Microstructure and mechanical properties of twin wire and arc additive manufactured Ni3Al-based alloy

Abstract

A Ni3Al-based alloy was prepared for the first time using a twin wire and arc additive manufacturing (T-WAAM) by adjusting the relative feeding speed of the Ni and Al wires, and the microstructure and mechanical properties of the deposited alloy were investigated. The results showed that the deposited Ni3Al-based alloy consisted of a dendritic γ + γ' dual-phase structure and an interdendritic γ' block. The interdendritic γ' block was partially transformed into a γ + γ' dual-phase structure owing to multiple thermal cycles during the deposition process. Thus, the proportion of the γ + γ' dual-phase structure gradually decreased with increasing building height. Meanwhile, the tensile strength and elongation of the deposited alloy exhibited a similar decline in the height direction. Fracture analysis revealed that the interdendritic γ' block hindered dislocation slip in the γ + γ' dual-phase structure, which caused dislocation stacking and stress concentration at the dendrite/interdendritic phase interface. The increase in the interdendritic γ' block was responsible for the decline in the tensile strength and elongation of the deposited alloy along the height direction. With the lowest proportion of interdendritic γ' block, the bottom deposited alloy had an optimal combination with a tensile strength of 817.3 MPa and elongation of 20.9%. Evaluation of the mechanical properties showed that the tensile strength and elongation of the T-WAAMed Ni3Al-based alloy were equivalent to those of commercial cast IC218 and IC221M Ni3Al-based alloys.