喷射沉积Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd合金组织与力学性能研究

利用XRD、OM、SEM、TEM研究了喷射沉积Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd合金挤压态的显微组织和合金的力学性能。结果表明:喷射沉积挤压态镁合金主要包含基体α-Mg和Al2Ca相,基体组织为等轴晶,平均晶粒尺寸为3μm;Al2Ca颗粒主要沿镁基体晶界分布,颗粒尺寸在1.0μm左右,并在Al2Ca相中存在孪晶结构;合金的σb、σ0.2、δ分别为450、325MPa,5%。在拉伸断口上存在大量石块状的Al2Ca相,表明合金的断裂方式为沿晶断裂;与经热挤压的铸造AZ91镁合金对比,该合金强度明显提高,但合金塑性降低;合金强度的提高主要来源于合金的细晶强化和Al、Zn对合金的固溶强化,而伸长率降低是由于合金中存在的大量Al2Ca颗粒是沿镁基体晶界分布,导致合金的塑性降低。

Microstructure and Mechanical Properties of Spray Deposited Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd Alloy

The microstructure and mechanical properties of a spray-deposited Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd alloy under the hot extrusion condition were studied by XRD, OM, SEM, TEM and tensile tester. The results show that the spray-deposited as-extruded Mg alloy mainly consists of α-Mg matrix and Al2Ca phases. The matrix structure is equiaxed grain and the average grain size is about 3 μm. The Al2Ca phases with the grain size of about 1.0 μm, mainly distribute along the boundaries of the Mg matrix; furthermore, the twin structures exist in the Al2Ca phase. The σb, σ0.2 and δ of the Mg alloy reach 450, 325 MPa and 5%, respectively. Fracture morphologies show the massive stone-like Al2Ca phases, and it is the characteristic of intergranular fracture mode. Compared with conventional cast AZ91 alloy after hot extrusion, the spray deposited Mg-12.55Al-3.33Zn-0.58Ca-1.0Nd alloy possesses higher strength, but with poor ductility. High strength of the spray deposited Mg alloy is attributed to fine crystal strengthening and solution strengthening of Al and Zn atoms in the Mg matrix, while massive Al2Ca phases distributing along grain boundaries of the Mg matrix are responsible for the poor ductility in the Mg alloy.