Grain Boundary/Interface Structure and Chemistry in Nanoscale Materials Prepared by Mechanical Attrition

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Nanoscale interfaces are examined in both single phase materials and multiphase materials. The goal is to obtain a better understanding of the atomic level structure and chemistry of interfaces in nanostructured materials. An initial comparison is made between grain boundary structures, energies and hardness in an iron-based alloy as a function of grain size and preparation technique (gas atomization and mechanical attrition). Intermetallic alloys and composites are included in the research for comparison to the single phase alloys. Deformation and grain refinement are followed as a function of mechanical attrition variables in multiphase alloys, including composites. Several techniques are used to characterize the nanostructured state: X-ray diffraction, transmission electron microscopy, high resolution electron microscopy for interface structure, and differential scanning calorimetry to measure the stored enthalpy of deformation. %%% This research examines the processing, structure, and chemistry of nanostructured materials. This is a new class of materials that can possess unique properties because of the extremely fine grain size developed in the processed structure. The research also examines the mechanical alloying process used in producing commercial quantities of metal alloys.