| In this paper,the precipitation and growth of equiaxed a phase of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy were discussed.Through studying the a phase transformation process and the growth mechanism analysis physical model,the modified morphology Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy will be heated and the flake a phase will be equalized,and the equiaxed a-phase size will gradually increase with increasing temperature.The precipitated a-grain grows from 3 to 5 ?m to 10 to 12 ?m.When the Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy is cooled rapidly,due to the relatively short time of grain boundary nucleation,an incomplete grain boundary a layer is formed.The similar a grains reduce the interfacial energy and encapsulate each other,and then continue to spread to the beta phase until reaching the lowest energy tends to be stable.The phase transformation process of Ti-5Al-5Mo-5V-1Cr-1Fe is mainly to consume the surrounding ? phase to complete the growth of equiaxed a grains.Through experiments,it was found that during the growth of equiaxed a phase,the bow-out mechanism was eliminated.The growth of the lower phase boundary to its own growth and coalescence mechanism reduces the surface interface energy to complete growth,the surface of the phase boundary also collapses,and the phase interface thickens.This is to prepare for the phase boundary merger.In this paper,based on the solution-aging heat treatment,the effect of intermediate temperature on the microstructure and physical and mechanical properties of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was discussed in detail by adjusting the annealing temperature and aging time.Ti-5Al-5Mo-5V-1Cr-1Fe Ti alloys gradually decrease the content of the medium-shaft a-phase in the matrix with the increase of the solution temperature at mid-temperature,and the needle-like a phase in the collective gradually disappears.The size of the equiaxed a-phase changes.It is small and there is a short rod-like structure formed by the connection of equiaxed a phases in the issue.The occurrence of the above phenomenon is related to the precipitation of a phase at different temperature intervals.When the solution temperature is relatively close to the phase transition temperature,the ?phase is mostly precipitated in an isometric state,and the secondary ? phase is dissolved in the matrix.The annealing temperature decreases far away from T?,and the precipitation tendency of ? phase becomes stronger,so that nucleation and precipitation can occur at the ?-phase grain boundaries where there are many defects.With the prolongation of solid solution time,the tensile strength of titanium alloy after aging is gradually increased,the tensile strength is about 1115Mpa at 1h,1190MPa after 2h,and 75MPa higher than before.After 3h,it is 140MPa higher than 1h,and 6h is 174MPa higher than 1h.Therefore,the extension of the aging time is limited to increase the strength of the titanium alloy,but it can better improve the plasticity and elongation of the titanium alloy. |
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