Huimin Liao, Tianchi Lan, Changqing Li, Ming Zeng, Hong Chen, Jianjun Zhang
November 2, 2018
The creep behavior of the extruded Mg alloys ZK60 and ZK60+1 %Y was investigated by means of the impression creep technique. The tests were carried out at a temperature in the range of 175–225 °C and under punching stress in the range of 25–100 MPa. The results showed that a 1 wt.-% yttrium addition could improve the creep resistance of ZK60. The creep mechanism of the extruded Mg alloy ZK60 consists of grain boundary diffusion by grain boundary sliding and that of the extruded Mg alloy ZK60+1 %Y grain boundary slip initiated by Mg. The microstructure of the extruded Mg alloy ZK60 consists mainly of the Mg phase and that of the Mg alloy ZK60+1 %Y in the extruded condition is composed of an α-Mg matrix and β-Mg 3 Zn 3 Y 2 phase. After the press-in creep, the extruded Mg alloy ZK60 precipitates MgZn 2 and MgZn phases and a small amount of the Zr-Zn phase, and the extruded Mg alloy ZK60+1 %Y precipitates MgZn 2 , MgZn, Y-Zn and the rare earth phase Mg-Y. The precipitation of the rare earth phase is represented by a discontinuous thin strip and a fine granular uniform distribution in the matrix. The precipitation of the rare earth compound phase shows high thermal stability, which can improve the creep resistance of the alloy. The Y-containing alloy ZK60 manifests higher threshold stress and better creep resistance due to the formation of the rare earth thermally stable particle.