Shear flow characteristics and crystallization kinetics during steady non-isothermal flow of Vitreloy-1

Abstract

The steady non-isothermal channel flow of Vitreloy-1 (Zr 41.25Ti 13.75Cu 12.5Ni 10Be 22.5) is simulated by means of finite element modeling. Non-Newtonian flow behavior is accounted for by employing a self-consistent shear-rate dependent flow law. Transition to non-Newtonian flow and shear localization is obtained by superimposing the computed flow evolution onto an experimentally developed flow diagram. The coordinate points that mark transition to shear localization form a narrow boundary layer ∼23% of the channel thickness. The deformation-induced enhancement of crystallization kinetics is approximately accounted for by utilizing the shear-rate dependent viscosity law to shift the transformation time in the apparent TTT diagram. The kinetics of crystallization during flow are assessed by superimposing the temperature evolution onto the “shifted” TTT diagram. The coordinate points that mark the onset of crystallization form a boundary layer ∼15% of the channel thickness, which are narrower than the shear localization boundary layer suggesting that crystallites will form in the shear-banded region.