Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW

Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc (GTAW). The in situ visualization austenitization upon subsequent α’-martensite formation cooling could be achieved with a temporal resolution 2 s for monochromatic imaging single wavelength 0.5 polychromatic full spectrum beam (white beam). spatial experiments was approximately 200 µm. transmitted intensity at λ = 0.395 nm significantly reduced below start Ms since emerging phase has ~10% higher attenuation coefficient than austenitic phase. Neutron influenced by coherent scattering caused thermal motion crystal lattice (Debye–Waller factor), resulting reduction approx. 15% 4% imaging.