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The Geometrically Necessary Dislocation (GND) density was estimated from Electron Backscatter Diffraction (EBSD) data for an AZ31/Mg-0.6Gd (wt.%) hybrid material fabricated by high-pressure torsion (HPT) at room temperature through an equivalent strain range of ϵeq = 0.3–144 using Kernel Average Misorientation (KAM) and the Nye tensor approaches. The results show that generally the GND densities are significant at the beginning of the deformation (ϵeq = 0.3) and decrease in both alloys when ϵeq increases. The Mg-0.6Gd alloy exhibits a lower GND density due to rapid dynamic recrystallization. These results were compared to the GND densities measured in AZ31 and Mg-0.6Gd mono-materials processed separately by HPT under the same experimental conditions. In these mono-materials the GND densities increase with increasing equivalent strain up to 7 and then decrease with further straining. The Mg-0.6Gd and AZ31 regions of the hybrid material exhibit higher GND densities than the mono-materials particularly at low strain where the disc thickness and the bonding of the AZ31/Mg-0.6Gd interfaces cause more deformation heterogeneity in the hybrid material. It is shown that the GND density evolution as a function of ϵeq has the same tendency for the KAM and the Nye approaches but the average values are significantly higher with the Nye approach. An analysis suggests that the Nye approach overestimates the GND density of the Mg-based alloys. [ABSTRACT FROM AUTHOR]

The present study investigated the effect of tool rotational speed on the microstructure and mechanical behavior of friction stir processed AA 7050 aluminum alloy using an optical micrograph, scanning electron microscope, tensile test, impact strength, and Vickers microhardness. The alloy was processed at 40 mm min−1 as a travel speed combined with three tool rotational speeds, 800, 1200, and 1600 rpm. The visual inspection of the surfaces of the samples revealed that the alloy could be successfully friction stir processed at any rotational speed. The results indicated that the mean grain size of the stir zone decreases with increasing the tool rotational speed (from 45 to 9 µm). The development of the precipitates θ, (η and η), (T and T), and S phases was significantly controlled by the tool rotational speed. Consequently, the microhardness, tensile strength, and impact strength of the AA7050 alloy were enhanced by friction stir processing due to the combination of grain refinement and precipitation strengthening. The optimum mechanical properties were obtained for the sample processed with a tool rotational speed of 1600 rpm. [ABSTRACT FROM AUTHOR]

High‐pressure torsion (HPT) processing is successfully applied to fabricate a novel hybrid material from separate discs of AZ31 (Mg–3Al–1Zn, wt%) and Mg–0.6Gd (wt%) alloys by straining through numbers of rotations, N, of 1/4, 1/2, 5, 10, and 20 turns at room temperature. The microstructure and texture are investigated near the bonding interface through the disc diameter using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The microstructure exhibits two grain refinement regimes with the first occurring during an equivalent strain range, εeq, of ≈0.3–72 and the second during εeq from ≈72 to 517. The general texture changes from B‐fiber to Y‐fiber and C2‐fiber through the HPT processing. The resultant microstructures and textures of this hybrid alloy are examined separately for the AZ31 and Mg‐0.6Gd alloys and found controlled by the presence of twinning, slip systems, and second phases and the occurrence of different dynamic recrystallization mechanisms. [ABSTRACT FROM AUTHOR]

The evolutions of microstructure and texture and the corrosion behaviour of low light rare-earth containing Mg-1.4Nd and low heavy rare-earth containing Mg-0.6Gd and Mg-0.4Dy (wt.%) were evaluated and compared after processing by high-pressure torsion (HPT) and isochronal annealing at 250 and 450 °C for 1 h using electron backscatter diffraction (EBSD) and electrochemical tests in a 3.5% (wt.%) NaCl solution. The EBSD results show that dynamic recrystallisation (DRX) was restricted in the Mg-1.4Nd alloy which led to a heterogenous deformation microstructure whereas the Mg-0.6Gd and Mg-0.4Dy alloys exhibited a homogenous deformation microstructure formed mostly of equiaxed dynamically recrystallised DRX grains. The HPT processing caused the development of a deviated basal texture in the three alloys. A good thermal stability of the three alloys was noticed after annealing at 250 °C. By contrast, annealing at 450 °C led to a homogenous equiaxed microstructure and weakening of texture for the Mg-1.4Nd alloy and a heterogenous bimodal microstructure with a stable basal texture for the Mg-0.6Gd and Mg-0.4Dy alloys. The HPT-processed Mg–RE alloys exhibited an improved corrosion resistance due to grain refinement. Thereafter, the corrosion resistance of the Mg-0.6Gd and Mg-0.4Dy alloys decreased with increasing annealing temperature due to an increase in grain size while the corrosion resistance of the Mg-1.4Nd alloy was improved after annealing at 450 °C due to precipitation and texture weakening. [ABSTRACT FROM AUTHOR]

