INVESTIGATION ON MICROSTRUCTURE AND PROPERTIES OF Ti-Al-Cr-Fe-V-Zr ALLOY

摘要

Ti-1023 alloy has been widely used in aerospace field as a typical titanium alloy with high strength and toughness. The relatively high content of Fe causes beta fleck which will make uneven microstructure and less plasticity. The new Ti-Al-Fe-V (Cr, Zr) alloys have been designed, based on Molybdenum equivalency and Bo-Md molecular orbital method, to aim at developing a new type of titanium alloy with high strength and fracture toughness. After primary design computation, Ti-Al-Fe-V (Cr, Zr) alloy was optimized finally. A large scale ingot was made by vacuum arc re-melting (VAR) for further property evaluation. Resultantly, it shows that athermal ω phase forms in Ti-Al-Cr-Fe-V-Zr alloy when solution treated at a temperature above the β-transus. Micro-hardness of alloy conducted to different aging conditions decreases with the aging temperature and time increasing respectively. Moreover, the new alloy has got a more sluggish age hardening response relating to the aging time. Additionally, after modulated aging treatment, the alloy can obtain high strength levels with acceptable ductility. When the alloy solution treated at 770 °C for 1h, followed by aging at 500 °C for 2h, the tensile strength of the alloy can achieve 1268 MPa, with an elongation of 11.5%, at the same time, the reduction of area has surpassed 30%. As a result, the newly designed alloy can achieve a good combination of tensile strength and plasticity through appropriate heat treatment.