Predicting Aspects of Mechanical Behavior via Fundamental Electronic Structure Characteristics of Homogeneous Phases and Intrinsic Interfaces
Abstract
To fulfill the great potential of intermetallic alloys for high temperature structural applications, it is necessary to understand the mechanisms controlling their mechanical behavior on the microscopic level, including such key phenomena as dislocation structure and mobility. We focused on the mechanical behavior of homogeneous intermetallics with L1(sub 2) and B2 structures and on two-phase gamma/gamma' alloys. Based on highly-accurate total energy calculations and large-scale Peierls-Nabarro modeling, the relation between electronic structure, phase stability and dislocation structure was investigated in the context of yield stress temperature anomaly (YSA) phenomena, which play a key role in high temperature applications of intermetallic alloys. The superdislocation structure in Ni3Al, Ni3Ge and Fe3Ge was studied and the lack of a yield stress temperature anomaly in Fe3Ge explained. The energetics of the interaction of the ?100! edge and screw dislocation in NiAl with different kinds of impurities (Ti, V, Cr, Mn, Zr, Mo, Si, Ge and Ga) was studied and the nature of the "extra" solid solution hardening effect caused by d-element impurities was understood. The origin of the "small" and "large" rhenium effects in Cr-Re alloys was investigated and their mechanisms were proposed. The interfacial strength of NiAl/Mo eutectic interfaces was studied and the detrimental effect of the misfit dislocations on it, leading to the interface debonding, was established. The connection between the low temperature yield stress anomaly in Pt3X alloys with a structural instability rather than with features of the dislocation structure in the L1(sub 2) phase was demonstrated. The dislocation structure and character of the yield stress temperature dependence in Ir-based L1(sub 2) alloys was predicted. The dislocation structure and energetics in B2 Co-base intermetallics was determined and slip modes operating in these alloys explained.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 29, 2004
- Accession Number
- ADA427674
Entities
People
- Authur J. Freeman
Organizations
- Northwestern University