Structural Features of Al–Hf–Sc Master Alloys
Autor: | P. V. Kotenkov, E. A. Pastukhov, E. A. Popova, A. B. Shubin |
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Rok vydání: | 2017 |
Předmět: |
Materials science
Scanning electron microscope 020502 materials Alloy Metals and Alloys Analytical chemistry chemistry.chemical_element 02 engineering and technology Liquidus engineering.material 021001 nanoscience & nanotechnology Surfaces Coatings and Films Hafnium 0205 materials engineering chemistry Mechanics of Materials Aluminium engineering Scandium Graphite 0210 nano-technology Ternary operation |
Zdroj: | Russian Journal of Non-Ferrous Metals. 58:639-643 |
ISSN: | 1934-970X 1067-8212 |
Popis: | 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. |
Databáze: | OpenAIRE |
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