EFFECTS OF LINE ENERGY ON MECHANICAL PROPERTIES, CORROSION AND SHAPE MEMORY BEHAVIOR OF LASER-WELDED NiTinol JOINTS

摘要

In this experimental work, the effects of line energy at constant scan speed on quality of bead-on-plate laser welding of NiTinol sheets were investigated. Variations of bead geometry, changes in microstructure, variation of micro-hardness value along the weld-bead, generation of new phase during welding, changes in tensile strength of the welded samples, corrosion behavior of welded and parent material, and changes in phase transformation temperatures were measured for characterization of welded samples. Laser weld-bead profile was changed from a wine glass without base to glass shape with the increasing line energy. Quality aspects of weld-bead geometry quality aspects showed an increasing trend with line energy. Microstructure was changed during welding due to competitive grain growth. Microhardness values gradually increased from weld centre line to base metal. Tensile strength of the material was reduced after welding due to the formation of brittle intermetallics compounds. A dual failure mode for the welded sample was observed; whereas a single mode of failure was detected for parent material. The corrosion properties of the welded samples were found to be better than that of parent material. Phase transformation temperatures were also found to be reduced after welding.