A challenge was made to examine the micro-structural evolution during thermomechanically
controlled processing (TMCP) by in situ neutron diffraction. Since the neutron beam
is too weak to achieve a time-division measurement to follow a rapid transformation in alow
carbon steel, 2%Mn was added to make the austenite to ferrite transformation slower. Round bar
specimens were heated up to 900°C with an electrical resistance method, then cooled down to
700°C, and compressed by 25% followed by step-by-step cooling. During the step-by-step cooling,
neutron diffraction profiles were obtained and the volume fraction of ferrite, phase stresses and
FWHM were analyzed. Using a similar TMCP simulator, specimens were quenched into water at
several stages of the heat schedule to freeze the corresponding microstructures, which were
observed with OM and SEM. As results, the ferrite volume fraction determined by neutron
diffraction on cooling agrees well with that by microscopy. It is found that the austenite deformation
and/or Nb addition accelerate the ferrite transformation to result in finer grain size.
A Unique Quenching and Deformation Dilatometer for Combined
in‐situ
Neutron diffraction Analysis of Engineering Materials
