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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
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Ubiquitous short-range order in multi-principal element alloys
Ying Han1, Hangman Chen2, Yongwen Sun1
1Department of Engineering Science and Mechanics and Materials Research Institute, The Pennsylvania State University, University Park, PA, USA.
Nature Communications
|August 1, 2024
Summary
Short-range order (SRO) is an inherent characteristic of multi-principal element alloys (MPEAs). Its formation during solidification is rapid and largely independent of processing conditions, challenging SRO engineering efforts.
Area of Science:
- Materials Science
- Metallurgy
- Computational Materials Science
Background:
- Short-range order (SRO) significantly impacts multi-principal element alloy (MPEA) performance.
- Understanding and controlling SRO formation mechanisms are critical for advancing MPEA engineering.
- Current knowledge on SRO formation and its precise control in MPEAs remains limited.
Purpose of the Study:
- To investigate the formation and characteristics of SRO in CoCrNi-based face-centered-cubic (FCC) MPEAs.
- To elucidate the influence of processing parameters, particularly cooling rates, on SRO development.
- To determine the fundamental mechanisms governing SRO formation during alloy solidification.
Main Methods:
- Utilized advanced additive manufacturing to create MPEA samples across a broad spectrum of cooling rates (up to 10^7 K/s).
- Employed an enhanced semi-quantitative electron microscopy technique for detailed SRO characterization.
- Performed atomistic simulations to model SRO formation at the liquid-solid interface under extreme cooling conditions (up to 10^11 K/s).
Main Results:
- Observed consistent levels of SRO in CoCrNi-based FCC MPEAs, regardless of processing history and thermal treatments.
- Atomistic simulations demonstrated that local chemical order forms rapidly at the solidification front.
- Atomic diffusion in the supercooled liquid phase was found to be comparable to or faster than solidification rates, even at extremely high cooling rates.
Conclusions:
- Short-range order is an intrinsic property of most FCC MPEAs, forming inherently during solidification.
- SRO formation is largely insensitive to experimental variations in cooling rates and annealing treatments.
- The findings suggest that SRO engineering in MPEAs may require approaches beyond conventional processing modifications.
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