| ?-TiAl-based alloy has the advantages of low density,high specific strength,good flame resistance and creep resistance,etc.As a lightweight high-temperature structural material,it has great application prospects in the aerospace field.Among them,through the introduction of disordered ? phase,the beta-gamma TiAl alloy's high-temperature deformation ability is greatly improved,which is conducive to the subsequent development of high-temperature forging and rolling processes.Therefore,in this paper,the beta-gamma series Ti-43Al-9V-Y alloy was prepared by gas atomization method combined and hot isostatic pressing sintering technology.And the microstructure and mechanical properties of the sintered Ti-43Al-9V-Y alloy were characterized by XRD,SEM,TEM,EBSD,room temperature,high temperature tensile and other analysis and testing methods;and subsequent heat treatment was conducted to study the influence of technology on the microstructure of the alloy and the mechanical properties at room temperature.Through the finite element analysis software MSC.Marc,the thermo-mechanical coupling model was established for the hot isostatic pressing process of Ti-43Al-9V-Y prealloyed powder.The influence of temperature,pressure,holding time and other process conditions on the sintering process was studied.By analyzing the change of displacement and relative density,the paper summarizes the influence of processing parameters on the powder densification process,and determines the best sintering process as heat preservation and holding pressure at 1200?/140 MPa for 5h.The hot isostatic pressing blank obtained under the best process conditions was selected for analysis,and it was found that the block piece had an uneven shrinkage deformation during the forming process,and the maximum displacement occurred at the center of the end face of the cladding.The displacement of the powder core at the corner of the sleeve is the smallest.Except for the edges and corners,the relative density of the powder is basically the same,indicating that the density distribution of the alloy prepared by hot isostatic pressing is relatively uniform.Using Ti-43Al-9V-Y pre-alloyed powder as raw material,the sintered alloy billet prepared by hot isostatic pressing has little difference in density at different positionsand a uniform structure.The results are consistent with the results of finite element analysis.The microstructure of the sintered Ti-43Al-9V-Y alloy mainly includes equiaxed ?-phase grains,?/? lamellar clusters,?-phase continuously distributed at the lamellar clusters and ?-phase grain boundaries,and bright white Al2 Y phase with spherical distribution.In the tensile test at room temperature,the yield strength and tensile strength of the sintered Ti-43Al-9V-Y alloy were 691 MPa and 788 MPa,respectively,and the elongation was 0.7%;When stretching at 800?,the yield strength and tensile strength of the alloy are reduced to 428 MPa and 435 MPa,respectively,but due to the coordination of high temperature soft ? phase,the elongation is greatly improved,up to 46.3%.Through thermal analysis experiments and Ti-Al-V ternary phase diagrams,it is speculated that the sintered Ti-43Al-9V-Y alloy's ? single phase zone exists in the temperature range of 1270 ??1335 ?,(? + ?)two-phase zone's temperature range of existence is 1180??1270?,and the temperature range of(?/?2+?+?)three-phase region is 1126??1180?,the actual phase transition process may be: L?L+?????+?????+???+?+???2/?+?+???2/?+?+B2.When the sintered Ti-43Al-9V-Y alloy is heat-treated between 1200? and 1320?,different alloy microstructures can be obtained.After heat treatment at 1200°C/1h/FC,a near-gamma structure was obtained,and its maximum tensile strength and elongation were 766 MPa and 0.62%,respectively;after heat treatment at 1250°C/1h/FC,the micromorphology began to transform into a dual structure,Its maximum tensile strength and elongation are 836 MPa and 0.95%respectively;after heat treatment at 1300?/1h/FC,the grains are significantly reduced,its maximum tensile strength and elongation are 845 MPa and 1.09%;after1320?/1h/FC heat treatment,?+? dual-phase structure was formed and the grains were coarsened,and the mechanical properties decreased. |
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