坯料细化处理对AZ31镁合金挤压组织的影响

Effect of pre-treating for refining on microstructure of hot extruded AZ31 magnesium alloy

对超声细化和未细化的AZ31镁合金棒料进行均匀化退火后热挤压,并对热挤压后的组织和硬度进行了对比分析。结果表明,与未经过晶粒细化处理棒料的热挤压组织相比,预先经过晶粒细化处理的AZ31镁合金棒热挤压组织更加均匀。当挤压比λ为16、挤压料温度为380℃、挤压速度为0.9 m/min时,组织发生回复再结晶。与未经晶粒细化处理棒料的挤压组织相比,经过晶粒细化处理的挤压组织更加细小;挤压速度增加到10 m/min时,经过晶粒细化处理后的AZ31镁合金挤压变形后棒料边缘容易发生二次再结晶现象,形成一条宽约75μm的粗晶组织,边缘附近区域组织中有孪晶形成。同时,经过晶粒细化处理后的AZ31镁合金挤压棒的硬度较高。

The hot extrusion experiments were perfurmed at oil hydraulic press about AZ31 magnesium alloy bar treated with ultrasonic refining and non-preconditioned, which were all treated with homogeneous annealing. In addition, the microstruc- lures and hardness in the extruded AZ3I magnesium alloy were studied and analyzed comparatively. The results showed that there were more homogeneous extruded issues in the AZ31 magnesium alloy bar which was treated by grain refining than that was not pre-treated. Recovery and recrystatlization were found in the extrusion organization when the extrusion ratio A was 16,the extrusion temperature was 380~C and the extrusion speed was 0.9 nv/min. The grain of AZ31 which was treated with grain refining was smaller. When the speed of extrusion increased to 10m/rain, the edge of AZ31 after grain refining was easy to occur the second recrystallization and formed a width of 75 μm coarse grain structure. The twin-grain was formed near the edge of AZ31 magnesium alloy. At the same time, the hardness of AZ31 magnesium alloy extrusion bar which was pre-treated with grain refining was also improved.