Determination of instability in Zr-2.5Nb-0.5Cu using Lyapunov function

Abstract

Hot workability of Zr-2.5Nb-0.5Cu alloy has been investigated by means of hot compression test using Gleeble-3800®, in the temperature and strain rate range of 700 to 925°C and 0.01 -10s-1, respectively. Deformation behavior was characterized in terms of flow instability using peak stress with the help of Lyapunov Function. The true stress- strain curves shows that softening occurs at all lower temperature and for entire strain rates of deformation. The instable flow was suggested by negative m value at deformation condition of 700°C (5 and 10 s-1), while s value at 925°C (10 s-1). The combined result of rate of change of m and s with respect to log strain rate suggest that the deformation condition ranges from 725- 780°C (10-1- 10-1 s-1) and 700°C (1- 10 s-1) representing safe domain for stable flow. © (2015) Trans Tech Publications, Switzerland.