Study On Superplasticity Deformation Mechanism Base On The Minm Method Of Damage Tolerance TC4-DT Titanium Alloy

Titanium alloys are widely used in aerospace, shipbuilding, automobile, chemicalindustry, energy and other fields. As a new type of titanium alloy, damage tolerancetitanium alloy’s demand is growing in the field of modern aviation.How can we get easyforming and high efficiency of damage tolerance type titanium alloy products alsobecome a problem needs to solve.This paper puts forward high efficiency superplasticforming Minm method originality, compared with the traditional method of superplasticforming, cannot only receive the titanium industry in the process of superplasticforming deformation needs, and can greatly improve the efficiency of superplasticforming.This new method can significantly increase the productivity of the complexcomponents of titanium alloy superplastic forming, and shows the broad marketprospect in the field of engineering application.This paper is developed the Minm method process control software duringsuperplastic deformation of tensile experiment based on Visual Basic language. Thissoftware can accord to the principle of Minm method during superplastic deformation oftensile experiments for real-time control, and timely feedback information.In this paper superplastic deformation characteristics of TC4-DT titanium alloywere investigated within temperature of850℃－900℃by the method of Maximum mvalue method and the Minm method. The experimental results show that: The maximumelongation reached1240%based on maximum m value method under the deformation temperatureof870℃, the deformation efficiency is3.76. And Minm method in the m a value of0.35,0.4,0.45, the elongation were35.85,458.46%,701.13%, and the correspondingdeformation efficiency is18.67,17.7,16.34, respectively. Minm method than theMaximum m method deformation of high efficiency. And the m value is smaller,the higher the efficiency of the deformation. When m=0.35, the highest efficiency ofdeformation of Minm method, is four times higher than Maximum m method.Analysis of experimental results of superplastic tensile available: With the increaseof experimental temperature, elongation present a growth trend, and reach the maximumat870℃. But temperatures continue to rise, elongation showing a downward trend, thisis because as the temperatures continue to rise, grain began to grow up, when surpassthe critical temperature, the grains growing up quickly lead to a drop in the superplastic. After forging TC4-DT titanium alloy superplastic can significantly improve. Analysisof microstructure shows that the dynamic recrystallization occurred during superplastictensile deformation.The superplastic constitutive relation of TC4-DT titanium alloy was performed onsuperplastic tensile testing machine in the temperature range of870℃-890℃based onthe strain rate circulation method. Using the method of stepwise regression in buildingthe constitutive relationship of TC4-DT titanium alloy. Established the TC4-DTconstitutive model of titanium alloy based on the Arrhenius equation, and calculate theactivation for171.9kJ/mol. But the error of testing shows that the building constitutiveequation is a lack of accuracy. So again through1stopt software regression fitting to fixthe constitutive model. The precision of TC4titanium alloy superplastic constitutiveequation is0.99. The constitutive model accurately reflects the material flow stress anddeformation temperature, strain rate, the relationship between the strains. This equationcan be used in the actual deformation resistance calculation of hot working process, alsocan be used as the constitutive equation of the finite element simulation.