热挤压和热处理对Mg_(95)Y_4Zn_1合金显微组织及力学性能的影响

Effects of Hot Extrusion and Heat Treatments on Microstructure and Mechanical Properties of Mg_(95)Y_4Zn_1 Alloy

采用热挤压、固溶和时效对Mg_(95)Y_4Zn_1合金进行处理,利用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电子万能试验机研究合金的显微组织及力学性能。结果表明,铸态合金由α-Mg基体、网状18R-LPSO相和块状M_(24)Y_5相组成,在α-Mg相内存在大量堆垛层错。热挤压后,网状第二相破碎,18R相呈带状沿挤压方向排列,同时α-Mg基体内析出少量14H-LPSO层片。经固溶处理,14H层片的尺寸和数量显著增多。时效处理后,在α-Mg相内部析出大量的β'共格沉淀。与铸态合金相比,挤压态合金的强度显著升高。由于β'沉淀相的析出,时效态合金的强度达到最高,其抗拉强度和屈服强度分别为372 MPa和248 MPa。

The effect of hot extrusion, solid solution treatment and aging on the microstructure and tensile properties of Mg95Y4Zn1 alloy were systematically investigated by OM, SEM, TEM and electronic universal testing machine. The results show that the as-cast alloy is composed of α-Mg matrix, network 18R LPSO phase, block Mg24 Y5 phase and abundant stacking faults within α-Mg grains. After hot extrusion, the network is broken and strip shaped 18R phase is aligned along the direction of extrusion. Moreover, a few 14H-LPSO lamellas are precipitated within α-Mg matrix of extruded alloy, and their sizes and volume fractions increase obviously after solid solution treatment. In aged sample, a great number of coherent β＇ precipitates are generated within α-Mg grains. Compared with as-cast alloy, the strength of extruded alloy is improved remarkably. In addition, the aged alloy exhibits supreme strength with ultimate tensile strength of 372 MPa and yield strength of 248 MPa, which could be ascribed to the precipitation of coherent β＇ phase.