A multiscale experimental analysis of mechanical properties and deformation behavior of sintered copper–silicon carbide composites enhanced by high‑pressure torsion

Experiments were conducted to investigate, within the framework of a multiscale approach, the mechanical enhancement, deformation and damage behavior of copper–silicon carbide composites (Cu–SiC) fabricated by spark plasma sintering (SPS) and the combination of SPS with high-pressure torsion (HPT). The mechanical properties of the metal–matrix composites were determined at three different length scales corresponding to the macroscopic, micro- and nanoscale. Small punch testing was employed to evaluate the strength of composites at the macroscopic scale. Detailed analysis of microstructure evolution related to SPS and HPT, sample deformation and failure of fractured specimens was conducted using scanning and transmission electron microscopy. A microstructural study revealed changes in the damage behavior for samples processed by HPT and an explanation for this behavior was provided by mechanical testing performed at the micro- and nanoscale. The strength of copper samples and the metal–ceramic interface was determined by microtensile testing and the hardness of each composite component, corresponding to the metal matrix, metal–ceramic interface, and ceramic reinforcement, was measured using nano-indentation. The results confirm the advantageous effect of large plastic deformation on the mechanical properties of Cu–SiC composites and demonstrate the impact on these separate components on the deformation and damage type

Multiscale modelling for fusion and fission materials: the M4F project

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.This work has received funding from the Euratom research and training programme 2014-2018 under grant agreement No. 755039 (M4F project)

Shift in low-frequency vibrational spectra measured in-situ at 600 °C by Raman spectroscopy of zirconia developed on pure zirconium and Zr–1%Nb alloy

In this study displacement of monoclinic bands of zirconia were investigated in the function of oxidation time using the Raman spectroscopy technique. Oxidations were performed on pure zirconium and zirconium alloy in-situ at 600 °C for 6 h. Analysis of the absolute intensities as well as the positions of the characteristic for monoclinic and tetragonal phase Raman bands were performed. Reported results has highlighted that monoclinic phase of zirconia undergoes a continuous band displacement, individual for each Raman mode. Recorded shift of low frequency vibrational spectra of monoclinic phase was employed to study stress developed in zirconia during high temperature oxidation – herein called as growing stress. In addition, based on the Raman band intensity we discuss observed transition of the metastable tetragonal phase to stable monoclinic phase. Reported results, for the first time showed that studied metals (pure zirconium and its alloy) behave similarly in terms of band shift. However the resulting value of growing stress associated to the band displacement is slightly different in regards of individual band and studied sample. © 2016 Elsevier B.V

Microstructure and corrosion resistance of highly <111> oriented electrodeposited CoNiFe medium-entropy alloy films

The medium-entropy alloy is a newly intriguing material showing superb properties. A simple, one-step method was developed to electrodeposit CoNiFe medium-entropy alloy films from a sulfate and citrate bath. The microstructure and corrosion resistance were investigated in CoNiFe films with varying deposition current densities. It shows the facecentered cubic structure with a preferential orientation. HRTEM-EDS observations further show information on the nanostructure and element distribution. The films exhibit a strong corrosion resistance in 3.5 wt.% NaCl solution. The films electrodeposited with a current density of 44.4 A/dm2 shows a low self-corrosion current density of 4.72 106 A,cm2 in 3.5 wt.% NaCl solution. The corrosion mechanism was proposed in combination with electrochemical impedance spectroscopy results. The outstanding properties were attributed to the near-equimolar ternary components. The results lay a solid foundation for developing of highly oriented medium-entropy alloy films with strong corrosion resistance.Wenyi Huo, Shiqi Wang, Feng Fang, Shuyong Tan, Łukasz Kurpaska, Zonghan Xie, Hyoung Seop Kim, Jianqing Jian