Alloying, thermal stability and strengthening in spark plasma sintered AlxCoCrCuFeNi high entropy alloys

• Published in: Journal of alloys and compounds Vol. 583; pp. 419 - 426
• Main Authors: Sriharitha, R., Murty, B.S., Kottada, Ravi S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 2014; Elsevier
• Subjects: Alloying; Alloys; Aluminum; Applied sciences; Contact of materials. Friction. Wear; Cross-disciplinary physics: materials science; rheology; Entropy; Exact sciences and technology; Hardness; Materials science; Mechanical alloying; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Nanostructured materials; Physics; Sintering; Solid solution, precipitation, and dispersion hardening; aging; Strengthening; Thermal stability; Treatment of materials and its effects on microstructure and properties; X-ray diffraction; X-ray diffraction; Nanostructured materials; Mechanical alloying; Sintering; high entropy alloy; Scanning electron microscopy; Strengthening; XRD; Hardness; Heat treatments; Solid solution hardening; Thermal stability; Spark plasma sintering; Chemical composition; Microstructure; Hall Petch relationship
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.08.176

•Microstructure of AlxCoCrCuFeNi (x=0.45,1,2.5,5) is sensitive to fraction of Al.•AlxCoCrCuFeNi (x=0.45,1) exhibit excellent thermal stability at high temperatures.•Quantification of strengthening is presented for AlxCoCrCuFeNi (x=0.45,1,2.5,5).•Better estimate of theoretical density for HEA using phase fractions is discussed. AlxCoCrCuFeNi (x=0.45, 1, 2.5 and 5mol) multi-component high entropy alloys synthesized by mechanical alloying were spark plasma sintered to produce high dense compacts. X-ray diffraction and scanning electron microscopy studies reveal that these sintered alloys exhibit varying microstructures from single phase to three phases depending on Al content. The thermal stability studies carried out in the temperature range of 400–600°C for duration of 2–10h in Ar atmosphere suggest that these alloys exhibit excellent thermal stability in terms of phases and crystallite size. Highest specific hardness of 160 (HV/gcm−3) is achieved in the sintered Al5CoCrCuFeNi alloy and there is no significant change in the hardness after heat treatment of Al0.45CoCrCuFeNi and AlCoCrCuFeNi alloys. Hall–Petch analysis based on hardness measurements carried out on sintered samples reveals that solid solution strengthening seems to increase with increase in Al content.