Journal Article

IMPULSE-2025-00063

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Dislocation dissociation assisted formation mechanism of sigma phase and its impact on producing heterogeneous lamellar microstructure in CoCrV medium-entropy alloy

Wang, L. ; Yan, H.-L. (Corresponding author) ; Zhang, Y. (Corresponding author) ; Beausir, B. ; Gan, W.MLZ* ; Laurent, P. ; Siredey-Schwaller, N. ; Esling, C. ; Zhao, X. ; Zuo, L.

2025
Pergamon Press Frankfurt, M. [u.a.]

Please use a persistent id in citations: doi:10.1016/j.ijplas.2025.104260

Abstract: Control of topologically close-packed sigma phase, meaning limiting its massive presence to avoid embrittlement but benefiting its refinement and strengthening effect, is of particular interest. In-depth knowledge of dislocation-associated formation mechanisms is needed but not well addressed. In this work, an FCC-phased Co66.66Cr16.67V16.67 medium entropy alloy (MEA) with a propensity to form the sigma phase at non-equilibrium conditions was studied. The alloy was conventionally cold-rolled and heat-treated. The dislocation activity rooted formation mechanisms of the sigma phase were thoroughly characterized and evidenced by in-situ and ex-situ multi-scale diffraction techniques. It was revealed that nano-sized sigma particles enriched in Cr and V and depleted in Co were precipitated ultra-rapidly and uniquely during the heating process after the cold-rolling. The precipitation is spatially inhomogeneous, mainly in the severely deformed regions. The ultra-rapidity of the precipitation was achieved by the segregation of the Cr and V atoms via crystal defect-aided diffusion for composition change and by structure transformation via dislocation dissociation. The similarity of the atomic arrangement of the partial dislocations to that of the {001} sigma planes provides favorable structure transformation stimulus. In consequence, the orientations of the intensively activated dislocation slip planes dictated those of the sigma {001} planes via the FCC {111} to sigma {001} heredity, leading to the specific sigma texture. Owing to the spatially inhomogeneous precipitation, a heterogeneous lamellar microstructure was formed, composed of alternatively distributed fine dual-phased layers and coarse single-phased layers. This work provides comprehensive information on the dislocation-dissociation-assisted formation mechanism of sigma phase.

Keyword(s): Engineering, Industrial Materials and Processing (1st) ; Materials Science (2nd)

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Contributing Institute(s):

1. MATSCI (MATSCI)
2. STRESSI (STRESSI)

Experiment(s):

1. No specific instrument

Appears in the scientific report 2025

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Engineering, Computing and Technology ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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