Phase transformations in dissimilar resistance spot welds of dual phase steel and ferritic stainless steel are analysed. In contrast to a full martensitic microstructure predicted by the Schaeffler and Balmforth diagrams, a ferrite-martensite microstructure was observed in the fusion zone. The formation of ferrite phase in the fusion zone can be attributed to the rapid cooling rate of resistance spot welding, which suppresses the post-solidification ferrite-austenite transformation. The grain growth and martensite formation were main metallurgical features of the heat affected zone of ferritic stainless steel side. Microstructure gradient of heat affected zone in dual phase steel side was dictated by martensitic transformation. The effect of weld thermal cycle on the mechanical performance of the joint is discussed.

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The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load-displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter controlling the mechanical properties of DP600 resistance spot welds in terms of peak load, maximum displacement and failure energy.

Tin Babbitt is an ideal journal bearing material, because of its microstructural properties, which qualifies these alloys as a bearing material. Effect of the Babbitt die casting (ASTM B23 Alloy 2) on its microstructure and the hardness properties were studied. The forward extrusion type was carried out using cosine profile and the five different reduction area such 5%, 10%, 15%, 20% and 40%. The results show that the refinement of hard phases of Cu6Sn5 and SbSn led to increasing the hardness value after casting, and after extrusion for all reduction percent, except reduction 40%, the dynamic recrystallization is dominant which led to hardness decrease. The result also shows that the extrusion pressure increases with increasing the reduction value. Moreover, cold deformation improved the hardness properties for Babbitt alloy by refinement of the Cu6Sn5 phase.

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