Analytical electron microscopy of thin segregated layers

Abstract

Analytical convolution methods used to explain the interaction of a fine electron beam with a thin segregated layer in a typical electron microscope specimen are described. Expressions are derived which quantify the shape of the measured concentration profile determined in the microscope by scanning the beam acrass the segregated layer. The expression contains parameters concerned with the beam profile and the thickness of the segregated layer. The method is applied to grain boundary segregation studies of neutron-irradiated femticmartensitic steels. S P CrNi MO v Nb Wt.% Balance 0.10 0.38 1.01 0.016 0.006 10.65 0.64 0.64 0.16 0.30

Effect of hafnium on radiation-induced inter-granular segregation in ferritic steel

“…6 and 7, respectively. Here, the experimental data are corrected according to an analytical convolution method established by Faulkner et al [16] because the actual segregated solute grain boundary concentration should be much higher or lower in the case of enrichment or depletion than those determined by the FEGTEM microanalysis because of its limited spatial resolution. The calculated results show a good agreement with experimental data when the change of FMD population B in the presence of Hf is considered.…”

Hardening Embrittlement and Non-Hardening Embrittlement of Welding-Heat-Affected Zones in a Cr-Mo Low Alloy Steel

“…However, as the special resolution of FEGSTEM-EDS (often greater than 2 nm [15]) rarely approximates the grain boundary thickness (less than 1 nm [16]), the measured result should be a convolution value of the actual compositional distribution near the grain boundary. For this reason, the measured results were corrected by a convolution method and the details of the correction for the measured values can be seen elsewhere [17][18][19].…”

“…(less than 1 nm [16]), the measured result should be a convolution value of the actual compositional distribution near the grain boundary. For this reason, the measured results were corrected by a convolution method and the details of the correction for the measured values can be seen elsewhere [17][18][19]. The fracture appearance transition temperatures (FATTs) of the HAZs were determined by Charpy impact tests combined with fracture appearance observations with the use of scanning electron microscopy (SEM, HITACHI S4700, Tokyo, Japan).…”

Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

“…It is noted that earlier studies [8] on these weldments emphasized solute segregation effects, which were quantified at interfaces using a Vacuum Generators HB501 field emission scanning electron microscope (FEGSTEM) to provide high resolution solute concentration profiles [12]. These earlier data are referred to in the present paper.…”