Effects of underwater friction stir welding tool pin profiles were studied on mechanical properties of AA5182 alloy and St-12 steel dissimilar joint. For this purpose, frustum, triangle, cubic, and hexagonal pin profiles were selected. Thermal history, microstructure analysis, tensile strength, and hardness of joint lines were assessed. The obtained results indicated that due to the high cooling rate of water environment conditions, the presence of edges in the tool pin shape (triangle, cubic, and hexagonal) improves internal material flow. Also, edged pin profiles increase the generation of frictional heat, the thickness of Intermetallic Compounds (IMC), and mechanical interlocking at base materials' interface. The hexagonal pin profile had the most significant favourable influence on the aluminium-steel joint properties among selected tool profiles. The chemical composition of IMCs at the materials interface was FeAl₃ and Fe₂Al₅, and the thickest IMC was formed near 6.5 μm. According to the results, the joint's highest tensile strength was ~69% of aluminium alloy strength, which was obtained with a hexagonal pin profile.

研究了水下搅拌摩擦焊工具销型材对AA5182合金和St-12钢异种接头力学性能的影响。为此，选择了平截头体、三角形、立方体和六边形销轮廓。评估了接合线的热历史、微观结构分析、拉伸强度和硬度。获得的结果表明，由于水环境条件的高冷却速率，工具销形状（三角形、立方体和六角形）中边缘的存在改善了内部材料流动。此外，边缘销轮廓会增加摩擦热的产生、金属间化合物 (IMC) 的厚度以及基材界面处的机械互锁。在选定的工具轮廓中，六角销轮廓对铝钢接头性能的影响最显着。材料界面处 IMCs 的化学成分为 FeAl₃和 Fe ₂ Al ₅，最厚的 IMC 形成在 6.5 μm 附近。根据结果​​，接头的最高抗拉强度是铝合金强度的 69%，这是通过六角形销轮廓获得的。