Effect of Diffusion Welding Parameters on the Microstructure and Mechanical Properties of Al-9.6at%Sc/6061Al Dissimilar Joints

The fundamental physical properties of the Al-9.6at%Sc alloy were experimentally determined, and diffusion welding experiments on Al-9.6at%Sc targets were performed. The results of the study revealed the following key findings: For the Al-9.6at%Sc alloy, the average coefficient of thermal expansion is 28.310 / (within the range of 25~520 ), the average thermal conductivity is 161 W/(mK) (25~600 ), Youngs modulus decreases from 93 GPa at 25 to 74 GPa at 600 , the density is 2.66 g/cm, and the specific heat capacity is 1.05 J/(gK). In diffusion welding of Al-9.6at%Sc alloy to a 6061Al alloy backing plate, as the maximum residual stress at the interface is only 19.62 MPa. In the hot isostatic pressing diffusion welding process, a high-strength joint can be obtained when the surface roughness is below 0.8 m, the welding temperature is maintained between 450 and 500, the welding pressure is around 125 MPa, and the holding time ranges from 3 to 5 hours. Furthermore, Mg atoms from the 6061Al alloy accumulate around the AlSc phase in the Al-9.6at%Sc alloy, forming stable Mg-Al solid solutions at the weld joint.