Stability and strengthening effect of aging induced-nanofeatures in δ-ferrite in an austenitic stainless-steel weld

The deformation behavior of δ-ferrite in an aged austenitic stainless-steel weld was investigated to obtain insights on the contribution of aging-induced nanofeatures, such as spinodal decomposition and G-phase precipitation, to aging embrittlement. To evaluate the hardening effect of the G-phase, a reversion heat treatment was applied to the aged weld. The strengthening effect of spinodal decomposition and the G-phase was measured using nanopillar compression tests. The deformed microstructure exhibited the dissolution of G-phases but a slight change in the spinodal nanostructure, indicating a clear difference in the stability of the nanofeatures during deformation. The quantitative measurement of the G-phase and the application of the Orowan model showed that the measured strengthening effect from the G-phase was less than that of the estimation, implying that the G-phase was not as effective as an impenetrable obstacle. On the other hand, spinodal decomposition showed high stability after deformation, leading to a noticeable hardening effect.