Neutron beam is one of quantum beams widely known for materials characterization due to its unique properties. Neutrons are used to investigate stresses and crystallographic microstructures inside engineering materials, taking advantage of their large penetrating power and the ability to see the arrangement of atoms by diffraction methods. Pulsed neutron diffraction with the time-of-flight method is suitable for microscopic structural observation as a bulk average behavior because of the simultaneous measurement of multiple Bragg peaks. Careful analysis of the Bragg peaks in a neutron diffraction pattern can reveal important structural details of a sample material such as internal stresses, phase conditions, dislocations, texture etc. Such information is often crucial in engineering applications and the ability to carry out either ex-situ or in-situ measurements makes neutron diffraction particularly useful in this respect. The large penetrating power of neutrons also allows in-situ investigation of crystallographic information on engineering materials under various environments, including operando monitoring during deformation at a wide temperature range from cryogenic to high temperatures, thermo-mechanical processes, and so on.

The pulsed neutron diffraction with the time-of-flight method will be briefly introduced, and a pulsed neutron diffractometer for engineering materials studies in J-PARC with some highlighted researches using operando observations will be introduced.