中文摘要：

采用搅拌摩擦焊技术对5mm厚的2024-T4高强铝合金进行对接焊试验.研究粒子贫乏区的微观组织特征、形成机理及其对力学性能的影响.结果表明：粒子贫乏区位于紧靠焊核区的前进侧热机影响区一侧,与前进侧热机影响区具有一致的方向性;和相邻区域相比,出现第二相粒子的显著贫乏,贫乏区宽度平均约30μm.粒子贫乏区的形成是由于前进侧热机影响区晶粒拉长、弯曲,而弯曲的晶界曲率引起界面能差,从而使得晶界发生迁移;晶界迁移的驱动力主要为搅拌针旋转所产生的剪应力.第二相粒子对晶界的钉扎能随着第二相体积分数的降低而降低,粒子贫乏区的存在减弱第二相粒子对晶界的钉扎作用,使得前进侧热机影响区在拉伸过程中易于断裂,成为接头的薄弱区.

英文摘要：

Butt welding test for two 2024 high-strength aluminum alloy planks 5 mm thick was conducted with friction stir welding technique. The Microstructure and formation mechanism of the particle depleted zone in the joint and its influence on mechanical properties of the joint were investigated. The investigation result showed that the particle depleted zone was located at thermo-mechanical affection zone （TMAZ） on the advancing side of nugget zone close up to it, and oriented as TMAZ on advancing side. As contrasted to the adjacent zone, a remarkable depletion of second-phase particles took place thereby. The average width of the particle depleted zone was about 30 b~m. The formation of the particle depleted zone was originated from elongation and curvature of the grains in TMAZ on advancing side and the curvature of curved grain interface induced a interface energy difference, thus making the grain interface to migrate. The driving force of grain interface migration was mainly the shearing stress due to stirring pin rotation. The pinning energy of second-phase particles on to grain interface decreased with the decrease of their volume fraction. The presence of particle depleted zone weakened the pinning effect of second-phase particles onto the grain interface, making TMAZ on advanced side easy to fracture due to tension and becoming a weak zone in the joint.