Dissimilar friction-stir welding of 430 stainless steel and 6061 aluminum alloy: Microstructure and mechanical properties of the joints

摘要

The effect of friction-stir welding parameters on the microstructure and the mechanical properties of the dissimilar 430 stainless steel and 6061 aluminum alloy joints were investigated. Optical and scanning electron microscopes in conjunction with energy dispersive X-ray analysis were employed to study the microstructure of the joints. Tensile and microhardness tests were used to evaluate the mechanical properties. The results showed that the best appearance quality was achieved at a rotational speed of 900 r/min, a traverse speed of 120 mm/min, and a tool offset of zero. The tool offset was the most effective parameter affecting the weld quality. The stir zone of the joints had a composite structure in which the dispatched steel particles were distributed in aluminum. The best interface quality belonged to the joints welded at an offset of zero, which had a serrated nature with mechanical locking of the dissimilar parts. However, at negative and positive values of offsets, formation of voids and microcracks reduced the tensile properties of the joints. The tensile fracture of the joints occurred in the heat affected zone of the aluminum part, which had the lowest hardness amount between the microstructural zones. The fracture surfaces of the tensile specimens showed bimodal behavior.