Enhanced Sintering of Pre-Alloyed Binary TiAl Powder by a Small Addition of Iron

Abstract

TiAl alloy powder is difficult to sinter unless assisted with pressure and/or pulsed current. This paper investigates the effect of a small addition of iron on the sintering behaviour of γ-TiAl alloy powder at 1350 °C in vacuum. Thermodynamic calculations using Thermo-Calc and the Ti-alloy database TTTI3 predict that iron is a potential sintering aid for TiAl powder. The relative sintered density (RSD) increased with increasing Fe content and peaked at an addition of 2at.%Fe, at which the RSD increased from ~ 60% theoretical density (TD) without iron to ~ 97%TD. The enhanced densification is attributed to liquid formation induced by iron based on both thermodynamic predictions and differential scanning calorimetry (DSC) analysis. The as-sintered microstructures and phase constituents were analysed by scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS) microanalysis system and X-ray diffraction (XRD) analysis.