TIG-cladding of Al-Cu and Al-Cu-Sn alloys on pure Al substrate

A tungsten inert gas (TIG) welding process was utilized successfully to produce a dense and hard cladding layer on a commercial purity Al substrate using two commercial filler wires (L-CuP6 and L-CuSn6). Effect of the type of filler wire, welding frequency, and the type of electrical current (AC or DCEN) on the microstructure, hardness, and the residual stress of the cladding layer were studied using scanning electron microscopy, X-ray diffraction, and a hardness test. The results showed that the L-CuP6 wire produced a homogeneous layer containing Al2Cu-Al eutectic in an alpha-Al matrix. The microstructure of the cladding layer formed with the L-CuSn6 wire also contained Al2Cu (theta) primary intermetallic and beta-Sn grains. The hardness of the cladding layer was found to depend on the fraction of Al2Cu intermetallic formed in the microstructure. Increasing the frequency or using a DCEN instead of AC caused the fraction of Al2Cu formed to decrease. These effects were attributed to the decrease in the volume of the weld pool and the inability of the DCEN to remove the oxide film from the Al substrate, respectively.