利用3D转模等通道转角挤压(3D-RD ECAP)设备,对AZ31镁合金进行了A',B'_A,B'_C与C'_4种路径的ECAP实验.对试样的显微组织观察显示,经4种路径挤压后合金显微组织都明显细化,但不同路径对微观组织和力学性能的影响不同.经A'和B'_A路径挤压的试样组织中晶粒尺寸和硬度分布比其它两种路径挤压的试样更均匀,且显示出更高的塑性.通过对各种路径挤压过程中试样内部立方单元的变形分析,揭示了传统的剪切模型理论的不足.利用有限元方法模拟了试样ECAP的形变过程,证实材料在变形过程中各部位受力差异很大.ECAP对试样变形的均匀性主要取决于拉/压应力交替作用于试样各个部位的顺序,而与传统剪切模型中的立方单元变形规律没有直接关系.
Using a 3D rotary-die equal-channel angular pressing (3D-RD ECAP) mold, the commercial wrought magnesium alloy A231 has been processed through 4 routes (A',B'_A,B'_C and C') and microstructures as well as mechanical properties of the samples processed were investigated. The results reveal that all the 4 routes can refine microstructures of the alloy, however, the effects on microstructural homogeneity and tensile elongations of the samples are different. The grain sizes of the samples processed through routes A' or B'_A are more uniform and their tensile elongations at ambient temperature are also higher than those through B'_C or C' routes. The distributions of hardness on the central longitudinal planes of samples extruded through different routes are well consistent with the microstructural characters at the corresponding positions. Strain analysis on the cubic elements in the samples reveals the limitation of the traditional shear mode for ECAP. Based on experimental results and finite element method (FEM) simulation, the deformation homogeneity caused by ECAP processing is closely related to the alternative action of tensile and compressive stresses at the different positions in the samples and is independent of the deformation regularity of the cubic elements in the shear model proposed in the previous studies.
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