Crescent-shaped inclusion was found in the friction stir weld of 2219 aluminum alloy

X-ray detection

optical microscopy and energy spectrum analysis were used to study the distribution characteristics

microstructure and chemical composition of inclusions. The cause of inclusion formation was determined by experimental verification. At last

the influence of inclusion formation mechanism and tensile properties on joints was analyzed. The results show that the inclusions were composed of many abnormally grown Al

2

Cu particles. The abnormal growth of Al

2

Cu was due to metal material attached at the thread and the groove of friction stir weld tool during the welding process. Al

2

Cu particles coarsened under high temperature

Al particles were segregated and peeled off into the weld during welding randomly

the separated Al

2

Cu formed crescent-shaped inclusion under the action of friction stir weld tool. Crescent-shaped inclusions could be avoided by improving friction stir weld tool structure. It was found by tensile test that the inclusion had no effect on the tensile properties of the joint.