| TC4(Ti-6Al-4V)alloy is widely applied in the key and core parts of aviation weapon equipment owing to its high specific strength,antioxidation ability and thermoforming processing performance.XX new-generation air-to-air missiles are high-performance weapons independently studied,developed,designed and manufactured by China.Particularly,the loading per unit area and pneumatic heat intensifying performance of fins and wings under service will be significantly enlarged with the prolonging of flying speed.To meet the design requirements of air-to-air missiles,the choice for design and manufacture of fins and wings is TC4 alloy.Based on the designing philosophy of reinforced rib sandwich structures,the forming manufacture of multilayer structured missile fins and wings can be realized using the superplastic forming/diffusing interconnection technique.Hence,low-temperature superplastic deformational behaviors and deformation mechanism of TC4 alloy become hot spots of relevant fields.In this study targeting at TC4 alloy plates,adopts heat treatment and rolling methods to realize the adjustment of the alloy's phase ratio and grain size.Then low-temperature superplastic tensile tests were conducted at different temperatures(850,800,750?)and strain rates(3×10-2,1×10-2,5×10-3 s-1),then obtained the superplastic deformation behavior of the alloy under the above conditions.The strain rate sensitivity index m,and thermal deformation activation energy Q-value of this alloy were calculated,and constitutive equations were established.The microstructure evolving laws of this alloy during superplastic deformation were uncovered through microstructure characterization.The RWS deformation mechanism maps involving the dislocation count were established and its mechanism of superplastic deformation was predicted.In the research process,back-propagation artificial neural network technology was used to predict the thermal deformation activation energy Q-value.The main research results are as follows:(1)After normalizing(970?×2 h)and rolling at 400?,the?phase proportion of TC4was 50%?60%and the grain size was 5.5?m.The elongation at break at 800? and 5×10-3 s-1was 1220%.(2)The strain rate sensitivity index m of TC4 alloy increased with the rise of deformation temperature(750?850?)and maximized to 0.35.The activation energy of deformation(Q-value)was 191.73?353.3 k J/mol and increased with the increment of strain rate,but decreased with the rise of deformation temperature.An Arrhennius superplastic constitutive equation was set up,and its rheological stress was predicted,with the coefficient of multiple correlation of0.87.(3)The RWS deformation mechanism maps of TC4 involving the dislocation count at 750and 850? were plotted.The deformation mechanism at 750? was a dislocation glide under lattice diffusion control with the stress index of 5.The deformation mechanism at 850? was a grain boundary slide under lattice diffusion control with the stress index of 2.(4)Back-propagation artificial neural networks were established,and used to predict the superplastic deformation activation energy Q-value of TC4 alloy.The coefficient of multiple correlation was 0.85502 and the average relative error was 4.35%. |
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