A simple variant selection in stress-driven martensitic transformation.

Area of Science:

• Materials Science
• Crystallography
• Solid State Physics

Background:

• Martensitic transformations are crucial in materials science, driven by temperature, pressure, or stress.
• Understanding orientation variant selection is key to controlling these transformations.
• The influence of stress and pressure on variant selection is less understood compared to temperature effects.

Purpose of the Study:

• To investigate the orientation variant selection during the cubic-to-orthorhombic martensitic transformation in Mn2O3 under high pressure and stress.
• To elucidate the role of applied stress and pressure in dictating the preferred crystallographic orientation of the transformed phase.

Main Methods:

• In situ synchrotron X-ray diffraction using diamond anvil cells in radial geometry.
• Application of pressures up to 51.5 GPa and stresses up to 5.5 GPa.
• Analysis of crystal orientation changes and texture development during the phase transformation.

Main Results:

• Observed a specific crystallographic relationship: {110} <001> // (100) <010> during the transformation.
• Demonstrated preferential selection of the {110} plane perpendicular to the stress direction.
• Revealed the formation of a very strong texture in the orthorhombic phase due to this selection.

Conclusions:

• The study identified a clear and simple variant selection mechanism in Mn2O3 under combined pressure and stress.
• This selection is attributed to the structural distortions induced by the applied pressure and stress.
• Findings contrast with more complex variant selection observed in other martensitic transformations.