Deformation Behaviour of Friction Stir Welded Cu-Cr-Zr-Ti Alloy Sheet During Single Point Incremental Forming
摘要
In the present work, Cu-Cr-Zr-Ti alloy sheets were joined through friction stir welding (FSW), and subsequently, the welded blank was deformed to obtain a truncated conical geometry with variable wall angle using a single point incremental forming (SPIF) process. Through uniaxial tensile tests of monolithic and welded specimens, it was found that the presence of weld zone had decreased yield strength, ultimate tensile strength and total elongation by 21%, 13% and 8%, respectively, compared to the as-received monolithic specimen. The occurrence of final rupture in the base material away from the weld zone confirmed sufficient weld integrity produced through the FSW process. Microstructure of the weld cross-section revealed very fine equiaxed grains in the stir zone (SZ) and coarser elongated grains in the thermo-mechanically affected zone (TMAZ), while the heat-affected zone (HAZ) contained even coarser grains with annealing twins. Microhardness was found to be higher in SZ than TMAZ and HAZ due to the increased contribution from grain boundary strengthening. Further, the welded specimen failed during the forming process at a cup height of 37.32 mm with a wall angle of 75.88° through occurrence of fracture in the base material at the cone bottom, resulting from maximum thinning. Based on these results, it was inferred that the welded alloy sheets fabricated by joining monolithic sheets through FSW technique can be potentially deformed into large depth parts of cryogenic engines employing the SPIF process.