I-phases could reduce the accumulation of creep damage at triangular grain boundaries, hinder grain boundary sliding, and delay the generation of cracks. As a result, the ZMAX6000 alloy exhibited far superior creep properties compared to ZK60 and AZ91 alloys. During the creep process, non-basal slip occurred and the texture intensity of the sample was weakened. Dislocation characterization results showed that the creep mechanisms of the alloy at 448 K under 90 MPa were cross-slip and pyramidal < c + a > slip.