skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Journal Article · · Journal of Geophysical Research. Solid Earth
DOI:https://doi.org/10.1029/2020jb021077· OSTI ID:1785995

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 crystallization rather than as the result of postsolidification plastic flow.

Research Organization:
Univ. of Illinois, Chicago, IL (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); H2020 European Research Council (ERC)
Grant/Contract Number:
NA0003975; DGE1745303; EAR-1654687; NA0003858; 724690
OSTI ID:
1785995
Alternate ID(s):
OSTI ID: 1786806
Journal Information:
Journal of Geophysical Research. Solid Earth, Vol. 126, Issue 3; ISSN 2169-9313
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English

References (93)

The structure of Fe–Si alloy in Earth's inner core journal May 2015
Density and composition of mantle and core journal October 1964
Seismic anisotropy of the inner core journal March 1989
Elasticity of iron at the temperature of the Earth's inner core journal September 2001
Elasticity and constitution of the Earth's interior journal June 1952
Estimates of the Earth's inner core grain size journal May 1998
Seismic parameters of hcp‐Fe alloyed with Ni and Si in the Earth's inner core journal February 2016
Erratum: Elasticity and rheology of iron above 220 GPa and the nature of the Earth's inner core journal May 1999
Strength of iron at core pressures and evidence for a weak Earth’s inner core journal May 2013
Convection and anisotropy of the inner core journal January 1988
High pressure metal–silicate partitioning of Ni, Co, V, Cr, Si, and O journal October 2015
Rietveld refinement guidelines journal February 1999
On the viscosity and creep mechanism of Earth's inner core journal January 2004
Texturing of the Earth's inner core by Maxwell stresses journal September 2001
Elastic Properties of Metals and Alloys, I. Iron, Nickel, and Iron‐Nickel Alloys journal July 1973
Toward an internally consistent pressure scale journal May 2007
In situ phase transformation and deformation of iron at high pressure and temperature journal November 2008
High-Pressure Elasticity of Iron and Anisotropy of Earth's Inner Core journal March 1995
Simulations of texture evolution for HCP metals: Influence of the main slip systems journal February 2015
Phase transition boundary between fcc and hcp structures in Fe-Si alloy and its implications for terrestrial planetary cores journal January 2019
Seismic response and anisotropy of a model hcp iron inner core journal May 2014
The plastic deformation of iron at pressures of the Earth's inner core journal June 2000
Deformation of directionally solidified alloys: Evidence for microstructural hardening of Earth's inner core? journal May 2014
The composition of the Earth journal March 1995
Modelling solid solution hardening in high entropy alloys journal February 2015
The innermost inner core of the earth: Evidence for a change in anisotropic behavior at the radius of about 300 km journal October 2002
High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys journal September 2019
Silicon in the metal phase of enstatite chondrites and some geochemical implications journal August 1961
X-ray Imaging of Stress and Strain of Diamond, Iron, and Tungsten at Megabar Pressures journal May 1997
Predictive mechanism for anisotropy development in the Earth's inner core journal December 2011
High-pressure melting experiments on Fe–Si alloys and implications for silicon as a light element in the core journal December 2016
DIOPTAS : a program for reduction of two-dimensional X-ray diffraction data and data exploration journal May 2015
Deformation-induced crystallographic-preferred orientation of hcp-iron: An experimental study using a deformation-DIA apparatus journal May 2018
Ab initio calculations of the elasticity of hcp-Fe as a function of temperature at inner-core pressure journal November 2009
BEARTEX: a Windows-based program system for quantitative texture analysis journal April 1998
A Statistical Theory of Solid Solution Hardening journal January 1970
Grain growth of ε -iron: Implications to grain size and its evolution in the Earth's inner core journal February 2017
Sound velocities of Fe and Fe-Si alloy in the Earth's core journal June 2012
The Structure of Iron in Earth's Inner Core journal October 2010
Equations of state in the Fe-FeSi system at high pressures and temperatures: Equations of state in the Fe-FeSi system journal April 2014
Hemispherical structure in inner core velocity anisotropy journal January 2011
Analysis of lattice strains measured under nonhydrostatic pressure journal June 1998
Thermochemical flows couple the Earth's inner core growth to mantle heterogeneity journal August 2008
Quasi-hydrostatic compression of magnesium oxide to 52 GPa: Implications for the pressure-volume-temperature equation of state journal January 2001
Phase relations in the Fe–FeSi system at high pressures and temperatures journal July 2013
Texture and elastic strains in hcp-iron plastically deformed up to 17.5 GPa and 600 K: experiment and model journal February 2012
Terrestrial Accretion Under Oxidizing Conditions journal January 2013
Lopsided Growth of Earth's Inner Core journal April 2010
