In this study, a new modified cyclic extrusion channel angular pressing (CECAP) process with multi-pass capability is presented for producing ultrafine-grained (UFG) Mg alloy. In this method, an additional extrusion stage with a low extrusion ratio is added at the end of the CECAP process to enhance hydrostatic stresses, equivalent strain, and facilitation of the process implementation. The experimental results showed a remarkable grain refinement with a relatively uniform distribution of microstructure and β-phase in the new CECAP processed sample. The average grain size decreased from ~75 µm in annealed condition to 4.5 µm and 3.5 µm in CECAP and new CECAP processes, respectively. Also, more dispersion of the β-phase with smaller sizes was observed in the processed microstructure. The hardness and its uniform distribution were increased significantly. The compressive yield stress (CYS) was enhanced to about 153.3 MPa from the initial value of ~85 MPa. Also, both the strength and ductility of the new CECAP processed sample were higher than those of CECAP processed one. These excellent properties might attribute to higher hydrostatic compressive stresses resulting from the last low ratio extrusion stage which was almost 50% higher in the new CECAP process.

在这项研究中，提出了一种新的改进的具有多次通过能力的循环挤压通道角挤压（CECAP）工艺，用于生产超细晶粒（UFG）镁合金。在此方法中，在CECAP过程结束时添加了一个具有低挤压比的附加挤压阶段，以增强静液压应力，等效应变并简化过程的实现。实验结果表明，在新的CECAP处理样品中，晶粒细化显着，微观结构和β相分布相对均匀。在CECAP和新的CECAP工艺中，平均晶粒尺寸分别从退火后的约75 µm降至4.5 µm和3.5 µm。另外，在加工的微结构中观察到具有较小尺寸的β相的更多分散。硬度及其均匀分布明显增加。压缩屈服应力（CYS）从〜85 MPa的初始值增加到约153.3 MPa。而且，新的CECAP处理样品的强度和延展性均高于CECAP处理的样品。这些优异的性能可能归因于最后的低比例挤出阶段所产生的更高的静水压应力，在新的CECAP工艺中，其静压压力几乎提高了50％。