Effect of a micro-scale dislocation pileup on the atomic-scale multi-variant phase transformation and twinning

Journal Article · Tue Sep 26 00:00:00 EDT 2023 · Computational Materials Science

DOI:https://doi.org/10.1016/j.commatsci.2023.112508· OSTI ID:2476048

Peng, Yipeng ^[1]; Ji, Rigelesaiyin ^[2]; Phan, Thanh ^[3]; Capolungo, Laurent ^[4]; Levitas, Valery I. ^[5]; Xiong, Liming ^[6]

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1. North Carolina State University, Raleigh, NC (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
2. Schlumberger, Sugar Land TX (United States)
3. Iowa State University, Ames IA (United States)
4. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
5. Ames Laboratory, and Iowa State University, Ames, IA (United States)
6. North Carolina State University, Raleigh, NC (United States); Iowa State University, Ames IA (United States)

In this paper, we perform concurrent atomistic–continuum (CAC) simulations to assess the contribution of the internal stress induced by the microscale dislocation pileup at an atomically structured interface to the atomic-scale phase transformations (PTs), reverse PTs, and twinning. The main novelty of this work is to unify the atomistic description of the interface and the coarse-grained (CG) description of the lagging dislocations away from the interface within one single framework. Our major findings are: (a) the interface dynamically responds to a pileup by forming steps/ledges, the height of which is proportional to the number of dislocations arriving at the interface; (b) the pileup-induced internal stress concentration profile follows neither the classical Eshelby model nor the super-dislocation model alone, but a combination of them; (c) when the pre-sheared sample is compressed, a direct square-to-hexagonal PT occurs ahead of the pileup tip and eventually grows into a wedge shape. The two variants of the hexagonal phases form a twin with respect to each other; (d) upon a further increase of the loading, part of the newly formed hexagonal phase transforms back to the square phase. The square product phase resulting from this reverse PT forms a twin with respect to the initial square phase. All phase boundaries (PBs) and twin boundaries (TBs) are stationary and correspond to zero thermodynamic Eshelby driving forces; and (e) the microscale dislocation pileup-induced internal shear stress and the structural change at the atomic-scale interface reduces the stress required for initiating a PT by a factor of 5.5, comparing with that in the sample containing no dislocations. This work is the first characterization of the behavior of PTs/twinning resulting from the reaction between a microscale dislocation slip and an atomically structured interface. In conclusion, the gained knowledge will advance our understanding of how the multi-phase material behaves in many complex physical processes, such as the synthesis of multi-phase high-entropy alloys or superhard ceramics under high-pressure torsion, deep mantle earthquakes in geophysics, and so on, which all involve dislocation slip, PTs, twinning, and their interactions across from the atomistic to the microscale and beyond.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Science (SC). Office of Basic Energy Sciences (BES); U.S. National Science Foundation (NSF); Extreme Science & Engineering Discovery Environment; XSEDE
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 2476048
• Report Number(s): LA-UR--22-27289
• Journal Information: Computational Materials Science, Journal Name: Computational Materials Science Vol. 230; ISSN 0927-0256
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Atomistic and multiscale simulations
Dislocations
Interface
Phase transformation
Twinning