Dynamic precipitation, microstructure and mechanical properties of Mg-5Zn-1Mn alloy sheets prepared by high strain-rate rolling

Mg-5Zn-1Mn (wt%) alloy sheets with good strength-ductility balance were successfully fabricated by high strain-rate rolling (HSRR) in a wide temperature range from 250 degrees C to 400 degrees C. The microstructural evolution, dynamic precipitation characteristics and mechanical properties of the as-rolled sheets were investigated. The results show that the dynamic precipitation plays a key role in the as-rolled microstructural evolution and the mechanical properties. The uniform and dispersive precipitates with high spatial distribution density mainly nucleated on the alpha-Mn particles and along the dislocations during the HSRR. A typical bimodal microstructure can be obtained even at the high rolling temperature (400 degrees C) by the HSRR process due to the dynamic precipitates strongly pinning the boundaries of the dynamic recrystallization (DRX) grains or subgrains. The sheet fabricated by HSRR at 300 degrees C exhibits high strength and excellent ductility, with the ultimate tensile strength (UTS), yield tensile strength (YS) and elongation (EL) to failure of 359 MPa, 258 MPa and 20.1%, respectively. The superior mechanical properties can be attributed to the ultrafine DRX grains featured with the bimodal microstructure and the precipitates with high density. (C) 2016 Elsevier Ltd. All rights reserved.