Irradiation-assisted pseudoelasticity in 316L stainless steel through dislocation loop-controlled martensitic phase transformations

We present pseudoelasticity activated by neutron irradiation in 316L austenitic stainless steel. Wrought and powder metallurgy with hot isostatic pressing (PM-HIP) specimens are irradiated to ∼4 displacements per atom at ∼400°C, then nanoindented. In wrought 316L, irradiation-induced voids and dislocation loops provide mechanical energy for γ→α′ martensitic transformation. But lower loop density in PM-HIP 316L changes the martensitic transformation pathway to reversible γ↔ε, enabling pseudoelasticity. Loops induce ε-martensite formation through compressive strain, with tensile strain driving ε-martensite growth. Strain recovery in PM-HIP 316L is superior to that in Fe-based shape memory alloys, providing promise for irradiation-engineered pseuoelasticity in austenitic steels.