SELECTIVE LASER MELTING OF INTERMETALLIC TITANIUM ALLOY

Abstract

The in-situ synthesis of the Ti2AlNb-based intermetallic alloy using selective laser melting of powder materials was studied. The object of research is the Ti–22Al–25Nb alloy (at.%), the main phase of which is the Ti2AlNb intermetallic compound with an ordered orthorhombic lattice (O phase). The Ti–22Al–25Nb alloy has good mechanical properties at room and elevated temperatures, low specific weight, and is considered as a promising material for aerospace industry applications. Experiments used a mechanical mixture of pure titanium, aluminum and niobium powders in a ratio required for Ti–22Al–25Nb alloy synthesis. Selective laser melting as an additive technology is the most promising way for additive layer manufacturing of parts. This technology allows manufacturing complex-shaped items based on CAD model data. Selective laser melting was used to make compact samples for investigations. Their microstructure, density, phase composition and microhardness were studied. In addition, the effect of heat treatment homogenization at 1250 °C for 2,5 h and then aging at 900 °C for 24 h on the microstructure and chemical homogeneity of samples were studied. It was shown that the compact material obtained by selective laser melting contains unmelted niobium particles. Homogenization annealing makes it possible to dissolve these particles completely in the alloy. As a result, the material microstructure consists of B2 phase grains of different sizes and needle-like precipitates of the orthorhombic phase.