Apport de la diffraction synchrotron à l’étude de la transformation martensitique dans les aciers

Martensite and nanobainite transformations in a low alloyed steel studied by in situ high energy synchrotron diffraction

“…With the temperature decrease, the mean compression stress increases. Similar evolutions were already observed during martensitic transformation followed by in situ methods [52,53,56,57]. In some cases, the austenite went into tension in a first stage, but it always reached a compression state, with the progression of the martensitic transformation.…”

“…Estimate of the hydrostatic component of the stress (σ H = 3 L K where σ H is the hydrostatic stress, L is the deformation and K the bulk modulus) gives respectively 3.9 and 2.5 GPa for LNM and RTM at room temperature (how to derive L from a γ is detailed in reference [39]), in agreement with the higher and lower fractions of austenite respectively. These values are higher than in [52,[56][57][58].…”

“…Thanks to the Rietveld analysis, the mean lattice parameters of investigated phases are recorded during the transformation. Generally, their evolutions during phase transformations are related to the temperature, the internal stresses and the chemical composition variations [50,52,53].…”