Tensile creep behaviors of Mg-10Gd-0.4Zr alloy under the different applied stresses at 260 °C

Tensile creep behaviors of aging-treated Mg-10Gd-0.4Zr (wt.%) alloy were investigated under 60 MPa and 90 MPa at 260 °C. The continuous change of the stress exponent (n = 3.6, 50–70 MPa; n = 7.5, 70–90 MPa) was found, indicating different creep behaviors under the low and high stress conditions during the secondary creep stage. It can be ascribed to the faster transformation of the initial β′ phase into β₁ phase and the wider precipitate-free zones (PFZs) during creep testing under high stress condition, which weakened the creep resistance of the alloy. Observation of dislocation configuration further revealed that dislocation cross-slip and pyramidal < c + a > dislocations with stepped < c > dislocations dominated the creep process under high stress condition, resulting in the higher steady creep rate and the larger creep strain.