Relation between Vickers Hardness and Bragg-Edge Broadening in Quenched Steel Rods Observed by Pulsed Neutron Transmission Imaging
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The width of crystal lattice plane spacing (<i>d</i>-spacing) distribution related to microscopic-strain and crystallite size in a martensite phase in a 2 cm thick quenched-ferritic steel sample was quantitatively mapped in real space by a Bragg-edge broadening analysis of spectral data from a pulsed neutron transmission experiment. This analysis was performed under the condition that the instrumental resolution parameters, determined from the data of ferrite in the same sample without microscopic-strain and crystallite size effects, were unchanged over the sample area, and assuming that the <i>d</i>-spacing was distributed according to a Gaussian function in the martensite area. As a result, the full width at half maximum (FWHM) of the Gaussian <i>d</i>-spacing distribution in the martensite was extracted at each position in a sample. Consequently, it was found that the real-space distribution of the FWHM of the <i>d</i>-spacing distribution is closely correlated with a real-space distribution of the Vickers hardness that corresponds to the quantity of martensite. Furthermore, it was indicated that the Vickers hardness was proportional to the FWHM of the <i>d</i>-spacing distribution. The results suggest that it will be possible to measure the Vickers hardness in the martensite non-destructively by using the Bragg-edge neutron transmission method.
- MATERIALS TRANSACTIONS
MATERIALS TRANSACTIONS 56(8), 1147-1152, 2015
The Japan Institute of Metals and Materials