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The effect of scandium ternary intergrain precipitates in Al-containing high-entropy alloys

DOI: 10.3390/e20070488 DOI Help

Authors: Sephira Riva (Swansea University) , Shahin Mehraban (Swansea University) , Nicholas P. Lavery (Swansea University) , Stefan Schwarzmüller (Leipzig University) , Oliver Oeckler (Leipzig University) , Stephen G. R. Brown (Swansea University) , Kirill V. Yusenko (Swansea University; Institute of Solid State Chemistry)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Entropy , VOL 20

State: Published (Approved)
Published: June 2018
Diamond Proposal Number(s): 13987

Open Access Open Access

Abstract: We investigate the effect of alloying with scandium on microstructure, high-temperature phase stability, electron transport, and mechanical properties of the Al2CoCrFeNi, Al0.5CoCrCuFeNi, and AlCoCrCu0.5FeNi high-entropy alloys. Out of the three model alloys, Al2CoCrFeNi adopts a disordered CsCl structure type. Both of the six-component alloys contain a mixture of body-centered cubic (bcc) and face centered cubic (fcc) phases. The comparison between in situ high-temperature powder diffraction data and ex situ data from heat-treated samples highlights the presence of a reversible bcc to fcc transition. The precipitation of a MgZn2-type intermetallic phase along grain boundaries following scandium addition affects all systems differently, but especially enhances the properties of Al2CoCrFeNi. It causes grain refinement; hardness and electrical conductivity increases (up to 20% and 14% respectively) and affects the CsCl-type → fcc equilibrium by moving the transformation to sensibly higher temperatures. The maximum dimensionless thermoelectric figure of merit (ZT) of 0.014 is reached for Al2CoCrFeNi alloyed with 0.3 wt.% Sc at 650 °C.

Journal Keywords: high-entropy alloys; in situ X-ray diffraction; grain refinement; thermoelectric properties; scandium effect

Diamond Keywords: Alloys

Subject Areas: Materials, Chemistry

Instruments: I11-High Resolution Powder Diffraction

Other Facilities: PETRA III

Added On: 25/07/2018 14:01


Discipline Tags:

Physical Chemistry Chemistry Materials Science Metallurgy

Technical Tags:

Diffraction X-ray Powder Diffraction