Fabrication of Metal/Oxide Composites via Internal Oxidation & Severe Plastic Deformation
Abstract
We propose a unique processing route to make thermally stable metal matrix composites with a dispersion of nanometer-sized oxides that starts with bulk alloys, not powders. The oxides will be introduced by in situ internal oxidation and oxidized alloys will be subjected to equal channel angular pressing (ECAP) to homogenize and refine the microstructure. The systems to be studied are Fe-Y and Ni-Y. Our preliminary work in Fe-Y shows rapid internal oxidation occurs with formation of nanoscale Y2O3. The same is expected in Ni-Y. The oxides follow the spatial arrangement of initial alloy microstructure so the alloy microstructure acts as a template for the MMC. By changing alloy composition, we change the size and spacing of the initial oxidized regions. The proposed oxidation experiments will describe the effect of base alloy and oxide size on oxidation kinetics while also creating samples with a variety of oxide sizes and initial distributions for ECAP. The results from Task 1 will contribute to the description of in situ internal oxidation kinetics by studying connection between oxidizing conditions, oxide size, and oxidation rate. These connections are not unique to oxidation; nitridation and carburization would also be possible using similar fundamentals. We will ECAP samples at room temperature with multiple process routes. After ECAP, we will characterize microstructures on length scales from hundreds of ÀÀm (homogeneity of the oxides) to nm (grain and dislocation structure after ECAP). In our preliminary work, oxidized regions of an Fe-Y alloy had larger grains after ECAP. We propose here to test if that was the result of particle stimulated nucleation of recrystallized grains. We will use transmission electron microscopy- automated correlation orientation microscopy (TEMACOM) to examine local (length scale of grains) changes to microstructure due to the presence of the particles. From this we will be able to assess the influence oxide particle size and homogeneity on nucleation of recrystallized grains and the evolution of microstructure during deformation. After assessing mechanical properties and thermal stability we will identify process variables that produce the best-performing materials. If successful this processing scheme will produce Fe- and Ni-based composites with properties previously unattainable without powder metallurgy. The ability to manipulate microstructure over the multiple length scales explored in this work will enable more control over structure, processing and properties for the creation of materials with desirable properties.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810002
Entities
People
- Bryan Webler
Organizations
- Army Contracting Command
- Massachusetts Institute of Technology
- United States Army