UC Berkeley

Several mesoscale models have been developed to consider

a number of mechanical properties and microstructures

of Ti-V approximants to Gum Metal and steels from the atomistic scale.

In Gum Metal, the relationships between phonon properties

and phase stabilities are studied. Our results show that

it is possible to design a BCC (&beta-phase)

alloy that deforms near the ideal strength,

while maintaining structural stability

with respect to the formation of the &omega

and &alpha'' phases. Theoretical diffraction patterns reveal

the role of the soft N-point phonon

and the BCC-to-HCP transformation

path in post-deformation samples. The total energies

of the path explain the formation of the giant faults

and nano shearbands in Gum Metal.

In the study of steels, we focus on the carbon-solute dislocation

interactions. The analysis covers the Eshelby's model of point defects

and first principles calculations. It is argued that the effects

of chemistry and magnetism, omitted in the elasticity model,

do not make major contributions to the segregation energy.

The predicted solute atmospheres are in good agreement

with atom probe measurements.