Correlation-Space Description of the Percolation Transition in Composite Microstructures

We explore the percolation threshold shift as short-range correlations are introduced and systematically varied in binary composites. Two complementary representations of the correlations are developed in terms of the distribution of phase bonds or, alternatively, using a set of appropriate short-range order parameters. In either case, systematic exploration of the correlation space reveals a boundary that separates percolating from nonpercolating structures and permits empirical equations that identify the location of the threshold for systems of arbitrary short-range correlation states. Two- and three-dimensional site lattices with two-body correlations, as well as a two-dimensional hexagonal bond network with three-body correlations, are explored. The approach presented here should be generalizable to more complex correlation states, including higher-order and longer-range correlations

Analysis of Precipitate Redistribution in Inconel 617 Using Integrated Electron Backscatter Diffraction and Energy Dispersive Spectroscopy

Inconel 617 (IN617), a candidate alloy for applications in the Next Generation Nuclear Plant, derives its oxidation resistance and strength at temperatures above 900°C from both solid solution strengthening and the precipitation of carbides [1]. Cr-rich carbides (usually M23C6) reside primarily on grain boundaries, while Mo-rich carbides (usually M6C) tend to be within grains [1-4]. Both intragranular and intergranular carbides play an important role in the creep behavior of the alloy [1]. During creep, intragranular carbides can dissolve and re-precipitate at grain boundaries, especially on boundaries in tension [1]. While the precipitate distribution before and after creep deformation has been investigated, the role of grain boundary character has not been included in the analysis

Data Management Plan for Graduate Identity Formation Through Teaching

Data management plan for NSF Education and Human Resources (EHR) Innovations in Graduate Education (IGE) Program Proposa

Influence of Grain Boundary Character on Creep Void Formation in Alloy 617

Alloy 617, a high temperature creep-resistant, nickel-based alloy, is being considered for the primary heat exchanger for the Next Generation Nuclear Plant (NGNP) which will operate at temperatures exceeding 760oC. Orientation imaging microscopy (OIM) is used to characterize the grain boundaries in the vicinity of creep voids that develop during high temperature creep tests (800-1000oC at creep stresses ranging from 20-85 MPa) terminated at creep strains ranging from 5-40%. Observations using optical microscopy indicate creep rate does not significantly influence the creep void fraction at a given creep strain. Preliminary analysis of the OIM data indicates voids tend to form on grain boundaries parallel, perpendicular or 45o to the tensile axis, while few voids are found at intermediate inclinations to the tensile axis. Random grain boundaries intersect most voids while CSL-related grain boundaries did not appear to be consistently associated with void development

Powder-Route Synthesis and Mechanical Testing of Ultrafine Grain Tungsten Alloys

We report a W-rich alloy (W-7Cr-9Fe, at. pct) produced by high-energy ball milling, with alloying additions that both lower the densification temperature and retard grain growth. The alloy’s consolidation behavior and the resultant compacts’ microstructure and mechanical properties are explored. Under one condition, a 98 pct dense compact with a mean grain size of 130 nm was achieved, and exhibited a hardness of 13.5 GPa, a dynamic uniaxial yield strength of 4.14 GPa in Kolsky bar experiments, and signs of structural shear localization during deformation.United States. Defense Threat Reduction Agency (Grant No. HDTRA1-11-1-0062)United States. Department of Defense (NDSEG fellowship program