Abstract Travel speeds between 25–300 mm/min and tool rotational speeds of 800 and 1250 rpm were employed for this study. The microstructure, mechanical properties and fracture surfaces of the joints were studied. Underwater environment and an increase in travel speed significantly increase the precipitates’ volume fraction, reduce the average grain and precipitate sizes of the weld nugget zones. A critical travel speed of 150 mm/min is attained in underwater welds beyond which the average grain sizes remain relatively the same. Average grain and precipitate sizes have linear relationships with the tool rotational and travel speed ratio. Optimum weld strengths of 396 and 360 MPa were obtained in the underwater and air-cooled welds at tool rotational and travel speeds of 800 rpm and 50 mm/min respectively.

中文翻译：

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Al7075铝合金水下搅拌摩擦焊的冶金和力学性能

摘要 本研究采用 25-300 毫米/分钟的行驶速度和 800 和 1250 rpm 的工具旋转速度。研究了接头的显微组织、力学性能和断口面。水下环境和行进速度的增加显着增加了析出物的体积分数，降低了焊接熔核区的平均晶粒和析出物尺寸。在水下焊缝中达到 150 毫米/分钟的临界行进速度，超过该速度后平均晶粒尺寸保持相对相同。平均晶粒和沉淀尺寸与工具旋转和移动速度比呈线性关系。在工具旋转速度和行进速度分别为 800 rpm 和 50 mm/min 的情况下，水下和风冷焊缝获得了 396 MPa 和 360 MPa 的最佳焊接强度。