Effect Of Heat Treatments On Microstructure And Mechanical Properties Of AZ61 Magnesium Alloy As Extruded

Along with the energy and the environmental protection problem outstanding, make the research of the magnesium alloy already become hot in recent years, but mostly concentrated in the technique of smelting, molding and rot-resistant etc. For the strength and plasticity of the extruded magnesium alloy, people also have done some research works, but the research impact toughness, especially impact toughness under low temperature, is less. And this performance embodies a comprehensive index of the mechanical properties of magnesium alloys. It influences the application of the magnesium alloy directly. In this paper, influences of four kinds of heat treatment processes on the microstructure and strengths and plasticity of extruded AZ61 magnesium alloy under the room temperature were investigated, the impact toughness under the room and low temperatures were specially investigated.Through the tensile tests under the different states for AZ61 magnesium alloys and the impact tests under the different temperature, combined with the analysis of the organization structure, a conclusion was drawn. The extruded AZ61 magnesium alloy through solution heat treatment (385°C×12h), the artificial aging process (260°C×4h and 215°C×5h) and solution treatment plus artificial aging process (385°C×12h + 215°C×5h) change the microstructure of the extruded AZ61 magnesium alloy;solution treatment and solution treatment plus artificial aging process make the tensile strength σb and yield strength σ_0.2 of extruded AZ61 magnesium alloy decrease slightly, tensile strength changed from 314.5 MPa to 299.7 MPa and 297.2 MPa , yield strength changed from 223.5 MPa to 196.4 MPa and 208.5 MPa . But the fracture elongation changed from 16.2% to 19.8% and 22.6%, indicating that plasticity was increased dramatically, it has no influence on the extruded AZ61 magnesium alloys in this test only by aging procedure.After extrusion, experimental temperature( 20°C^-60 °C) had little influence on impact toughness, and this property under room temperature can be improved through solution treatment, reaching 17.88 J/cm², but experimental results under lower temperatures were almost the same. Other methods of heat treatment will lower the impact toughness, and this kind of decrease was not apparent under lower experimental temperatures. Impact toughness is roughly same under the two kinds of aging process;compared to solution treatment plus artificial aging process, solution treatment has a greater influence upon it.