Ti40阻燃合金大晶粒超塑性变形特性及唯象型本构关系研究

The superplastic tensile tests of Ti40 burn-resistant alloy with large grains were conducted, the intervals of deformation parameters in which can achieve the large-grained superplasticity were determined,and the phenomenological constitutive equation of superplastic deformation of Ti40 alloy with large grains was established. The results indicate that the large grain Ti40 alloy does not exhibit superplasticity at the conditions of low temperatures and high strain rates (T≤800 ℃,ε^•≥5×10^-3s^-1), however, good superplasticity can be obtained at the conditions of high temperatures and low strain rates, and the maximum elongation of 436% occurs at the condition with temperature of 840 ℃, strain rate of 1×10^-3s^-1. The true stress-strain curves present the classic characteristic of four stages. The strain rate sensitivity exponent m increases first and then remains unchanged with increasing deformation temperatures and the maximum of m is 0.41. The activation energy of Ti40 alloy superplastic deformation was calculated by Arrhenius equation and the value was 263.3 kJ•mol^-1. The phenomenological constitutive equation of Ti40 alloy was constructed by BP neural networks. Error analysis shows that the mean relative error value is 2.342% and the mean relative error value for prediction is 2.715%, indicating a good accuracy of the constitutive equation.