Mechanical mechanism and deformation behavior of polycrystalline and gradient Ni50−xTi50Alx alloys using molecular dynamics

Chang, Man-Ping; Lu, Yu-Sheng; Fang, Te‐Hua

doi:10.1016/j.mtcomm.2021.102724

Cited by 5 publications

(4 citation statements)

References 54 publications

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“…The results reveal that shear strain mainly propagates through grain boundaries. For samples with a small GNG, the smaller the grain size, the greater the grain boundary density and the wider the shear strain diffusion range into the material’s interior [ 26 ]. As the average grain size of the GNG sample increases, the range of shear strain influence decreases, and the internal strain gradually converges within the grain boundaries and in front of the tool.…”

Section: Resultsmentioning

confidence: 99%

Effects of cutting tool geometry on material removal of a gradient nanograined CoCrNi medium entropy alloy

Lu,

Hung,

Bui

et al. 2024

Beilstein J. Nanotechnol.

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CoCrNi medium-entropy alloys (MEAs) have attracted extensive attention and research because of their superior mechanical properties, such as higher ductility, strength, and toughness. This study uses molecular dynamics (MD) simulations to investigate the cutting behavior of a gradient nanograined (GNG) CoCrNi MEA. Moreover, it explores the influence of relative tool sharpness and rake angle on the cutting process. The results show that an increase in the average grain size of the GNG samples leads to a decrease in the average resultant cutting force, as predicted by the Hall–Petch relationship. The deformation behavior shows that grain boundaries are crucial in inhibiting the propagation of strain and stress. As the average grain size of the GNG sample increases, the range of shear strain distribution and average von Mises stress decreases. Moreover, the cutting chips become thinner and longer. The subsurface damage is limited to a shallow layer at the surface. Since thermal energy is generated in the high grain boundary density, the temperature of the contact zone between the substrate and the cutting tool increases as the GNG size decreases. The cutting chips removed from the GNG CoCrNi MEA substrates will transform into a mixed structure of face-centered cubic and hexagonally close-packed phases. The sliding and twisting of grain boundaries and the merging of grains are essential mechanisms for polycrystalline deformation. Regarding the cutting parameters, the average resultant force, the material accumulation, and the chip volume increase significantly with the increase in cutting depth. In contrast to sharp tools, which mainly use shear deformation, blunt tools remove material by plowing, and the cutting force increases with the increase in cutting-edge radius and negative rake angle.

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Section: Resultsmentioning

confidence: 99%

Effects of cutting tool geometry on material removal of a gradient nanograined CoCrNi medium entropy alloy

Lu,

Hung,

Bui

et al. 2024

Beilstein J. Nanotechnol.

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“…The influence of grain gradient size on the microstructure of new morphological HEA materials is a topic of excellent research potential. Previous studies have indicated that the technology for designing gradient nanostructured substrates and processing simulation by MD is mature [23,24]. Therefore, this study investigates the effects of small to large gradient nano-grained (GNG) structures, large to small GNG structures, and cutting velocities on the machining performance of CoCrFeMnNi HEA.…”

Section: Introductionmentioning

confidence: 99%

Effects of grain boundary and gradient structure on machining property of CoCrFeMnNi alloys

Lu,

Bui,

Fang

2024

Modelling Simul. Mater. Sci. Eng.

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CoCrFeMnNi high-entropy alloy (HEA) has a high degree of thermodynamic stability and excellent ductility, making it a crucial structural material. However, the plastic deformation and microstructural behavior of gradient grain structured CoCrFeMnNi HEA under cutting remain unclear. In this study, the machining properties of gradient nanostructured CoCrFeMnNi HEA under conventional cutting were investigated by molecular dynamics (MD) simulation. The results displayed that the small grain gradient samples exhibited grain size softening. The shear angle and cutting ratio increased with the increase in the grain gradient. The grain boundaries of the low grain gradient samples were damaged and slid during the cutting process. Moreover, the dislocation density increased with the increasing grain gradient. The multi-dislocation nodes and the Lomer-Cottrell junction were produced in the grain coarsening gradient samples, contributing to work hardening. The cutting forces from low to high cutting velocities were 136.70, 147.91, 165.82, and 164.79 nN, which confirmed that the cutting forces increased with increased cutting velocity. This work elucidated the cutting mechanism of the nanostructured CoCrFeMnNi HEA and highlighted the influence of the gradient grain sizes.

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“…Chen et al [30] conducted MD simulations on the effects of varying Co content and temperature on the shear mechanical properties of Ni-Co alloys and found that the incorporation of Co atoms into pure Ni causes lattice distortion, increasing the resistance to dislocation motion and thereby enhancing the material's strength. Chang et al [31] utilized MD simulations to investigate the impact of grain size, temperature, and gradient Al content on the deformation mechanism of Ni 50-x Ti 50 Al x polycrystalline alloys, identifying the content of Al atoms and temperature as primary factors affecting the material's failure mechanism. Numerous studies have shown that inclusions are one of the key factors affecting the mechanical properties of materials [32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Effect of Bi content and temperature on the shear mechanical properties of Fe-Bi nanocomposites: a molecular dynamics study

Li,

Wang,

et al. 2024

Modelling Simul. Mater. Sci. Eng.

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In this study, the effects of Bi content and temperature on the mechanical properties of Fe-Bi nanocomposites were investigated using molecular dynamics simulation. The research reveals that the nanocomposite's shear strength reaches a peak of 3.785 GPa at a Bi content of 0.15%, attributed to the impediment of dislocation movement by twin boundaries during shearing, resulting in a dynamic "Hall-Petch" effect and exceptional shear performance of the material. The abundant twinning induced around Bi phase inclusions introduces orientational disparities within the crystal, leading to grain misalignments, with dislocations in the grains slipping near the twin boundaries. In the nanocomposites, <100>dislocations merely act as initial sites for reactions, reducing their impact on the material's strength and fracture behavior. The maximum stress decreases with increasing temperature while the magnitude of atomic transformations increases. The proportion of atoms at grain boundaries is higher at higher temperatures, and the arrangement of atoms at grain boundaries is more complex. At a temperature of 100K, the dislocation density is highest with the smallest variation, forming a reinforced region within the material. The above results have significant implications for the design of environmentally friendly Bi-containing free-cutting steels.

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Mechanical mechanism and deformation behavior of polycrystalline and gradient Ni50−xTi50Alx alloys using molecular dynamics

Cited by 5 publications

References 54 publications

Effects of cutting tool geometry on material removal of a gradient nanograined CoCrNi medium entropy alloy

Effects of cutting tool geometry on material removal of a gradient nanograined CoCrNi medium entropy alloy

Effects of grain boundary and gradient structure on machining property of CoCrFeMnNi alloys

Effect of Bi content and temperature on the shear mechanical properties of Fe-Bi nanocomposites: a molecular dynamics study

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