Abstract
The grain growth behavior in a typical Ni-based superalloy was investigated using isothermal heat treatment experiments over a holding temperature range of 1353–1473 K. The experimental results showed that the grain structure continuously coarsened as the holding time and holding temperature increased during heat treatment. A classical parabolic grain growth model was used to explore the mechanism of grain growth under experimental conditions. The grain growth exponent was found to be slightly above 2. This indicates that the current grain growth in the studied superalloy is mainly governed by grain boundary migration with a minor pinning effect from the precipitates. Then, the grain growth in the studied superalloy during isothermal heat treatment was modelled by a cellular automaton (CA) with deterministic state switch rules. The microscale kinetics of grain growth is described by the correlation between the moving velocity and curvature of the grain boundary. The local grain boundary curvature is well evaluated by a template disk method. The grain boundary mobility was found to increase with increasing temperature. The relationship between the grain boundary mobility and temperature has been established. The developed CA model is capable of capturing the dependence of the grain size on the holding time under different holding temperatures.
Highlights
The mechanical performances of components are sensitive to their microstructures, especially the grain size [1,2,3,4,5]
The study of grain growth behavior in Ni-based superalloys is of interest to many researchers [13,14,15,16,17,18]
A cellular automaton model is developed to describe the evolution of grain structure in the studied Ni-based superalloy during isothermal heat treatment
Summary
The mechanical performances of components are sensitive to their microstructures, especially the grain size [1,2,3,4,5]. Grain refinement can improve the strength and ductility of components at the same time by activating more slip systems [6,7]. This renders the control of grain size an important task. The study of grain growth behavior in Ni-based superalloys is of interest to many researchers [13,14,15,16,17,18]. Isothermal heat treatment experiments were conducted to investigate the grain growth behavior in a typical Ni-based superalloy. A cellular automaton model is developed to describe the evolution of grain structure in the studied Ni-based superalloy during isothermal heat treatment
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