Research On Mechanical Properties Of TC4 Titanium Alloy Plate After Superplastic Forming

With the development of the aviation engine technology, and the increase of thrust weight ratio, more and more new structure and technology have been applied to aviation engine. Superplastic forming structure has being used in fan blades and some other component of the engine step by step. Thus strength assessment applied to SPF structure must be put forward too. This paper takes TC4 titanium alloy as research object and researches how the SPF process influence the mechanical properties of TC4 titanium alloy.Via the SPF tensile of TC4 board pieces, we got TC4 pieces with different SPF deformation rate. And then we did static tensile test to above pieces. In this way we researched the changing rules of yield strength, extension strength and elongation rate of TC4 alloy before and after superplastic deformation.We got rules of grain diameter changing with the different SPF deformation rate by metallographic test. And then we divided superplastic process into two parts which are temperature process and deformation process. Based on Hall- Petch formula and the relationship between the work hardening rateand the strain, we derived the yield strength formula after SPF. And after verifing the formula with the test results, we find that the calculated results are in good agreement with the test results.We defomed two orrugated plates with superplastic gas bulging forming. After that we cut out the fatigue test pieces from the corrugated plates by the thickness of each part. Totally we did three groups of fatigue test in room temperature which are TC4 alloy raw material, TC4 alloy after high temperature process, and TC4 alloy after SPF. And then we researched in which way the SPF process influence the TC4 titanium alloy fatigue performance.