Study On Heat Treatment Strengthening And Phase Transformation Behavior Of TC4 Titanium Alloy

Titanium alloys are widely used in aerospace,aviation,marine engineering and petrochemical industry,due to their high specific strength,good plasticity,toughness,excellent corrosion resistance and high temperature stability.At present,in order to meet the performance requirements of titanium alloys in various fields,the development of new titanium alloys and the full exploitation of the performance potential of existing titanium alloys have become the research focus.In this paper,TC4 titanium alloy is taken as the research object,the comprehensive mechanical properties were improved by means of heat treatment strengthening,so as to fully tap its performance and expand its application scope.The results have important practical value for improving the mechanical properties of TC4 titanium alloy.Firstly,the composition and phase transition temperature of TC4 titanium alloy were measured,and the solid solution treatment process and aging treatment process were developed.The X-ray diffraction,Scanning electron microscope,Transmission electron microscope and Mechanical properties testing machine were used,the effects of solution temperature,solution time and cooling ways on the microstructure and phase composition during solution treatment were investigated,and the effects of aging temperature and aging time on the microstructure and mechanical properties during aging treatment were analyzed.The precipitation strengthening mechanism of TC4 titanium alloy during Solution-Aging heat treatment was obtained.Secondly,thermal expansion measurements were carried out in the heating and continuous cooling stages of solid solution treatment.The effects of different heating rates on the phase transformation behavior of ?+??? during heating and the effects of different cooling rates on the phase transformation behavior of ??? or ???? during cooling were studied respectively.The phase transformation model of heating was builted on the basis of modified Johnson-Mehl-Avrami equation.Finally,thermal expansion measurements were carried out in the heating and holding stages of aging treatment.The effects of different heating rates on the precipitates behavior of ?? during heating and the effects of different aging temperatures on the transformation behavior of ????+? during holding were explored respectively.The phase transformation model of holding was builted on the basis of Johnson-Mehl-Avrami equation,and TTT curve was drawn.