Effect of Cr/Ni ratio on phase stability and σ-phase precipitation kinetics in CrMnFeCoNi high-entropy alloys (27/01/22)

Speaker and Affliation:

Apl. Prof. Dr. Guillaume Laplanche
Ruhr-Universität Bochum,
Fakultät für Maschinenbau Institut für Werkstoffe
Lehrstuhl Werkstoffwissenschaft Universitätsstr.150
D-44780 Bochum, Germany

When?

27^th January, 2022 (Thursday), 04:00 PM (India Standard Time)

Location

Microsoft Teams Meet-up

Abstract

The equiatomic CrMnFeCoNi high-entropy alloy (HEA), also called Cantor alloy, was initially believed to form a stable face-centered cubic (FCC) solid solution because many studies showed that it solidified in this state and remained so, after forming and recrystallization. Further works have however demonstrated that the initially single-phase Cantor alloy decomposes into multiple phases when annealed below ~800°C for long durations [1-3]. In this presentation, the effect of Cr/Ni ratio on the stability of the Cantor alloy is reported. It is found that an increase in the Cr/Ni ratio stabilizes the topologically close-packed σ-phase and accelerates its precipitation kinetics [4], which is also enhanced by a decrease in mean grain size. By analyzing the temporal evolutions of the concentration profiles forming at FCC/σ interfaces and the dimensions of σ-phase precipitates, the diffusion processes responsible for the precipitation kinetics were identified [5]. As the σ-phase is known to cause embrittlement in austenitic alloys, its influence on tensile properties was investigated. Overall, this work not only sheds light on the factors affecting the long-term stability of HEAs from the Cr-Mn-Fe-Co-Ni system and the precipitation kinetics of secondary phases, but it also motivates the investigation of other HEAs that are considered for applications at high temperatures.

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