【摘要】 采用重力铸造制备Mg-6Al-3Ca-1Zn-0.3Mn合金(质量分数，%)并对其均匀化处理和差速挤压，使用EBSD和TEM等手段表征其不同部位的组织并使用Deform-3D对差速挤压进行了有限元模拟，研究了差速挤压对其组织和性能的影响。结果表明：差速挤压中的温度场和应力场是影响板材微观组织和性能的关键因素。在差速挤压初期板材前端的温度迅速降低，与模具内部的温度差使再结晶不彻底而留下了大量未再结晶的晶粒。在差速挤压后期板材各部分的温度一致且较高，型腔内部坯料受到的应力增大而生成部分孪晶促进了动态再结晶。板材的前端由粗大的未再结晶晶粒和细小的动态再结晶晶粒组成，在未再结晶内部发生了颜色梯度变化，在未再结晶晶粒中有大量的小角晶界，其再结晶机制是连续动态再结晶。板材的尾部由等轴晶粒组成，晶界局部突出，原始晶界呈现锯齿状，再结晶机制是不连续动态再结晶。差速挤压板材头部的抗拉强度最高(328 MPa)，其原因是再结晶的细晶强化和未再结晶晶粒的位错强化。板材尾部的延伸率最高(约为16.6%)，是晶粒细化和织构弱化所致。更多还原

【Abstract】 Mg-6Al-3Ca-1Zn-0.3Mn alloy(mass fraction, %) was prepared by gravity casting, and the alloy was homogenized and differential speed extruded. The effect of differential speed extrusion on the microstructure and properties of different portions of the plates were investigated by using EBSD and TEM, and meanwhile the differential speed extrusion process was analyzed via finite element simulation with Deform-3D. As indicated by the results, that the temperature field and stress field in the extrusion process are the key factors affecting the microstructure of the plate. The temperature at the front end of the plate drops rapidly at the early stage of extrusion, forming a temperature difference with the inside of the die, which results in incomplete recrystallization, and thereby emergence of a large number of un-recrystallized grains. In the late stage of extrusion, the plate temperature is consistent and high, and the billet inside the cavity is subjected to increased stress, which produces partial twinning and promotes dynamic recrystallization. The starting portion of the plate consists of coarse un-recrystallized grains and fine dynamically recrystallized grains, and there is a color gradient within the un-recrystallized grains, and a large number of LAGBs are distributed among the un-recrystallized grains, and the recrystallization mechanism may be continuous dynamic recrystallization. The end portion of the plate consists of equiaxed grains with locally protruding grain boundaries, and the original grain boundaries show jagged shape, and the recrystallization mechanism may be ascribed to discontinuous dynamic recrystallization. Finally, the starting portion of the plate is obtained as the highest tensile strength of 328 MPa, which is due to the combined effect of fine crystal strengthening of the recrystallized grains and dislocation strengthening of the un-recrystallized grains. The end portion of the plate shows the best elongation of about 16.6%, which is mainly due to grain refinement and weakening of the weave structure.更多还原