Study On Stability And Decomposition Mechanism Of Metastable Phase In TiZrAl Alloys

Titanium and titanium alloys are widely used in aerospace,marine,medical and chemical fields due to their excellent comprehensive properties.However,the continuous development of industrial technology and science has put higher requirements on titanium alloys.Compared with traditional low alloying titanium alloys,a large number of studies have shown that high alloying titanium alloys have better comprehensive properties.In addition,high alloying is conducive to the formation of richer metastable phases.The precise regulation of rich metastable phases is both an opportunity and a challenge.Therefore,in this paper,the metastable phase stability and decomposition mechanism of high alloying TiZrAl alloys are studied in depth.A series of (Ti₆₀Zr₄₀)_100-xAl_x alloys were prepared by non-consumable vacuum arc furnace melting,and the effect of Al on the metastable phase of TiZrAl alloy was studied.The results show that Al element shows a different effect from traditional titanium alloy in highly alloyed TiZrAl alloy.Under non-equilibrium conditions,due to the combined effects of binding energy and local stress,the Al element appears as a ?-stabilizing element;while under equilibrium conditions,the Al element appears as a conventional ?-stabilizing element.In addition,(Ti₆₀Zr₄₀)₈₅Al₁₅alloy was selected for further research.Studies have shown that stress-induced martensite transformation occurs in the metastable phase under stress,and the reverse transformation of the martensite phase is conducive to grain refinement.On the other hand,the metastable isothermal decomposition mechanism was studied,and the solid solution(Ti₆₀Zr₄₀)₈₅Al₁₅alloy was subjected to aging treatment at different temperatures and times.The results show that during the aging process,the alloy undergoes a solid phase transformation of ???+???,and eventually ? will be completely transformed into ? phase.The ? phase grows nucleated preferentially at the grain boundaries.As the aging temperature increases or the aging time increases,the needle-like ? phase grows toward the inside of the grain,and the ? phase also nucleates and grows inside the grain.The phase growth pattern is a triangular and quadrangular arrangement.