Simulation of thermal desorption spectrum of hydrogen from austenite embedded in the martensite matrix

Abstract

Thermal desorption spectra of hydrogen of martensite (or ferrite), austenite and a composite of them in which austenite is a minor phase are simulated using McNabb–Foster theory. Whereas the peak temperature of desorption rate is markedly dependent upon the specimen thickness in all specimens, it did not decrease below a certain limit in thin martensite specimens where hydrogen desorption is controlled by detrapping of hydrogen from the trap site. The peak temperature in the two-phase specimen depends strongly upon the thickness of austenite if the initial amount of hydrogen in the ferrite matrix can be ignored, becoming close to or lower than the room temperature for the austenite thickness less than ∼10 μm. For larger austenite particles the release rate of hydrogen from the austenite governs the peak temperature. For small particles such as interlath retained austenite the release time of hydrogen from the particle is so short that re-capture of hydrogen at matrix dislocations and martensite/austenite interfaces can enhance the peak of martensite and/or cause an independent peak at a higher temperature.