2024-T4铝合金搅拌摩擦焊搅拌区位错及组织性能

采用金相、显微硬度及透射分析方法对2024铝合金搅拌摩擦焊接头搅拌微区的组织性能和位错分布特征进行试验分析,基于位错分析深入了解各微区位错形成与接头组织结构与硬度变化之间的关系。研究表明,WNZ位错主要分布在晶粒内部,大部分是以位错缠结的形式存在,并伴随有大量的沉淀强化析出相Cu_2Mg;而在TMAZ区,大量的位错是以位错塞积的形式存在于晶界或晶粒内部;HAZ区域的位错多以位错塞积的形式存在于晶界附近,并伴随一些典型的Al Cu_3析出相。WNZ和TMAZ区中并未随晶粒细化而造成位错数量和类型的减少,这与FSW特殊的动态回复和动态再结晶过程有关,此外位错分布特征与接头微区硬度分布特征基本吻合。

Analysis of dislocation and microstructure properties in stir zone of friction stir welded for 2024-T4 aluminum alloy

The microstructure and properties of 2024 aluminum alloy friction stir welded joints were analyzed by means of metallography,microhardness and transmission electron microscope The relationship between the formation of dislocations and the changes of the microstructure and hardness of the joints was studied based on the dislocation theory.The results show that the WNZ dislocations are mainly distributed in the grain interior,and most of them exist in the form of dislocation entanglement,accompanied by a large number of precipitation strengthening precipitates Cu2Mg.In the TMAZ area,a large number of dislocations exists in the grain boundaries or grain interior in the form of dislocation pile-up.The dislocation in HAZ area exists near the grain boundaries in the form of dislocation pile-up along with some typical AlCu3 precipitates.In WNZ and TMAZ,the number and types of dislocation are not reduced along with the grain refinement because of the dynamic recovery and dynamic recrystallization process.The dislocation distribution is consistent with microhardness distribution of welded joints.