High-Temperature Scanning Indentation: A new method to investigate in situ metallurgical evolution along temperature ramps

A new technique, High-Temperature Scanning Indentation (HTSI), is proposed to investigate metallurgical evolution occurring during anisothermal heat treatments. This technique is based on the use of high-speed nanohardness measurements carried out during linear thermal ramping of the system with appropriate settings. A specific high-speed loading procedure, based on a quarter sinus loading function, a creep segment and a three-step unloading method, permits the measurement of elastic, plastic and creep properties. The indentation cycle lasts one second to minimize thermal drift issues. This approach enables quasi-continuous measurements of elastic modulus and hardness as a function of temperature in much shorter times than previous techniques. The HTSI technique is validated on fused silica and pure aluminum. The application to cold-rolled aluminum undergoing thermal cycling highlights the potential of the HTSI technique to investigate in situ thermally activated mechanisms linked with microstructural changes such as viscoplasticity, static recovery and recrystallization mechanisms in metals. Results on aluminum were confirmed using Electron Back-Scattering Diffraction measurements