Research On The Heat Treatment Process Of Ti-4.5Al-2.5V-1.5Fe-0.25O High-strength Titanium Alloy Sheet

Ti-4.5-Al-2-5-V-1.5-Fe-0.25O is a newly developed of two-phase titanium alloys which is on the basic research of Ti-6Al-4V.This alloy has high strength,excellent corrosion resistance,high wear resistance and low cost,thus has a good application prospect in the aerospace,military industries,shipbuilding and other high-tech fields.At present,the major application of Ti-4.5-Al-2.5-V-1.5-Fe-0.25O alloys in foreign countries are focused on the military industries,and the annealing organization of this titanium alloy are only announced,while reinforcement mechanism and microstructures evolution of alloy elements have not been reported.Therefore,the domestic study of this titanium alloy was still in the blank stage.For the above reasons,in this paper,solution and aging treatments of Ti-4.5-Al-2.5-V-1.5-Fe-0.25O alloys were tested,as well as microstructures and mechanical properties under different treatment processes was studied.In this paper,microstructures and mechanical property transformations of a cold rolled Ti-4.5-Al-2.5-V-1.5-Fe-0.25O titanium alloy sheet were investigated using an optical microscope(OM),scanning electron microscopy(SEM,XL30 ESEM-TMP)equiped with the energy dispersive spectroscope(EDS),X-ray crystallography was carried out with a Cu Ka X-ray source,a type of HR-100ZDT Rockwell hardness tester.Microstructure features and evolution mechanism of the Ti-4.5-Al-2.5-V-1.5-Fe-0.25O titanium alloy in heat treatment processes as well as solution and aging treatments,quenching temperatures,cooling rates and aging effects on the microstructures and mechanical properties in the solution and aging processes were discussed and analyzed.The results show that,in annealing state,the titanium alloy was mainly composed of equiaxial a phase,it was gradually disappeared with the increase of colling rates(furnace cooling-air cooling-water cooling)under 910? solution process.The microstructures of titanium alloy were no obvious change after the furnace cooling,but appeared segregations after air colling.In contrast,the microstructures after water colling were homogeneous distributed,equiaxial a phase changed into granular a phase.For the microstructures of the titanium alloy under solution process after water colling,a phase gradually reduced and eventually disappeared through different solution temperatures(910?,940?,970?,1000?).In two phase region of solid process at 910? and 940?,the microstructures were mainly composed of granular a phase and a small amount of acicular a phase,segregation appeared in the a clusters.When the solution temperature is 970?,microstructures of double-phases appeared,and segregation disappeared.While under 1000? Single-phase solid solution process,the organization of a phase are completely disappear and all transformed into ? phase.The tensile strength and elongation after annealing are 980MPa and 15.3%,respectively.With the increase of solution temperature,tensile strength increases then decreases,but elongation decreases.In 970?solid solution+water cooling,the alloy are with best comprehensive mechanics performance,the tensile strength and elongation are 1260MPa and 6.5%.At 1000? single-phase solution process,“?fragment"appeared,reduced the tensile strength and elongation.The effect on the hardness of the alloy during single-phase and double-phase solution treatments are the same,it increases when the solution temperature increases.