Segregations and complexions in high-entropy alloys

Segregations and complexions in high-entropy alloys

In this project, we investigate the segregation behavior and complexions in the CoCrFeMnNi high-entropy alloys (HEAs). The structure and chemistry in the HEAs at varying conditions are being revealed systematically by combining multiple advanced techniques such as electron backscatter diffraction (EBSD) and atom probe tomography (APT). Based on the obtained results, the phase transformation mechanisms especially that associated with defects can be understood.

Both substitutional (Mn, Ni, etc.) and interstitial elements (C, B, etc.) can segregate at grain boundaries (GBs) or dislocations influencing the phase transformation and mechanical properties of materials. In HEAs with multiple principal elements, single phase can form although the stability is not well understood. The presence of multiple principal elements in HEAs makes the segregation rather intriguing and challenging. With this project, we reveal the fundamental mechanisms related to the phase transformation especially that associated with defects. Also, we aim to find a strategy to tune the chemical homogeneity states and hence improve the material properties of HEAs.

A typical APT analysis showing the segregation in an equiatomic CoCrFeMnNi HEA. (a) The 30 at. % Ni and (b) 30 at. % Mn concentration isosurfaces with all atoms; (c) The interface proxigram of 30 at. % Ni isosurface.

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