73 / 2023-04-12 16:22:06

Influence of the dislocation microstructures and load orientation on yielding behavior in tungsten under high strain rates

tungsten; dislocation microstructures; orientation-dependence; dynamic yield behavior; dislocation dynamics

高压物理与材料科学 > 动高压-海报

Though it is well known that initial dislocation microstructures and loading directions play an important role in the deformation behavior of materials, how they affect the macroscopic properties is still subjected to intensive research due to the complexity of dislocation evolution. In this work, we use discrete dislocation dynamics (DDD) to understand the effect of initial dislocation microstructures and loading directions on the dynamic yield behavior of single-crystal tungsten. DDD results suggest that the dislocation source length and the dislocation density  are responsible for the initial yield stress and the flow stress of tungsten under dynamic loading, respectively. As length density increase, the plastic yield mechanism transforms from dislocation-source activation into dislocation-dislocation interactions, resulting in the initial yield stress decreasing and the flow stress increasing. In high strain rate loaded single crystal tungsten, [100] and [110] HELs are near identical with the [111] HEL having the highest flow stress. It depends on the [111] direction having a faster rate of dislocation proliferation than the other two directions. From the analysis of dislocation microstructure evolution, it can be seen that the slip system leading tungsten plastic deformation is different along different loading directions. Specifically, there is negligible effect of strain rate in the high symmetric direction [100], and the plastic deformation is dominated by four slip systems uniformly distributed. However, the low symmetry directions [110] and [111] have obvious rate effect. Under low strain rate loading, the distribution of slip system is not uniform in the deformation process, but It tends to homogenize at high strain rates. Our results could be a valuable piece that connects dynamic yield behavior to the initial dislocation microstructures and orientation-dependent. The dislocation source length, the dislocation density, three typical loading directions on the dynamic yield behavior of single crystal tungsten, are investigated in detail by tracing the evolutions of dislocation.