搅拌针偏移量对A356/6061铝合金搅拌摩擦焊的影响

Effect of Stir Pin Offset on the FSW of A356-T6&6061-T6 Dissimilar Aluminum Alloy

对66mm厚的A356-T6／6061T6异种铝合金的搅拌摩擦焊工艺进行了试验研究，采用OM、SEM、万能拉伸试验机、显微硬度仪等分析了搅拌针偏移量对搅拌摩擦焊接头组织和性能的影响。研究结果表明：搅拌针的偏移量在-0．4-0．4mm范围内均可获得外表美观、内部无明显缺陷的搅拌摩擦焊接头；焊核区两种材料的分界线非常清晰，分别由焊核区、热机影响区和热影响区组成，混合区主要分布在前进侧的焊核区；焊核区由晶粒细致的等轴晶组成，随厚度方向从上而下细化程度逐渐增加。搅拌针向6061侧偏移，有利于焊核区面积、接头强度以及延伸率的增加。当搅拌针向6061偏移0．4mm时，焊核区较-0．4mm时面积增大10％，接头强度和延伸率分别达到210MPa和8．8％，分别为A356母材的74．6％和65．2％；同时，接头断裂位置由返回侧逐渐向前进侧转移，断口位置与焊缝区最低硬度区相吻合；向A356侧偏移时，两侧的热影响区宽度变窄，硬度值增大。

The stirring friction welding process test of 6mm thickness of A356-T6/6061-T6 of dissimilar alumi- num alloy were researched. The effects of pin offset on microstructure and mechanical properties of joint of friction stir welding （FSW） were analyzed by using analysis instruments such as OM, SEM, universal tensile testing machine and micro hardness. The results show that the good appearance and no obvious defects joints were obtained when pin off- set in the range of -0. 4-0. 4 mm. The boundaries between dissimilar aluminum alloy in nugget zone appeared dis- tinctly, and each materials side composed of nugget zone, thermal mechanical effect zone and heat affected zone, re- spectively. The mixed zone distributed at the advancing side of the weld nugget zone. The weld nugget zone is com- posed of fine and equiaxed grains, and with the refinement degree increased with thickness direction of top-down gra- dually. The pin offset to the 6061 side is beneficial to improve the welding area, joint strength, and elongation. The nugget zone increased 10%when the pin offset 6061 to 0.4 mm compared with -0. 4 mm. The strength and elongation of joint were up to 210 MPa and 8. 8%, respectively, about 74. 6% and 65.2% of A356 base metal. Meanwhile, the fracture position from retreating side transfer to advancing side gradually when the pin offset changed from -0. 4 mm to 0. 4 m The fracture position located in the lowest hardness zone of joints. The heat affected zone width be- came narrow when the pin offset to A356 side and the hardness value increased.