Effect of Mn Addition on Microstructural Changes and Mechanical Properties of Ti–5Al–2.5Fe Alloys

The microstructures and mechanical properties were investigated in newly developed Ti–5Al–2.5Fe and Ti–5Al–2.5Fe–2Mn alloys, which were fabricated by two-step hot rolling processes. Lamellar structures were observed in the Ti–5Al–2.5Fe–2Mn alloy aged at 600 °C for 24 h, depending on the viewing directions (normal, rolling, and transverse). In the aged Ti–5Al–2.5Fe alloy, a spheroidized α matrix and TiFe precipitates in the α grain boundary were observed, with a crystallographic orientation relationship of (011)TiFe//(01\(\overline{1}\)0)α. It was found that Mn addition improved the mechanical properties, attributed to the increased β phase (approximately 4.3 times relative to the Ti–5Al–2.5Fe alloy) and solid solution strengthening. Interestingly, in the Ti–5Al–2.5Fe alloys, the oxygen was enriched by the TiFe phase rather than the α phase, which may weaken the oxygen solute dragging effect.