Relationship between damage and hardness profiles in ion irradiated SS316 using nanoindentation – Experiments and modelling

Comparative Study of Two Nanoindentation Approaches for Assessing Mechanical Properties of Ion-Irradiated Stainless Steel 316

“…The oblique pattern of indent rows allowed a large number of indents to be made in the thin irradiated region, thus enhancing the spatial resolution of the data even further, over and above that enabled by the oblique cross-sectioning. There were about 10 rows of 40-60 indents made in each sample (for more details, see [14]).…”

“…The simulated displacement damage profiles (in dpa) obtained from SRIM calculations are shown in Figure 2 (after the authors' previous publication [14]). The plot shows the damage in SS316 as a function of depth and energy of the incoming He + ion-beam.…”

“…Experiments by Byun et al [19] on SS316 suggests that hardening due to irradiation is comparable to hardening by deformation-induced dislocation formation. The approach taken herein is analogous to the study detailed in the authors' previous work [14], where the influence of the most pronounced Frank loop obstacles [20] and forest dislocation obstacles in stainless steel are reduced to a simplified fitted model, where σ rad (σ 0 ,dpa) is a first order function that expresses the irradiated hardening and provides a continuum level bulk property response as outlined in [21]…”

“…The hardness results reported are expressed in terms of computed hardness derived from the load and area function of the Berkovich tip. The material is characterized by the experimentally derived elastic modulus, E = 192 GPa, Poisson's ratio, ν = 0.3 and a yield stress versus plastic strain curve as user inputs for the varying dpa outlined in the earlier study [14]. In the following treatment, we compare the results of the modelling of the samples irradiated with 2 MeV He 2+ ions, tested in the top-down and the OCS mode.…”

“…Here, the authors attempt to compare the efficacy of the two methods mentioned above in studying the relationship between the calculated depth of peak damage and the corresponding depth of hardness peak as a function of ion irradiation energy. A finite element model, developed by the authors in previous works [14,15] for both nanoindentation methods has been used to understand the deformation behaviour in the plastic zone below the indents. The nature of the dependence of measured hardness on indentation depth vis-à-vis the ion beam energy is discussed for both methods, and appropriate ranges of applicability for each method are suggested based on the experimental results and analysis.…”