MICROSTRUCTURE AND TEXTURE ANALYSIS OF FRICTION STIR WELDS OFCOPPER

摘要

Copper is readily joined by friction stir welding (FSW) due to its relatively low meltingpoint. The stacking fault energy (SFE) of copper is comparatively low, resulting in adiscontinuous dynamic recrystallization (DRX) mechanism operating at the temperature andstrain rate range typical for FSW. To study the textures in the weld area, several FSWed copper(Cu-OFEP) samples were studied. A sample representing the optimum process conditions (tooltemperature 850 °C) of a full scale 50 mm thick FSW weld of copper capsule for spent nuclearfuel was obtained from Swedish Nuclear Fuel and Waste Management Co (SKB). Smaller sizedwelds with varying processing parameters were also prepared to study the effects of theprocessing parameters deviating from optimal. The microstructure was studied with opticalmicroscopy, FEGSEM and EBSD. New metallographical methods were developed to be able todistinguish the different zones in the weld area. The texture in FSW welds of copper is weak andit varies slightly according to the location in the weld, because the direction of the flow ofmaterial in FSW varies constantly in the weld area. The main texture component found in FSWwelds of copper is <101> fibre texture.