Tension/Compression Difference in Creep Resistances of Wrought Mg-Zn-Based Alloy with Icosahedral Quasicrystal Phases

In this work, icosahedral quasicrystal phases (I-phases) distributed at grain boundary triple junctions were successfully obtained in Mg-6Zn-0.4Mn-0.3Al-0.2Ca (ZMAX6000) alloy through heat treatment. The effects of I-phases on tensile and compressive creep behaviors were investigated separately. The tensile creep resistance of the sample containing I-phases was superior to its compressive creep resistance under the same test conditions. Moreover, the sample exhibited a significant tension/compression difference in creep resistance. Tensile and compressive creep stress exponents of the sample were ~ 4.9 and ~ 2.3, which implied that the tensile and compressive creep mechanisms might be dislocation slip and grain boundary sliding, respectively. Microstructural characterizations revealed that I-phase could suppress the premature convergence of cracks at grain boundary triple junctions during tensile creep deformation. Nevertheless, cracks might be preferentially generated around I-phases distributed at grain boundary triple junctions due to grain boundary sliding, during compressive creep deformation. The different effects of I-phases on crack development could cause the tension/compression difference in the creep resistance of the alloy.