AZ451镁合金薄带的组织和力学性能研究

STUDY ON MICROSTRUCTURES AND MECHANICAL PROPERTIES OF AZ451 MAGNESIUM ALLOY SHEETS

利用OM,SEM,TEM,数字显微硬度计和电子万能试验机,对常规轧制与铸轧法制备的AZ451镁合金薄带的显微组织和力学性能进行了分析.常规铸锭轧制后仍为等轴晶组织,晶粒尺寸明显细化.铸轧条带在350℃多道次轧制后显微组织由树枝晶转变为纤维状变形组织,350℃/10 min热处理后合金发生再结晶,得到等轴晶组织.轧制后两种合金均具有良好的力学性能,双辊铸轧合金的强度和延伸率均明显高于传统铸造合金的强度和延伸率,两种合金1 mm厚薄带经350℃/10 min均匀化退火后的抗拉强度、屈服强度和延伸率分别为334.4 MPa,229.3 MPa,23.8%和270.8 MPa,174.4 MPa,10.8%.两种合金的断口形貌均呈现河流花样,撕裂棱和韧窝共存,是明显的韧性断裂,铸轧合金的韧窝更明显,尺寸更小一些,这与铸轧合金的组织更细小有关.

The microstructures and mechanical properties of AZ451 magnesium sheets produced by different processes were analyzed by OM, SEM, TEM, digital microhardness tester and a standard universal testing machine. For conventional casting alloy, the equiaxed structure was refined after hot rolling. But for twin roll casting alloy, the microstructure changed from dendrite to fibrous deformation structure after several passes hot rolling at 350℃. Recrystalhzation occurred in twin roll casting alloy after heat treatment at 350℃/10 min and equiaxed structure was obtained. After hot rolling both of the two alloys possess good mechanical properties, but the strength and elongation of twin roll casting alloy are much higher than those of conventional casting alloy. After annealing at 350 ℃ /10 min, the Cb, c0.2 and $ of twin roll casting and conventional casting alloy sheets with a thickness of 1 nun are 334.4 MPa, 229.3 MPa, 23.8%, and 270.8 MPa, 174.4 MPa, 10.8%, respectively. The fracture surfaces of the alloys exhibited ductile fracture characteristics, but the twin roll casting alloy has more evident and smaller ductile dimples because of finer grain of twin roll casting alloy.