Study On The Density Evolution Of Multi-directional Loading Of TC4 Titanium Alloy End-frame Powders

In this study,hot isostatic pressing and plasma discharge sintering was uesd for the densification of TC4 titanium alloy powder.Hot compressive deformation of HIPed TC4titanium alloy was carried out with the hot simulation machine of Gleeble-1500D at the deformation temperature range from 850?to 1050?,the strain rate range from 0.001 s^-1to 5s^-1The complex structure of titanium alloy end frame was analyzed by numerical simulation.The degree of densification and density distribution of the powder body in the pre-forging stage and the multi-directional loading forming stage.The main work includes:analysis of the characteristics of true stress-true strain curve and thermal deformation parameters of HIPed TC4 and SPSed TC4 under different deformation temperatures?850¹050??and different strain rates(0.001⁵s^-1).Arrhenius equations and DMM processing maps for high temperature rheological behavior of HIPed TC4 and SPSed TC4 were established.Deform-3D software was used to simulate the multi-directional loading of titanium alloy end-frame complex structures,and different loading methods and processing parameters were analyzed.The densification degree and density distribution of TC4 and SPSed TC4 end-frame powders were found.The best processing technology was found.The effect and feasibility of multi-directional loading of titanium alloy complex structures under different schemes were systematically analyzed,and the plasticity of titanium alloy was enriched.Processing and extrusion theory.The main results show that:?1?The flow stress curves of HIPed TC4 and SPSed TC4 under the conditions of temperature 850¹050?and strain rate 0.01⁰.1s^-1are typical dynamic recrystallization true stress-true strain curves after hot-compressed.The peak stress increases with the increase of strain rate and the decrease of deformation temperature.The dynamic softening phenomenon of TC4 titanium alloy in both states during thermal compression,the main mechanism of softening is dynamic recrystallization.?2?The thermal deformation activation energy of HIPed TC4 alloy is 548.262kJ/mol,which is much higher than the deformation activation energy of pure?-titanium 204kJ/mol.The Arrhenius constitutive equation is:???The error analysis shows that the absolute relative error of the calculated value of peak stress and the experimental value is only 6.77%,which proves that the established Arrhenius constitutive equation can accurately predict the flow stress of HIPed TC4 at high temperature deformation.?3?The thermal deformation activation energy of SPSed TC4 alloy is 747.403kJ/mol,and its value is also much higher than the deformation activation energy of pure?-titanium204kJ/mol.The Arrhenius constitutive equation is:???The error analysis shows that the absolute value of the average relative error between the calculated value of the peak stress and the experimental value is only 5.66%,which proves that the established Arrhenius constitutive equation can accurately predict the flow stress of SPSed TC4 at high temperature deformation.?4?Using the dynamic material model?DMM?to establish the thermal processing map of HIPed TC4 and SPSed TC4,combined with the microstructure analysis,the optimal processing interval of HIPed TC4 is temperature 850⁹50?,strain rate 0.01⁰.1s^-1The optimal processing interval of SPSed TC4 is temperature 880⁹40?,strain rate 0.01⁰.1s^-1.?5?Numerical simulation analysis shows that the pre-forging forming stage of HIPed TC4 and SPSed TC4 end frames should adopt the multi-directional loading mode with simultaneous inner and outer diameter loading,which can obtain end-frame blank powder with better densification degree and uniform density distribution;The multi-directional loading forming stage of HIPed TC4 and SPSed TC4 end frames has better axial compression than the axial compression after the first axial extrusion and the axial extrusion after the first lateral extrusion.Density distribution uniformity,multi-directional axial axial simultaneous extrusion at a temperature of 910?and a extrusion speed of 1.5 mm/s is the most suitable process for processing HIPed TC4 end frame;The multi-directional loading method with axial lateral simultaneous extrusion under the condition of 920?and extrusion speed of 1.5 mm/s is the most suitable process for processing SPSed TC4 end frame.When SPSed TC4 titanium alloy is used as the material,the processing is labor-saving.Therefore,SPSed TC4 titanium alloy is used as the material,and the multi-directional loading method of axial lateral simultaneous extrusion at the temperature of 920?and the extrusion speed of 1.5 mm/s is the end frame structure.The most suitable processing solution.