Molecular Dynamics as a Means to Investigate Grain Size and Strain Rate Effect on Plastic Deformation of 316 L Nanocrystalline Stainless-Steel

Abstract

In the present study, molecular dynamics simulations were employed to investigate the effect of strain rate on the plastic deformation mechanism of nanocrystalline 316 L stainless-steel, wherein there was an average grain of 2.5–11.5 nm at room temperature. The results showed that the critical grain size was 7.7 nm. Below critical grain size, grain boundary activation was dominant (i.e., grain boundary sliding and grain rotation). Above critical grain size, dislocation activities were dominant. There was a slight effect that occurred during the plastic deformation mechanism transition from dislocation-based plasticity to grain boundaries, as a result of the stress rate on larger grain sizes. There was also a greater sensitive on the strain rate for smaller grain sizes than the larger grain sizes. We chose samples of 316 L nanocrystalline stainless-steel with mean grain sizes of 2.5, 4.1, and 9.9 nm. The values of strain rate sensitivity were 0.19, 0.22, and 0.14, respectively. These values indicated that small grain sizes in the plastic deformation mechanism, such as grain boundary sliding and grain boundary rotation, were sensitive to strain rates bigger than those of the larger grain sizes. We found that the stacking fault was formed by partial dislocation in all samples. These stacking faults were obstacles to partial dislocation emission in more sensitive stress rates. Additionally, the results showed that mechanical properties such as yield stress and flow stress increased by increasing the strain rate.

Mechanical comparison of cold-worked versus cold-worked hot-forged dynamic hip screw system

“…However, bigger grain size offers low resistance to fatigue reaching the plastic deformation region. 22 Hall–Petch equation 23 shows the association between yield strength and the grain diameter (equation (4))where σy is yield stress, d is grain diameter, σ0 is stress upon the friction and k refers to a constant coefficient. 23 Based on this equation, increasing the grain diameter would end up in decreasing the yield stress.…”

“…However, bigger grain size offers low resistance to fatigue reaching the plastic deformation region. 22 Hall-Petch equation 23 shows the association between yield strength and the grain diameter (equation ( 4))…”

Development of a Cavitation Generator Mimicking Pistol Shrimp

“…As the dislocation density of cavitation-peened stainless steel was also smaller than that of shot peening at equivalent compressive residual stress conditions, it was found that this is one of reasons why the relaxation of cavitation peening is less than that of shot peening. It was also reported by using tensile testing that the yield stress of stainless steel increased from 6% to 8% with increasing high strain rate [24][25][26][27]. Cavitation peening is a kind of shockwave process that occurs at bubble collapse; thus, the strain rate of cavitation peening is larger than that of shot peening.…”

Molecular Dynamics Study on Adding Tungsten‐Carbide Grains to 304 Stainless Steel Polycrystals

“…The main deformation mechanisms of small-sized grains are grain boundary sliding, grain boundary rotation, and partial dislocations, while the main deformation mechanisms of large-sized grains are extended dislocations and grain boundary rotation. Abdelrahim Husain et al [9,10] studied the mechanical properties of nanocrystalline 316 L stainless steel under tensile load and the effect of strain rate on the plastic deformation mechanism of stainless steel, the main deformation mechanisms of polycrystals are deformation twinning and extended dislocations when grain size is larger than the critical average grain size, and the main deformation mechanisms of polycrystals are grain boundary sliding and grain rotation when the grain size is smaller than the critical average grain size.…”