Differential thermal analysis (DTA) and microstructural and microprobe measurements of DTA and as-cast Ni-Re alloys with compositions between 0.20 and 0.44 mass fraction Re provide information to resolve differences in previously published Ni-Re phase diagrams. This investigation determines that the peritectic invariant between liquid, Re-rich hexagonal close packed and Ni-rich face center cubic phases, L + HCP → FCC, occurs at 1561.1 °C ± 3.4 °C (1σ) with compositions of liquid, FCC and HCP phases of 0.283 ± 0.036, 0.436 ± 0.026, and 0.828 ± 0.037 mass fraction Re, respectively. Analysis of the microsegregation in FCC alloys yields a partition coefficient for solidification, k = 1.54 ± 0.09 (mass frac./mass frac.). A small deviation from Scheil behavior due to dendrite tip kinetics is documented in as-cast samples. No evidence of an intermetallic phase is observed.
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William J. Boettinger acknowledges support from the U.S. Department of Commerce, National Institute of Standards and Technology, under financial assistance Award 70NANB15H279. The DTA measurements of K. Hildal and T. Sossaman, Department of Materials Science and Engineering, University of Wisconsin, the metallographic preparation of Sandra Claggett and the initial TEM work by Yaakov Idell, NIST, are greatly appreciated. Michael Katz is employed by the University of Maryland and is supported by NIST Grant 70NANB16H003.
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