Effect of Scroll Pin Profile and Tool Rotational Speed on Mechanical Properties of Submerged Friction Stir Processed AZ31B Magnesium Alloy

In this study, an effort has been made to choose an appropriate tool pin profile and rotational speed for a tool using a submerged friction stir processed hot rolled AZ31B magnesium alloy. A defect free process region was obtained using a novel tool shoulder, which consisted of a scroll. Three tool pin profiles, namely, simple cylindrical, stepped cylindrical and stepped square pin have been used. Tensile properties and fracture behavior revealed defect free friction stir processed specimens. The microstructural studies reveal the possibility of producing a defect free processed region using the stepped square pin tool geometry. The presence of fine recrystallized grains (1.99 µm) and the absence of defects in the processed region lead to higher hardness and superior tensile properties.

本研究针对经水下搅拌摩擦加工处理的热轧AZ31B镁合金，开展了适配搅拌针形貌与旋转转速的选取工作。本次研究采用带有涡旋纹路的新型搅拌轴肩，成功获得了无缺陷的加工区域。实验共选用三种搅拌针形貌，分别为普通圆柱型、阶梯圆柱型与阶梯方型搅拌针。拉伸性能与断裂行为分析表明，所有搅拌摩擦加工试样均无明显缺陷。微观组织研究证实，采用阶梯方型搅拌针几何结构可实现无缺陷的加工区域制备。加工区域内存在尺寸为1.99 μm的细小再结晶晶粒且无缺陷，这使得材料具备更高的硬度与更优异的拉伸性能。