Strengthening a high-strength TiAl alloy by hot-forging

As part of efforts to expand the range of applications for TiAl alloy, strengthening was pursued through hot-forging. Using Ti–42Al–10V (at.%), the hot workability of which was improved by introduction of the β phase, formability testing and material property evaluation were carried out. Blade formation was found to be possible by means of closed-die forging. A fine lamellar structure characterized by an average grain size of 9 μm and average lamellar spacing of 40 nm composed about 70% of the area fraction in the microstructure; tensile strength was improved as a result of this fine lamellar structure, and strength of over 1200 MPa was maintained up to 700 °C. Charpy absorbed energy at room temperature using a 2 mmV-notch specimen was 5 J/cm2, which is satisfactory for a TiAl alloy. This alloy is a potential substitute for conventional forged alloys used at temperatures up to 700 °C.