Coherent ω phase induced yield strength improvement in Ti-19Nb-1.5Mo-4Zr-8Sn alloy

Abstract

The solution treated β type Ti-19Nb-1.5Mo-4Zr-8Sn (TNMZS) alloy plate was rolled for minor deformation 2%~8%, followed by low-temperature ageing. The stress-induced α″ martensite and isothermal ω phase was characterized. The results showed that, coherent ω and β phase also satisfied the lattice constant relationships: 2aβ = aω = bω, 32aβ = cω. The pre-deformation caused the rapid hardness increase of the TNMZS alloy in the early stage ageing at 400 °C, and the yield strength improved from 459 MPa to 725 MPa, with elongation 6.9–7.9% after ageing for 10 min. Ageing response acceleration by pre-deformation contributed to the precipitation of coherent ω phase, this would provide a possible way for utilizing transition ω phase to improve strength and ductility in similar series of β titanium alloy.

Keywords

• β Titanium alloy
• Mechanical properties
• Ageing
• ω Phase
• Low misfit