Abstract
Microstructural evolution and plastic flow characteristics of a Ni-based superalloy were investigated using a simulative model that couples the basic metallurgical principle of dynamic recrystallization (DRX) with the two-dimensional (2D) cellular automaton (CA). Variation of dislocation density with local strain of deformation is considered for accurate determination of the microstructural evolution during DRX. The grain topography, the grain size and the recrystallized fraction can be well predicted by using the developed CA model, which enables to the establishment of the relationship between the flow stress, dislocation density, recrystallized fraction volume, recrystallized grain size and the thermomechanical parameters.
Highlights
The mechanical properties of a metallic component such as high-temperature alloy are largely depended on their chemical composition and microstructures, resulting from processing and heat treatment history in industrial production
Where the two terms represent a competition between storage of mobile dislocations and dynamic annihilation of dislocations, k1 represents work hardening, k2 is the softening parameter that represents the recovery of dislocation. k1 and k2 in Eq (3) can be evaluated from the measured flow stress and can be expressed as functions of temperature and strain rate
In the cellular automaton (CA) model for recrystallization, the transformation of a cell from the unrecrystallized state to the recrystallized state can be initiated when the following conditions are fulfilled simultaneously: (1) The driving force is positive; (2) The cell is at the grain boundary; at least one cell in the von Neumann neighborhood is already in the recrystallized state; (3) The recrystallized fraction variable is equal to 1; (4) The computer-generated random number is less than the transformation probability P, which is defined as P = i/4, where i is the number of neighboring cells, which have the same orientation in the von Neumann neighborhood
Summary
The mechanical properties of a metallic component such as high-temperature alloy are largely depended on their chemical composition and microstructures, resulting from processing and heat treatment history in industrial production. There are many cases of successful application of CA in modeling microstructural evolution In these studies, Ding et al [5], Raabe [6], Kugler and Turk [7], Xiao and Zheng [8] and Jin and Cui [9] contributed greatly to the development of the CA method for the simulation of DRX from the aspects of optimization algorithm, grain morphology change and. In order to deeply understand DRX mechanism and to predict and control the microstructure evolution during DRX for IN718, there is a need to develop new model to simulate the grain refinement during hot working from mesoscale aspect. By using the developed model, a wide range of deformation temperature and strain rate over DRX were examined to investigate the quantitative and topographic prediction of the microstructural evolution during hot working for IN718 superalloy. The appropriate hot working parameters for IN718 were recommended based on the CA simulations
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