搅拌摩擦加工镁合金变形行为的研究

发布时间：2018-03-30 03:21

  本文选题：搅拌摩擦加工　切入点：镁合金　出处：《西安建筑科技大学》2016年硕士论文

【摘要】：本文以搅拌摩擦加工(Friction stir processing,FSP)AZ31、FSP AZ80镁合金为研究对象,研究晶粒尺寸、晶粒取向、应变速率对FSP AZ31镁合金室温力学性能的影响;探究晶粒尺寸、晶粒取向对FSP AZ31镁合金高温力学性能的影响;在不同温度、不同应变速率条件下对FSP AZ80镁合金进行高温拉伸试验,探究其超塑性变形行为。所得主要结论如下:随晶粒尺寸增大,FSP AZ31镁合金沿垂直加工方向(TD)的强度降低,延伸率增大,沿加工方向(PD)的力学性能基本保持不变;TD方向的变形机制主要是柱面滑移,PD方向的变形机制主要是基面滑移;沿TD方向拉伸后的断口表面产生解理台阶,沿PD方向拉伸后的断口表面产生韧窝,PD方向表现出较好的塑性。随应变速率增加,FSP AZ31镁合金的抗拉强度增大,延伸率减小;不同应变速率下的真应力真应变曲线形状相似且均表现出上凹特征,加工硬化率曲线整体呈“驼峰状”;应变速率敏感性指数在变形初始阶段为负值,随应变量的增加逐渐表现为正值。FSP AZ31镁合金的强度随温度升高而降低,350℃时晶粒尺寸、晶粒取向对力学性能的影响减弱。在300℃、350℃时随应变速率增大,FSP AZ80镁合金的延伸率逐渐降低,在400℃时随应变速率增大,延伸率逐渐升高。在温度为400℃、应变速率为1×10-3 s-1的条件下获得了最佳超塑性,所得最大延伸率为413%。最佳超塑性试样的应变速率敏感性指数m值为0.37,高温拉伸后的显微组织中有空洞产生,断口表现出沿晶断裂特征。
[Abstract]:The effect of grain size, grain orientation and strain rate on the mechanical properties of FSP AZ31 magnesium alloy at room temperature was studied in this paper.The effect of grain orientation on the high temperature mechanical properties of FSP AZ31 magnesium alloy and the tensile test of FSP AZ80 magnesium alloy at different temperature and different strain rate were carried out to investigate the superplastic deformation behavior of FSP AZ80 magnesium alloy.The main conclusions are as follows: with the increase of grain size, the strength of FSP AZ31 magnesium alloy decreases along the vertical processing direction, and the elongation increases.The deformation mechanism in the direction of cylinder slip and PD direction is the base slip, and the cleavage step is produced on the fracture surface stretching along TD direction.The ductility of the fracture surface along the PD direction is better than that in the PD direction.With the increase of strain rate, the tensile strength of FSP AZ31 magnesium alloy increases and the elongation decreases, and the true stress true strain curve at different strain rates is similar in shape and concave in shape, and the work hardening rate curve is "hump" as a whole.The strain rate sensitivity index is negative at the initial stage of deformation, and the strength of positive. FSP AZ31 magnesium alloy decreases at 350 鈩，

本文编号：1684105