AZ31B镁合金板料分步成形实验研究

发布时间：2018-02-14 14:02

  本文关键词： 镁合金 AZ31B Arrhenius本构方程 分步成形 二次拉伸　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：镁合金被誉为是21世纪最绿色、轻质的金属材料之一。由于镁合金的比强度高,密度小,减震性能和电磁屏蔽性能优越,因而在交通运输、电子设备及国防军工中都有广泛的需求和应用前景。但镁合金内部为密排六方结构,滑移系较少,室温下塑性成形能力较差,且变形过程中对于温度、变形速率等条件要求相对较高,使其塑性变形工艺发展受到限制。为提高镁合金塑性成形能力,扩大镁合金运用领域,需要对镁合金塑性成形工艺进行研究和优化。本构方程是反映材料力学性能的重要参数,描述了材料在变形过程中内部应力应变的变化关系,在数值模拟中是设置模拟运算的必要参数,在实际生产中本构关系也是各项生产参数设置的依据,因此研究本构关系对提高镁合金塑性,优化镁合金变形工艺有重要意义。本构方程模型种类较多,其中Arrhenius方程较适用于镁合金板料变形。除此之外,拉伸实验是研究材料力学性能的重要手段,由于镁合金内部为密排六方结构,在室温下塑性成形能力较差,因而采用分步拉伸实验对镁合金板料进行研究。分步拉伸实验将拉伸过程分成两个或多个部分进行,通过控制每个部分的变形条件来提高材料塑性成形能力。本文通过高温拉伸实验对AZ31B镁合金板料的本构关系和分步成形性能进行了研究,详细分析了拉伸过程中材料力学性能的变化规律,讨论了实验参数对镁合金塑性变形的影响。论文主要研究内容如下:首先,通过单次高温拉伸实验构建了 AZ31B镁合金板料Arrhenius本构方程。拉伸温度分别为423K、473K、523K、573K,变形速率分别为0.4s-1、0.1 s-1、0.01 s-1、0.001 s-1。该部分主要研究了 AZ31B镁合金板料塑性成形的材料参数,得到了Arrhenius本构关系表达式。其次,进行AZ31B镁合金板料分步拉伸实验,研究了温度、拉伸速率及保温时间对其塑性成形能力的影响。实验温度设定为250℃-300℃,拉伸速率设定为1mm/min、0.3mm/min,保温时间为30min。该部分借助控制变量的方法研究了不同参数对于镁合金成形能力的影响情况,揭示了镁合金塑性成形的变化规律。同时通过金相显微组织观察,分析了拉伸实验后AZ31B镁合金断口附近组织形貌,揭示了镁合金板料塑性成形中内部晶粒结构的变化过程。
[Abstract]:Magnesium alloy is regarded as one of the greenest and light metal materials in 21th century. Because of its high specific strength, low density, excellent shock absorption and electromagnetic shielding performance, magnesium alloy is in transportation. Both electronic equipment and national defense military industry have wide demand and application prospect. However, magnesium alloy has a dense hexagonal structure, less slip system, poor plastic forming ability at room temperature, and temperature during deformation. The development of plastic deformation process is limited because of the relatively high deformation rate. In order to improve the plastic forming ability of magnesium alloy and expand the application field of magnesium alloy, It is necessary to study and optimize the plastic forming process of magnesium alloy. The constitutive equation is an important parameter to reflect the mechanical properties of materials. In the numerical simulation, it is necessary to set up the simulation operation parameters, and the constitutive relation is also the basis for the setting of the production parameters in the actual production. Therefore, the constitutive relation is studied to improve the plasticity of magnesium alloy. It is important to optimize the deformation process of magnesium alloy. There are many kinds of constitutive equation models, among which Arrhenius equation is more suitable for magnesium alloy sheet deformation. In addition, tensile test is an important means to study the mechanical properties of magnesium alloy. Due to the hexagonal structure inside magnesium alloy, the plastic forming ability of magnesium alloy is poor at room temperature, so the stepwise tensile test is used to study the sheet metal of magnesium alloy. The tensile process is divided into two or more parts by stepwise tensile test. The plastic forming ability of AZ31B magnesium alloy sheet was improved by controlling the deformation condition of each part. The constitutive relation and step forming property of AZ31B magnesium alloy sheet were studied by high temperature tensile test. The variation of mechanical properties of magnesium alloy during tensile process is analyzed in detail, and the influence of experimental parameters on plastic deformation of magnesium alloy is discussed. The main contents of this paper are as follows: firstly, The constitutive equation of AZ31B magnesium alloy sheet Arrhenius was constructed by a single high temperature tensile test. The tensile temperature was 423K / 473KN 523KN 523KN 573K, respectively, and the deformation rate was 0.4s-1n / 0. 1 / 1 / 0. 01 s / 1 / 0. 001 / s. The material parameters of AZ31B magnesium alloy sheet plastic forming were studied in this part. The constitutive expression of Arrhenius was obtained. Secondly, the effects of temperature, tensile rate and holding time on the plastic forming ability of AZ31B magnesium alloy sheet were studied. The experimental temperature was set at 250 鈩，

本文编号：1510870