Creep Resistance of As-extruded Mg-8Gd-1Er-0.5Zr Alloy

The creep behavior of the as-extruded Mg-8Gd-1Er-0.5Zr alloy at various temperatures (150~200℃) and stresses (50~70 MPa) for 100 h was studied. The microstructure evolution during creep was investigated by optical microscopy (OM) and transmission electron microscopy (TEM), and the creep mechanism was analyzed. The results show that the alloy exhibits good creep resistance under the experimental conditions. The creep curves can be divided into two stages: a deceleration creep stage and a steady creep stage. The steady-state creep rate is 6.48×10^-11 s^-1 and the creep strain is 0.007% at the temperature of 150℃ and the stress of 50 MPa, while the steady-state creep rate is 4.26×10^-9 s^-1 and the creep strain is 0.226% at the temperature of 200℃ and the stress of 50 MPa. In the case of lower temperature (150℃), diffusion mechanism acts as the main control mechanism, whereas dislocation mechanism dominates at higher temperatures (175, 200℃). Furthermore, the precipitates of β' phase in grains and the β phase at grain boundaries form during the creep process. The orientation relationship between the β' phase and the α-Mg matrix is (020)β'//[1010]Mg, [001]β'//[0001]Mg. The β' phase can effectively inhibit the dislocation gliding, and the β phase can pin gain boundaries, both of which play an important role synergistically in improving the high temperature creep resistance of the alloy.

Duke Scholars

Author Zhaohui Wang Pathology