Accession Number : AD0866795

Title :   Backscatter Mossbauer Techniques Applied to Deterioration Modes in Metals.

Descriptive Note : Final rept. 17 Apr 68-2 Aug 69,

Corporate Author : MITHRAS CAMBRIDGE MA

Personal Author(s) : Terrell, John H. ; Briskman, Richard K. ; Auth, Gerald L.

Report Date : SEP 1969

Pagination or Media Count : 91

Abstract : The effects of various experimental parameters on Mossbauer Effect reflection spectra using 6.3 keV X-rays, 14.4 keV gamma-rays and 7.3 keV internal conversion electrons were investigated. Source, sample, and detector geometry as well as shielding arrangements were studied in order to optimize resolution and signal to noise for a given measurement time. The effects of the single channel analyzer settings were determined. The experimental techniques acquired in this fashion were applied to studies of several deterioration modes in steel. Surface Stress: Magnetic domain ordering due to induced and residual stress caused a change in the peak height ratio A2/A1. The effect was observed in a sample of A515-60 steel under tensile test and in shot-peened cast iron. The ratio increases with increasing tension, and provides a useful means of monitoring surface stress. Dissolved Hydrogen: The predicted effect of dissolved hydrogen on reflection Mossbauer Effect spectra of steel, i.e., more positive values for the isomer shift, was observed. This indicates the possibility of devising an NDT for hydrogen embrittlement of high strength steels. Nitriding: The nitriding of 4140 steel had pronounced effects on the Mossbauer spectra. Based on this data, the Mossbauer Effect could be used as a quality control check on nitrided steel. (Author)

Descriptors :   *MOSSBAUER EFFECT), (*METALS, STEEL, STRESSES, HYDROGEN EMBRITTLEMENT, CASE HARDENING, NONDESTRUCTIVE TESTING.

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE