Static coarsening of titanium alloys in single field by cellular automaton model considering solute drag and anisotropic mobility of grain boundaries

Chuan Wu,Xiaoguang Fan,He Yang,Hongwei Li

doi:10.1007/s11434-012-5002-9

Chuan Wu, Xiaoguang Fan + Show 2 more

Open Access

https://doi.org/10.1007/s11434-012-5002-9

Copy DOI

Journal: Science Bulletin	Publication Date: Apr 22, 2012
Citations: 12	License type: CC BY 2.0

Affiliation: Northwestern Polytechnical University

Abstract

Static coarsening is an important physical phenomenon that influences microstructural evolution and mechanical properties. How to simulate this process effectively has become an important topic which needs to be dealt with. In this paper, a new cellular automaton (CA) model, which considers the effect of solute drag and anisotropic mobility of grain boundaries, was developed to simulate static grain coarsening of titanium alloys in the beta-phase field. To describe the effect of the drag caused by different solute atoms on coarsening, their diffusion velocities in beta titanium were estimated relative to that of titanium atoms (Ti). A formula was proposed to quantitatively describe the relationship of the diffusion velocity of Ti to that of solute atoms; factors influencing the diffusion velocity such as solute atom radius, mass, and lattice type were considered. The anisotropic mobility of grain boundaries was represented by the parameter c 0, which was set to 1 for a fully anisotropic effect. These equations were then implemented into the CA scheme to model the static coarsening of titanium alloys Ti-6Al-4V, Ti17 (Ti-5Al-4Mo-4Cr-2Sn-2Zr, wt%), TG6 (Ti-5.8Al-4.0Sn-4.0Zr-0.7Nb-1.5Ta-0.4Si-0.06C, wt%) and TA15 (Ti-6Al-2Zr-1Mo-1V, wt%) in the beta field. The predicted results, including coarsening kinetics and microstructural evolution, were in good agreement with experimental results. Finally, the effects of time, temperature, and chemical composition on grain coarsening and the limitations of the model were discussed.

Highlights

Static coarsening is an important physical phenomenon that influences microstructural evolution and mechanical properties
A new cellular automaton model, which includes the effects of solute drag and anisotropic grain boundary mobility on coarsening, was developed to simulate static grain coarsening
To quantitatively describe the drag effects produced by different solute atoms on coarsening, the diffusion velocities of alloy elements were calculated relative to that of titanium atoms (Ti)

Summary

Introduction

Static coarsening is an important physical phenomenon that influences microstructural evolution and mechanical properties. A new cellular automaton (CA) model, which considers the effect of solute drag and anisotropic mobility of grain boundaries, was developed to simulate static grain coarsening of titanium alloys in the beta-phase field. Ivasishin et al [4,5] investigated the effect of texture evolution on the values of the static coarsening exponent n and activation energy for Ti–6Al–4V alloy in the beta field They found values of n ranging from 0.22 to 0.31 at different temperatures, but there were marked deviations attributed to different materials and experiments when the results were compared with those of others. Raghavan et al [22,23] and Kugler et al [24] simulated the topological and kinetic features of grain coarsening in polycrystalline materials Most of these models neglected the effect of solute drag and the anisotropic mobility of grain boundaries on the microstructural evolution during the coarsening process [15]. The predicted results, including coarsening kinetics and topological evolution, generally deviated from the experimental results

Objectives

Results

Conclusion