Flow Stress of Wrought Magnesium Alloys during Hot Compression Deformation at the Medium and High Temperatures

摘要

Pure Mg and Mg alloys generally exhibit only limited ductilities at ambient temperatures as they have the crystal structure of hexagonal close packed lattice, so their forming technology should be proceeded at the medium and high temperature. The flow stress behaviors of magnesium alloys (AZ31 alloy and ZK60 alloy) were studied by means of hot compression deformation tests on Gleeble 1500D machines at different temperatures and strain rates. The results indicated that the thermal simulation curves of AZ31 and ZK60 have different forms. Most of the curves of AZ31 have the character of dynamic recrystallization that the flow stress rises by decreasing in temperature and increasing in strain rate and the specimen can be deformed successively, while most thermal simulation compressing curves of ZK60 have the obvious character that around 0.2 in strain the stress reaches the peak and declines rapidly afterwards and lands the lowest. The decline of the curve illustrates that the test specimen has been destroyed and the crackle can be found on the test specimen correspondingly. And the other true stress increases to a peak and then decreases to a steady state, indicating that dynamic recrystallization have occurred in ZK60 alloy. From the analysis the optimized composite table of the deformed parameters of ZK60 was established and the reasonable deformed temperatures of ZK60 was concluded to be 200 °C or 400 °C, which can play a directing role in determining the deforming technology of wrought magnesium alloys.