β/B2 phase content change and its effect on tensile properties of novel multiphase TiAl alloy

Abstract

The as-extruded microstructure of novel multiphase TiAl alloy（Ti-43.5Al-6（Nb，Cr，Ta））was taken as the research object，the evolution of the average content of β/B2 phase，α/α2 phase and γ phase in this alloy with the solution temperature and holding time was analyzed by heat treatment，and then the tensile properties of the alloy at room temperature and high temperature（750 ℃ and 800 ℃）with different β/B2 phase contents were tested. The results show that in the range of 1190 ℃ to 1350 ℃，the content of γ phase decreases gradually with the increase of solution temperature and holding time，and the γ phase disappears completely at 1270 ℃; the content of β/B2 phase first decreases and then increases with the increase of solution temperature，and gradually decreases with the prolongation of holding time，while the content and size of lamellar cluster have a negative correlation with the change of β/B2 phase content; The average content of β/B2 phase can be controlled below 10% in the range of 1230-1280 ℃; the average content of β/B2 phase can be controlled below 0.5% in the range of 1250-1270 ℃. When the alloy is in the three-phase region，the average content of β/B2 phase is about 6%，and the uniform and fine nearly lamellar structure with excellent comprehensive tensile properties can be obtained，and the tensile strength at room temperature exceeds 1050 MPa，the elongation at room temperature is 1.5%-2%; the tensile strength at 750 ℃ exceeds 950 MPa，and the tensile strength at 800 ℃ exceeds 850 MPa.

Keywords

• multiphase tial alloy
• β/b2phase
• wrought tial alloy
• fine nearly lamellar microstructure
• tensile properties