Study of grain growth kinetics of Zr-2.5%Nb alloy quenched from (α+β) and β-phase region

Abstract

The Zr-2.5 %Nb is used as the Pressure Tube (PT) material in Pressurized Heavy Water Reactors (PHWRs) in both cold worked and stress relieved as well as heat treated condition. For the development of heat-treated pressure tube, process parameters need to be tuned to achieve optimum microstructure and texture. In microstructural aspect, prior β grain size is a very important factor in influencing the property of the material. Hence, the prior β grain growth kinetics of the Zr-2.5 %Nb alloy has been investigated by subjecting the material to different heat treatments. Different heat treatment temperatures have been chosen from (α+β) and β phase region. The β transus temperature was measured through dilatometry. Specimens were soaked for different time and the grain size were measured using optical metallography. The evolution of grain size with soaking temperature and time were analyzed to study the grain growth kinetics.