Experimental Determination of the Allotropic Transition Temperature Between Tetragonal and Orthorhombic Al4Sm Metastable Phases
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The allotropic transition temperature associated with the metastable γ-Al4Sm (orthorhombic) and β-Al4Sm (tetragonal) phases was investigated experimentally. Low-energy X-ray diffraction and differential scanning calorimetry were found to be inconclusive due to the transient nature of the phases involved, which spontaneously decompose to the stable δ-Al3Sm and Al-fcc phases. High-energy X-ray diffraction, using synchrotron radiation, however, was able to resolve the transition during continuous heating, enabling detailed analysis of the temperature-dependent diffraction pattern. The γ-β transition temperature was determined to be 896 K, based on a well-resolved transition onset.
This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. The research was performed at the Ames Laboratory, which is operated for the U.S. DOE by Iowa State University under contract No. DE-AC02-07CH11358. The high-energy X-ray experiments were performed at the XOR beamline (sector 1) of the Advanced Photon Source, Argonne National Laboratory, under Grant No. DE-AC02-06CH11357. Yang acknowledges financial support from International Cooperation and Exchanges of National Natural Science Foundation of China (Grant No. 51611130058).
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