Elastic–plastic-damage model of nano-indentation of the ion-irradiated 6061 aluminium alloy

Abstract

The paper presents experimental and numerical characterization of damage evolution for ion-irradiated materials subjected to plastic deformation during nano-indentation. Ion irradiation technique belongs to the methods where creation of radiation-induced defects is controlled with a high accuracy (including both, concentration and depth distribution control), and allows to obtain materials having a wide range of damage level, usually expressed in terms of displacements per atom (dpa) scale. Ion affected layers are usually thin, typically less than 1 micrometer thick. Such a low thickness requires to use nano-indentation technique to measure the mechanical properties of the irradiated layers. The He or Ar ion penetration depth reaches approximately 150 nm, which is sufficient to perform several loading-partial-unloading cycles at increasing forces. Damage evolution is reflected by the force-displacement diagram, that is backed by the stress–strain relation including damage. In this work the following approach is applied: dpa is obtained from physics (irradiation mechanisms), afterwards, the radiation-induced damage is defined in the framework of continuum damage mechanics to solve the problem of further evolution of damage fields under mechanical loads. The nature of radiation-induced damage is close to porosity because of formation of clusters of vacancies. The new mathematical relation between radiation damage (dpa) and porosity parameter is proposed. Deformation process experienced by the ion irradiated materials during the nano-indentation test is then numerically simulated by using extended Gurson–Tvergaard–Needleman (GTN) model, that accounts for the damage effects. The corresponding numerical results are validated by means of the experimental measurements. It turns out, that the GTN model quite successfully reflects closure of voids, and increase of material density during the nano-indentation.

Modelling Irradiation Effects in Metallic Materials using the Crystal Plasticity Theory

“…There were so far many efforts to take into account the influence of irradation defects on the mechanical properties of metals and alloys in macroscopic phenomenological models, cf. e. g. [35][36][37][38][39][40]. However, as could be seen from the previous paragraphs, the phenomena related to radiation-induced microstructure changes appear at different time and length scales and therefore the multiscale modelling approach is the most appropriate in addressing them [18,23].…”

“…Since the thin surface of a material cannot be mechanically tested using conventional mechanical testing, typically the instrumented (nano)indentation test (cf. e. g. [39,40,[77][78][79][80][81][82]) is used in order to obtain the properties of the irradiated layer. As it was already mentioned in this review, the basic mechanistic effect of irradiation is irradiation hardening.…”

Mechanisms of strength and hardening in austenitic stainless 310S steel: Nanoindentation experiments and multiscale modeling

“…In nanoindentation testing, plasticity size effects were vastly experimentally studied [43][44][45] . In the case of strainhardening materials, hardness is less related to yield strength and plastic deformation, but it directly depends on a strain induced by the indenter geometry.…”

An elasto-plastic damage accumulation model for fatigue life predication of ductile metals at the yield stress

“…The second purpose of introducing the plastic weighting factors of W e and W p is to unify the fatigue life prediction from LCF to HCF as plotted in Figure 4(a) and (b). Since the strain energy density is an important parameter for the identification of fatigue damage (Ahmadzadeh and Varvani-Farahani, 2019; Ustrzycka et al, 2020), from the analysis of great amount test data, here we propose a strain-energy-density based weighting factors for W e and W p :…”