Engineering omega phase enables a wide temperature range Elinvar effect in metastable β-Ti alloys

Temperature-independent modulus, i.e., the Elinvar effect, over a high and broad temperature range (119°C to 400°C) was tailored in a solution-treated metastable Ti-15Nb-5Zr-4Sn-1Fe alloy. This Elinvar effect was attained by continued growth and structure transition of the quench-induced trigonal athermal ω phase towards the high modulus thermal-induced hexagonal isothermal ω phase, compensating for the modulus softening of the β matrix due to thermal expansion during heating. Such ω phase-induced Elinvar effect can be tuned by varying heating rates to control the evolution of the ω phase and is potentially attainable in other metastable β-Ti alloys. This study showcases a new strategy for developing Elinvar Ti alloys by engineering the development of ω phase during heating.