Shidong Feng

Effect of Voronoi volume on fluctuation at initial deformation of amorphous alloys

Quasi-static compressive behaviors of three amorphous alloys (Cu 50Zr50, Pd80Si20, and Ni 67Zr33) are investigated via molecular dynamics simulations. Compared to the crystalline counterpart, when the strain is below 1%, significant fluctuations can be observed in the stress-strain curves. Further analysis of the simulated data indicates that the fluctuations are associated with the variations of Voronoi volume. A gradient reduction model is proposed to explain the process of the evolution of Voronoi volume at the initial stage of the deformation.

Effects of Aspect Ratio on the Shear Band Arrangements of Zr-Based Metallic Glasses

Effects of aspect ratios of Zr-based metallic glasses on the shear band arrangements are investigated through molecular dynamics simulations and experiments. It is found that as the aspect ratio decreases, the dense multiple shear bands form, effectively depressing the formation of the penetrating shear bands, which improves plasticity and strength of metallic glass. Simulation reproduces the images of the evolution of the shear bands in metallic glass, explaining the experimental observation. It is found that as the aspect ratio decreases, shear transformation zones disperse evenly in the entire model, restraining connecting into penetrating shear bands.

Relationship between Voronoi entropy and the viscosity of Zr36Cu64 alloy melt based on molecular dynamics

Molecular dynamics simulation is used to investigate the relationship between Voronoi entropy and viscosity for rapid solidification processing of Zr36Cu64 binary alloy melt. The simulation results at different temperatures, cooling rates, and pressures, show that Voronoi entropy is able to accurately describe the relationship of the transition between the cluster structure and the viscosity of Zr36Cu64 binary alloy melt through Voronoi polyhedron analysis. That is, the higher the degree of order of the microstructure, the lower the Voronoi entropy is and the higher the viscosity is. The simulation provides an important reference for studying metallic glass with high glass-forming ability.

Molecular dynamics simulation of structural characterization of elastic and inelastic deformation in ZrCu metallic glasses

The nanoscopic deformation behaviors in a ZrCu metallic glass model during loading-unloading process under uniaxial compression have been analyzed on the basis of the molecular dynamics (MD). The reversible degree of shear origin zones (SOZs) is used as the structural indicator to distinguish the elastic deformation and inelastic deformation of ZrCu metallic glass at the atomic level. We find that the formation of SOZs is reversible at the elastic stage but irreversible at the inelastic stage during the loading and unloading processes. At the inelastic stage, the full-icosahedra fraction in SOZs is quickly reduced with increased strain and the decreasing process is also irreversible during the unloading processes.

Pressure-induced Structures and Structural Evolution in Iron

Molecular-dynamic simulations have been used to study the structure evolution in iron melts rapidly cooled under different pressures. An extreme cooling rate (4×1012K/s) was adopted in the cooling process. The simulation results show that at the ambient pressure, martensitic transformation happened. However, at a pressure of 1.4GPa, the system passes from bcc structure to a less closed packed structure which is composed of both full icosahedra clusters and bcc structure. With the increase of pressures, an amorphous state was observed, and a compacted local structure with more defected icosahedra is obtained. This work contributes to a better understanding about the dynamics of phase transitions in iron under high pressure, especially during the extremely fast cooling process.

Effects of Forming Pores on Mechanical Property of Zr70Cu30 Metallic Glass

Effects of forming pores in Zr70Cu30 metallic glass on the deformation behaviour is investigated through molecular dynamics simulations. The formation of pores leads to only a small reduction in strength, but dramatically enhanced plasticity in compression. The large plasticity of glass is attributed to the large effective free space induced by forming pores. It can also promote formation of crystalline phases in the amorphous matrix during deformation. Simulation reproduces the images of the evolution of pores in the metallic glass. The simulation results are in good agreement with experimental results.