Tomohito Tsuru

Atomistic simulations of (001), (110), and (111) nanoindentation are performed to investigate anisotropic effects in elastic and incipient plastic behavior under nanoindentation. We compared two materials, single-crystalline Al and Cu, focusing on the large difference between their anisotropic properties. The indent load-depth behavior of Al during elastic deformation exhibits slight anisotropy, while that of Cu varies greatly according to the indentation axis. In addition, incipient plastic def

Aluminium alloys are re-evaluated as most feasible way to satisfy the industrial needs of light-weight structural materials. However, unlike conventional structural metals such as iron and titanium, aluminium does not have easily accessible secondary phases, which means that aluminium-based alloys cannot be strengthened by harnessing multiple phases. This leaves age hardening as the only feasible strengthening approach. Highly concentrated precipitates generated by age hardening generally play a

Solution strengthening is a well-known approach to tailoring the mechanical properties of structural alloys. Ultimately, the properties of the dislocation/solute interaction are rooted in the electronic structure of the alloy. Accordingly, we compute the electronic structure associated with, and the energy barriers to dislocation cross-slip. The energy barriers so obtained can be used in the development of multiscale models for dislocation mediated plasticity. The computed electronic structure c

Refractory high-entropy alloys (RHEAs) are of interest for ultrahigh-temperature applications. To overcome their drawbacks - low-temperature brittleness and poor creep strength at high temperatures - improved fundamental understanding is needed. Using experiments, theory, and modeling, we investigated prototypical body-centered cubic (BCC) RHEAs, TiZrHfNbTa and VNbMoTaW. The former is compressible to 77 K, whereas the latter is not below 298 K. Hexagonal close-packed (HCP) elements in TiZrHfNbTa

There is a pressing need to improve the ductility of magnesium alloys so that they can be applied as lightweight structural materials. In this study, a mechanism for enhancing the ductility of magnesium alloys has been pursued using the atomistic method. The generalized stacking fault (GSF) energies for basal and prismatic planes in magnesium were calculated by using density functional theory, and the effect of the GSF energy on the dislocation core structures was examined using a semidiscrete v

Preliminary simulations of simple shear deformation and indentation simulations using different radii of a spherical indenter are performed using molecular dynamics in order to uncover the internal stress state for elastic deformation and subsequent initial plasticity under nano-indentation. An atomic single-crystalline aluminium model containing up to 1,372,000 atoms and an ideal friction-free spherical indenter are presented in a set of simulations. Effects of the stress distribution using sev

An incipient plastic deformation of several types of grain boundaries subjected to nanoindentation was investigated by atomistic simulations. Our previous study showed that the dislocation nucleation in the inner region of the defect-free metals occurs when the resolved shear stress exceeds a particular stress level slightly higher than the ideal shear strength. However, crystal defects such as grain boundaries undermine the nucleation resistance. In this paper, we examined the dislocation nucle

The interaction between dislocations and grain boundaries is the principal factor for determining the mechanical properties and the plastic deformation behavior of metals. It is possible to control the grain-boundary microstructure and the macroscopic behavior has been widely exploited for scientific and industrial applications. In atomic scale, however, specific interaction characteristics such as the reaction energy and pathway have yet to be revealed. We have investigated the interaction proc