Enhancing the creep resistance of a dilute Mg-1.5 wt%Nd alloy plate via pre-compression and subsequent peak-aging

Abstract

Both static precipitation and dynamic precipitation could hardly enhance the creep resistance of dilute Mg-Nd alloys. To solve this problem, the present paper proposed a practical method, which was combining pre-compression and subsequent peak-aging. A binary Mg-1.5 wt%Nd alloy plate, was prepared for researching the tensile creep behaviors at 523 K. Due to the aging hardening was weak, the directly aged sample was not studied. The pre-compressed sample was named PC sample, and the pre-compressed with subsequent peak-aged sample was named PC-AA sample, while the sample without any pre-compression or aging was named NPC sample. The PC-AA sample had the best creep resistance, followed by the NPC sample, and the PC sample had the poorest. For the NPC sample, twinning and dislocation slip (including basal slip, cross-slip and pyramidal<c+a>slip) jointly controlled the creep behavior. Various creep mechanisms led to the easy creep strain increment and the poor creep resistance. In regard to the PC sample, the thermal stability of the preset twins was inferior and twin widening happened, resulting in a faster increment in the creep strain and a poorer creep resistance. With respect to the PC-AA sample, the dominant creep mechanisms were basal slip and dislocation climb. The high-density particles inside the preset twins successfully delayed cross-slip and twin widening, leading to the enhanced creep resistance. Thus, the twins induced by the pre-compression and the particles inside the twins induced by the subsequent peak-aging successfully enhanced the creep resistance of the dilute Mg-Nd alloys.