铝合金型材搅拌摩擦焊对搭接接头的疲劳性能研究

Study on aluminum alloy profile friction stir welding effect on butt-lap joint fatigue properties

对6005A-T6铝合金型材对搭接接头实施了搅拌摩擦焊接,对焊后接头组织形貌及疲劳性能进行了分析,研究结果表明,对搭接接头组织分焊核区、热-力影响区、热影响区和母材区,搅拌头下方的材料也存在热-力影响区和热影响区。对搭接接头硬度分布呈“W”形,薄弱区为前进侧热影响区。采用主S-N曲线法分析接头疲劳性能方案可行。接头疲劳寿命与熔化焊相比,差异不大。经对疲劳断口分析,疲劳裂纹由焊缝根部起裂,表现出沿晶断裂特征,存在细小的疲劳辉纹。裂纹稳定扩展区域辉纹方向较为一致,均从焊缝根部指向焊缝表面。近焊缝表面区为瞬断区,可发现明显的韧窝特征。

Friction stir welding is used for butt-lap joint of 6005A-T6 aluminum alloy profile to study the Fatigue properties and Microstructure morphology of the joint.The experimental results indicate the following.The microstructure of the butt-lap joint is mainly divided into nugget zone,thermal-mechanical affected zone,heat affected zone and base metal zone.The material under the stirring head is also divided into the heat affected zone and thermal-mechanical zone.The hardness distribution of butt-lap joint is shaped as"W",and the weak area is the forward heat affected zone.The master S-N curve method can be used to analyze the fatigue performance of FSW joint.There is no obvious difference between the melt and friction stir welding for the fatigue life of FSW joint.Based on the analysis of fatigue fracture,fatigue crack starts from the root of welding which shows the characteristics of intergranular fracture with small fatigue bright lines.In the stable crack growth region,the direction of glow lines is relatively consistent,which is from the bottom to the surface.The area near the weld surface is transient where obvious dimple features can be identified.