Papers Published

1. Moore, K.D. and Cocks, F.H. and Jones, P.L., Positron evaluation of hydrogen in a 17 nickel maraging steel, J. Test. Eval. (USA), vol. 11 no. 5 , pp. 309 - 11 .
   (last updated on 2007/04/10)

   Abstract:
   Doppler broadening measurements of the γ-ray emission from positron annihilations have been made on a 17 nickel maraging steel, heat treated to Rockwell hardness, C Scale 49, and subsequently cathodically charged with hydrogen. Changes in the positron annihilation γ-ray spectra were measured using a line shape parameter (S) based on the ratio of central to total spectra area. The recovery of the S parameter as a function of time after hydrogen charging is correlated with hydrogen egress from the metal. The observed sensitivity of this Doppler broadening positron annihilation technique to hydrogen content is attributed to hydrogen compensation of lattice defects (dislocations) in the maraging steel

   Keywords:
   alloy steel;dislocation structure;impurities;impurity-dislocation interactions;nondestructive testing;positron annihilation in liquids and solids;