Effects of h-BN additives on tensile mechanical behavior of Fe matrix: A molecular dynamics study

Abstract

In this paper, the effect mechanism of h-BN size, strain rate and tensile direction on tensile mechanical properties of Fe matrix in the presence of h-BN inclusions was investigated by molecular dynamics simulations. The results showed that the existence of h-BN inclusions diminished the tensile mechanical properties of Fe, which was attributed to the large variation in Elastic modulus between the inclusions and matrix as well as stress concentration near the interface. When the h-BN inclusions was 1 nm in radius, the results of the CNA analysis showed that the crystal structure changes from ordered to disordered to partially ordered, and the DXA analysis indicated that the dislocation length increased, then decreased, and then increased again. The stress–strain curve showed a double-peak phenomenon. The first peak was caused by the change in the crystal structure, and the second peak aroused due to the regrowth of dislocations. By analyzed the stress–strain curves at different strain rates, it was found that the tensile strength increased with increasing strain rate, while the Elastic modulus was almost unaffected, from the perspective of potential energy, the conclusion was confirmed. The findings of different tensile directions indicated that the material’s tensile strength was affected by the tensile direction. When the h-BN inclusions are parallel to tensile direction, the h-BN inclusions hindered the plastic deformation and a second peak appeared in the stress–strain curve. This study is essential to comprehend the influence of h-BN inclusions on mechanical properties of free-cutting steel.