發(fā)布時間：2018-03-30 03:21

  本文選題：攪拌摩擦加工　切入點：鎂合金　出處：《西安建筑科技大學》2016年碩士論文

【摘要】：本文以攪拌摩擦加工(Friction stir processing,FSP)AZ31、FSP AZ80鎂合金為研究對象,研究晶粒尺寸、晶粒取向、應變速率對FSP AZ31鎂合金室溫力學性能的影響;探究晶粒尺寸、晶粒取向?qū)SP AZ31鎂合金高溫力學性能的影響;在不同溫度、不同應變速率條件下對FSP AZ80鎂合金進行高溫拉伸試驗,探究其超塑性變形行為。所得主要結(jié)論如下:隨晶粒尺寸增大,FSP AZ31鎂合金沿垂直加工方向(TD)的強度降低,延伸率增大,沿加工方向(PD)的力學性能基本保持不變;TD方向的變形機制主要是柱面滑移,PD方向的變形機制主要是基面滑移;沿TD方向拉伸后的斷口表面產(chǎn)生解理臺階,沿PD方向拉伸后的斷口表面產(chǎn)生韌窩,PD方向表現(xiàn)出較好的塑性。隨應變速率增加,FSP AZ31鎂合金的抗拉強度增大,延伸率減小;不同應變速率下的真應力真應變曲線形狀相似且均表現(xiàn)出上凹特征,加工硬化率曲線整體呈“駝峰狀”;應變速率敏感性指數(shù)在變形初始階段為負值,隨應變量的增加逐漸表現(xiàn)為正值。FSP AZ31鎂合金的強度隨溫度升高而降低,350℃時晶粒尺寸、晶粒取向?qū)αW性能的影響減弱。在300℃、350℃時隨應變速率增大,FSP AZ80鎂合金的延伸率逐漸降低,在400℃時隨應變速率增大,延伸率逐漸升高。在溫度為400℃、應變速率為1×10-3 s-1的條件下獲得了最佳超塑性,所得最大延伸率為413%。最佳超塑性試樣的應變速率敏感性指數(shù)m值為0.37,高溫拉伸后的顯微組織中有空洞產(chǎn)生,斷口表現(xiàn)出沿晶斷裂特征。
[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，

本文編號：1684105