A Study of Microstructural Stability of Friction Stir Welded Joints of Al-Mg Alloys during Subsequent Thermal Exposure

摘要

Al-Mg wrought alloys such as Al-2.6Mg, Al-4.6Mg and Al-4.6Mg- 1Si werernfriction stir welded and a subsequent thermal exposure was carried out in this study.rnThe effects of elements addition and exposure temperature on the microstructuralrnstability of welded zone were investigated. A grain refinement was found in the weldrnzone of each alloy and the average grain size of friction stir welded Al-2.6Mg,rnAl-4.6Mg and Al-4.6Mg- 1Si was 10.1μm, 7.4μm and 4.7μm, respectively. Thermalrnexposure caused drastic coarsening of grains in the stirred zone and abnormal grainrngrowth initiated at some preferred sites such as upper surface and bottom. The volumernfraction of coarsening grains increased with increasing exposure temperature;rnhowever an unexpected decrease in grain size was found at 550℃ in compare to 500rn℃. Besides, the addition of Mg and Si deteriorated the thermal stability of grainrnstructure in stirred zone.