Research On The Relationship Between The Superplastic Stain Rate Sensitivity Index M Value And The Elongation δ Of Titanium Alloy

Titanium alloy as an excellent high ductility, high strength, good heat resistance,excellent corrosion resistance, superior lightweight structural materials are widely usedin the mechanical industry, the electronics industry，the chemical industry andother fields. The main advantages of studying on titanium alloy superplastic formingare low deformation resistance, easy to shape and high precision product dimensions.This is not only to solve the large deformation resistance of titanium alloys, difficultforming, but also expand the use of titanium alloys. Therefore, to explore thesuperplastic forming technology of titanium alloys has an important meaning.This thesis studied the superplastic deformation mechanism of the setting m(superplastic stain rate sensitivity index value) method through the computerprogram by Visual Basic6.0environment. The computer program system can carryout automatic control, automatic data collection, analysis and post-processing. Thisnew program can analysis and judgement error sources, and automatically eliminatethe gross error of experiment, and reduce the influence of error form experiment data,so as to further explore in high temperature titanium alloy superplastic deformationprovides a reliable data.TC4and TB6titanium alloy superplastic forming process is studied through them method. Both the materials of TC4and TB6were stretched through maximum mmethod at first. The test temperatures were800℃、850℃、900℃and700℃、750℃、800℃respectively. The result shows that: the best of TC4titanium alloydeformation temperature is850℃and TB6titanium alloy deformation temperatureis750℃. Then respectively for the two materials using high temperature tensile testin the method of setting m. Through the integrated use of numerical analysis andregression fit and other means to establish the relation of the strain rate sensitivityindex m and the elongation and constructor expression. Thus can obtain therelationship of the strain rate sensitivity index m value and elongation. Thisrelationship has important theoretical basis and the actual engineering value forexploring the material superplasticity and instructing material superplastic formingprocess. After the above of the superplastic experimental study, summed up thefollowing law:1. The temperature has a significant impact on two titanium alloy superplastic. Accompanied by the elevated temperature, the elongation first increased and thendecreased.2. Grain boundary sliding is the main deformation mechanism of setting mmethod Superplastic deformation. Strain hardening effect is evident early in thedeformation, the flow stress increased faster peak, but then along with the dynamicrecovery, the strain rate deformation process was constantly decreasing.3. The deformation temperature and the set m value on tensile samplesmicrostructure effect is obvious. In the process of deformation occurred dynamicrecrystallization grain the equiaxed phenomenon.4. Experimental collected data without the impact of outliers. The relationshipbetween m and δ were built through the integrated use of numerical analysis andregression fitting method. Constructed two materials function expressions are asfollows:TC4alloy（Forging ratio13.8）： δ=-8m~3+56m~2-79m+716TC4alloy（Forging ratio17.1）：δ=-2.883m~3+16.5m~2+28.333m+662TB6alloy： δ=3.6667m~3-29m~2+94.333m+216Where, m is the strain rate sensitivity index, is the tensile specimenelongation.