Solidification and microstructure investigation on as-cast and annealed hypoeutectic Ti–Fe alloys

Abstract

This work explored the solidification behavior, microstructure development, and resulting mechanical properties of hypoeutectic Ti–Fe alloys under both as-cast and annealed conditions. Ti-(27, 28, 29)Fe (wt%) alloys were synthesized through arc-melting, followed by annealing at 950 °C for 24 h and slow furnace cooling. The investigation procedures included thermodynamic calculations, differential scanning calorimetry, scanning electron microscopy, high-temperature laser-scanning confocal microscopy, X-ray diffraction, hardness measurements, and compression tests. The study demonstrated the efficacy of annealing treatments in reducing excess eutectic in the as-cast structure formed during solidification. Results from both thermodynamic calculation and experiment for the solidification process demonstrated reasonable agreement. The high β-stabilizing effect of Fe ensured the presence of the β phase at room temperature under both studied conditions. The solid-solution hardening of the β phase, coupled with the TiFe intermetallic, substantially contributed to the increased hardness and mechanical strength, although the increase in brittleness was noticeable in the as-cast state. Subsequent annealing enhanced plasticity but resulted in a reduction in strength, albeit maintaining yield strength at a considerable level, approximately 1450 MPa.