LAUSR

It is useful to observe microstructure evolution directly during heat treatment of steels. As usual in the past, a specimen was interruptedly cooled from an elevated temperature in order to freeze microstructure and then observations were carried out at room temperature. However, in case of a low alloy steel, austenite phase at a high temperature transforms to martensite during quenching. It is also difficult to trace the microstructure change continuously at an identical position of one sample. Therefore, in situ observations or measurements of microstructural change during heat treatment have been attempted by using various techniques. For example, in situ observations or measurements using confocal scanning laser microscopy,1) transmission electron microscopy (TEM),2) scanning electron microscopy (SEM)/ electron back scatter diffraction (EBSD),3) X-ray diffraction,4) etc. have been employed to track microstructure evolution during heat treatment. But it should be noticed that the surface layer of a specimen is easily damaged at elevated temperatures even in vacuum or inert gas atmosphere: oxidation, decarburization, etc. hinder to obtain the information inside a sample. “Phase transformation is generally affected by stress. In situ Neutron Diffraction Study on Ferrite and Pearlite Transformations for a 1.5Mn-1.5Si-0.2C Steel