Loading Direction-Dependent Mechanical Properties of Columnar Polycrystal: A Molecular Dynamics Study

In this work, mechanical properties and plastic deformation behaviors of columnar polycrystal are examined by compression tests using molecular dynamics simulation. The results show that anisotropic mechanical properties occur to the fcc FeCrNi samples with different inclined angles between the orientation of columnar grains and loading direction. The yield stress and flow stress of the α = 0° sample are the highest, while the values of α = 45° sample are the lowest among the tested samples. The reasons for these differences derive from the geometric constraint of grain boundaries (GBs) and the available slip systems of different grains. The GBs serve as obstacles where extended dislocations are incorporated rather than dislocation pile-ups at GBs. For the α = 0° sample, the GBs bending toward the radius direction coupled with less partial dislocation motion and twinning compensates the compression strain. The strain-assisted GBs migration along loading direction extensively takes place in α = 90° sample, whereas the numerous partial dislocation activity and GBs gliding occur in samples with the angle close to 45°. This results from the higher Schmid factors of slip systems of columnar grains within these samples and long mean free sliding path for GBs gliding. Besides, the influence of radius size is probed, exhibiting a constant Young’s modulus, but slightly different plastic deformation characteristics.