Astudy Of Forging Process Optimization In Wrought Ti40Alloy Using Processing Maps

Ti40alloy is high alloying beta type titanium alloy with proprietary intellectualproperty rights of our country,which has good burn resistance and high temperaturemechanical property，but the alloy forging performance is poor, likely to producedeformation defects. Based on this, the isothermal and constant strain ratecompression tests of wrought Ti40alloy were carried out by using the hot workingsimulator in the temperature range of950～1100℃and strain rate range of0.001～1.0s-1, based on compression test results, the mechanical behaviors of the wroughtTi40alloy were first studied,and then the optimization of hot working processparameters for this alloy were studied by using the processing map technology basedon dynamic material mode. The main research results are as follows:The flow stress of wrought Ti40alloy is increasing with the increase of strain rateand the decrease of temperature, the ture stress and ture strain curves is flow steadilybasically, but the flow stress will appear softening phenomenon gradually in the strainrate of1.0s-1. After analysis shows that, hyperbolic sine equation is more suitable fordescribe the deformation behavior of wrought Ti40alloy in high temperature deform-ation and the average deformation activation energy of wrought Ti40alloy was calcu-lated as253.48KJ/Mol, This means the deformation mechanisms of this alloy is notonly controlled by self-diffusion of titanium atoms.In the test parameters range alsoestablished the wrought Ti40alloy peak flow stress model, the results show that themodel can achieve high precision.Based on dynamic material model theory, the processing maps of wrought Ti40alloy at various strains are drawn by using Prasad criterion, Murty criterion and Malascriterion. The analysis of processing maps show that the processing maps drawn byusing Prasad criterion and Murty criterion are approximately the same, but greatlydifferent from Malas criterion. Analysised shows that, better deformation regionsbelong to the instability deformation regions easily by Malas criterion, but Prasadcriterion and Murty criterion can well sure the flow instability area and flow stabilityarea.Because the instability area in the processing maps based on Prasad criterion isbigger than that based on Murty criterion, the optimized results obtained from the processing map based on Prasad criterion is much safer in actual production from asecurity processing angle considered. The flow instability regions based on Prasadcriterion are in the temperature range of950～1017℃and strain rate range of0.13～1.0s-1, the manifestation of flow instability is flow localization, the desired forgingprocess parameters are in the temperature range of950～1100℃and strain rate rangeof0.001～0.01s-1, the hot deformation mechanisms corresponding to desired forgingprocess parameters are primarily dynamic recrystallization, accompanied withdynamic recovery, the optimum forging process parameters are near1060℃and0.001s-1corresponding to fully dynamic recrystallization.，the deformation mechanisms ofthe rest are primarily dynamic recovery accompanied with dynamic recrystallization.