Constitutive equation for elevated temperature flow behavior of TiNiNb alloy based on orthogonal analysis

The high-temperature deformation behaviors of as-cast and as-forged TiNiNb shape memory alloy under compression in the temperature range of 923-1323 K and strain rate range of 0.01-10 s(-1) have been investigated with the view to acquiring the optimum hot deformation processing parameters. By the application of orthogonal experiment and variance analysis, the significance of the effects of strain, strain rate, deformation temperature as well as interaction between strain rate and deformation temperature on flow stress are evaluated, and the results indicate that the effect of interaction between strain rate and deformation temperature can be neglected in comparison with other factor. Thereafter, on the basis of the conclusions of orthogonal analysis, a new constitutive equation incorporating the effects of strain, strain rate and deformation temperature has been established. The developed constitutive equation enables to predict the flow stress accurately throughout the entire domain of temperature and strain rate, excepting at 973 K in 0.1 s(-1) and 10 s(-1) for as-cast TiNiNb alloy and at 923 K in 0.1 s(-1) and 1 s(-1) for as-forged TiNiNb alloy. (C) 2011 Elsevier Ltd. All rights reserved.