High-Pressure Deformation of Iron–Nickel–Silicon Alloys and Implications for Earth’s Inner Core

This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint.

Downloads

Download Preprint

Supplementary Files
Authors

Matthew C Brennan, Rebecca A Fischer , Samantha Couper, Lowell Miyagi, Daniele Antonangeli, Guillaume Morard

Abstract

Earth’s inner core exhibits strong seismic anisotropy, often attributed to the alignment of hexagonal close-packed iron (hcp-Fe) alloy crystallites with the Earth’s poles. How this alignment developed depends on material properties of the alloy and is important to our understanding of the core’s crystallization history and active geodynamical forcing. Previous studies suggested that hcp-Fe is weak under deep Earth conditions but did not investigate the effects of the lighter elements known to be part of the inner core alloy. Here, we present results from radial X-ray diffraction experiments in a diamond anvil cell that constrain the strength and deformation properties of iron–nickel–silicon (Fe–Ni–Si) alloys up to 60 GPa. We also show the results of laser heating to 1650 K to evaluate the effect of temperature. Observed alloy textures suggest different relative activities of the various hcp deformation mechanisms compared to pure Fe, but these textures could still account for the theorized polar alignment. Fe–Ni–Si alloys are mechanically stronger than Fe and Fe–Ni; extrapolated to inner core conditions, Si-bearing alloys may be more than an order of magnitude stronger. This enhanced strength proportionally reduces the effectivity of dislocation creep as a deformation mechanism, which may suggest that texture developed during core crystallization rather than as the result of post-solidification plastic flow.

DOI

https://doi.org/10.31223/X54K5D

Subjects

Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Keywords

Radial diffraction, Iron–Nickel–Silicon Alloys

Dates

Published: 2020-10-21 02:23

Last Updated: 2020-10-21 09:23

License

CC BY Attribution 4.0 International

Add a Comment

You must log in to post a comment.


Comments

There are no comments or no comments have been made public for this article.