Phase Field Simulation of Rafting Behavior of γ`Phase in Nickel Base Superalloy

2008 ◽  
Vol 33-37 ◽  
pp. 471-476 ◽  
Author(s):  
Akiyuki Takahashi ◽  
Yutaka Kobayashi ◽  
Masanori Kikuchi

This paper describes phase field simulations of the rafting behavior of γ’ phase with a simple interfacial dislocation network model. The interfacial dislocation network model accounts for the effect of the network on the lattice misfit between γ and γ’ phases and the subsequent rafting behavior. The model is implemented into the phase field simulation to see the dependence of the rafting behavior of γ’ phases on the interfacial dislocation network. Without the dislocation network model, the amount of the rafting was negligibly small. On the other hand, with the dislocation network model, the γ’ phases shows a large amount of rafting, which is in good agreement with the results of the experimental observations. Therefore, the combination of the phase field method and the simple interfacial dislocation network model developed in this work is appropriate for the simulation of the rafting of γ’ phases.

2011 ◽  
Vol 172-174 ◽  
pp. 1060-1065 ◽  
Author(s):  
Wei Xiong ◽  
Klara Asp Grönhagen ◽  
John Ågren ◽  
Malin Selleby ◽  
Joakim Odqvist ◽  
...  

This work is dedicated to simulate the spinodal decomposition of Fe-Cr bcc (body centered cubic) alloys using the phase field method coupled with CALPHAD modeling. Thermodynamic descriptions have been revised after a comprehensive review of information on the Fe-Cr system. The present work demonstrates that it is impossible to reconcile the ab initio enthalpy of mixing at the ground state with the experimental one at 1529 K using the state-of-the-art CALPHAD models. While the phase field simulation results show typical microstructure of spinodal decomposition, large differences have been found on kinetics among experimental results and simulations using different thermodynamic inputs. It was found that magnetism plays a key role on the description of Gibbs energy and mobility which are the inputs to phase field simulation. This work calls for an accurate determination of the atomic mobility data at low temperatures.


2007 ◽  
Vol 345-346 ◽  
pp. 935-938
Author(s):  
A. Yamanaka ◽  
Tomohiro Takaki ◽  
Yoshihiro Tomita

The integrated simulation model for microstructural design of Fe-C alloy using the phase-field method and the homogenization method is proposed. First, the phase-field simulation is performed to simulate the morphological change of the grain boundary ferrite to Widmanstätten ferrite. Then, in order to clarify the effects of the morphology of the ferrite phase on the micro- and macroscopic mechanical properties, the finite element analysis based on the homogenization method is conducted with the representative volume element obtained from the phase-field simulation. This numerical approach provides a powerful tool to investigate systematically the micro and macroscopic mechanical behavior with the morphological change of the ferrite phase in the Fe-C alloy.


2008 ◽  
Vol 584-586 ◽  
pp. 1045-1050 ◽  
Author(s):  
Mayu Muramatsu ◽  
Yuichi Tadano ◽  
Kazuyuki Shizawa

A new recrystallization phase-field method is proposed, in which the three stages of recrystallization phenomena, i.e., recovery, nucleation and nucleus growth are sequentially taken into account in a computation. From the information of subgrain patterns and crystal orientations in a polycrystal that are obtained by a dislocation-crystal plasticity FE analysis based on a reaction-diffusion model, subgrain groups surrounded by high angle boundary are found out. Next, subgrains in the group are coalesced into a nucleus by rotation of crystal orientation and migration of subgrain boundaries through a phase-field simulation. Then a computation of nucleus growth is performed also using the phase-field method on account of an autonomic incubation period of nucleation, in which stored dislocation energy assumes a role of driving force. It is shown that the present method can numerically reproduce the three stages of recrystallization as a sequence of computational procedure.


2012 ◽  
Vol 571 ◽  
pp. 3-7
Author(s):  
Jing Liu ◽  
Ying Shuo Wang

The phase field method is effective in simulating the formation of solidification microstructure. Based on the phase field models of coupling flow field and noise field proposed by Tong and Beckermann, using finite difference method to solve control equation, apartly simulating the dendritic morphology under the condition of convection or none convection, and drawing the following conclusions after comparing the results: in the side, the dendrite will no longer be symmetrical under the condition of countercurrent and downstream, the dendrite tip grows faster with countercurrent than that of the latter, while the dendrite grows almost naturally in the vertical direction of convection.


Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1095
Author(s):  
Zhiyuan Yu ◽  
Xinmei Wang ◽  
Fuqian Yang ◽  
Zhufeng Yue ◽  
James C. M. Li

Rafting is an important phenomenon of the microstructure evolution in nickel-based single crystal superalloys at elevated temperature. Understanding the rafting mechanism and its effect on the microstructure evolution is of great importance in determining the structural stability and applications of the single crystal superalloys. Phase-field method, which is an excellent tool to analyze the microstructure evolution at mesoscale, has been gradually used to investigate the rafting behavior. In this work, we review the crystal plasticity theory and phase-field method and discuss the application of the crystal plasticity theory and phase-field method in the analysis of the creep deformation and microstructure evolution of the single crystal superalloys.


2012 ◽  
Vol 326-328 ◽  
pp. 446-451 ◽  
Author(s):  
Toshiya Tanimoto ◽  
Yuhki Tsukada ◽  
Yoshinori Murata ◽  
Toshiyuki Koyama

Microstructural evolution in single crystal Ni-based superalloys is investigated by the phase field simulation. During creep, the morphology of theγphase changed from the cuboidal shape to the rafted one, and the rafted structure was collapsed in the late stage of creep. The simulation on the microstructural evolution is based on thermodynamic information, diffusion equation, elastic anisotropy and a homogeneous lattice misfit. It is found that caused by external stress result in the morphological change of theγphase to the rafted structure, and this rafted structure is collapsed by inhomogeneous lattice misfit. These morphological changes can be explained by the change in stable morphology of theγphase.


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