An investigation of the thermal stability of an Mg-Dy alloy after processing by high-pressure torsion

An Mg-0.41Dy (wt%) alloy was successfully processed by high-pressure tension (HPT) through 5 turns at room temperature. The evolution of the recrystallization microstructure and the texture and mechanical properties of the deformed alloy were investigated after annealing at 200 and 400 °C for 1 h using Electron Backscatter Diffraction (EBSD) and Vickers measurements. The recrystallization temperature and activation energy were evaluated using Differential Scanning Calorimetry (DSC). Processing by HPT led to significant grain refinement with an average grain size of ~0.5 ± 0.1 μm which increased to ~1.2 ± 0.8 μm after annealing at 400 °C. This slow increase in grain size at a high temperature demonstrates a good thermal stability of the microstructure. The alloy exhibited two main fiber textures after HPT processing: firstly a typical basal fiber (φ1 = 0–360°, Φ = 0° and φ2 = 0–60°) and secondly a fiber localized at φ1 = 180°, Φ = 60° and φ2 = 0–90°. These textures were retained after annealing at 400 °C. There was no change in the microhardness value after annealing at 200 °C (41 ± 1 Hv) and only a minor decrease after annealing at 400 °C (38.4 ± 0.5 Hv). The DSC results showed that the temperature associated with the recrystallization process increased with increasing heating rate and the activation energy for recrystallization was measured as ~25 kJ mol−1

Correlation of tensile properties of Arc-Sprayed coatings and easy testing methods

Different techniques are usually employed to evaluate the mechanical properties of arc-sprayed coatings. In many situations, comparing properties is complex, and values extracted from tensile tests are required for structural projects. X6CrNi18-8 stainless steel and molybdenum were sprayed onto a mild steel substrate using the electric arc thermal spray technique to discuss this issue. After a detailed microstructure characterization, tensile tests were performed on both coatings to determine the yield strength and total elongation. Easy techniques were also applied: Vickers hardness and Charpy impact test. Tensile tests have shown that applying coatings increased the steel substrate’s total elongation. Molybdenum coating presented a higher impact resistance than the X6CrNi18-8 one, resulting in no correlation between elongation and Charpy values. On the other hand, correlations between hardness and yield strength were identified, opening a discussion on the effects of the microstructure and type of test used

On the groove pressing of Ni-W alloy: microstructure, texture and mechanical properties evolution

International audienceThe microstructure, texture and mechanical properties of the Ni-14%W(wt.%) alloy with two different initial grain sizes and textures were investigated after groove pressing (GP) at 450 °C to 4 cycles using Electron Back Scatter Diffraction (EBSD) and microhardness measurements. The initial first series was characterized by small equiaxed grains and Cube dominant texture component. The second series has elongated grains and β-fiber texture. EBSD analysis has shown that GP processing led to a slight refinement (less than 15%) of equiaxed grains in series I while greater refinement (~55%) of the mean spacing along normal direction was observed in series II. The texture did not drastically change from the initial ones and was characterized by the weakening of the Cube component in series I and rapid decrease of Copper component for series II. GP processing reduces very slightly the plastic anisotropy of the alloy with initial elongated granular microstructure

Poopćenje analitičkih izraza za pseudo -voigtovu funkciju koja se rabi u analizama difrakcijskih vrhova

Nous revisitons ici la théorie, utilisée en analyse des profils de raies de diffraction des rayons X et des neutrons, relative à la fonction de forme du pic dite de pseudo -Voigt (notée pV). Nous présentons une généralisation des expressions de la largeur intégrale et à mi-hauteur de la fonction pV, de la transformée de Fourier de cette fonction ainsi que du seuil du paramètre de mélange h. Nous incorporons nos résultats dans la procédure de fit, ce qui améliore les facteurs de précision.Razmatramo teoriju koja se primjenjuje u analizi linija difraktiranog rentgenskog zračenja i neutrona a odnosi se na tzv. pseudo-Voigtovu (skraćeno pV) funkciju za opis oblika vrha. Dajemo poopćenje analitičkog izraza za ukupnu širinu i širinu na pola visine vrha funkcije pV, Fourierovu transformaciju izraza, kao i prag parametra miješanja η. Primijenjujemo naš postupak za prilagodbu i postižemo poboljšanje točnosti

The effect of the process on mechanical properties of polylactic acid - date palm leaf fibers composite films produced by extrusion blowing

Biocomposite films prepared with melt compounding and film blowing have become a new trend in plastic research to deliver more eco-friendly packages. Polylactic acid (PLA) was melt compounded with minimally processed date palm leaf fiber (DPLF) and converted into films by blown film extrusion. The compounding was done in order to enhance the film mechanical properties in one hand, and to decrease the film production cost in the other hand. In this present study, a reference PLA film and films with 1%, 2%, and 5% of DPLF (weight %) were produced with different process parameters. The spatial variations in films thickness and lay flat width indicate that the addition of DPLF up to 2% enhances the bubble stability for the tested process parameters. However, the composite with 5% DPLF shows nearly the same processability window as the neat PLA. The structural and mechanical characterizations of films suggest a reinforcing effect of the PLA matrix up to 2% of fiber (with an optimum at 1%). Larger DPLF loading leads to depressed and more anisotropic mechanical properties, related to an increased density of defects at the fiber-PLA fragile interface and to a DPLF-induced enhanced PLA thermal degradation and amorphous phase orientatio

