AZ61镁合金连续流变挤压成形过程的金属流动与组织演化

Metal Flow and Microstructure Evolution During Continuous Rheo-extrusion of AZ61 Magnesium Alloy

采用自行设计的连续流变挤压成形技术成功制备出Φ10mm的AZ61镁合金线材。在轧辊的挫动剪切作用下,合金从浇注口到挤压区,逐渐由发达的枝晶状组织演化为细小的等轴晶和球形晶。在挤压成形时,中心部位固相变形小,边部大,在圆弧流动区产生了优良的超细晶组织。在合理的技术条件下,制备的AZ61合金线材断面组织优良,呈现两相塑性流动的特征。浇注温度影响AZ61合金的固相率,进而对成形过程产生重要影响,合理的浇注温度为650℃左右。

By using self-designed continuous rheo-extrusion process, AZ61 alloy wire with the diameter of Φ10 mm was fabricated. Under the actions of kneading and shearing by the roll, microstructures of the alloy gradually evolve from dendrites at the pouring entrance to the fine equiaxed and spherical grains at the extrusion zone. During the extrusion forming process, solid structures in the central part have a small deformation, but that in the outside have a large deformation, and ultra-fine grain microstructures come into being in the arc flow part. Under proper process conditions, the microstructures on the transaction of the product are good and show the character of two-phase plastic flow. Casting temperature can affect solid fraction and further induces a great influence on the forming process; proper casting temperature is about 650 ℃.