Residual stress characterization in 12%-Cr steel friction stir welds by neutron diffraction

Abstract

In the present paper we report the results of a study into friction stir welds made in 12.7 mm-thick 12%-Cr steel plates. Residual stress measurements were performed using angle-dispersive neutron diffraction. Complete characterization of the three-dimensional residual stress state in friction stir weld samples was obtained by analysing diffracted peaks; peak broadening for identifying the regions of severe plastic deformation and the associated residual strain (eigenstrain) acting as the source of residual stress and peak shifting for evaluating residual elastic strains in the welded component. Three different methods were used to address the key issue of determining the d 0 variation across the weld. The comb (or matchstick) method was compared with two other approaches: the balance method, and the zero traction method. It was found that a combination of the comb and the zero traction methods allows reliable residual strain/stress distributions.

Evaluation of Residual Stresses in 12%-Cr Steel Friction Stir Welds by the Eigenstrain Reconstruction Method

“…The eigenstrain is a term indicating any permanent strain arising in the material due to some inelastic processes such as plastic deformation, crystallographic transformation, and thermal expansion mismatch between different parts of an assembly [8] . This indicates that the eigenstrain accounts for all permanent strains that arise in the material exhibiting inelastic behaviour.…”

“…The ERM methodology was developed based on the eigenstrain theory and elucidated in the previous works [7,8] . There are three essential components of the ERM, which are the residual strain measurements, the solution of the inverse problem of eigenstrain theory, and the Simple Triangle (SIMTRI)…”

Corrosion Susceptibility and Functionally Graded Properties of Ti-35Nb-4Sn Alloy Processed by Laser Remelting

“…Together, these two factors account for the broadening of XRD peaks from base metal to fusion zone regions, as observed by the increase in full width at half maximum (FWHM) measurements shown in Figure 5. The correlation of diffraction line broadening and lattice parameters distortions is well stablished 26 and has been used to assess the performance of welds 27 .…”

Influence of external weld flash on the in-plane plane-strain formability of friction stir welded sheets

“…The brittle fractures occurred in samples with features of defects inducing failure modes. The residual stress characterization of welds made by FSW was performed by Jun et al 18 and Fratini and Pasta. 19 Jun et al 18 analyzed the residual stress variation during FSW of 12%-Cr steel plates through different approaches of neutron diffraction technique.…”

“…The residual stress characterization of welds made by FSW was performed by Jun et al 18 and Fratini and Pasta. 19 Jun et al 18 analyzed the residual stress variation during FSW of 12%-Cr steel plates through different approaches of neutron diffraction technique. Fratini and Pasta 19 fabricated butt joint, lap joint, and T-joint made of AA2024-T4 and AA7075-T6 Al alloys and measured the residual stress through cut compliance method.…”