Poopćenje analitičkih izraza za pseudo -voigtovu funkciju koja se rabi u analizama difrakcijskih vrhova

Nous revisitons ici la théorie, utilisée en analyse des profils de raies de diffraction des rayons X et des neutrons, relative à la fonction de forme du pic dite de pseudo -Voigt (notée pV). Nous présentons une généralisation des expressions de la largeur intégrale et à mi-hauteur de la fonction pV, de la transformée de Fourier de cette fonction ainsi que du seuil du paramètre de mélange h. Nous incorporons nos résultats dans la procédure de fit, ce qui améliore les facteurs de précision.Razmatramo teoriju koja se primjenjuje u analizi linija difraktiranog rentgenskog zračenja i neutrona a odnosi se na tzv. pseudo-Voigtovu (skraćeno pV) funkciju za opis oblika vrha. Dajemo poopćenje analitičkog izraza za ukupnu širinu i širinu na pola visine vrha funkcije pV, Fourierovu transformaciju izraza, kao i prag parametra miješanja η. Primijenjujemo naš postupak za prilagodbu i postižemo poboljšanje točnosti

Cr cluster characterization in Cu-Cr-Zr alloy after ECAP processing and aging using SANS and HAADF-STEM

International audienceThe precipitation of nano-sized Cr clusters was investigated in a commercial Cu-1Cr-0.1Zr (wt.%) alloy processed by Equal-Channel Angular Pressing (ECAP) and subsequent aging at 550 °C for 4 hours using small angle neutron scattering (SANS) measurements and high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM). The size and volume fraction of nano-sized Cr clusters were estimated using both techniques. These parameters assessed from SANS (d~3.2 nm, Fv~1.1 %) agreed reasonably with those from HAADF-STEM (d ~2.5 nm, Fv~2.3%). Besides nano-sized Cr clusters, HAADF-STEM technique evidenced the presence of rare cuboid and spheroid sub-micronic Cr particles about 380-620 nm mean size. Both techniques did not evidence the presence of intermetallic CuxZry phases within the aging conditions

Modelling, control design, and analysis of the inner control's loops intended for single‐phase voltage‐controlled inverter‐based microgrid

In voltage-controlled voltage source inverters (VSIs)-based microgrids (MGs), the inner control is of prime interest task for guaranteeing safe and stable operation. In this paper, an in-depth investigation of the modelling, control design, and analysis of the voltage and current inner control loops intended for single-phase voltage-controlled VSIs is established. The main objective of this work is to provide a comprehensive study of the mathematical modelling, control design, and performance evaluation of the inner control's loops considering different proportional-integral (PI) controller types with and without compensation, and to determine the optimal scheme that can offer better performance in terms of implementation simplicity, robustness, and transient and steady-state responses. Thus, the mathematical closed-loop models of designed outer voltage and inner current control schemes based on PI, P, and feedforward controllers with and without compensation are, first, derived. Following this, a systematic and effective control design for tuning the different PI controllers’ parameters is proposed. Furthermore, an analysis revealing the performance of the designed voltage and current control schemes is provided. This analysis enables us to choose a P controller and PI feedforward controller for the current control loop and the voltage control loop, respectively. The chosen P and PI controllers should be simple; meanwhile, they should offer a wide bandwidth. A simulation study is carried out in MATLAB/Simulink software to assess the performance of the adopted inner control scheme for both linear and non-linear loads. In addition, an experimental setup, based on a TMS320F2837xD μC, of a single-phase VSI supplying linear and non-linear loads is built to verify the effectiveness and the robustness of the adopted inner controller. The results demonstrated: (1) the necessity of introducing the compensation term, which is responsible for offering control improvement against voltage perturbation, (2) the high tracking performance of the chosen controller in terms of dynamic and steady-state responses as well as its simplicity of implementation

Evaluating the textural and mechanical properties of an Mg-Dy alloy processed by high-pressure torsion

Samples of an Mg-0.41Dy (wt. %) alloy were severely deformed by high-pressure torsion (HPT) at room temperature up to 15 turns and the texture, microstructure and microhardness values in the centres, mid-radial points and edges of the HPT-deformed discs were investigated using X-ray diffraction, Electron BackScatter Diffraction and Vickers microhardness measurements. The textures in the centres of discs were characterized by a typical weak basal fiber whereas at both the mid-points and edges of the discs there was a strong basal texture where the c-axis of most grains was shifted 15° away from the shear direction. An almost homogeneous ultrafine-grained structure with a grain size of about 0.75 μm was achieved after 15 HPT turns. The microhardness values in these three positions increased with increasing numbers of turns, reached a maximum and then decreased to a lower steady-state level at large strains. In addition to dislocation and grain size hardening, the results show that texture strengthening contributes significantly to the rapid increase in hardening in the early stages of deformation