Role of Pd interlayer on NiTi to Ti6Al4V laser welded joints: Microstructural evolution and strengthening mechanisms

Obtaining a reliable NiTi to Ti6Al4V dissimilar joint exhibiting NiTi's superelasticity can provide design flexibility in aerospace and biomedical fields via integrating distinct material benefits. However, this materials couple is vulnerable severe embrittlement due the development of excessive intermetallic compounds (IMCs), namely Ti2Ni. Pd-free Pd-interlayered NiTi-Ti6Al4V laser joints were evaluated for their microstructure, compositional changes, thermodynamic mechanism, mechanical properties. The presence Pd constrained formation Ti2Ni IMC, with excellent properties demonstrating superelastic behavior achieved first time. tensile strength rupture strain Pd-added improved more than twofold, reaching 520 MPa 5.6%, respectively. During cyclic testing, demonstrated comparable irrecoverable (1 versus 0.65%). Multiscale characterization revealed that fraction decreased from 83 10% near boundary 24 6% at weld center compared joint. superior tendency Ti-Pd over IMC favored development, thus dominated fusion zone (FZ) expense explaining performance