SPF/DB Processing And Assessment For Multi-sheet Structure Of TA15Titanium Alloy

Superplastic forming/diffusion bonding(SPF/DB) had the advantage of low production and manufacturing cost, high efficiency and almost no residual, and it could amplify the structure-design at the great extent and also was used to make low-weight and good-integrity structural components. The integral structures contained double-sheet, three-sheet, four-sheet structure and so on. These multi-sheet structural components had the good integrity. Because there were little fixed components in addition to the need of assembling, so the weight loss was effective.In this paper, the superplastic forming/diffusion bonding process was studied on the base of research on four-sheet structure of TA15titanium.Not only the finite element simulation of superplastic forming process about the panel and core board and the experiment of SPF/DB process were researched, but also the microstructure and the bonded situation of diffusion bonding interface and the trail of mechanical properties for four-sheet structure were studied.The superplastic forming process of the panel and core board of the four-sheet hollow structure was simulated by using the finite element software MSC.MARC. The thickness and stress distribution of panel and core board were forecasted at the different part of structure and different time, at the same time the time-pressure loading curve which provided the theoretical basis for the subsequent experiment of SPF/DB was obtained under the condition of constant strain rate.Under the condition of using designed forming mold and gas-pressure controlling system, the SPF/DB experiment of four-sheet hollow structure was carried out and the four-sheet structure was formed. The microstructure before and after forming and the bonded situation of diffusion bonding parts were observed and analyzed. The bonding joint of core board was good and no bonding interface was observed. The formed stiffening ribs were basically upright and the diffusion bonding quality was good, because the ribs finally formed, so these parts had been serious thinning.The load response test of four-sheet specimen was carried out with the compressing test and bending test. The mechanical properties of four-sheet structure were researched and the deformation of specimen under the compressing and bending load was analyzed. The critical load existed when the four-sheet structure specimen was subjected to compressing load and bending load and the specimen would be unstable when the load was more than the critical load. The main failure was crack for compressed specimen and that of bended specimen was bending deformation on top panel board and stiffening ribs.