AN ATOMIC BONDING INFORMED APPROACH TO REWRITE THE RULES OF SOLID-SOLUTION AND PRECIPITATION STRENGTHENING
Abstract
Classical solid solution and precipitation strengthening models in alloys are indispensible in quantifying the overall balance of mechanical properties. However, the classical models did not include the influence of local electronic structure and atomic bonding between solute and solvent atoms as well as across precipitate/matrix interfaces, and do not explicitly factor short-range solute-solute and solute-solvent interactions, which if covalent in character will significantly increase the local (as opposed to bulk) stiffness of the material, and strongly influence defect interaction with solute/solvent atoms. Our extensive density functional theory (DFT) based calculations have clearly demonstrated that such localized bonding character, identified by the anisotropic localization of valence electrons along specific crystallographic directions, affect phase stability, the nature of precipitate/matrix interfaces, and defect processes driving deformation. These studies beg a fundamental question – How will such localized covalent bond character influence solid solution and precipitation strengthening? We answer this question through the study of two model alloys – a substitutional Ti binary alloy and an intermetallic Ni3Al intermetallic with a ternary solute substitution – that have well-known strengthening models based on size and modulus mismatch between the constituent solute and solvent atoms. Our proposal has four thrust areas which couple experiments with DFT and large-scale semi-empirical molecular dynamics (MD) simulations to (1) validate and quantify covalent-like bond character in solid solutions and intermetallics, (2) Create DFT validated semi-empirical interatomic potential framework that incorporate solute atom induced changes to the shape of local electron densities, and (3) use these new potentials to correlate systematically the effect of such covalent character on alloy deformation using large-scale MD simulations.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2021
- Source ID
- FA95502010169
Entities
People
- S. Srinivasan
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of North Texas