Bonding, Energetics and Mechanical Properties of Intermetallics

Abstract

Abstract : The objective of this research was to investigate fundamental aspects of the fracture and deformation behavior of ordered intermetallic aerospace alloys on the basis of the ab-initio determination of the parameters needed for further (1) model theoretical, (2) band structure and (3) chemical bonding analyses. The research was targeted at investigating the microscopic mechanisms governing the deformation and fracture behavior of intermetallic alloys in order to contribute to the development of a fundamental basis for computer-aided alloys design. Progress in this complex area required understanding such key phenomena as dislocation structure and mobility, and crack blunting and propagation: while they have been characterized by mesoscopic length and energy scales, they are determined on the microscopic level by the electronic structure. Thus, this most important and challenging component of our research was to bridge the gap between a microscopic quantum-mechanical description of the chemical bonding and the mesoscopic phenomena which govern the mechanical response of intermetallics. Especially for intermetallic compounds and metals of interest. we concentrated on (1) fundamental aspects of dislocation structure and mobility; (2) solid-solution hardening problems in the context of the fundamental aspects of impurity dislocation interaction theory; (3) the electronic structure of dislocations and related properties of real crystals. These important. complex problems required the use of a hierarchy of methods. We focussed on the application and further development of both state-of-the-art band structure and real-space large scale cluster electronic structure methods which provide parameters needed for atomistic simulations and model mesoscopic simulations. In this way, we greatly amplified the impact of our research based on our quantum-mechanical electronic structure simulations.