Effect of interlayer thickness on microstructure and mechanical properties of as welded Ti6Al4V/Cu/NiTi joints

• Thickness of Copper interlayer has a great influence on joint properties.
• Increase of interlayer thickness to 75 μm improves mechanical properties.
• More increase in interlayer thickness to 100 μm deteriorates mechanical properties.
• Cu-rich phases and shrinkage cavities formed due to Increase of interlayer thickness.
• Formation of Ti2Cu and Cu-rich brittle phases in weld metal leads to brittleness joints.

Dissimilar welding of Nitinol shape memory alloy to Ti–6Al–4V with copper interlayer was performed by a pulsed Nd:YAG laser beam and effect of interlayer thickness on microstructure, chemical composition, mechanical properties and fracture behavior was investigated. The results indicated that the thickness of interlayer has a great influence on chemical composition and Ultimate Tensile Strength of joints. With the increase of interlayer thickness to 75 µm, tensile strength and elongation of the joint reached the maximum value of 300 MPa and 3.3%. Further increase in interlayer thickness resulted in deterioration of mechanical properties because of formation of Ti–Cu IMCs and shrinkage cavities in weld metal. This shows that the thickness of the copper interlayer for dissimilar welding of these alloys needs to be optimized.