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Abstract Syntectonic microstructural evolution is a well‐known phenomenon in the mantle and lower crust associated with two main processes: grain size reduction through dynamic recrystallization and development of crystallographic preferred orientation (CPO). However, the effects of annealing via static recrystallization on grain size and CPO have been largely overlooked. We investigated mantle annealing by analyzing a suite of kimberlite‐hosted garnet peridotite xenoliths from the Wyoming Craton. We focus on five xenoliths that show microstructures reflecting different degrees of recrystallization, with annealed grains characterized by distinctive faceted boundaries crosscutting surrounding, nonfaceted matrix grains. These textures are indicative of discontinuous static recrystallization (DiSRX). Electron backscatter diffraction analysis further demonstrates a ∼10°–20° misorientation between DiSRXed grains and the matrix grains, resulting in an overall weaker CPO. These characteristics are remarkably similar to microstructures observed in samples that were annealed after deformation in the laboratory. Measurements of the thermal conditions and water contents associated with the last equilibration of the xenoliths suggests that high homologous temperatures (T/Tm > 0.9) are necessary to induce DiSRX. We postulate that annealing through DiSRX occurs under high temperatures after a short episode of intense deformation (years to hundreds of years) with timescales for annealing estimated as weeks to years, significantly slower than the timescale of hours expected for a kimberlitic magma ascent. We conclude that microstructural transformation due to DiSRX will occur during transient heating events associated with mantle upwelling, plumes, and lithospheric thinning.
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This content will become publicly available on February 5, 2026
Primary recrystallization of a magnesium hybrid material fabricated by high-pressure torsion
The static recrystallization and grain growth of a hybrid AZ31/Mg-0.6Gd (wt%) material fabricated by high pressure torsion (HPT) through 20 turns were explored after isochronal annealing at 150, 250, 350 and 450 ◦C for 1 h using electron backscatter diffraction, transmission electron microscopy and Vickers microhardness measurements. The results reveal heterogeneity in the grain size distributions of the AZ31 and Mg-0.6Gd regions after annealing at the lower temperatures of 150 and 250 ◦C leading to a clear AZ31/Mg-0.6Gd interfacial border. At the higher temperatures of 350 and 450 ◦C the AZ31/Mg-0.6Gd interfaces were not well-defined owing to the occurrence of grain growth. It is shown that grain growth is restricted in the AZ31 and Mg-0.6Gd regions due to the presence of stable nano-size Al8Mn5 particles and the precipitation of Mg17Al12 and Mg12Zn at 250 ◦C and of Mg5Gd and Mg12Gd phases at 350 and 450 ◦C. The distribution of the basal texture in both regions was strongly controlled by dynamic recrystallization, precipitation and grain growth. The values of the microhardness over the radial cross-sections of the hybrid discs decrease and become more uniform, in the range of ~35–66 Hv, with increasing annealing temperature.
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- Award ID(s):
- 2051205
- PAR ID:
- 10643546
- Publisher / Repository:
- ELSEVIER
- Date Published:
- Journal Name:
- Materials Today Communications
- Volume:
- 38
- ISSN:
- 2352-4928
- Page Range / eLocation ID:
- 108305
- Subject(s) / Keyword(s):
- High-pressure torsion Hybrid metal Magnesium Precipitation Recrystallization
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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