Investigations On Microstructure And Properties Of Powder Metallurgy Ti6Al4V2Cr Alloy With Mo And Y Elements Addition

Titanium alloy as an commonly structure and functional materials and it has excellent comprehensive performance,the application is very extensive,it mainly applicabled to the key components of the engine,is also the alternative materials of aircraft air bottles.The requirements of the materials performance is getting higher and higher with the development of industry,the performance of materials in various aspects of titanium alloy must be improved in order to adapt to the better development,so it has great application value in the high-performance of titanium alloy.Titanium alloy was prepared by power metallurgy method in this experiment,the alloying elements was used to improve the performance of titanium alloy,the microstructure and mechanical properties and heat treatment process of the alloys with Mo and Y elements were investigated by the equipment of optical microscopy,scanning electron microscopy,X-ray diffraction(XRD),transmission electron microscopy,precision universal testing machine and muffle furnace et al to determine the best amount of alloying elements and heat treatment process.The high temperature deformation behavior of Ti6Al4V2Cr1.5Mo0.5Y alloy was also analyzed by Gleeble thermal simulation experiment,and the stress-strain curve of alloy and the relationship between the parameters of deformation temperature,strain rate and stress et al were discussed,and then the constitutive equation was established.The experimental results of adding Mo elements show that: the best content of Mo element was 1.5wt.%.When the content of Mo element was less than 1.5%,the microstructure of the alloy was equiaxed,and the strength,hardness and elongation of alloy increased with the increased of Mo content.When the content of Mo element was more than 1.5% and less than 3.0%,the strength,hardness and elongation of alloy decreased with the increased of Mo content,and when the content of Mo was 3.0%,the hard and brittle precipitated TiCr2 was found in the microstructure,which affects the mechanical properties of the alloy.The microstructure and properties of Ti6Al4V2Cr1.5Mo alloy were studied by different heat treatment.The results show that: the strength,hardness and elongation curve of alloy increased first and then decreased with the increase of the solution temperature,and reached the peak at 920 ?,the optimum solution temperature of alloy was 920 ?;the same method was used for aging treatment,the optimum agingtemperature was 520 ?,so the best heat treatment process of Ti6Al4V2Cr1.5Mo alloy was 920 ?×30 min(water quench)solution and 520 ?×8 h(air cooling)aging.Precipitation of granular Ti2 Mo Al was found along the interface between ?-Ti and?-Ti,and it produced a pinning enhancement effect on the titanium substrate.The addition of rare earth Y element has a good refining effect on the matrix.The formation of Y2O3 can effectively refine the grain,strengthen the titanium matrix.Through the analysis of nucleation theory,it is found that rare earth oxide Y2O3 can be used as nucleation substrate to promote heterogeneous nucleation,which is an effective nucleating agent.It was found that the precipitated phase Y2O3 was spherical and precipitated in the ?-Ti crystal in the microstructure,and there was a semicoherent interface between Y2O3 and ?-Ti.The results of thermal deformation behavior show that: Ti6Al4V2Cr1.5Mo0.5Y alloy was a negative temperature sensitive material and a positive strain rate sensitive material,the activation energy of the alloy was 286.1654685 KJ/ mol.