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Russian Journal of Non-Ferrous Metals

, Volume 58, Issue 6, pp 639–643 | Cite as

Structural Features of Al–Hf–Sc Master Alloys

  • E. A. Popova
  • P. V. Kotenkov
  • A. B. Shubin
  • E. A. Pastukhov
Physical Metallurgy and Heat Treatment
  • 17 Downloads

Abstract

Microstructural features of new master alloys of the Al–Hf–Sc system with metastable aluminides with a cubic lattice identical to the lattice of a matrix of aluminum alloys are investigated using optical microscopy, scanning electron microscopy, and electron probe microanalysis. Binary and ternary alloys are smelted in a coal resistance furnace in graphite crucibles in argon. Alloys Al–0.96 at % Hf (5.98 wt % Hf) and Al–0.59 at % Hf (3.77 wt % Hf) are prepared with overheating above the liquidus temperature of about 200 and 400 K, respectively. Alloys are poured into a bronze mold, the crystallization rate in which is ~103 K/s. Metastable Al3Hf aluminides with a cubic lattice are formed only in the alloy overheated above the liquidus temperature by 400 K. Overheating of ternary alloys, in which metastable aluminides Al n (Hf1–xSc x ) formed, is 240, 270, and 370 K. Depending on the Hf-to-Sc ratio in the alloy, the fraction of hafnium in aluminides Al n (Hf1–xSc x ) varies from 0.46 to 0.71. Master alloys (at %) Al–0.26Hf–0.29Sc and Al–0.11Hf–0.25Sc (wt %: Al–1.70Hf–0.47Sc and Al–0.75Hf–0.42Sc) have a fine grain structure and metastable aluminides of compositions Al n (Hf0.58Sc0.42) and Al n (Hf0.46Sc0.54), respectively. Sizes of aluminides do not exceed 12 and 7 μm. Their lattice mismatch with a matrix of aluminum alloys is smaller than that for Al3Sc. This makes it possible to assume that experimental Al–Hf–Sc master alloys manifest a high modifying effect with their further use. In addition, the substitution of high-cost scandium with hafnium in master alloys can considerably reduce the consumption of the latter.

Keywords

Al–Hf–Sc system alloys metastable aluminides cubic lattice supersaturated solid solutions 

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Copyright information

© Allerton Press, Inc. 2017

Authors and Affiliations

  • E. A. Popova
    • 1
  • P. V. Kotenkov
    • 1
    • 2
  • A. B. Shubin
    • 1
  • E. A. Pastukhov
    • 1
  1. 1.Institute of Metallurgy, Ural BranchRussian Academy of SciencesYekaterinburgRussia
  2. 2.Ural Federal UniversityYekaterinburgRussia

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