Microstructure and Texture Analyses of Similar Welded Industrially Relevant Materials through Friction Stir Welding: D6AC Steel, AISI 316L Steel and Ti-6Al-4V Alloy

In this project, microstructural and textural analyses of similar welded industrially relevant materials (D6AC steel, AISI-316L steel and Ti-6Al-4V) by friction stir welding is studied. Initially similar friction stir welding of D6AC steel and AISI-316L steel is performed using PCBN tool whereas similar plates of Ti-6Al-4V were welded using W-La tool. All welds are mechanically characterized by tensile strength, hardness measurement and microstructural studies are carried out using optical microscopy and EBSD analysis.\ud In case of D6AC steel, defect free welds are obtained with welding parameters of rotation speed 1100 RPM and welding speeds of 40mm/min and 20 mm/min. Microstructural characterization indicated formation of lath martensite in stir zone. Ultimate tensile strengths of these welded plates are higher than the base material with an increase in hardness (approximately three times of base metal) in the nugget zone

Texture analyses of friction stir welded austenitic stainless steel AISI-316L

Low stacking fault energy AISI-316L stainless steel of 4 mm thick plates are friction stir welded at 1100 RPM and 8 mm/min welding speed using cubic boron nitride-tungsten rhenium composite tool. Large area orientation image mapping of the stir zone using electron backscatter diffraction scanning electron microscopy is performed to comprehensively characterise its microstructure and is searched for torsion shear texture components. Kernel average misorientation analysis revealed that top layer of the stir zone is almost fully recrystallised which experienced highest temperature and strain; middle layer has more deformed grains than recrystallised, showing partial recrystallisation while the bottom layer which encountered low strain but high temperature is almost fully recrystallised. Texture analyses showed variation from A {111} partial fiber type of texture in the top layer and C {001} and A {1 (Formula presented.) 1} type shear texture components in the middle layer followed by (Formula presented.) {1 (Formula presented.) 1} type of shear texture in the bottom layer. It is evident from Kernel average misorientation analysis and texture evolution studies that recrystallised region produced A {111} partial fiber/ (Formula presented.) {1 (Formula presented.) 1} shear component while deformed region produced C {001} shear component