A mechanistic model for depth-dependent hardness of ion irradiated metals

Abstract

A mechanistic model was developed for modeling the depth-dependent hardness in ion irradiated metallic materials. The model is capable of capturing the indentation size effect, ion irradiation induced damage gradient effect, and effect of unirradiated region acting as a soft substrate. A procedure was developed and described in detail to parametrize the model based on experimentally obtained hardness vs. indentation depth curves. Very good agreement was observed between our model predictions and experimental data of several different stainless steels subjected to various ion irradiation conditions. In addition, two hardening mechanisms are revealed in the new model. One is the well-known indentation size effect arising from the creation of geometrically necessary dislocations as the indenter pierces into the materials. The other is the irradiation hardening due to the presence of irradiation-induced defects. As a function of indentation depth h, the hardening due to indentation size effect is described by * hh , while the hardening due to irradiation first follows a power law form n Ph , then changes to 3 Z h Q h  , where * h , P, n , Z and 0 Q  are constants. This transition occurs at the indentation depth when the plastic zone reaches the end of the irradiated layer.

Hardening and Creep of Ion Irradiated CLAM Steel by Nanoindentation

“…On the other hand, the curves for the irradiated specimens are approximately bilinear. When the indentation depth is greater than ~265 nm, the plastic zone extends beyond the irradiated layer and the hardness is largely affected by the unirradiated substrate [21,22,57,62,63]. However, when the indentation depth is less than ~265 nm, the hardness is affected mainly by the irradiated layer and can be well fitted by the Nix-Gao model, as reported by Kasada et al [64].…”

Initial Observation of Grain Orientation Dependent Nanoindentation Hardness of Al 6061 Gas-atomized Powder

“…tion-based stress-strain curves [6], fracture toughness [7], and tribological properties as well as wear characteristics [8,9], among others, such as irradiation-induced hardening [10,11].…”

Fundamental Mechanisms for Irradiation-Hardening and Embrittlement: A Review

“…For instance, under neutron irradiation, the irradiated materials can be easily got through by neutrons (given the typical dimension of in-vessel nuclear components), which makes the irradiation-induced damage profile be uniformly distributed throughout the whole component. As a comparison, for the case of ion irradiation, the generated defects are usually within the shallow region (up to a few micrometers) because of the limited penetrating capacity of ions, and the defect distribution is non-uniform making standardized mechanical testing almost inapplicable [52,64,90,91]. Though the distribution of irradiation-induced defects might not be the same for neutron and ion irradiation, the dominant defect type is usually identical, which mainly depends on the crystalline structure and irradiation temperature.…”

“…The observation of irradiation-induced defects by advanced experimental techniques, and their interaction with gliding dislocations detected by in situ experiments could tremendously enrich our understanding of the plastic deformation in irradiated materials. In addition, the measured density and size of irradiation defects can be adopted as the input parameters for numerical simulations and theoretical models [37,38,64].…”