This study deals with the DC and HiPIMS reactive magnetron deposition process using a pure nickel target (99.995%) in an Ar-N2 gas mixture with varied nitrogen gas flow and bias voltage (floating or ...-100 V). The characterization of the NiN films has been carried out by X-ray diffraction (XRD), X-ray photoelectrons spectroscopy (XPS) and Energy dispersive X-ray Spectroscopy (EDXS). XRD measurements have highlighted the deformation of the Ni cubic cell as a function of nitrogen content, and a mixture of nitrided phases (Ni4N, Ni3N and Ni2N) appears for 20% N2 in the discharge. XPS and EDX are well correlated and permit us to determine three zones: metallic between 0 and 20% N2, Ni4N between 20% and 42% N2 and finally Ni3N for N2 above 50%. These three zones are in good agreement with deposition rates and optical emission spectroscopy measurements. Cyclic voltammetry has been performed in a conventional three-electrode cell using neutral, alkaline and acidic aqueous electrolytes. The NixN electrochemical behavior shows a pseudocapacitive charge storage mechanism in LiNO3 and KOH electrolytes using an appropriate voltage window, suitable for supercapacitors, whereas NixN exhibits reversible faradaic redox peaks beyond one potential in KOH, depicting NixN film as a battery-type electrode.
•Influence of nitrogen content in the discharge on the plasma, and the composition and crystallization of NixN films,•Electrochemical characterization of NixN films deposited by a composition of DCMS and HiPIMS
An experimental and theoretical investigation was carried out to study the in-depth distribution of residual stress after a cold-rolling test in a zirconium alloy. Grazing incidence X-ray diffraction ...was used to analyze the heterogeneous stress field with regard to different diffraction volumes below the surface of the sample. An interpretation of the intergranular stress analysis based on in-depth stress development has been made using an elastoplastic self-consistent model in order to account for the effect of plastic anisotropy. The contribution and the magnitude of both the first- and second-order residual stresses as a function of the penetration depth has been correctly evaluated using information from the model. The results show the complementarity of the methods used.
Additive manufacturing processes and especially the family of laser powder bed fusion technologies have a great industrial potential since it enables, from metal powder beds, to produce full density ...complex monolithic parts. The high-temperature gradient resulting from the locally concentrated energy input leads to strong temperature fields driving non-negligible residual stress gradients, part deformations and crack formation. Resulting stress and texture gradients arise from the interdependent physical phenomena (metallurgical, thermal, mechanical and fluid mechanics) occurring during the process. Present work focuses on the residual stress being built in an austenitic stainless steel cubical shaped part of 1 cm side, prepared by a laser powder bed fusion process from a gas-atomized metallic powder (from martensitic X40CrMoVN16-2 stainless steel), through a full residual stress tensor mapping achieved thanks to neutron diffraction. Stress analyses incorporate morphological and crystallographic textures, as well as elastic anisotropy. Components of the principal stress tensor display compressive values close to the baseplate that develop into low compression, and a tensile stress state at the subsurface (surrounding thermal history effects). Results also underline the strong impact of matter environment (and thus thermal environment) onto stress gradient magnitude and the complex loading origins of the residual stress.
In situ neutron diffraction experiments have been performed under uniaxial tensile testing in a commercially pure titanium in order to determine strain pole figures. The evolution of intergranular ...strains was observed in the bulk material along multiple orientations for 4 reflections: {10.0}, {10.1}, {11.0} and {00.2}. The experimental data was used to test an elasto-plastic self-consistent model. A particular focus has been devoted to the relationship between the internal strains and the deformation systems activity. The model was in agreement with the experiments, and the simulations reproduced the main features observed on the in situ measured strain pole figures.
Complementary methods were used to analyse residual stresses and texture evolution in Zircaloy-4 sheets which had undergone cold-rolling deformation: X-ray diffraction and the self-consistent model. ...A modified elastoplastic self-consistent model, adapted to large deformation, was used to simulate the experimental results and showed close agreement with the experimental data. A new formulation of crystal plasticity is proposed. The influence and the role of elastoplastic anisotropy were also studied and explained in this work. Good agreement was found between experimental and predicted crystallographic textures. The contribution and the magnitude of the first- and second-order residual stresses were correctly evaluated using information from the model. Comparison between the X-ray diffraction results and the simulations confirms that prismatic slip is the main active deformation mode in this alloy under large strain.
The scope of this work is the determination of the coefficients of thermal expansion of the Ti-17 β-phase. A rigorous inverse thermo-elastic self-consistent scale transition micro-mechanical model ...extended to multi-phase materials was used. The experimental data required for the application of the inverse method were obtained from both the available literature and especially dedicated X-ray diffraction lattice strain measurements performed on the studied (α
+
β) two-phase titanium alloy.
Hygrothermal cycles are known to cause degradation of fiber-reinforced polymer composite materials due to moisture uptake and thermal expansion. The knowledge of internal stresses due to cyclic ...environmental conditions is necessary to forecast a possible damage occurrence in the material during its service life. The accelerated cycles are studied so as to define the material geometry and environmental conditions to reproduce the in-service material state in a shorter time. In the present work, a self-consistent (SC) model is used in order to predict the stress state at the microscopic scale (fiber and matrix) induced by the real and accelerated cycles. The main aim is to compare the local states induced by the real and accelerated cycles in particular near to the edges where hold periodic conditions.
X-ray diffraction is used to assess the development of residual stresses within the grains of Zr alloy tubes processed via cold pilgering. A modified elastoplastic self-consistent model was used to ...simulate the texture and the internal stresses developments. The influence and the role of elastoplastic anisotropy were also studied and explained in this work. The contribution and the magnitude of the first- as well as the second-order residual stresses were correctly evaluated using information from the model. Comparison between the X-ray diffraction results (texture
and residual strains) and the simulations confirms that prismatic slip is the main active deformation mode in this alloy under large strain.
Complementary methods have been used to analyse residual stresses in a heat‐treated Zr702 sheet which had undergone uniaxial plastic deformation: X‐ray diffraction and self‐consistent models. The ...elastoplastic self‐consistent model has been used to simulate the experiments and exhibits agreement with experimental data. X‐ray diffraction analysis in the rolling direction shows opposite stress values for {} and {} planes, respectively. The measured strains were generated by an anisotropic plastic deformation. The comparison between ɛφψversus sin2ψ and simulations confirms that prismatic slip is the main active deformation mode. Plastic incompatibility stress in X‐ray measurements should be taken into account in order to make a correct interpretation of the experimental data.
Internal stresses due to anisotropic thermal and plastic properties were investigated in a rolled Zirconium-α. The thermal stresses induced by a cooling process were predicted using a self-consistent ...model and compared with experimental results obtained by X-ray diffraction. The study of the elastoplastic response during uniaxial loading was performed along the rolling and the transverse direction of the sheet, considering the influence of the texture and the thermal stresses on the mechanical behaviour. We used an elastoplastic self-consistent formulation and the predicted results are compared with mechanical tests. The role of twinning and slip on the development of internal stresses is also discussed.
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