In the present work, an autogenous TIG welding technique was used to join 2 mm thick sheets of a TiNi binary shape-memory alloy at three different values of current (80 A, 90 A and 100 A). The effects of the welding current on microstructures, residual stresses, mechanical properties and nano-mechanical behaviour were investigated. Microstructure analysis revealed that with an increase in current, the columnar grain size decreased, which had a significant effect on mechanical properties. The tensile strength of the weldment at 100 A was ∼92% of that base alloy’s (BA) and elongation of approx. 14%. The reduction in elongation was due to the formation of Ti2Ni and Ti3Ni4 type precipitates. The microhardness profile in all the weldments showed an increase of approx. 30% between the base alloy and the fusion zone due to the formation of Ti2Ni and Ti3Ni4 type precipitates during welding. Residual stress analysis suggested the tensile residual stresses in the longitudinal direction are minimum in the weldment performed at 100 A. The nanoindentation results revealed that the weldment obtained at 100 A had the least plastic deformation (∼45.5% less than the 80 A weldment) owing to a decrease in inter-dendritic spacing and high proportion of IMCs: Ti2Ni and metastable Ni4Ti3.

Pulsed Nd:YAG laser beam welding was performed at five different power levels (360 W, 380 W, 400 W, 420 W and 440 W), and the relationship between microstructure and nano creep behaviour was investigated for Ti5Al2.5Sn alloy. Microstructural analysis indicated a reduction in grain size in fusion zone, with an increase in the average laser power. In the fusion zone (FZ) of all the beads, acicular α and ά martensite were observed and confirmed by SEM analysis. Due to the formation of the α and ά phases during welding, the microhardness and nanohardness in the FZ increased by ∼71% and ∼58%, respectively, above that of the base alloy. Nano creep analysis suggested diffusional creep as the deformation mechanism in all the beads, except the one performed at an average power of 440 W since its stress exponent was less than 2.

A study has been conducted to evaluate the mechanical and fatigue crack propagation properties of wire + arc additively manufactured ER70S‐6 components. A parallel‐built deposition strategy was employed to fabricate the additively manufactured wall. The hardness values were slightly higher at the bottom and top of the wall due to the presence of Widmanstätten ferrite and carbides. The characterization of mechanical properties in both orientations; parallel and perpendicular to the deposition direction showed a marginal difference in yield strength and ultimate tensile strength. The crack growth rates were correlated with linear elastic fracture mechanics parameter ΔK and compared with an oscillation‐built deposition strategy from the literature. The crack growth rates of both deposition strategies were found to be very similar to each other. Furthermore, it has been demonstrated that the variability in the crack growth histories can be reasonably well captured by using the NASGRO crack growth equation.

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