Optical full-field strain measurement within a diamond anvil cell

Area of Science:

• Materials Science
• Geophysics
• Solid State Physics

Background:

• Phase transformations in iron under high pressure are crucial for understanding Earth's deep interior.
• Previous methods for studying these transitions have limitations in strain measurement.

Purpose of the Study:

• To develop and validate a method for measuring in-plane strain components during iron phase transitions under high pressure.
• To investigate the strain localization associated with the alpha-Fe to epsilon-Fe phase transformation.

Main Methods:

• Utilized Digital Image Correlation (DIC) on optical images of iron samples within a diamond anvil cell (DAC).
• Collected strain data up to 17 GPa.
• Analyzed strain fields to identify phase transition onset and coexistence pressures.

Main Results:

• Successfully identified the alpha-Fe to epsilon-Fe transition onset and phase coexistence domains.
• Observed strain localizations during both direct and reverse transitions, correlating with microstructural variants.
• Deduced specific volumes that agree within 0.4% with literature data.

Conclusions:

• The Digital Image Correlation within a Diamond Anvil Cell (DICDAC) setup is a suitable tool for studying phase transformation strains.
• This technique provides valuable insights into the mechanical behavior of materials under extreme pressure conditions.
• The findings contribute to a better understanding of iron's behavior relevant to geophysics and materials science.