Strain Determination In A Friction-welded Sample Using Non-destructive Neutron Diffraction

Author:  Priesmeyer, H.G. and Schroder, J.
Source:  Shot Peening Theory and Appl., IITT Intl. 1991
Doc ID:  1991041
Year of Publication:  1991
Abstract:  
Neutrons can penetrate thick layers of many engineering materials and therefore provide a useful technique to investigate internal strains reproduced by lattice deformations in a nondestructive way. The method uses high-resolution neutron diffractometry to determine lattice parameter variations (d-do)/do of the order of 10-3 to 10-4 caused by internal or external forces. The strain distribution across the weld in an friction-welded sample of a Ni-base superalloy (Waspaloy) has been investigated. To determine the absolute amount of deformation, the unaffected lattice parameters d-o must be known. The lattice parameters in regions far from both weld and heat affected zone seem to be a good choice, whereas a high-resolution measurement on Waspaloy powder clearly showed prestress of the powder grains; subsequent annealing caused the precipitation of a 71-phase. The results of the experiments are presented and discussed and conclusions are drawn concerning the design of a neutron spectrometer optimized for strain measurements at Geesthacht.