Study of metallographic structures in replicated heat-treated specimens from ancient Korea using neutron beam diffraction analysis

This study uses neutron beam diffraction to nondestructively analyze microstructures in specimens produced through replicated ancient Korean heat treatment techniques. As a result of an experiment using SK5 steel with varying quenching times (1, 5, and 10 s) and clay thicknesses (0, 1, and 3 mm), the largest amount of martensite was generated when the quenching time was 5 s. Four specimens were examined: one before and three after heat treatment. Optical and scanning electron microscopy revealed ferrite structures in the specimen before heat treatment, martensite in the specimen after heat treatment (0 mm, 5 s), and pearlite in the remaining specimen after heat treatment. Neutron beam diffraction analysis quantified peak broadening under tensile stress. All specimens demonstrated increased peak broadening upon tensile deformation, with significant differences in the peak positions and widths between the heat treatment specimen and heat-treated specimens due to microstructural variations. Meanwhile, heat-treated specimens demonstrated greater peak width increases than before heat treatment specimens, indicating higher defect concentrations in the before heat treatment specimens. Results confirmed that martensite formation could be identified nondestructively. However, as accurate structure identification is not possible with neutron beam diffraction analysis alone, neutron imaging technology is required.