Effect of Ambient Atmosphere and the Rate of Heating on the Behavior of Thermal Decomposition Titanium Hydride (TiH2) Powder

Friction stir welding (FSW) can be used to join aluminum alloys such as Al-2024 that are hard to weld by conventional fusion welding. Although this welding process can eliminate defects, the softening problem of heat-affected zone can be a non-acceptable problem. To recover the strength of joint, one option is fully post weld heat treatment of welded components. However, it has been reported that fine grains in the stir zone are not stable during solution treatment. In this study, a 2024-T8 aluminum alloy with 5 mm thickness is selected as the experimental material for FSW to reveal the effect of rotational speed of tool before and after post weld heat treatment on the microstructure of stir zone. It was found that the particles are broken up during friction stir welding, and the severity of the breaking up of particles and grain size in the stir zone increase with increasing rotational speed. Consequently stability of grains increases