Introduction of ternary alloying element in wire arc additive manufacturing of titanium aluminide intermetallic

Abstract

In order to introduce vanadium as a ternary alloying element during the wire arc additive manufacturing (WAAM) of titanium aluminide intermetallic alloys, alloy and elemental wire consumables (Ti6Al4V and Al wires, respectively) were used with the WAAM process. A crack-free TiAl bulk with nominal chemical composition of Ti45Al2.2 V was successfully fabricated for the first time through dynamic in situ alloying using WAAM method. The experimental results showed that the introduction of V from Ti6Al4V alloy does not change the flat features of lamellar interface and also does not alter the phase composition of the resultant TiAl alloy. The fabricated Ti45Al2.2 V alloy consists of lamellar colonies and γ interdendritic phase in the top region, fully lamellar structure with unclear grain boundaries in the band regions and large equiaxed α2 with fine γ laths precipitated at grain boundaries in the layers. The microhardness and tensile properties were greatly increased by introducing V due to the general absence of interdendritic γ phase and the V ductilization effect. In addition, the influences of two-step post-heat treatments on the microstructure and mechanical properties are analysed. Results indicate that the microstructure and mechanical properties of the fabricated alloy can be considerably modified after applying different solution treatment temperatures.