在强制冷却环境下,对2024铝合金进行了搅拌摩擦加工,并采用电子背散射衍射技术对加工后各区域的晶粒特征及演化进行了研究.结果表明,从母材区、热机影响区到搅拌区,晶粒尺寸逐渐减小,搅拌区组织明显细化,且分布均匀,平均晶粒尺寸为1.89 μm.母材区大角度晶界居多,而热机影响区小角度晶界居多,搅拌区取向差分布呈现双峰现象.母材区为{124}〈211〉R取向,热机影响区主要为{001 }〈110〉R-cube取向,搅拌区表现出较强的{113}〈110〉取向,热机影响区晶粒取向与搅拌区晶粒取向相近,表明在低温高应变条件下连续动态再结晶是搅拌区晶粒细化的主要机制.拉伸试样的断裂位置位于热机影响区,这与{001}〈ll0〉R-cube取向的可动滑移系数量和滑移难易程度一致.
The electron backscatter diffraction technique was employed to study the evolution of grain characteristics during friction stir processing (FSP) of 2024 aluminum alloy in the forced cooling condition.The results show that the grain size of the friction stir processed sample decreases gradually from the base metal zone (BM),through the thermo-mechanically affected zone (TMAZ),to the stir zone (SZ).The microstructure in the SZ is significantly refined and the grains are distributed uniformly with an average grain size of 1.89 μtm.BM exhibits a large number of high-angle grain boundaries,while TMAZ has numerous low-angle grain boundaries.The distribution of misorientation angle in the SZ presents a bimodal phenomenon.The {124} 〈211〉R orientation exists in the BM,and the {001} 〈110〉R-cube orientation is mainly in the TMAZ.However,SZ exhibits a significant { 113 } 〈110〉 orientation.The grain orientation of the TMAZ is similar to that of the SZ,which shows that the continuous dynamic recrystallization is the primary mechanism for grain refinement in the low-temperature and high-strain deformation condition in the SZ.The fracture location of tensile specimen is in the TMAZ,which is consistent with the number of movable slip systems and the slip difficulty of the {001 } 〈 110〉R-cube orientation.
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