Simulation Of Dynamic Mechanical Behavior Of Near Lamellar TiAl At Elevated Temperature Containing The Grain Boundary Effect

In this paper, a three-dimensional polycrystalline finite element model based on Voronoi arithmetic is built to simulate Near lamellar TiAl (hereinafter referred to as NL TiAl) containing the grain boundary effect, which further improves the work of NL TiAl numerical simulation.Based on rate-dependent crystal plasticity theory, by adding the constitutive model of grain boundary with the effect of slip and expansion, the constitutive model of this paper contains the effect of slip, twinning and grain boundary .Using the Voronoi arithmetic, a three-dimensional NL TiAl polycrystalline finite element model is built with randomly grain group size, shape, spatial orientation distribution, and shell elements is used to describe the grain boundaries at the junction of grain groups. Besides, the effects of model size and element number to the results of the simulation are investigated. In addition, the model is further improved by dividing each grain group into a number of grains and introducing shell elements between grains to better reflect the real microstructure of NL TiAl.These two finite element models are used to simulate the elasto-plastic mechanical behavior of NL TiAl under temperatures of Room temperature, 500℃, 700℃and tensile strain rates of 0.001, 320, 800 and1350/s. The conclusions drawn from those two simulations agree well with the experimental results. Besides, the effect of grain boundary on the mechanical behavior is investigated. The calculated result shows that the stress distribute of the grains has significant change after adding grain boundary shell elements, and certain stress concentration appears near the grain boundaries. In addition, the calculated also shows that the grain group boundaries obstruct the twinning, leading the volume ratio of deformation twin near the grain group boundaries smaller than the average value of deformation twin of the whole model.The summary of this paper and the prospect of future work are under presentation in the final part of this paper.