Theoretical Studies of the Electronic Structure and Mechanical Properties of Intermetallics

摘要

It is now clear that the high temperature intermetallics have become a major focus of research effort -both experimental and theoretical- driven in large part by their potential for important aerospace applications at elevated temperatures. State-of-the-art first-principles total-energy electronic structure calculations based on the full-potential linear-muffin-tin-orbital method were employed to study systematically issues of metallurgical nature, such as bonding, cohesion and phase stability and the role of ternary additions on their electronic and mechanical properties. More specifically, we have investigated: 1) The effect of impurities (boron and hydrogen) in Ni3 Al; 2) The contrasting effect of boron and sulfur impurities on the ideal cleavage fracture; 3) The variation of the elastic constants with chemical environment across the Ni3 X(X = Al, Si, Ga, Mn) intermetallics and their correlation to plastic deformation; and 4) The anisotropy of the antiphase boundary (APB) energy between the (001) and (111) slip planes, responsible for the anomalous temperature dependence of the yield strength.