Recently, there have been few reports on the hot extrusion process of magnesium (Mg) alloy square tubes. In this work, we introduce a novel hot extrusion process called tube continuous expanding shear extrusion (tCESE) to produce Mg alloy square tubes with heterogeneous structures. Compared to previously reported hot-extruded Mg alloy tubes, the tCESE samples exhibit simultaneous enhancements in both strength and ductility. The microstructure evolution during the tCESE process was analyzed in detail. It was found that the microstructure developed consecutively as a result of twinning-induced dynamic recrystallization (TDRX), discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) with different nucleation of new orientations, while static recrystallization (SRX) promoted the formation of heterogeneous structures. The strengthening mechanism in the tCESE samples was revealed by loading-unloading-reloading (LUR) tensile tests, viscoplastic self-consistent (VPSC) simulation and intermittent tensile tests. The improvement of the strength in the tCESE samples is attributed to the size refinement of the grains and the second-phases, and more importantly, to hetero-deformation induced (HDI) strengthening. The improvement of the ductility in the tCESE samples can be attributed to the significant increase in non-basal dislocations within the heterogeneous structures during tensile deformation.

中文翻译：

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通过新型管材连续膨胀剪切挤压加工实现 AZ31 镁合金方管的强度-延展性同步增强


近年来，关于镁 （Mg） 合金方管热挤压工艺的报道很少。在这项工作中，我们介绍了一种称为管材连续膨胀剪切挤压 （tCESE） 的新型热挤压工艺，以生产具有非均相结构的 Mg 合金方管。与以前报道的热挤压镁合金管相比，tCESE 样品在强度和延展性方面同时表现出增强。详细分析了 tCESE 过程中的微观结构演变。研究发现，孪晶诱导动态再结晶 （TDRX）、不连续动态再结晶 （DDRX） 和连续动态再结晶 （CDRX） 的微观组织连续发展，新取向的成核不同，而静态再结晶 （SRX） 促进了异质结构的形成。通过加载-卸载-重新加载 （LUR） 拉伸试验、粘塑性自洽 （VPSC） 模拟和间歇拉伸试验揭示了 tCESE 样品中的强化机制。tCESE 样品强度的提高归因于晶粒和第二相的尺寸细化，更重要的是，异质变形诱导 （HDI） 强化。tCESE 样品延展性的改善可归因于拉伸变形过程中非均质结构内非基位错的显着增加。