A cellular automata (CA) method was employed to model static coarsening controlled by diffusion along grain boundaries at 1173K and through the bulk at 1213 and 1243K for a two-phase titanium alloy. In the CA model, the coarsening rate was inversely proportional to the 3rd power of the average grain radius for coarsening controlled by diffusion along grain boundaries, and inversely proportional to the 2nd power of the average grain radius for coarsening controlled by diffusion through the bulk. The CA model was used to predict the morphological evolution, average grain size, topological characteristics, and the coarsening kinetics of the Ti-6Al-2Zr-1Mo-1V (TA15) alloy during static coarsening. The predicted results were found to be in good agreement with the corresponding experimental results. In addition, the effects of the volume fraction of the phase (Vf ) and the initial grain size on the coarsening were discussed. It was found that the predicted coarsening kinetic constant increased with Vf and that a larger initial grain size led to slower coarsening.
Substructure evolution significantly influences the flow behavior of titanium alloys in isothermal hot compression.This paper presents a physical experiment(isothermal hot compression and electron backscatter difraction,EBSD)and a cellular automaton(CA)method to investigate the substructure evolution of a near-αtitanium alloy Ti-6Al-2Zr-1Mo-1V(TA15)isothermally compressed in theα+βtwo-phase region.In the℃A model,the subgrain growth,the transformation of low angle boundaries(LABs)to high angle boundaries(HABs)and the dislocation density evolution were considered.The dislocation density accumulating around the subgrain boundaries provided a driving force and made the transformation of the LABs to HABs.The℃A model was employed to predict the substructure evolution,dislocation density evolution and flow stress.In addition,the efects of strain,strain rate and temperature on the relative frequency of the HABs were analyzed and discussed.To verify the℃A model,the predicted results including the relative frequency of the HABs and the flow stress were compared with the experimental values.
Quantitative analysis of deformation-induced textures and texture-induced mechanical properties is an important issue for optimal design and control of plastic forming of metals.Deformation-induced textures were predicted through the crystal plasticity finite-element method(CPFEM)in this study,and varying deformation modes,including uniaxial compression,uniaxial tension,simple shear,and plane-strain compression,were considered.The predicted textures were proven by experiments.Then,a theoretical model was proposed to build the quantitative relation between textures and the corresponding mechanical properties.This model takes into account the effects of grain’s orientation,grain’s interaction,and the property in the level of single grain.It captures the macroscopic anisotropy owing to textures and microscopic anisotropy owing to crystallographic structures.By applying this model,the macroscopic stress responses of grains’aggregate with varying textures were calculated according to grain’s orientations and the intrinsic properties of the single crystal along[100]and[111]crystallographic directions.The theoretical model is proven to have high efficiency and acceptable accuracy in the prediction of texture-induced mechanical properties comparing with CPFEM model.
