Wang Jinxing, Wan Zhicheng, Wang Xiyu, Wang Jiaxu, Zou Yi, Wang Jingfeng, Pan Fusheng
College of Materials Science and Engineering, Chongqing University, Chongqing 400030, China.
National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030, China.
Materials (Basel). 2024 Aug 24;17(17):4190. doi: 10.3390/ma17174190.
Mg-Gd-Y-Zn-Mn (MVWZ842) is a kind of high rare earth magnesium alloy with high strength, high toughness and multi-scale strengthening mechanisms. After heat treatment, the maximum tensile strength of MVWZ842 alloy is more than 550 MPa, and the elongation is more than 5%. Because of its great mechanical properties, MVWZ842 has broad application potential in aerospace and rail transit. However, the addition of high rare earth elements makes the deformation resistance of MVWZ842 alloy increase to some extent. This leads to the difficulty of direct plastic processing forming and large structural part shaping. Friction stir welding (FSW) is a convenient fast solid-state joining technology. When FSW is used to weld MVWZ842 alloy, small workpieces can be joined into a large one to avoid the problem that large workpieces are difficult to form. In this work, a high-quality joint of MVWZ842 alloy was achieved by FSW. The microstructure and properties of this high-strength magnesium alloy after friction stir welding were studied. There was a prominent onion ring characteristic in the nugget zone. After the base was welded, the stacking fault structure precipitated in the grain. There were a lot of broken long period stacking order (LPSO) phases on the retreating side of the nugget zone, which brought the effect of precipitation strengthening. Nano-α-Mn and the broken second phase dispersed in the matrix in the nugget zone, which made the grains refine. A relatively complete dynamic recrystallization occurred in the nugget zone, and the grains were refined. The welding coefficient of the welded joint exceeded 95%, and the hardness of the weld nugget zone was higher than that of the base. There were a series of strengthening mechanisms in the joint, mainly fine grain strengthening, second phase strengthening and solid solution strengthening.
镁-钆-钇-锌-锰（MVWZ842）是一种具有高强度、高韧性和多尺度强化机制的高稀土镁合金。经过热处理后，MVWZ842合金的最大抗拉强度超过550兆帕，伸长率超过5%。由于其优异的力学性能，MVWZ842在航空航天和轨道交通领域具有广阔的应用潜力。然而，高稀土元素的加入使MVWZ842合金的抗变形能力有所提高。这导致了直接塑性加工成型和大型结构件成型的困难。搅拌摩擦焊（FSW）是一种便捷的快速固态连接技术。当使用搅拌摩擦焊焊接MVWZ842合金时，可以将小工件连接成大工件，避免大工件难以成型的问题。在这项工作中，通过搅拌摩擦焊获得了高质量的MVWZ842合金接头。研究了这种高强度镁合金搅拌摩擦焊后的组织和性能。在焊核区有明显的洋葱环特征。母材焊接后，堆垛层错结构在晶粒中析出。在焊核区的后退侧有大量破碎的长周期堆垛有序（LPSO）相，带来了析出强化效果。纳米α-Mn和破碎的第二相在焊核区基体中弥散分布，使晶粒细化。焊核区发生了较为完全的动态再结晶，晶粒得到细化。焊接接头的焊接系数超过95%，焊缝焊核区的硬度高于母材。接头中存在一系列强化机制，主要有细晶强化、第二相强化和固溶强化。
