The yield asymmetry and precipitation behavior of pre-twinned ZK60 alloy

This study aims to investigate the tension and compression properties and precipitation behavior of pre-twinned ZK60 alloys. It was found that aging treatment can effectively reduce the tension-compression yield asymmetry of pre-twinned ZK60 alloy. For the pre-twinned sample with 10 h aging treatment, the yield asymmetry ratio is nearly equal to 1. Precipitate behavior in {10-12} extension twins of ZK60 Mg alloy were characterized by TEM. Three different morphologies of precipitates, [0001]twin rods, (0001)twin plates and [11-20]twin laths were observed in {10-12} extension twins. The precipitates constituted Mg4Zn7 or MgZn2 phases. The Mg4Zn7 phases have two variant orientations of the [010] zone axis, [010]Mg4Zn7 ‖ [0001]twin and (−201)Mg4Zn7 ‖ (‐12‐10)twin or (−201)Mg4Zn7 ‖ (10-10)twin, while the MgZn2 phases have an orientation of [‐12‐10]MgZn2 ‖ [0001]twin and (10-12)MgZn2 ‖ (10-10)twin. [11-20]twin laths as a new morphology of the precipitates have been found in ZK60 alloy, which have an orientation relationship of [010] Mg4Zn7 ‖ [0001] twin and (−201)Mg4Zn7 ‖ (‐12‐10)twin. Finally, the influences of aging treatment on yield asymmetry of pre-twinned ZK60 alloy are addressed and discussed.