Imaging of boron distribution in steel with neutron radiography and tomography

DI LUOZZO, NICOLÁS; SCHULZ, MICHAEL; FONTANA, MARCELO

JOURNAL OF MATERIALS SCIENCE

SPRINGER

Lugar: Berlin; Año: 2020 vol. 55 p. 7927 - 7937

0022-2461

B distribution in steel was investigated using neutron imaging techniques, on amillimetric scale with a spatial resolution below 100 lm. Steel structural com-ponents joined using the transient liquid-phase bonding (TLPB) process, withFe-based B-alloyed foils as filler material, were observed. By means of neutronradiography and with the proposed calibration method, a quantitative profile ofB concentration was attained across the joint, in particular in the region wherethe completion of the TLPB process was achieved. It is noteworthy that B con-centration did not exceed the typical specified range of B-alloyed steels. Thisresult explains why prior austenite grain boundaries are boride-free. To test the validity of the measured B concentrations, they were compared with those of the numerically simulated TLPB process. As a result, the calculated and experi-mentally measured values are in good agreement, within the estimated error.On the other hand, in regions where the TLPB process was not finished,athermally solidified liquid (ASL) was found at the joint, in the form of borides.In addition, neutron tomography enabled us to attain a three-dimensionalvisualization of the size and distribution of ASL, highlighting its potential as a non-destructive testing technique of TLPB weldments.