Role of crystallographic orientation on intragranular void growth in polycrystalline FCC materials

ABSTR A C T In this work, we study the effect of crystallographic orientation and applied triaxiality on the growth of intragranular voids. Two 3D full-field micromechanics methods are used, the dilata-tional visco-plastic fast-Fourier transform (DVP-FFT) and the crystal plasticity Finite Elements (CP-FE), both of which incorporate a combination of crystalline plasticity and dilatational plas-ticity. We demonstrate with several select cases that predictions of void growth from both for-mulations agree qualitatively. With the more computationally efficient DVP-FFT, additional effects of polycrystalline microstructure and the influence of nearest neighborhood are investi-gated. Crystals bearing a single intracrystalline void are studied in three types of 3D micro-structural environments: isolated single crystals, individual equal-sized grains within a regular polycrystal, and individual variable sized grains within a polycrystal with grains and voids randomly located. We show that loading type plays a significant role. In strain-rate controlled conditions, voids in the hardest [111]-crystals grow the fastest in time, whereas in stress-controlled conditions, voids in the softest [100]-crystal grow the fastest in time. The analysis reveals that on average void growth is slower for the same starting orientation in the polycrystal than in the single crystal. We find that at the highest triaxiality tested that the correlation between crystal orientation and void growth rate in the polycrystal strengthens, drawing closer to that seen in the isolated single crystals. These results and model can help guide the microstructural design of polycrystalline materials with high strength and damage-tolerance in high-rate deformation.

Automated summary

This study investigates the effect of crystallographic orientation and applied triaxiality on the growth of intragranular voids using two 3D micromechanics methods. The results show that loading type significantly influences void growth rate, and void growth is slower in polycrystals compared to single crystals. Furthermore, at the highest triaxiality tested, the correlation between crystal orientation and void growth rate in polycrystals strengthens.