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Transition to abnormal grain growth from the pinned state and from normal growth.

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Bibliographic Details
Title:	Transition to abnormal grain growth from the pinned state and from normal growth.
Authors:	Patterson, Burton R.¹ (AUTHOR) patters@mse.ufl.edu
Source:	Acta Materialia. Jun2026, Vol. 311, pN.PAG-N.PAG. 1p.
Subjects:	Grain size, Microstructure, Aluminum alloys, Metal crystal growth, Crystal grain boundaries
Abstract:	Abnormal grain growth (AGG) in particulate structures has been experimentally studied and modeled for initiation from the pinned state and from normal grain growth, with different mechanisms and microstructural paths. From the pinned state AGG initiates after reduction in resisting pressure by particle coarsening and/or dissolution, releasing some grains to grow into the surrounding pinned structure until most of it is consumed. The boundary curvature and driving pressure of the abnormal grain increases with increasing number of faces as it grows, allowing it to progress unstopped into the structure from which it initiated. In the second case, during normal grain growth in the presence of a coarser particulate structure, the increasing grain size reduces driving pressure to the point of partial pinning with some grains continuing growth and hindering that of the abnormal grain, resulting in a broad size distribution, less extreme than in the first case. The initiation of these two variants is quantified in terms of a proposed unitless "grain anchorage" parameter, G A , that is the ratio of the resisting and driving pressures. A similar term has been proposed in prior 2D analytical models but has never been experimentally tested in 3D Experiments with aluminum alloy AA3105 containing soluble constituent particles and dispersoids showed abnormal growth initiating at consistent values of G A ≈ 4 for the NGG → AGG transition and ≈ 6 for Pinned → AGG over a range of temperatures, particulate structures and initiation times. These results should be general among particulate materials. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

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Abstract:	Abnormal grain growth (AGG) in particulate structures has been experimentally studied and modeled for initiation from the pinned state and from normal grain growth, with different mechanisms and microstructural paths. From the pinned state AGG initiates after reduction in resisting pressure by particle coarsening and/or dissolution, releasing some grains to grow into the surrounding pinned structure until most of it is consumed. The boundary curvature and driving pressure of the abnormal grain increases with increasing number of faces as it grows, allowing it to progress unstopped into the structure from which it initiated. In the second case, during normal grain growth in the presence of a coarser particulate structure, the increasing grain size reduces driving pressure to the point of partial pinning with some grains continuing growth and hindering that of the abnormal grain, resulting in a broad size distribution, less extreme than in the first case. The initiation of these two variants is quantified in terms of a proposed unitless "grain anchorage" parameter, G A , that is the ratio of the resisting and driving pressures. A similar term has been proposed in prior 2D analytical models but has never been experimentally tested in 3D Experiments with aluminum alloy AA3105 containing soluble constituent particles and dispersoids showed abnormal growth initiating at consistent values of G A ≈ 4 for the NGG → AGG transition and ≈ 6 for Pinned → AGG over a range of temperatures, particulate structures and initiation times. These results should be general among particulate materials. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:	13596454
DOI:	10.1016/j.actamat.2026.122176