Precipitation hardening of high entropy alloy CoCrFeMnNi containing titanium

• Published in: Journal of alloys and compounds 2021-03, Vol.857, p.157610, Article 157610
• Main Authors: Eißmann, Nadine, Mühle, Uwe, Gaitzsch, Uwe, Walther, Gunnar, Weißgärber, Thomas, Kieback, Bernd
• Format: Article
• Language: English
• Subjects: Alloys; Hardness; Heat treatment; High entropy alloys; Precipitates; Precipitation; Precipitation hardening; Scanning electron microscopy (SEM); Titanium; Transmission electron microscopy (TEM)
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.157610

The effect of titanium addition beyond the solubility limit was investigated in order to proof the precipitation hardening possibility of the Cantor alloy CoCrFeMnNi. As high entropy alloys are currently in the focus of interest, this method is a highly suitable possibility to further improve their remarkably properties. After appropriate heat treatment consisting of homogenisation, solution and precipitation annealing a significant increase in hardness was detected. The high hardness was caused by nanometer sized precipitates, which were identified by TEM-analysis. Titanium is a suitable element to facilitate precipitation hardening in CoCrFeMnNi HEAThe maximum solubility in the investigated temperature regime is about 2 at. %The maximum hardness was reached at a concentration of 6 at. % after annealing at 750 °C for 10 h.For higher concentrations the annealing temperature has to be increased to achieve the maximum hardness.TEM investigation revealed nano-scale precipitations only after heat treatment for a concentration of 5 at. %.