Study of deformation and aging behaviour of iron–silicon alloys journal February 2007
Silicon in the Earth’s core journal June 2007
The axial ratio of hcp Fe and Fe–Ni–Si alloys to the conditions of Earth’s inner core journal November 2015
Heterogeneity and Anisotropy of Earth's Inner Core journal May 2014
Inner core anisotropy inferred by direct inversion of normal mode spectra journal December 1999
Inner Core Anisotropy Due to the Magnetic Field--induced Preferred Orientation of Iron journal December 1993
Implementation and application of the peak scaling method for temperature measurement in the laser heated diamond anvil cell journal August 2018
Building a regime diagram for the Earth’s inner core journal October 2015
X-ray transparent gasket for diamond anvil cell high pressure experiments journal April 2005
Sound velocities of iron-nickel and iron-silicon alloys at high pressures journal January 2003
Isotropy overlying anisotropy at the top of the inner core journal November 2001
Melting of Fe–Ni–Si and Fe–Ni–S alloys at megabar pressures: implications for the core–mantle boundary temperature journal July 2011
Elastic anisotropy in hcp metals at high pressure and the sound wave anisotropy of the Earth's inner core journal January 2006
Melting-induced stratification above the Earth’s inner core due to convective translation journal August 2010
Velocity‐Density Systematics of Fe‐5wt%Si: Constraints on Si Content in the Earth's Inner Core journal April 2019
Measurements of electric anisotropy due to solidification texturing and the implications for the Earth's inner core journal September 1997
Stability field of the hcp-structure for Fe, Fe-Ni, and Fe-Ni-Si alloys up to 3 Mbar: FE-NI-SI ALLOY UP TO 3 MBAR journal May 2011
Fluid motions induced by horizontally heterogeneous Joule heating in the Earth’s inner core journal February 2011
Axial Compressibility and Thermal Equation of State of Hcp Fe–5wt% Ni–5wt% Si journal January 2020
Thermal convection in Earth's inner core with phase change at its boundary journal June 2013
Quasihydrostatic Equation of State of Iron above 2 Mbar journal November 2006
Deformation of Earth Materials book January 2008
Significance of mechanical twinning in hexagonal metals at high pressure journal January 2012
TEM study of an analogue of the Earth’s inner core ε-Fe journal February 2002
The effect of nickel on the strength of iron nickel alloys: Implications for the Earth’s inner core journal October 2018
A constitutive model for metals applicable at high‐strain rate journal March 1980
An in situ experimental study of grain growth in a nanocrystalline Fe91Ni8Zr1 alloy journal November 2012
Anisotropy of the inner core from differential travel times of the phases PKP and PKIKP journal March 1992
Deformation of polycrystalline iron up to 30GPa and 1000K journal July 2004
In situ radial X-ray diffraction study of texture and stress during phase transformations in bcc-, fcc- and hcp-iron up to 36GPa and 1000K journal August 2013
Nonbasal deformation modes of HCP metals and alloys: Role of dislocation source and mobility journal March 2002
Sound velocity measurements of hcp Fe-Si alloy at high pressure and high temperature by inelastic X-ray scattering journal January 2018
Viscosity of the Earth's inner core: Constraints from nutation observations journal August 2011
Onset and orientation of convection in the inner core journal November 2009
Preliminary reference Earth model journal June 1981
Growth model of the inner core coupled with the outer core dynamics and the resulting elastic anisotropy journal December 1996
A beamline for high-pressure studies at the Advanced Light Source with a superconducting bending magnet as the source journal August 2005
Temperature effects on the mobility of pyramidal < c + a > dislocations in magnesium journal January 2017
Multiscale model of global inner‐core anisotropy induced by hcp alloy plasticity journal February 2016
Inner core anisotropy in three dimensions journal June 1995
The structure of Fe-Ni alloy in Earth's inner core: FE-NI ALLOY IN THE INNER CORE journal June 2012
Grain growth and loss of texture during annealing of alloys, and the translation of Earth’s inner core: GRAIN GROWTH AND LOSS OF TEXTURE journal November 2010
Aggregate shear moduli of iron up to 90 GPa and 1100 K journal February 2000
Elastic and attenuation anisotropy in directionally solidified (hcp) zinc, and the seismic anisotropy in the Earth's inner core journal January 2000
Sound velocities and density measurements of solid hcp-Fe and hcp-Fe–Si (9 wt.%) alloy at high pressure: Constraints on the Si abundance in the Earth's inner core journal January 2018

Similar Records

Crystallographic texture formation in Fe-9wt%Si alloy during deformation and phase transition at high pressure
Journal Article · Fri Mar 10 00:00:00 EST 2023 · Geophysical Journal International · OSTI ID:1785995

Seismic parameters of hcp‐Fe alloyed with Ni and Si in the Earth's inner core
Journal Article · Thu Feb 18 00:00:00 EST 2016 · Journal of Geophysical Research. Solid Earth · OSTI ID:1785995

Deformation and strength of mantle relevant garnets: Implications for the subduction of basaltic-rich crust
Journal Article · Thu Jul 01 00:00:00 EDT 2021 · American Mineralogist · OSTI ID:1785995