Crystal structure evolution in mehcanical alloying and spark plasma sintering of AlxCoCrCuFeNi HEAs

ABSTRACT

Al_xCoCrCuFeNi high entropy alloys were synthesised through mechanical alloying and spark plasma sintering. Different alloys were produced by varying the aluminium content (x = 0.5, 1.5, 2.5 and 4). The influence of the milling duration on the evolution of microstructure, constituent phases and morphology was studied. Milling time increasing resulted in grain refinement and higher solid solution homogenisation characterised by a high internal strain. As a consequence of aluminium addition, the materials’ microstructure evolved from FCC and BCC phases to FCC, BCC and ordered BCC phases. Both mechanical alloying and SPS conditions as well as aluminium content let to grain refinement and mechanical properties variations. In particular, hardness increased with increasing the aluminium content. The aluminium percentage and the consequent phases evolution is responsible for the microstructural stability at high temperatures.

KEYWORDS:

• HEA
• SPS
• phase transformation
• mechanical properties

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Hossein Ziaei is a PhD student in Materials Science and Engineering at Shanghai Jiao Tong University, China. He is working on metal matrix composites, specially aluminum matrix composites reinforced by carbon nano tubes.

Niloofar Ebrahimzadeh Esfahani has a master of science physics with major of Photonics from Kashan University. Niloofar's master research is focused on Plasmonic and nanophotonic. She is passionate about working on biophysics.

Zainab Marfavi is a PhD student in Materials Science and Engineering at Shanghai Jiao Tong University, China. She is working on biomaterials, lanthanide Nano particles.

Dr. Behzad Sadeghi has a PhD in Nanomaterials Engineering from Isfahan University and Technology, Iran. He worked as a postdoctoral researcher at Shanghai Jiao Tong University, China from 2018 until 2020. He also been as visiting scholar at Salento university, Italy from 2016 to 2017. His research mainly focuses on microstructure-property relationships and understanding the underlying deformation mechanisms in advanced engineering materials especially aluminum matrix composites. Areas of research include light metals such as Aluminum, Copper and their alloys, as well as high entropy alloys. He has rich experience of Flake powder metallurgy, Severe plastic deformation techniques such as equal-channel angular (ECAP), Extrusion, Fast assistant sintering such as Spark plasma sintering (SPS), Hot/cold rolling process, Solid state joining such as Friction stir welding (FSW), making surface nanocomposites through Friction stir processing (FSP) and also producing high entropy alloys via powder metallurgy.

Pasquale Cavaliere, PhD in Materials Engineering University of Rome "Tor Vergata", Professor of Metallurgy University of Salento