The local microstructure, texture gradient and mechanical properties through the shoulder dimension (10 mm) of upper and lower AA5182 aluminum sheets were investigated using electron backscatter diffraction (EBSD) and Vickers microhardness after friction stir spot welding (FSSW). Based on the microstructural features (mean grain size, grain boundary type and dynamic recrystallization (DRX)), the upper sheet was found to be mainly composed of the stir zone (SZ) and thermomechanically affected zone (TMAZ) due to the high deformation induced simultaneously by the tool rotation and the shoulder download force, while the SZ, TMAZ, heat-affected zone (HAZ) and base metal (BM) were detected in the lower sheet due to the limited effect of the shoulder on the lower sheet. The texture changes, due to the nature of the deformation, demonstrated a shear-type texture at the SZ to a plane strain compression deformation type texture at the TMAZ and then a recrystallization texture at the HAZ and BM. The microhardness gradually decreased with the increasing distance from the keyhole along the SZ, TMAZ and HAZ regions. Eventually, the microstructure and microhardness evolutions were correlated based on the Hall–Petch relationship. [ABSTRACT FROM AUTHOR]

• Effect of HPT on the dissolution kinetics of Mg-0.6Gd alloy was examined using DSC. • After HPT, the dissolution peak decreased from 634 to 658 to 601–633 K. • After HPT, the activation energy decreased from 135 ± 9 to 118 ± 10 kJ/mol. • The dissolution mechanism was unaffected by HPT. The dissolution reaction kinetics were determined by differential scanning calorimetry (DSC) analysis for Mg-0.6Gd (wt.%) in an as-cast condition and after processing by high-pressure torsion (HPT) at room temperature for 20 turns. For the as-cast condition, the dissolution temperature was in the range of 634–658 K with an activation energy of 135 ± 9 kJ/mol. After HPT, the range of dissolution temperature decreased to 601–633 K, with a lower activation energy of 118 ± 10 kJ/mol. In both conditions, the Avrami and growth exponents are around 1.5, which suggests that the dissolved precipitates exhibit polyhedron-like morphology and that the dissolution process is dominated by bulk dissolution with a constant rate controlled by diffusion. [ABSTRACT FROM AUTHOR]

The residual strain determination by neutron diffraction has been performed on a set of five natural quartzite samples collected from Betic Cordilleras (Spain) and Sivas Basin (Turkey). The starting idea was to document an earlier conclusion about the texture components related either to deformation or recrystallization phenomena. Thereafter, as a consequence of the rock inhomogeneity, the complete strain tensor has been determined for each sample and discussed by taking into consideration the present‐day knowledge in material sciences. The imposed macroscopic deformation observed at the sample locality led us to consider the form of the residual strain tensor as possibly representative of the natural finite plastic deformation suffered at the sample scale. Based on this, those tensors have been fitted to plastic tensors and introduced in texture simulations using a visco‐plastic self‐consistent (VPSC) model. The results demonstrate that the complete and meaningful strain tensor determination in rocks could be used as an experimental input in numerical modelling. This new combination of experimental and numerical approaches was validated and could help to better understand some geological phenomena. [ABSTRACT FROM AUTHOR]

