Room temperature tensile creep behavior of Mg-6Zn-0.4Mn-0.3Al-0.2Ca (wt%) alloy containing icosahedral quasicrystals

Abstract

The poor creep resistance at room temperature is the critical issue limiting magnesium (Mg) alloys to be structural components in engineering fields. In this study, we designed a novel Mg-6Zn-0.4Mn-0.3Al-0.2Ca (ZMAX6000) alloy, which had superior creep properties at room temperature, and the steady creep rate of ZMAX6000 (2.52×10−9 s−1) alloy was one order of magnitude lower than that of pure Mg (5.0×10−8 s−1) and AZ31 alloy (1.5×10−8 s−1), when the creep stress is equivalent to the 0.8 yield stress (YS). The ZMAX6000 alloy featured icosahedral quasicrystal phases (I-phases) distributed at almost all triangular grain boundaries. The room temperature creep threshold stress (σ0) and stress exponent (n) for the I-phase enhanced ZMAX6000 alloy were σ0 = 209 MPa and n = 4.9, respectively. I-phases can act as barriers to grain boundary sliding, and the high-density nanoscale second phases inside the grains can impede the dislocation slip. Consequently, the ZMAX6000 alloy exhibits excellent creep properties at room temperature. The cross-slip consisting of basal < a > dislocation and prismatic < a > dislocation, as well as the pyramidal <c + a> slip are the main creep mechanisms of the ZMAX6000 alloy at room temperature.