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The M4F project brings together the fusion and fission materials communities working on the prediction of radiation damage production and evolution and its effects on the mechanical behaviour of irradiated ferritic/martensitic (F/M) steels. It is a multidisciplinary project in which several different experimental and computational materials science tools are integrated to understand and model the complex phenomena associated with the formation and evolution of irradiation induced defects and their effects on the macroscopic behaviour of the target materials. In particular the project focuses on two specific aspects: (1) To develop physical understanding and predictive models of the origin and consequences of localised deformation under irradiation in F/M steels; (2) To develop good practices and possibly advance towards the definition of protocols for the use of ion irradiation as a tool to evaluate radiation effects on materials. Nineteen modelling codes across different scales are being used and developed and an experimental validation programme based on the examination of materials irradiated with neutrons and ions is being carried out. The project enters now its 4th year and is close to delivering high-quality results. This paper overviews the work performed so far within the project, highlighting its impact for fission and fusion materials science.

The M4F project brings together the fusion and fission materials communities working on the prediction of radiation damage production and evolution and its effects on the mechanical behaviour of irradiated ferritic/martensitic (F/M) steels. It is a multidisciplinary project in which several different experimental and computational materials science tools are integrated to understand and model the complex phenomena associated with the formation and evolution of irradiation induced defects and their effects on the macroscopic behaviour of the target materials. In particular the project focuses on two specific aspects: (1) To develop physical understanding and predictive models of the origin and consequences of localised deformation under irradiation in F/M steels; (2) To develop good practices and possibly advance towards the definition of protocols for the use of ion irradiation as a tool to evaluate radiation effects on materials. Nineteen modelling codes across different scales are being used and developed and an experimental validation programme based on the examination of materials irradiated with neutrons and ions is being carried out. The project enters now its 4th year and is close to delivering high-quality results. This paper overviews the work performed so far within the project, highlighting its impact for fission and fusion materials science.

Mechanical size effects in ZrxNi100-x thin metallic glass films are investigated for thicknesses from 200 to 900 nm. Local order, elastic properties and rate sensitivity are shown to be thickness independent, while hardness and fracture resistance are not. The increase of hardness with decreasing thickness is related to the substrate constraint on shear banding. Fracture surfaces exhibit a corrugated morphology, except for thickness below 400 nm exhibiting perfectly flat surfaces. The corrugations appear again on the thinnest films when adding a cap layer, indicating that the fracture mechanisms are primarily dominated by the loading configuration and geometry which constrain the plastic zone extension. Increasing the Ni content from 25% to 58% leads to an increase of elastic modulus, Poisson ratio, strength, activation volume, and fracture toughness. These changes can be understood based on the change in thermodynamic fragility and Zr–Ni bonds formation. Zr75Ni25 composition shows exceptionally large rate sensitivity exponent equal to 0.058. The fracture mechanisms are not modified by composition and the fracture toughness is systematically low due to the confinement of the plastic zone. zone.

The nature of the elementary deformation mechanisms in small-grained metals has been the subject of numerous recent studies. In the submicron range, mechanisms other than intragranular dislocation mechanisms, such as grain boundary (GB)-based mechanisms, are active and can explain the deviations from the Hall-Petch law. Here, we report observations performed during in situ transmission electron microscopy (TEM) tensile tests on initially dislocation-free Al thin films with a mean grain size around 250 nm prepared by microfabrication techniques. Intergranular plasticity is activated at the onset of plasticity. It consists of the motion of dislocations in the GB plane irrespective of the GB character. Surface imperfections, such as GB grooves, are supposed to trigger intergranular plasticity. At larger deformations, the motion of the intergranular dislocations leads to GB sliding and eventually cavitation. In the meantime, GB stress-assisted migration and dislocation emission inside the grain from GB sources have also been observed. The observation of these different mechanisms during the deformation provides an important insight into the understanding of the mechanical properties of metallic thin films. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.