Study On Extrusion And Heat Treatment Process Of AZ61 Magnesium Alloy

For AZ61 magnesium alloy, some processes including homogenization, extrusion and heat treatment were studied. Firstly, the casting ingots were homogenized at different temperature for different time. The optimal parameters of AZ61 magnesium alloy for homogenization were determined according to its microstrures. Then, extrusion test was carried out at different deformation temperature and extrusion ratio. Finally, heat treatments for extruded specimens were finished according to T4, T5 and T6 heat treatment respectively. On the basis of testing data and analysis, some conclusions can be drawn as follows.1. Based on XRD analysis, microstructure of AZ61 magnesium alloy is mainly composed of primary α-Mg and secondary Mg17Al12 phase. The optimal parameter of homogenization is temperature of 390°C for 4 hours.2. Dynamic recrystallization occurs during extrusion process, which leads to grain refinement of AZ61 magnesium alloy. The optimal extrusion temperature for AZ61 magnesium alloy was determined in the range of 350 to 370°C. The more the extrusion ratio is, the finer grains are, and the better the mechanical properties are.3. After heat treatment for extruded specimens of AZ61 magnesium alloy, the characteristic of static recrystallization was found. At condition of T4 treatment, elongation of AZ61 magnesium alloy can be greatly improved and strength decrease. Heat treatment of T5 and T6 will lead to grain refinement, which will improve mechanical properties of AZ61 magnesium alloy. The optomal parameters of heat treatment for AZ61 magnesium alloy is solution temperature of 325°C for 2 hours and aging temperature of 180°C for 24 hours.4. XRD and EDS testing results show that the strength of AZ61 magnesium alloy increases after T6 heat treatment. The reason is that single-phase decomposes and the dispersed β-Mg17Al12 phase precipitates after solid solution, which leads to improvement of the mechanical properties for AZ61 magnesium alloy. Wear test results show that heat treatment of T6 can greatly enhance the wear resistance because of the grain refinement.5. The SEM images from tensile fracture show that the fracture morphology is substantially similar regardless of its different states.6. The properties of corrosion resistance for AZ61 magnesium alloy have not been improved after extrusion and heat treatment.These experiments show the optimal process parameters for AZ61 magnesium alloy which includes homogenization, deformation and the heat treatment. All these experiment results will be helpful to produce parts of AZ61 magnesium alloy.