Diffraction measurements for evaluating plastic strain in A533B ferritic steel—a feasibility study

Abstract

It is known that the physical properties of many engineering materials may be strongly affected by previous loading, in particular prior plastic deformation. Most obviously, work hardening will alter subsequent yielding behaviour. Plastic deformation may also preferentially align the material microstructure, resulting in anisotropy of subsequent behaviour and a change in material fracture resistance. When physical characterisation is undertaken by experimental testing it is, therefore, important to have some knowledge of the current state of the material. As a result, it is desirable to have methods of quantitatively evaluating the level of plastic deformation which specimen material may have experienced prior to testing. This paper presents the results of a feasibility study, using a ferritic reactor pressure vessel steel, into the use of diffractive methods for plastic strain evaluation. Using neutron diffraction, changes in diffraction peak width and anisotropy of peak response were correlated with plastic deformation in a tensile test. The relationships produced were then used to evaluate permanent deformation levels in large samples, representative of standard fracture toughness test specimens.

Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

“…No obvious trend is observed for other reflections. The 211, 110 [59], and 310 [60] planes of BCC steels (textured or non-textured) have been suggested to predict macroscopic strains/stresses due to their linearity response to the applied stress and the little effect of residual intergranular strains in both elastic and plastic regions. It is also found that at low stresses, 211-oriented grains mimic the elastic-lattice response of the matrix (close to the Rietveld strain) and shows a diffraction elastic constant of 158 GPa, close to 156 GPa of the matrix.…”

Residual stress relief in the aluminium alloy 7075

“…Application of plastic deformation also leads to peak broadening during diffraction caused by non-uniform strain and a reduced effective crystallite size [14]. If it can be demonstrated that there is a systematic relationship between plastic deformation and diffraction peak widths, this could be a useful quantitative characterisation tool [15], for example, to quantify the amount of plastic deformation that occurs during the imposition of thermal gradients, when quenching in different media, or media at varying temperatures. Experimentally, this information is difficult to elucidate and is currently estimated from numerical modelling techniques.…”

In-situ measurements of stress during thermal shock in clad pressure vessel steel using synchrotron X-ray diffraction

“…Attempts have been made to qualitatively measure plastic strain from the diffraction peak width (e.g. see full width half maximum method [19]), however, the beamline used has strong influence on such measurements and requires accurate calibration for every specimen geometry. The short timeframe allocated to the experiment precluded a lengthy calibration, thus limiting our measurements to elastic strains only.…”