中文摘要：

为了深入了解循环闭式模锻过程中变形行为规律,改进制备工艺,为下一步工业化应用奠定基础,采用Deform-3D数值模拟软件对循环闭式模锻进行有限元分析,探讨了模锻过程中试样的温度场、应变场、速度场、应力场。结果表明：加工时,坯料上端先于下端镦粗变形,逐步充满下型腔;变形过程中,试样内部大多数部位承载三维方向压缩应力,各质点流动速度不同,流动方向各异,造成剪切塑性变形始终存在;初始道次结束后试样内部各部位应变差异很大,随着后续道次的进行,应变的分布呈均匀化趋势,累积应变不断提高;温度场模拟表明,坯料模锻后棱边和表面温升很高,坯料内部大部分区域温升较低。在400℃加工铸态AZ31镁合金的实验表明：4道次后,晶粒分布均匀,平均尺寸由约178μm细化到约19μm。

英文摘要：

In order to understand the law of deformation behavior in the process of cyclic closed-die forging（CCDF）,to improve the preparation process and to lay the foundation for further industrial application,the finite element analysis was performed on CCDF by numerical simulation software Deform-3D. The features of temperature field,strain field,velocity field and stress field of the sample in die forging were discussed. The results show that the upsetting deformation of the upper end of billet is earlier than the lower end when filling the cavity. Most parts of the internal sample bear compressive stress in three-dimensional directions,and the shear plastic deformation always exists because of different values and directions of flowing speed in forging. Therefore,the strain distribution is very inhomogeneous on the whole sample after an initial pass,and both strain uniformity and accumulated strain increase as sequential passes are carried on. The temperature field simulation shows that the temperature rising in the edge and surface are very apparent,while it is lower in most areas of the internal part. The experimental investigation of processing cast magnesium alloy AZ31 at 400 ℃ shows that the average grain size is refined about from 178 μm to 19 μm after four passes,and the distribution of grain is homogeneous.