Surface modification of pure aluminum via Ar ion bombardment for Al/Al solid-state diffusion bonding

Ar ion bombardment was applied to modify the aluminum surface and a subsequent solid-state diffusion bonding was performed. The effect of Ar ion bombardment on surface conditions and properties was studied to analyze the relationship between surface modification and joint performance. With increase of the Ar ion energy, the surface oxide film was removed and its surface roughness tended to decreased first and then increased. The oxide-free aluminum surface with minimal roughness of 0.61 nm was obtained by 1 keV bombardment while the numerous small dislocation loops uniformly distributed in the aluminum surface structure enhanced the surface hardness. Under high-energy bombardment (>5 keV), the surface became swollen or even porous due to the growth of dislocation loops and Ar bubbles that made the surface rough and embrittled, which deteriorated the microstructure and strength of bonded joints. The well-bonded joint with shear strength of 45.9 MPa was obtained at 1 keV bombardment and diffusion bonding temperature of 450 °C. The specific shear strength of ~60% was higher than that of conventional Al diffusion bonded joints. This work is of significance for the manufacture of well-bonded aluminum microchannel heat exchangers.