模具结构对AZ91镁合金挤压成形性能的影响

The influence of die structure on the extrusion ability of AZ91 magnesium alloy

AZ91镁合金由于强度高、流动性好等特点,通常用作铸造合金。研究该合金合理的挤压温度、挤压速度及模具结构,对提高其塑性成形性能、开发高强度变形镁合金有重要的理论和实际意义。文章通过热模拟试验研究了AZ91镁合金应力应变关系,确定了最佳变形温度。在此基础上,采用三维有限元法模拟分析了不同挤压速度、模具结构对挤压过程温度场、速度场及应力场的影响。结果表明,采用锥模和流线模时,当定径带长度为15mm^20mm时,可在挤压速度达到5mm/s的条件下成形出表面光滑无裂纹的镁合金棒材;而采用平模挤压时,当定径带长度为10mm^20mm时,获得良好表面质量的挤压速度达到2.5mm/s。在650t的卧式挤压机上,进行了该合金的挤压实验,实验结果与模拟结果相吻合。

With higher strength and better flowing ability, AZ91 magnesium alloy is used as cast alloy commonly. It is necessary to determine appropriate extrusion temperature, extrusion speed and die structure for improving the plastic properties of AZ91 and developing new wrought magnesium alloy with higher strength. In this paper, the stress-strain relationship of the AZ91 magnesium alloy is investigated by thermal simulation test, and the suitable deformation temperature is determined. Based on the stressstrain relationship, the influence of the extrusion speed and die structure on the thermal field, velocity field and stress field are analyzed by FEM. The results show that, when the bearing length of tapered and streamline die is 15mm-20mm, a smooth surface and flawless magnesium alloy rod can be obtained with 5mm/s extrusion speed. When the bearing length of flat die is 10mm-20mm, the extrusion speed can reach 2. 5mm/s to obtain high surface quality. The extrusion experiment of AZ91magnesium alloy is carried out adopting 650T horizontal extruder, and the experimental results is in agreement with the FEM results.