Cast Al-Ce based Eutectic Alloys with High Creep Resistance
Tiffany Wu ,*Yang Liu, and *Daniel Ng,
co-advised by Dr. Alex Plotkowski and Dr. Ryan Dehoff, Oak Ridge National Laboratory
Previous studies on Al-Ce-Mg alloys have demonstrated thermal stability of Ce-rich eutectic strengthening phases up to 540°C. These results show promise for the development of Al-Ce alloys which maintain their strength at elevated temperatures. Our work involves microstructural investigations and compression creep testing of Al-Ce binary alloys, with the goal of studying how Ce additions may be utilized to develop alloys with enhanced creep resistance. Initial microstructural investigations have revealed a coarse grain structure with millimeter-scale grains expected to be resistant to diffusional creep. In addition, we observe a fine dispersion of eutectic Ce-rich phases which provide strength to the alloy. During compression creep testing at 300°, we have observed creep deformation at lower rates and higher stresses than those of Er-free L12 -strengthened alloys extensively studied in our group, suggesting that Ce-additions may be used in developing the next generation of creep-resistant aluminum alloys.
With promising creep- and coarsening resistance, the two binary eutectic systems, Al-Ni and Al-Ce, are combined into a ternary Al-Ce-Ni eutectics. Microhardness and microstructure evolution demonstrate excellent coarsening up to 425?C, with a gradual decrease in microhardness over long times. The sub-micron eutectic Al11Ce3 phase shows superior thermal stability and maintain its submicron fiber morphology, whereas the sub-micron eutectic Al3Ni rods coarsen faster into equiaxed micron-size precipitates. Creep resistance of as-cast eutectic Al-Ce-Ni at 300?C is comparable with binary eutectic Al-Ni and higher than binary eutectic Al-Ce. Overaged samples show higher creep rates than as-cast states due to their coarsened microstructures, but retains significant creep resistance, implying that load transfer is an important strengthening mechanism.
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- D. S. Ng and D. C. Dunand, "Coarsening- and Creep-Resistant Cast Hypoeutectic Al-Ce-Mg Alloy," SSRN Journal, 2019, doi: 10.2139/ssrn.3485043.
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- Oak Ridge National Laboratory