Molecular dynamics simulation of vacancy and void effects on strain-induced martensitic transformations in Fe-50 at.% Ni model concentrated solid solution alloy

Probing the Damage Recovery Mechanism in Irradiated Stainless Steels Using In-Situ Microcantilever Bending Test

“…Dislocations likely nucleate or glide towards the crack tip-cross-slip driven or dislocation multiplication mechanism (Bitzek and Gumbsch, 2013;Daly et al, 2017;Ast et al, 2019) as well as active sources such as heterogeneities generated by extreme conditions (Lucas, 1993;Sun et al, 2021). In the base metal (Figure 7A), the existence of radiation-induced cavities could activate the martensitic transformation near cavities through shear deformation (Yang et al, 2022). However, in the HAZ or the archive materials (Figure 7B), dislocations are active sources for slip and work hardening.…”

Model for deformation-induced martensitic transformation in irradiated materials

“…Nevertheless, these factors cannot fully explain the irradiation-enhanced DIMT. As mentioned in §1, extensive experimental [14,26] and simulation [16,32] studies have shown that irradiation-induced voids can have a contribution by providing additional nucleation sites. Apart from the nucleation sites responsible for DIMT in unirradiated materials, α′-martensite can nucleate on the surface of irradiation-induced voids [14,16,32], which is along the pathway γfalse→α′.…”

“…As mentioned in §1, extensive experimental [14,26] and simulation [16,32] studies have shown that irradiation-induced voids can have a contribution by providing additional nucleation sites. Apart from the nucleation sites responsible for DIMT in unirradiated materials, α′-martensite can nucleate on the surface of irradiation-induced voids [14,16,32], which is along the pathway γfalse→α′. Therefore, the number density of all possible nucleation sites considering irradiation effects can be expressed as Nnormalm=Nunirr+Nnormalv=Npre+fnormalIv¯normalI+Nnormalv,where Nv is the number density of additional nucleation sites on the surface of irradiation-induced voids.…”

“…Therefore, the number density of all possible nucleation sites considering irradiation effects can be expressed as Nnormalm=Nunirr+Nnormalv=Npre+fnormalIv¯normalI+Nnormalv,where Nv is the number density of additional nucleation sites on the surface of irradiation-induced voids. Furthermore, as indicated in the MD simulation of martensitic transformations, voids with larger surface area have a more pronounced acceleration effect on DIMT [32]. For this reason, a linear relationship is adopted to describe the correlation between the number of nucleation sites provided by voids per unit volume of the austenite phase and the surface area: Nnormalv=λnormals⋅false(πdnormalv2⋅ρnormalvfalse),where dnormalv is the diameter of voids, ρnormalv is the number density of voids.…”

“…The role of voids is confirmed by tensile tests on irradiated 12Cr18Ni10Ti AustSS [26], and martensite nucleation at the void surface is observed directly in additively manufactured 316L steels containing fabrication-induced nanovoids [31]. In addition, martensite nucleation from voids is found to be prominent by MD simulations of a Fe-C alloy [16] and a Fe-Ni alloy [32] with a tensile stress state. As a general mechanism, the importance of voids for martensitic transformation is also confirmed in other alloy systems such as shape memory alloys [17] and high entropy alloys [33].…”