Intermetallic phases transition mechanism of the interface of Ti6Al4V-Inconel718 graded material by laser additive manufacturing

The brittle intermetallic phases in the interface of Ti6Al4V-Inconel 718 graded material limits its application. It is of great significance to reveal the formation and transformation mechanism of intermetallic phases for the regulation of interface. In this paper, Ti6Al4V-Inconel 718 graded material was manufactured by laser additive manufacturing technology. In the gradient interface region, Ti2Ni, TiNi and Ni3Ti were successively formed with the decrease of Ti element and the increase of Ni element. At the same time, intermetallic phases such as Fe2Ti and FeTi are formed in the interface near Inconel 718. The gradient interface was divided into three regions according to the types of intermetallic phases. The main phase is mostly precipitated directly from the liquid phase, and there are two types of eutectic reactions (L -> beta-Ti + Ti2Ni, L -> Ni3Ti + gamma) and two types of peritectic reactions (L + TiNi -> Ti2Ni, L + Fe2Ti -> FeTi). The Ti6Al4V region has a stronger texture strength than the gradient interface. Due to toughness difference and thermal stress, the Ti2Ni phase in gradient interface have higher KAM values. At the same time, the variation trend of each phase content was predicted by thermodynamic calculation, which reflects the phase transition process of the interface. The research on the formation mechanism of intermetallic phase and the prediction of the content of phases by thermodynamic calculation has guiding significance for the regulation of interface phase and the manufacture of graded materials.