不同温度场下AZ31镁合金筒形件反挤压成形规律研究

Investigation on backward extrusion forming laws of AZ31 magnesium alloy tubular parts under different temperature fields

为了探索不同温度场对AZ31镁合金筒形件反挤压成形的影响规律,采用数值模拟与实验相结合的方式,控制模具温度为200℃,通过改变坯料温度探究温度场和应变场的分布规律,以及筒形件的力学性能和微观组织。结果表明:在筒形件的成形过程中坯料自身热量、模具与坯料之间热传递以及形变热形成一定温度场;即使坯料为室温,挤出时最高温度都达到290℃。在不同坯料温度条件下,等效应变主要集中在筒形件的转角处和内壁,筒壁同一高度沿着内壁到外壁等效应变值逐渐减小。反挤压成形后的筒形件的微观组织和力学性能得到了明显的改善,坯料室温时成形的筒形件相比较于原始材料,平均晶粒尺寸从25. 58μm减小到2. 39μm,屈服强度和抗拉强度分别提高了119%和74. 7%,伸长率提高了67. 7%。分析可知反挤压过程中发生了动态再结晶,晶粒显著细化,提高了材料的力学性能。

To invesgated the effect laws of different temperatures on the backward extrusion forming of AZ31 magnesium alloy tubular parts,numerical simulation and experimental investigation were used. By changing the temperature of billets under the die temperature of200 ℃,the distribution law of temperature field and strain field,as well as the microstructure and mechanical properties of the tubular parts were investigated. The results show that during the deformation process,a certain temperature field is formed by the billet body heat,heat transfer between die and billet and the heat of deformation. The maximum temperature reaches 290 ℃ even when the billet is at room temperature. Under different conditions of billet temperature,the effective strain mainly concentrates on the corner and inner wall of tubular parts,and the effective strain decreases gradually along the inner wall to the outer wall at the same height. In addition,the microstructure and the mechanical properties of the tubular parts formed by backward extrusion are improved obviously. Compared with the original materials,the average grain size of the tubular parts formed by the billet at room temperature decreases from 25. 58 to 2. 39 μm,the yield strength and tensile strength increase by 119% and 74. 7% respectively,and the elongation increases by 67. 7%. The analysis shows that dynamic recrystallization occurs during the backward extrusion process,which significantly refines the grain and improves the mechanical properties of the material.