In-situ investigation of the oxidation kinetics of Fe-12Cr-2Si using time-resolved transient grating spectroscopy

Abstract

The design and validation of new alloys for engineering applications is limited by the speed at which materials may be tested. In particular, there exist few methods by which the thermal, mechanical, and structural properties of materials may be monitored in conditions that are dynamically changing their microstructure. These conditions, such as heat treatments, radiation exposure, or corrosive environments, are common when material performance needs to be validated. To offset this lack of capability, new non-destructive experimental tools must be developed to facilitate on-line, realtime testing of materials undergoing some type of evolution. In this thesis, a flexible, all-optical methodology known as dual heterodyne phase collection transient grating spectroscopy is developed for this purpose. This method adapts a traditional spectroscopic technique sensitive to thermal and mechanical properties for real-time use. A formalism is also developed to quantify both elastic and thermal transport properties of materials with second-scale resolution. These new tools are then used to study the short-timescale oxidation kinetics of Fe-12Cr-2Si, a model alloy with oxide layer formation properties similar to large classes of Fr-Cr alloys. By monitoring the effect of thin oxide layers on surface thermal transport, there exists a pathway to continuously determine the thickness of a tens of nanometers thick growing oxide layer in real-time. Despite the lack of clarity in the particular set of experimental results presented here, the potential for the methods developed in this thesis is large. In-situ materials testing of this type may allow for a drastic increase in the pace of materials development by reducing the need for post-evolution, destructive materials testing between each design iteration.