Microstructure and Mechanical Properties of Mg-Al-Zn Alloys Processed by Different-Speeds-Rolling

摘要

In this investigation, a different-speeds-rolling (DSR) processing was carried out on AZ31 and AZ91 alloys, aimed at improving metallurgy quality and mechanical property of the two Mg-Al-Zn based alloys by the severe shear deformation induced during the DSR process. The start materials were cut from the cast billets and rolled in a specific mill of which the rotation speed ratio of the upper roll and the lower roll could be varied from 1 to 1.364. Further, both rolls of the mill might be heated up to 300℃, which is beneficial to the processing of Mg alloys which are poor in bulk workability at ambient or low temperatures. For present study, the speed ratio of the upper roll and lower one was selected as 1.364, while the rolls temperature controlled from ambient temperature to 300℃. The preheating temperature of the rolled sample was also varied within a wide range in that to obtain the Mg-Al-Zn alloys sheets free of crack with the final thickness of about 1.1 mm. The influence of rolling conditions and post heat treatment on microstructure and mechanical property of the rolled Mg-Al-Zn sheets were examined by several techniques such as optical microscopy, SEM, hardness test, and tensile test either at ambient or at elevated temperature. It is found that the DSR processing has a remarkable effect on grain refinement of the investigated Mg-Al-Zn alloys, and the rolled sheets exhibit appropriate mechanical properties under the testing conditions. The current work is a primary attempt and further detailed investigations are necessary in order to produce high performance Mg alloy sheet by the DSR technique.