The Microstructure and the Study of Elevated Temperature Property of ZM6 Alloy

　　The Microstructure and the Study of Elevated Temperature Property of ZM6 Alloy
　　The microstructure and mechanical behaviors at elevated temperature of ZM6 were investigated in this study. The microstructure and phase of as-cast and heat treated ZM6 were analyzed by means of optical microscope(OM),scanning electron nicroscopy(SEM),transmission electron microscope(TEM).Gleeble-1500D was employed to study the mechanical behaviors at elevated temperature of ZM6.The results show that the massive Mg-RE neodymium magnets phase Mg12Nd is mainly distributed on the grain boundary of as-cast ZM6 alloy.Only a small amount of flaky and grainy Mg12Nd distribute in intracrystalline and grain boundary. Mg12Nd phase is uniformly distributed on the matrix as criss-cross flak gathered by spotted state phase after solution and aging treatmentIt is shown that cleavage fracture is the main mechanism accompanied with elongated dimple fracture at 100℃,while the fracture is typical dimple fracture above 250℃.The dimples have began to melt at the strain rate of 10-4s-1 at 250℃at the edge of specimen. Elongation percentage and contraction of area increase as the temperature rise to the maximum of 36.6% and 55.7%, respectively.
　　Tensile stress is decreased as the increased temperature. The maximum tensile strength reaches 220MPa at the strain rate of 10-2s-1 at 100℃. The higher strain rate leads to increase of stress .The results of compression test show that fracture occurs below 250℃. Cleavage fracture emerges below 100℃.It is mixed mechanism with the shallow dimple at 250℃.The lower strain rate resulted in more dimple and the deeper tearing edge. Compression stress is lower http://www.chinamagnets.biz at the elevated temperature. The ultimate compress strength is 295MPa at the strain rate of 10-2s-1 at room temperature. The phase of Mg12Nd is stretched into fibre yarn at 300℃, but it is dispersed in the matrix as the spotted state phase at 400℃. The dispersity is higher at low strain rate.The average strain rate sensitivity exponent of ZM6 alloy was calculated to be 0.235 and the average activation energy was 185.4kJ/mol at the temperature of 300℃to 400℃which is far from self-diffusion energy of magnesium alloy .It is