Microstructure and mechanical properties of Al-10at% Sc/6061Al dissimilar diffusion welding

The fundamental physical properties of Al-10at%Sc alloy were tested experimentally, the residual stress distribution in the diffusion welding process were simulated, and the diffusion welding experiments of Al-10at%Sc target has been conducted. The research results indicated that, for Al-10at%Sc alloy, average coefficient of thermal expansion is 28.8×10⁻⁶/℃(25 ~ 520°C), average thermal conductivity is 158W/(m·K)(25 ~ 600°C), Young’s modulus decreases from 91 GPa at 25°C to 71 GPa at 600°C, density is 2.68 g/cm³ and specific heat capacity is 1.07 J/(g·K); an interlayer is not needed in diffusion welding of Al-10at%Sc alloy and 6061 Al alloy backing plate due to the maximum residual stress of 19.62 MPa at the interface significantly lower than the 50% yield strength of both materials; in the hot isostatic pressing diffusion welding process, a high-strength weld joint can be achieved when the surface roughness is below 0.8 µm, the welding temperature is between 450–500°C, the welding pressure is around 125 MPa, and the holding time is 4–5 hours; Mg atoms from the 6061 Al alloy are enriched around the Al₃Sc phase in the Al-10at%Sc alloy, a stable Mg-Al solid solutions at the weld joint is formed, and there is no noticeable diffusion of Sc into the 6061 Al alloy.