Papers by Keyword: Superplastic Bulging

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Authors: Chuan Yun Wang, Jin Shan Li, Bin Tang, Hong Chao Kou
Abstract: The superplastic bulging process of TiAl sheet was simulated by coupling superplastic constitutive equation to finite element model. Based on this model, the effect of coefficient of friction between the sheet and mold and the size of the mold fillet on the superplastic bulging (SPB) performance of TiAl alloys sheet were studied by analyzing the evolution of equivalent plastic strain and thickness distribution in the sheet. The results showed that friction was the dominant factor of the nonuniform thickness of the sheet, while higher friction and smaller radius of mold fillet inhibited the over-thinning of sheet on the entry of mold cavity. The simulation results were in good agreement with the experimental results. Therefore, the present model could be used for optimizing the selction of the deformation parameters and the design of the structures.
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Authors: G. Wang, Kai Feng Zhang, Wen Bo Han, D.Z. Wu, C.W. Wang
Abstract: The superplastic bulging capabilities of Ti-6Al-4V butt-welded plates with 0.8mm in thickness with high energy beam welding methods namely plasma arc welding (PAW), electron beam welding (EBW) and laser beam welding (LBW) are studied in virtue of superplastic bulging tests. Superplastic bulging tests are performed at the superplastic forming temperature 925°C under 1MPa gas pressure. The superplastic bulging capability is represented by the maximum relative bulging height h after fracture. Experimental results suggest that all of butt-welded plates with high energy beam welding methods possess good superplastic bulging capability. Among them, the maximum relative bulge height of LBW is the highest, that of EBW is slightly lower and that of PAW is the lowest. The higher the input energy density is, the bigger the bulge height will be. Furthermore their microstructure evolutions of various weld metals during superplastic bulging were systematically analyzed via metallographical tests. The relation between the microstructure of weld metal and its superplasticity is found. Metallographical analysis shows that the microstructure of Ti-6Al-4V weld metal with high energy beam welding methods is composed of fine acicular martensite. The higher the input energy density is, the finer the martensite structure will be. Upon heating, this martensite changes to a basketweave-like structure and upon bulging, the martensite structure have the trend of transforming to fine equiaxed grain. This can explained the reason why the Ti-6Al-4V butt-welded plates with high energy beam welding methods have excellent superplastic bulging capability.
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