Optimization and characterization of friction stir welded NAB alloy using multi criteria decision making approach

Abstract

The paper deals with the friction stir welding of the NAB alloy plates. Major process parameters that includes tool rotational speed (rpm), traverse speed (mm min−1) and axial load (kN) were varied for getting an understanding of the mechanical properties. In this study, friction stir welding trials were performed according to L9 orthogonal array. The multi criteria decision making methods namely Grey Relational Analysis (GRA) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) were used in the exploration of the optimum process parameters. The same combination of process parameter was obtained for both conditions and optimum process parameter as rotation speed of 1600 rpm, welding speed of 80 mm min−1 and axial load of 16 kN. characterization of the microstructure of the welded joints was done using optical microscopy and transmission electron microscopy for the confirmation test. The diverse phases of welded NAB alloy containing α phase, β′ phase and intermetallic κii, κiii, and κiv phases and grain refinement mechanisms of different phases are investigated separately. There was a significant improvement in microhardness which was the result of work hardening and grain refinement.