高温クリープ疲労損傷における粒界割れ加速現象の結晶方位依存性のMD解析

抄録

To suppress climate change, thermal power generation must operate under random output change at elevated temperatures for compensating the unstable output of renewable energies. Creep-fatigue damage of heat-resistant alloys has been found to increase and accelerate intergranular cracking, resulting in the drastic decrease of their lifetime. Creep-fatigue damage is known to degrade the crystallinity around grain boundary and thus, the strength of grain boundaries drastically. In order to clarify the degradation mechanism, molecular dynamics was applied to the deformation and fracture behaviors of bicrystal structures. It was found that the local energy concentration near the grain boundary activated the outward diffusion of atom around the grain boundaries and caused grooving at the edge of the grain boundaries due to the lattice mismatch between the facing grains and the mismatch of elastic constant (Young’s modulus). The drastic decrease in the local potential energy around the grain boundaries due to the strain energy caused by those mismatches was the main reason for the acceleration of the degradation,