Macroscale stress induced stabilization of coherent precipitates

• Published in: Journal of crystal growth Vol. 588; p. 126667
• Main Authors: Raghavendra, R.M., Jha, Anurag, Iyer, Ganesh, Kumar, Arun, Subramaniam, Anandh
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.06.2022; Elsevier BV
• Subjects: A1.Elastic Stress Fields; A1.Finite Element Method; A2.Coherent to semi-coherent transition; A2.Critical size; A2.Interfacial misfit dislocation; A2.Stability of coherent precipitate; Chemical energy; Coherence; Compressive properties; Crystal growth; Dislocation loops; Domains; Misfit dislocations; Nucleation; Precipitates; Stress distribution; Tensile stress; A2.Stability of coherent precipitate; A1.Elastic Stress Fields; A2.Coherent to semi-coherent transition; A2.Critical size; A2.Interfacial misfit dislocation; A1.Finite Element Method
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2022.126667

•The Interplay between stress fields and finite size effects profoundly influences the coherent to semi-coherent transition.•Compressive stress expands the phase field of the coherent state, while tensile stress has the opposite effect.•The re-entrant interface character transition to the coherent state can be suppressed by tensile stress.•In 'very small' domains the coherent state can be stabilized in spite of being subjected to tensile stress. In systems with 'moderate' misfit, on nucleation and in the initial stages of the growth, precipitate crystals may be coherent with the matrix. This reduces the interfacial chemical energy; but a higher cost is paid in terms of the energy stored in the long range strain fields. On the growth beyond a critical size (r*), the energy of the system is minimized via the formation of interfacial misfit dislocation loops. It has been shown that the coherent state is stable in two separate size regimes of the precipitate in finite bodies (i.e. shows a re-entrant interface character transition) and further the coherent state can be fully stabilized below a critical size of the domain (R*). The presence of stress fields in the material, either due to internal sources or due to externally applied loads, is expected to alter the magnitude of the r*. In the current work, finite element simulations are used to study the effect of elastic stress fields on r*. The Cu-2wt.%γFe alloy is used as a model system towards this end. A map is generated demarcating the regions of stability of the coherent and semi-coherent states; with normalized r*, domain size (R) and elastic stress (σyy) as axes. We conclude the following. (i) Stresses of the order of GPa leads to a change in r*. (ii) The re-entrant interface character transition to the coherent state is suppressed by tensile stress. (iii) The coherent state is stabilized due to compressive stress. (iv) Compressive stress expands the phase field of the coherent state, while tensile stress has the opposite effect. (v) In 'very small' domains the coherent state can be stabilized in spite of being subjected to tensile stress.