Stable Speckle Patterns for Nano-scale Strain Mapping up to 700 °C.

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Digital Image Correlation (DIC) is effective for strain mapping at submicron resolution.
• Previous gold speckle patterns were limited to lower temperatures (200-350°C).
• High-temperature DIC is crucial for understanding material behavior under extreme conditions.

Purpose of the Study:

• To develop a gold speckle pattern stable at 700°C for high-temperature DIC.
• To enable nano-scale strain mapping of a commercial TiAl alloy at elevated temperatures.
• To assess the suitability of the pattern for long-term high-cycle fatigue testing.

Main Methods:

• Fabrication of a gold speckle pattern using vapor-assisted gold remodeling.
• Characterization of the pattern's stability and properties at temperatures up to 700°C.
• Application of nano-scale DIC (nDIC) for strain mapping with small subset sizes (60x60 nm²).

Main Results:

• A thermally stable gold speckle pattern with uniformly sized Au islands (as small as 15 nm) was created.
• The pattern demonstrated suitability for nDIC strain mapping at 700°C for extended periods.
• The pattern exhibited good particle adhesion, resistance to ultrasonic cleaning, and high atomic number contrast.

Conclusions:

• The developed gold speckle pattern overcomes previous temperature limitations for DIC.
• This technique allows for detailed analysis of deformation in materials like TiAl alloys at high temperatures.
• The pattern is robust and suitable for various high-temperature material testing applications, including fatigue analysis.