The stored energy and activation energy for recrystallization were investigated for a Cu-Ni-Si alloy after high-pressure torsion processing for N = ½, 1, 5 and 10 turns at room temperature. The contributions of geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs) and vacancies to the stored energy were calculated through the Vickers microhardness measurements, kernel average misorientation (KAM) measurements and an analysis by differential scanning calorimetry (DSC). The results show that the total stored energy decreases rapidly after equivalent strain of εeq ∼ 9 and then saturates through εeq ∼ 86 at ∼70 J/mol. Concurrently, the local stored energy in GNDs and SSDs was found to depend strongly on the radial distance from the centre of the disc and increase with increasing equivalent strain at εeq ∼ 16 and saturate with further straining. Accordingly, the results indicate that the GNDs and vacancies are responsible for the high stored energy in the initial stage of deformation at equivalent strain range of εeq = 8.6–16 and thereafter their contribution decreases slightly due to the occurrence of dynamic recrystallization and the formation of fine grains. At the same time, the contribution of the SSDs is similar to that of the GNDs only in high strain deformation as at εeq = 49.3 to accommodate the deformation process. An activation energy for recrystallization was estimated in the range of ∼ 89.7–98.7 kJ/mol, thereby suggesting poor thermal stability. [ABSTRACT FROM AUTHOR]

Plastic deformation of Fe-27%Co alloy at room temperature was investigated. The present alloy, usually delivered with a low-texture component for the magnetic core in rotating machines, develops a rather high intensity of Goss texture after recrystallization, when a suitable manufacturing process is applied. Thanks to this texture and its magnetic properties, this material can replace the grain-oriented Fe-3%Si alloy in electric transformer application. The intensity of the recrystallization Goss component depends directly on the sharpness of the {111}〈112〉 orientation developed during cold rolling. Thus, the origin of this {111}〈112〉 deformation texture has been studied using visco-plastic self-consistent (VPSC) simulations. This model showed that only the {110}〈111〉 slip systems allow developing the {111}〈112〉 texture. The predominance of this slip system has been effectively identified from slip markings on the deformed sample by EBSD. More, this simulation has shown that a Goss texture at the hot-rolled state favors the {111}〈112〉 development during cold rolling, as observed experimentally. [ABSTRACT FROM AUTHOR]

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 (φ 1 = 0–360°, Φ = 0° and φ 2 = 0–60°) and secondly a fiber localized at φ 1 = 180°, Φ = 60° and φ 2 = 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. • Processing by HPT up 5 turns produces a significant refinement in grain size. • The recrystallization temperature was measured in the range of ~120–200 °C. • The activation energy for recrystallization was ~25 kJ mol−1. • The texture was retained after subsequent annealing at 400 °C for 1 h. • A good thermal stability was demonstrated after annealing at 400 °C for 1 h. [ABSTRACT FROM AUTHOR]

Abstract The microstructure and texture of an Al1050/AZ31/Al1050 laminated composite fabricated by accumulative roll bonding at 400 °C up to 5 cycles are investigated using Electron BackScatter Diffraction, neutron diffraction, microhardness measurements and tensile tests. EBSD analysis has shown that ARB processing led to microstructural refinement with equiaxed grain microstructure in AZ31 layers and to the development of elongated grains parallel to the rolling direction in Al 1050 layers. No new phases formed at the bond interface after the first ARB cycle while Mg 17 Al 12 and Mg 2 Al 3 phases appeared after subsequent cycles. During the ARB processing, a typical strong basal (0002) texture is observed in AZ31 layers along with a weak rolling texture showed in Al 1050 layers with a dominant Rotated Cube {001}〈110〉 component. The microhardness of Al1050/AZ31/Al1050 laminated composite increased with increasing ARB cycles and almost saturated after five ARB cycles. The yield strength and ultimate strength increased gradually between 1 and 3 ARB cycles due to the strain hardening and grain refinement. They decreased with further increasing of the ARB cycles because of crack and failure of the Mg x Al y intermetallic compounds which developed during 4th and 5th ARB cycles. The deformation behavior of the laminated composite becomes rather similar to the behavior of AZ31 alloy that underwent a dynamic recrystallization during processing. Highlights • Formation of Mg 17 Al 12 and Mg 2 Al 3 phases was obtained near the interface after 2 ARB cycle. • The average grain size of AZ31 layers was about 0.8 μm after 5 ARB cycles. • The Al 1050 layers contain elongated grains parallel to rolling direction. • A typical strong basal (0002) texture has been observed in AZ31 layer. • A weak rolling texture showed in Al 1050 layer with domination of Rotated Cube. [ABSTRACT FROM AUTHOR]

