AZ31镁合金限制性模压与退火工艺研究

发布时间：2018-02-28 17:22

本文关键词： 镁合金限制性模压力学性能金相组织剧烈塑性变形　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：作为目前最轻的金属结构材料,镁及其合金自上世纪90年代以来便迅猛发展,在有色金属产业中占据非常重要的地位。由于比强度、比刚度高,具有良好的减震性能、铸造以及加工性能等优点,其在国防、交通以及电子电器设备等行业都具有广阔的应用前景以及市场需求。但由于镁独特的密排六方结构,常温下塑性较差,限制了其在塑性成形领域的应用。限制性模压(CGP)变形技术作为一种自上而下制备超细晶材料的方法,通过累积应变将原有晶粒破碎来细化金属材料从而提高金属的加工塑性和超塑性。它不改变材料的外观形状及尺寸,通过变形过程中引入大的应变量使板材晶粒得到细化,从而使材料机械性能得到提高,该技术在低碳钢、纯铝、纯铜等金属上得到应用并取得良好效果。本文通过数值模拟与工艺实验相结合的方法对AZ31镁合金板材的限制性模压变形进行研究,详细分析了 CGP变形过程对板材力学性能和微观组织的影响规律,讨论了 CGP变形对镁合金板材晶粒细化的变形机理,揭示了后续退火工艺过程中板材力学性能与微观组织的变化情况。论文主要研究内容如下:利用有限元模拟技术基于DEFORM软件建立镁合金CGP工艺模型并进行变形工艺仿真分析。通过镁合金CGP变形过程中的载荷、网格变形、材料流动以及应变场分布的变化规律,分析了镁合金CGP变形过程中模具与板材的变化情况,研究了变形过程中板材的变形机理与应变累积分布规律。为实验模具的设计与工艺实验的进行建立了理论依据。进行AZ31镁合金板材限制性模压实验,通过调整不同的变形温度、变形速率、模压方式与模压次数分析不同CGP变形参数对镁合金板材的影响规律,讨论镁合金CGP变形的最优条件。通过对CGP变形板材的拉伸测试,分析CGP变形对镁合金板材在沿模压方向与垂直模压方向上力学性能的影响特点。通过金相显微组织观察分析,揭示CGP变形对板材晶粒组织的影响变化规律。进行CGP退火工艺实验分析,通过对退火温度与退火时间的调整,分析CGP板材在不同退火工艺参数下力学性能与晶粒组织的变化情况,讨论CGP变形后的AZ31镁合金板材最优退火条件。进行退火板材的热拉伸实验与金相组织观察,研究镁合金CGP板材在退火过程中宏观性能与微观组织的变化机理。
[Abstract]:As the lightest metal structural material at present, magnesium and its alloys have developed rapidly since -10s, and occupy a very important position in the nonferrous metal industry. It has broad application prospects and market demand in the fields of national defense, transportation, electronic and electrical equipment and so on. However, due to the unique dense hexagonal structure of magnesium, the plasticity is poor at room temperature. Limiting its application in the field of plastic forming. As a top-down method for the preparation of ultrafine grained materials, limited moulding CGP-based deformation technology, The original grain is broken by cumulative strain to refine the metal material and improve the working plasticity and superplasticity of the metal. It does not change the appearance and size of the material, and the grain size of the plate is refined by introducing large strain variables in the process of deformation. So that the mechanical properties of the materials are improved, the technology in low carbon steel, pure aluminum, Pure copper and other metals have been applied and good results have been obtained. In this paper, the restrictive moulding deformation of AZ31 magnesium alloy sheet was studied by means of numerical simulation and process experiment. The effect of CGP deformation process on mechanical properties and microstructure of magnesium alloy sheet was analyzed in detail. The deformation mechanism of CGP deformation on grain refinement of magnesium alloy sheet was discussed. The changes of mechanical properties and microstructure of magnesium alloy during subsequent annealing process are revealed. The main contents of this paper are as follows: the finite element simulation technology is used to establish the CGP process model of magnesium alloy based on DEFORM software and the deformation process is carried out. Through the load of magnesium alloy CGP deformation process, The variation law of mesh deformation, material flow and strain field distribution is analyzed. The change of die and plate during CGP deformation of magnesium alloy is analyzed. The deformation mechanism and strain accumulation distribution of AZ31 magnesium alloy sheet during deformation were studied. The theoretical basis for the design of experimental die and process experiment was established. The limiting molding experiment of AZ31 magnesium alloy sheet was carried out, and different deformation temperatures were adjusted. The influence of different CGP deformation parameters on magnesium alloy sheet was analyzed, and the optimum conditions of CGP deformation of magnesium alloy were discussed. The tensile test of CGP deformed sheet was carried out. The influence of CGP deformation on the mechanical properties of magnesium alloy sheet in the direction of molding and vertical molding was analyzed. The effect of CGP deformation on the grain structure of sheet metal was revealed. The experimental analysis of CGP annealing process was carried out, and the annealing temperature and time were adjusted. The change of mechanical properties and grain structure of CGP sheet under different annealing process parameters is analyzed. The optimal annealing conditions of AZ31 magnesium alloy sheet after CGP deformation are discussed. The thermal tensile test and metallographic observation of annealed sheet are carried out. The change mechanism of macroscopic properties and microstructure of magnesium alloy CGP sheet during annealing was studied.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;TG166.4

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