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37XV International Symposium on Self-Propagating High-Temperature Synthesis
STRUCTURAL EVOLUTION AND MAGNETIC PROPERTIES OF HIGH ENTROPY CuCrFeTiNi ALLOYS PREPARED BY MECHANICAL ALLOYING AND SPS
N. F. Shkodich*"'0, M. Spasovac, M. Farlec, D. Yu. Kovalev", A. A. Nepapushev0, K. V. Kuskov0, Yu. S. Vergunova0, Yu. B. Scheck", and A. S. Rogachev"0
aMerzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow, 142432 Russia
bCenter of Functional Nano-Ceramics, National University of Science and Technology MISIS, Moscow, 119049 Russia
cFaculty of Physics and Center of Nanointegration (CENIDE), University of Duisburg-Essen, Duisburg, 47057 Germany *e-mail: [email protected]
DOI: 10.24411/9999-0014A-2019-10160
A novel approach to the fabrication of a new class of alloys—also known as high-entropy alloys (HEAs)—was developed by Yeh et al. [1-3]. The HEAs containing at least 5 components in equiatomic or nearly equiatomic amounts (ranging between 5 and 35 at %) are attractive in terms of hardness, wear resistance, high-temperature strength, corrosion resistance, low-temperature ductility, glass forming ability, super-plasticity, and some magnetic properties [4, 5]. These HEA are stabilized by the increase of the mixing entropy which is thought to suppress the formation of metallic phases and thus favors the formation of simple solid solutions with a fcc or bcc or bcc + fcc structure.
HEAs have been fabricated by several methods, including arc melting and casting, mechanical alloying, and laser cladding [6-8]. Among these, especially promising seems to be high-energy ball milling (HEBM) in planetary ball mills that can yield stable microstructures and nanocrystalline alloys of better homogeneity compared to other non-equilibrium processes. In this communication, we report the first preparation of CuCrFeTiNi HEA particles by high-energy ball milling (HEBM) and spark plasma sintering (SPS) and provide a structural and magnetic characterization. The powder of equiatomic CuCrFeTiNi high-entropy alloy was prepared by short-term HEBM. Our XRD, SEM, and EDX results showed that a bcc CuCrFeTiNi solid solution with refined microstructure of nanosized grains (~ 6 nm) could be obtained starting from 30 min of HEBM. Produced HEA powders were studied by DSC and showed a thermal stability of up to 500°C. The as-milled HEA powder was subsequently consolidated by spark plasma sintering at 700°C, and the bcc and fcc phases were found to coexist in consolidated HEA. The kinetics and structural transformations upon heating to 1000°C were studied by high-temperature X-ray diffraction (HTXRD) (Fig. 1).
The Vickers hardness of the HEA CuCrFeTiNi alloy (milled for t = 180 min) consolidated by SPS was markedly higher (7.7 GPa) than that of SPS-produced ones without HEBM (2.1 GPa). Electrical resistance of consolidated CuCrFeTiNi alloys was 10-6 Q m. The influence of HEBM duration on the magnetic properties of HEA powders were determined at different temperatures. The HEA powder formed after 180 min of HEBM exhibited paramagnetic behavior at room temperature with a small ferromagnetic contribution at low fields: small hysteresis is observed at 5 K and 300 K with a coercive field of around 16 kA/m. Above 100 K, the inverse susceptibility of HEA powder (t = 240 min) shows the linear response to increasing temperature typical of paramagnets. A Curie temperature Tc = 50 K was measured.
iSHS 2019
Moscow, Russia
Fig. 1. High-temperature XRD for CuCrFeTiNi powder mixtures milled for 180 min.
We thank M. Acet and U. Wiedwald for helpful discussions and G.V. Trusov., and I. D.
Kovalev for their kind help in experiments. This work was financially supported by Russian
Foundation for Basic Research through grant 18-53-15006.
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