Microstructure and mechanical properties of Al-10at% Sc/6061 Al dissimilar diffusion welding
摘要
The fundamental physical properties of the Al-10at%Sc alloy were tested experimentally; the residual stress distribution in the diffusion welding process was simulated, and the diffusion welding experiments of the Al-10at%Sc target have been conducted. The research results indicated that, for the Al-10at%Sc alloy, the average coefficient of thermal expansion is 28.8 × 10−6/°C (25~520 °C), the average thermal conductivity is 158 W/(m·K) (25~600 °C), Young’s modulus decreases from 91 GPa at 25 °C to 71 GPa at 600 °C, the density is 2.68 g/cm3, and specific heat capacity is 1.07 J/(g·K); an interlayer is not needed in the diffusion welding of the Al-10at%Sc alloy and the 6061 Al alloy backing plate due to the maximum residual stress of 19.62 MPa at the interface being 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 and 500 °C, the welding pressure is around 125 MPa, and the holding time is 4–5 h; Mg atoms from the 6061 Al alloy are enriched around the Al₃Sc phase in the Al-10at%Sc alloy, a stable Mg-Al solid solution at the weld joint is formed, and there is no noticeable diffusion of Sc into the 6061 Al alloy.