CC BY
19XV International Symposium on Self-Propagating High-Temperature Synthesis
SHS AND SPS CONSOLIDATION OF COMPLEX COMPOSITIONAL REFRACTORY ALLOYS
S. Dine", V. Kentheswaran", G. Dirras", and D. Vrel*"
aLSPM, UPR 3407 CNRS, Villetaneuse, 93430 France *e-mail: dominique.vrel@lspm.cnrs.fr
DOI: 10.24411/9999-0014A-2019-10032
Complex compositional alloys (CCAs) are a recent breakthrough in material science. Classical metallurgy indeed focuses on alloys made of a single main element, to which different alloying elements may be added in small proportions; in addition, binary phase diagrams have been extensively studied, but the practical use of alloys rich in at least 2 elements is mainly focused on specific compositions such as eutectics or intermetallics. In sharp contrast, CCAs, often called high entropy alloys when, depending on the author, 4 or 5 (or more) elements are considered, are made with compositions where all the elements can be considered as principal, with an atomic content of each element ranging from 5 to 30%.
Following our researches on tungsten (S. Dine et al., this conference), we have thus been studying the synthesis of refractory CCAs, by co-reducing various oxides of metals, including WO3, Ta2O5, MoO3, Nb2O5, Cr2O3, and V2O5, to produce binary, ternary or quaternary solid solutions, all these elements having a bcc crystal structure.
Mixtures of these oxides, magnesium and a moderator (NaCl or MgO), for a total mass sample of up to 1.2 kg were ignited after a thorough mixing, using a newly developed water cooled SHS reactor. The resulting products, made of metallic alloys, magnesia and possibly salt were then lixiviated in a hydrochloric acid solution to dissolve salt and magnesia, then filtered. To insure the purity of the final product, this step has been repeated, and a third filtering finally performed after rinsing. The resulting powders are then dried, softly grinded, and then densified using spark plasma sintering.
Results concerning binary, ternary and quaternary alloys will be presented, with a description of the influence of the size of the sample on the purity, the microstructure and the crystal structure of the resulting products. Finally, a methodology for the optimisation of the composition of the alloys and resulting preliminary results will also be presented.
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