LAUSR

Abstract To address the challenges of joining of dissimilar thickness plates, single pass bottom flat (SPBF), single pass top flat (SPTF) and double pass bottom flat (DPBF) joint configurations were investigated for improvement of weld qualities in friction stir welding. The tensile strength, yield strength and percentage of elongation of the specimen welded by DPBF configuration was 99% of base material (BM). Flexural strength and bending angle were 95% and 100%, respectively, to the BM. Drop weight impact test revealed impact energy absorbed by DPBF welded specimen is comparable with the BM and it was highest at tool rotational speed of 1100 rev/min. The fatigue life at lower stress amplitude was similar as BM but differed at higher stress. The hardness of the weld nugget was higher compared to the other zones and BM. DPBF specimens gave highest hardness because of higher grain refinement and it is increased with tool rotational speed and plate thickness ratio. Weld bead geometry and macro/microstructure at various weld zones were also studied. The material flow inside the weld zone of DPBF differs from the SPBF and SPTF specimens. Among the proposed joint configurations, DPBF is most suitable for joining large dissimilar in thickness.