焊接速度对6005A-T6铝合金双轴肩搅拌摩擦焊接头力学性能的影响

Effect of welding speed on mechanical properties of bobbin tool friction stir welded 6005A-T6 aluminum alloy joints

关键词:  6005A-T6铝合金  双轴肩搅拌摩擦焊  力学性能  断裂形式

Key words:  6005A-T6 aluminum alloy  bobbin tool friction stir welding  mechanical properties  fracture type

摘要:

文中研究了转速和热输入特征值WP一定两种条件下焊接速度对6005A-T6铝合金双轴肩搅拌摩擦焊接头力学性能的影响. 结果表明，转速一定时，接头抗拉强度随焊接速度的增加呈先增大后减小的趋势；热输入特征值WP一定时，随着焊接速度的增加，接头的抗拉强度持续减小；接头呈现出三种断裂方式，分别为发生于热影响区的Ⅰ型断裂、发生于焊核区的Ⅱ型断裂和发生于热力影响区的Ⅲ型断裂；Ⅰ型断裂和Ⅱ型断裂为韧性断裂；Ⅲ型断裂为包含韧性断裂和脆性断裂的混合型断裂；接头拉伸断裂位置并非总出现在硬度最低处；焊接速度小于1 000 mm/min时，WP ≤ 1有利于提高接头力学性能，而焊接速度大于1 000 mm/min时，WP > 1更有利于提高接头力学性能.

Abstract:

Effect of welding speed on mechanical properties of 6005A-T6 aluminum alloy joints welded by bobbin tool friction stir welding method was investigated under a constant rotation speed and heat input factor (Ratio of welding speed and rotation speed, WP). The results show that under a certain rotation speed, the tensile stress increased and then decreased with the increasing of welding speed. While under a certain WP, the tensile stress decreased continuously with the increasing of welding speed. Three typical fracture morphology were found in bobbin tool friction stir welded joints, namely, I type fracture at the heat affected zone (HAZ), Ⅱ type fracture at the weld nugget zone (WNZ) and Ⅲ type fracture at the thermal-mechanical affected zone (TMAZ). The macro morphology of I and Ⅱ type fracture were cup and cone morphology, serrated morphology, respectively. However, the microstructure indicated that both of them featured with toughness failure. Ⅲ type fracture was identified to be mixed fracture which consists of toughness failure and brittle failure. The tensile fracture position is not always occurred at the position with minimum microhardness. When the welding speed was lower than 1 000 mm/min, WP less than 1 is benefit to obtain joints with higher tensile strength and I type fracture. On the contrary, when welding speed was higher than 1 000 mm/min, WP more than 1 is benefit to obtain joints with higher tensile strength and I type fracture.