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Development Of Precipitation Hardenable Al-Sc-Zr-Hf Quaternary Alloys Through Thermodynamic Modeling, And Room-Temperature And Elevated Temperature Hardness, Matthew J. Wong

Dissertations, Master's Theses and Master's Reports - Open

Aluminum alloyed with small atomic fractions of Sc, Zr, and Hf has been shown to exhibit high temperature microstructural stability that may improve high temperature mechanical behavior. These quaternary alloys were designed using thermodynamic modeling to increase the volume fraction of precipitated tri-aluminide phases to improve thermal stability. When aged during a multi-step, isochronal heat treatment, two compositions showed a secondary room-temperature hardness peak up to 700 MPa at 450°C. Elevated temperature hardness profiles also indicated an increase in hardness from 200-300°C, attributed to the precipitation of Al₃Sc, however, no secondary hardness response was observed from the Al …