The Microstructure And Properties Of Ti-43Al-9V Alloy With Low Oxygen Content After High Temperature Deformation

TiAl-based intermetallic compounds have received extensive attention from scientific researchers because of their high specific modulus and specific strength,low density,excellent oxidation resistance and creep resistance.However,due to the inherent brittleness of TiAl alloys,TiAl alloys have disadvantages such as lower room temperature plasticity and fracture toughness,and difficulty in hot working,which limits their development and application.Studies have shown that hot working can effectively improve the mechanical properties of TiAl alloys.According to previous research experience,it is found that the oxygen content in the alloy can affect the mechanical properties of the alloy.The lower the oxygen content in the titanium alloy,the better the plasticity.However,there are few studies on the effect of oxygen content on the mechanical properties of TiAl alloys.Therefore,this article selects Ti-43Al-9V alloy with excellent high temperature deformation ability as the research object,selects high-purity raw materials to prepare low-oxygen content Ti-43Al-9V alloy,analyzes and tests the microstructure and properties of the ingot,and analyzes the as-cast alloy Carry out hot compression simulation test,explores the evolution law of alloy microstructure after hot compression under different deformation conditions,constructs the alloy constitutive equation,uses sheath forging technology to prepare low oxygen content Ti-43Al-9V alloy forging.The organization and mechanical properties are analyzed and tested.A low-oxygen content Ti-43Al-9V alloy ingot was prepared by VAR technology.The structure of the ingot is uniform and coarse.The microstructure is composed of?/(?/B₂)layers and blocky?and?/B₂ grains.The structure from the center to the edge transitions from the near lamellar to the duplex,and the grains and The layer spacing gradually decreases,and the Y precipitated phase changes from granular to network.The structure of the ingot along the radial direction is relatively uniform.Tensile tests at room temperature and high temperature were performed on the ingot.The results showed that the middle section of the ingot has the best tensile properties,with a tensile strength of 612MPa and an elongation of 0.5%,which is a typical brittle fracture.As the temperature increases,the tensile strength of the alloy gradually decreases,and the elongation gradually increases.The brittle-to-ductile transition temperature is between 700-750?.The tensile strength at 750?and800?are 525MPa and 407MPa respectively,and the elongation is 3.29%and35.64%respectively.The hot isostatic pressing process of the ingot showed that the microstructure of the alloy became more uniform than before the hot isostatic pressing,the interlaminar spacing and grains were increased,and the shrinkage cavity and microcracks in the structure were largely affected.The tensile properties of the alloy after hot isostatic pressing are tested,and the results sh ow that the tensile strength of the alloy becomes lower after hot isostatic pressing,while the elongation below700?does not change much,and the elongation at 750?and 800?increases greatly..The thermal compression simulation test of the as-cast Ti-43Al-9V alloy with low oxygen content after hot isostatic pressing is carried out,and it is found that the alloy is a positive strain rate sensitive and negative temperature sensitive material.As the thermal compression strain rate decreases and the defor mation temperature increases,the original?phase and coarse?/(?/B₂)layers in the alloy are gradually replaced by fine equiaxed dynamic recrystallized?grain and phase transformation precipitated?phase.The organization is gradually refined.However,when the temperature is greater than 1200°C,the grains and lamellae in the microstructure tend to grow gradually,which will adversely affect the performance.Therefore,the optimal compression process parameters for Ti-43Al-9V alloy with low oxygen content are 1200?,0.01s^-1.The thermal compression simulation true stress-true strain curve of the as-cast Ti-43Al-9V alloy with low oxygen content is drawn,the hot deformation activation energy Q=657k J/mol of the alloy is calculated,and the alloy constitutive equation is constructed.The sheath forging technology is used to prepare low-oxygen content Ti-43Al-9V alloy forging blanks,and it is determined that the internal oxygen content of the alloy is basically maintained at about 500ppm.The forged structu re is more uniform and finer than the as-cast structure.The tensile properties of the forged alloy are tested,and it is found that the room temperature and high temperature tensile strength and elongation of the forged alloy have a certain increase compared with the as-cast alloy,especially the elongation of the forged alloy increased from 10.81%and 46.75%of the as-cast alloy at 750°C and 800°C to46.2%and 86.9%.Compared with Ti-43Al-9V alloy made of ordinary titanium sponge,Ti-43Al-9V alloy with low oxygen content has good mechanical properties,especially in forging state,has better elongation.