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Estimation of Quality Characteristics of Pulsed Nd:YAG Fibre Laser Welded Thin Sheet Ti6Al4V
S. Chatterjee, S.S. Mahapatra, V. Bharadwaj, B.N. Upadhyaya and K.S. Bindra

Further understanding of the influence of laser process parameters on the mechanical behavior of the welded joints produced through laser welding of thin sheets (0.45 mm) of Ti6Al4V titanium alloy is presented. The thin sheets of the Ti6Al4V have been joined in butt joint alignment using a millisecond pulsed Nd:YAG laser. The microstructural behavior and quality of weld bead have been characterized under optical microscope and scanning electron microscope (SEM). Radiographic inspection has also been made to check the internal flaws and material distribution in the welded joints. The study indicates that the weldments are free from cracks and possess high concentration of material in the welded region. The mechanical behavior of the welded joints has been examined for microhardness, residual stress and tensile strength. Finally, a surface morphological study of fractured surface obtained from tensile test has been analysed. The analysis indicates that the fracture is ductile in nature. The surface having a greater number of dimples exhibits high welding strength as compared to samples having a smaller number of dimples. An empirical equation relating welding strength with process parameters has been developed through non-linear multiple regression analysis. Since welding strengths predicted from the empirical model are in good agreement with the experimental results, the model is said to be valid and adequate for further use.

Keywords: Nd:YAG laser, Ti6Al4V, titanium alloy, laser welding, fractographic inspection, radiographic inspection, residual stress analysis, face-centred central composite design (FCCCD), response surface methodology (RSM), empirical equation

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