Mechanical properties and microstructure of AZ31 Mg alloy containing Ca element fabricated by various rolling speeds.

It was reported that the yield strength (YS) of a rolled Mg-3 wt%, Al-1 wt%, Zn-0.3 wt%, Ca alloy reached 340 MPa. The YS value of a rolled Mg-Al-Zn alloy decreases with increasing the rolling speed but that of a rolled Mg-Al-Zn-Ca alloy remains unchanged until the rolling speed of 5 m/min. Static recrystallization behavior in Mg-Al-Zn alloy occurred as a function of rolling speeds; on the other hand, it did not happen in Mg-Al-Zn-Ca alloy. A number of fine precipitates were observed in the grain of the latter alloy, suggesting that they restrain the dislocations from moving during rolling processes and keep the high strength. From the result of boss-forming test, the Mg-Al-Zn-Ca alloy shows more boss-formability than Mg-Al-Zn alloy.