In recent years, a lot of process innovations are strongly required for cost and weight reductions in addition to upgrading driving performance and reducing green house gasses in automotive industry. In case of manufacturing automotive parts, a number of materials are used to satisfy their high accuracy and cost reduction. Dissimilar metal joint such as combination of aluminum alloy and austenitic stainless steel is increasing to apply them based on this background. In this joint, an index to guarantee the quality is indispensable, because the formation of inter metallic compounds introduces brittle fracture at the interface between two metals. It is described that plastic flow is applied for dissimilar metal (aluminum alloy and stainless steel) joint in this paper. Based on this research, it is possible to control the break point by forming projection on aluminum alloy. Projections are formed to promote the plastic flow and they are formed by keeping aluminum alloy on softening temperature. It is clear that joint boundary is composed of two reaction layers, one contains Al-Fe-Si-O and the other contains (Fe-Cr-Ni) Al₃ inter metallic compound. New process described in this paper is available for application to production line of various precise sensors for automotive parts.

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Weldability of Al-Cu series alloy 2219 with MIG process was investigated in comparison with that of Al-Cu-Mg series alloys 2024. On weld cracking sensitivity, 2219 is superior to 2024 and as for the combination with filler metal, the decrease of Mg content in weld metal makes a crack resistance to increase. And a liquation cracking in heat affected zone was easily initiated in case of Mg contents more than 1.6 mass%and Cu/Mg(ratio in mass%) less than 1.8 in weld metal.Welded joints were mostly fractured in weld metal even reinforcement on during tensile testing, so the intensification of weld metal is directly connected with the improvement of joint strength and fractured mode. The results of investigation of correlation between the strength and chemical composition in weld metal revealed that the joint strength increased with an increase of magnesium and manganese but encouraged the weld cracking simultaneously. However the author has also found that silicon was available for decreasing weld crack and the possibility of consistence with joint strength and crack resistance by control of these contents of Mg,Mn and Si.

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