The aim of the present study is to investigate the effect of deformation conditions on the corrosion behavior of AZ31 (Mg-3Al-1Zn, % wt.) in 0.9% NaCl (wt.%) solution. The AZ31 alloy was hot rolled at 360 °C to 20 and 50% of thickness reduction. Electrochemical measurements were used to study the corrosion behavior of AZ31 alloy. Analysis of corrosion products after immersion test was performed using optical microscopy, X-ray diffraction and Raman spectroscopy. The mechanical properties of corroded samples were investigated using tensile test at room temperature. Results indicated that the corrosion rate was strongly affected by the hot rolling level. A lower corrosion potential and reduced polarization resistance was observed after hot rolling compared to the as received AZ31 alloy. The corrosion product was evidenced mainly as Mg(OH)2 compound exhibiting a filiform-like morphology. Apparently, the corrosion improved the room temperature ductility of AZ31 alloy. [ABSTRACT FROM AUTHOR]

Microstructure and texture evolution of Fe-36%Ni (wt. %) alloy after 1, 5 and 10 accumulative roll-bonding (ARB) cycles and annealing at 600 °C up to 3600 seconds were studied using electron backscatter diffraction. Microstructural and textural changes after ARB and annealing were compared to those existing in the literature after conventional rolling. The microstructure was not stable at 600 °C for all ARB samples even after 3600 seconds of annealing. The recrystallization texture was dominated by the Cube {001}<100> texture component. Recrystallization kinetics were determined using microhardness measurement and were close to those after cold rolling with Avrami time exponent around unity. The texture evolution at high strain was discussed in terms of grain boundary migration obstruction by the formation of layer interfaces and small recrystallized grains near the bonded interfaces. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of Mg-0.3Ce, Mg-0.41Dy, Mg-0.63Gd, Mg-1.44Nd and Mg-1.43La (wt.%) alloys in 3.5 wt% NaCl solution was investigated using electrochemical tests. The as-cast microstructures of the Mg-RE alloys were characterized by the presence of second phases (Mg x Ce, Mg 41 Dy 5 , Mg 12 Gd, Mg 12 Nd, Mg 41 Nd 5 , Mg 24 Nd and Mg 12 La) with different volume fraction and distribution. Results show that the corrosion mechanism was altered from uniform to localized corrosion mechanism depending on the specific RE alloying elements. The corrosion resistance of the Mg-RE alloys is increasing in the following order: Mg-1.43La, Mg-1.44Nd, Mg-0.3Ce, Mg-0.63Gd and Mg-0.41Dy. Accordingly, the corrosion morphology in the best resistant Mg-0.41Dy alloy and the worst Mg-1.43La alloy were observed and compared after 2h and 24 h of immersion using SEM-EDS, XPS and XRD analysis. The formation of the Dy 2 O 3 oxide prevents the Mg-0.41Dy alloy from pitting corrosion and lead to an excellent corrosion surface even after 24 h of immersion. Meanwhile, the presence of a high fraction of the Mg 12 La phase along the grains boundaries in the Mg-1.43La alloy causes severe pitting corrosion by acting as anodic phase. • The corrosion behaviour of Mg-RE alloys was largely influenced by RE addition element. • The corrosion resistance increases in the order: Mg-1.43La, Mg-1.44Nd, Mg-0.3Ce, Mg-0.63Gd and Mg-0.41Dy. • A uniform corrosion film composed of Mg(OH) 2 and Dy 2 O 3 formed on Mg-0.41Dy alloy. • The Mg 12 La phase is the main causes of the poor corrosion resistance of the Mg-1.43La alloy. [ABSTRACT FROM AUTHOR]

• EXAFS was used to study the atomic environment of the HPT and aged Mg-1.44Nd alloy. • Two Nd-Mg bonds were found belonging to the α -Matrix and Mg 12 Nd second phase. • Interatomic distance and the coordination number are influenced by HPT and ageing. The local atomic structure of an Mg-1.44Nd (wt.%) alloy was investigated after solution annealing, high-pressure torsion (HPT) processing up to 1 and 10 turns and ageing at 250 °C for 5 h using X-ray absorption fine structure (XAFS) measurements at the Nd L III -edge. The results show that HPT processing has no effect on the atomic structure around Nd atoms compared to the unprocessed state, whereas ageing at 250 °C for 5 h induces a significant modification in the coordination number and interatomic distances around the Nd atoms. These variations are analyzed based on the correlations between precipitation, defects and atomic mobility of the chemical species. [ABSTRACT FROM AUTHOR]