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New U–Pb SHRIMP zircon ages from the Bou Azzer-El Graara onlier constrains the Neoproterozoic evolution of the Anti-Atlas during Pan-African orogenesis. Within the Central Anti-Atlas, the Bou Azzer-El Graara inlier exposes a dismembered ophiolite, long considered to mark a late Neoproterozoic suture between the West African Craton in the south, and Neoproterozoic arcs to the north. From north to south, this inlier includes four main geological units: a volcanic-arc, an ophiolite, a metamorphic complex and a continental platform. Several plutons intrude the volcanic-arc, the ophiolite, the metamorphic complex, and post-orogenic volcanic and sedimentary deposits unconformably cover these terranes. The age of the volcanic-arc is reported here for the first time. Analyses of zircon of two rhyolites provide ages of 761 ± 7 Ma and 767 ± 7 Ma. Zircons from two gneisses provide dates of 755 ± 9 Ma and 745 ± 5 Ma. Both dates are considered best estimates of the crystallization ages of their igneous protoliths. Analyses of zircon from two granitic bodies, which crosscut gneisses, provide younger dates of 702 ± 5 Ma and 695 ± 7 Ma. The age of an aplitic body of the ophiolite is reported here for the first time, as 658 ± 8 Ma (SHRIMP U–Pb on zircons). Theses ages suggest the existence of three distinct orogenic events during Cryogenian times: (i) 770–760 Ma Tasriwine-Tichibanine orogeny with rollback of the subducting oceanic plate, leading to the formation of back-arc basins; (ii) 755–695 Ma Iriri-n’Bougmmane orogeny; and (iii) the 660–640 Ma Bou Azzer orogeny involving the formation and the emplacement of the Bou Azer ophiolite. During Ediacaran times, the Bou Azzer-El Graara inlier is characterized with the development of a continental volcanic arc between 630 and 580 Ma (Bou Lbarod Group, 625 ± 8 Ma; Bleïda granodiorite, 586 ± 15 Ma), and strike-slip pull-apart basins (Tiddiline Group, 606 ± 4 Ma and 606 ± 5 Ma). These volcanic and sedimentary Lower Ediacaran sequences are deformed before the felsic pyroclastic deposits of the Ouarzazate Group (567 ± 5 Ma and 566 ± 4 Ma). Finally, the Ouarzazate Group is overlain by early Cambrian volcanic deposits of the Jbel Boho Formation (541 ± 6 Ma). [ABSTRACT FROM AUTHOR]

Paleoproterozoic metamorphic and igneous rocks, Tonian (?)-lower Cryogenian passive margin sedimentary rocks, Neoproterozoic dolerites, and Upper Ediacaran volcaniclastic, volcanic and pyroclastic rocks are exposed in the Agadir Melloul, Iguerda and the southern edge of the Sirwa inliers. A recent field mapping program of the Ediacaran Ouarzazate Group in these areas allow to distinguish three principal volcanic sequences. The first sequence (Adrar-n-Takoucht Formation) outcrops mainly south of the Sirwa inlier, and is composed of felsic pyroclastic deposits and local basaltic lavas with ages ranging between 572 and 570 Ma. The second sequence (Anammar and Tadoughast formations) occurs primarily in the Agadir Melloul-Jbel Iguiguil inlier. The Anammar Formation contains essentially volcano-detrital sediments, with fine airfall pyroclastic deposits. The Tadoughast Formation is composed of felsic pyroclastic deposits and rhyolitic domes with ages ranging between 567 and 564 Ma. The third sequence (Fajjoud Formation) contains felsic pyroclastic deposits, with an age of 556 Ma, associated with porphyritic basalts. The magmatism of the Ouarzazate Group was not continuous between 572 and 556 Ma, but related to distinct pyroclastic pulses. Geochemical data indicate that the pyroclastic rocks of the Ouarzazate Group have a highly potassic calc-alkaline to shoshonitic affinity. However, the basaltic facies associated with the Adrar-n-Takoucht Formation demonstrate a calc-alkaline affinity whereas those associated with the Fajjoud Formation have a tholeiitic affinity. Rhyolitic domes were derived from hyperaluminous leucogranites. In sum, the typology of zircons defines three poles: (i) subalkaline granites; (ii) calc-alkaline monzogranites and granodiorites frequently associated with basic rocks; and (iii) aluminous leucogranites. In addition, the volcaniclastic deposits of the Ouarzazate Group are submitted to a syn-sedimentary tectonic. The Adrar-n-Takoucht Formation is folded and unconformably overlain by the Anammar and Tadoughast formations. The Anammar and Tadoughast formations were deposited and deformed in a transtensional rift basin as indicated by basaltic lava flows. Hence, the Upper Ediacaran Ouarzazate Group formed in a wrench tectonic regime with extensional and local compressional deformation. [ABSTRACT FROM AUTHOR]

Abstract: The crystallographic texture and microstructure of an electrolytic tough pitch copper have been investigated by Electron Back Scattered Diffraction (EBSD) after cold wire drawing (reduction in area between 52% and 94%) and after primary recrystallization. The material presents a deformation texture composed of major 〈111〉 and minor 〈100〉 fibers. The evolution of the quality index of the Kikuchi patterns shows that the stored energy is lower in the 〈100〉 fiber than in the 〈111〉 fiber. Then, after recrystallization, the volume fraction of the 〈100〉 fiber increases at the expense of the other texture components. The study of the grain boundary nature shows that the recrystallization twin fraction decreases with increasing strain. It is shown that this evolution is the consequence of the grain size reduction. [Copyright &y& Elsevier]

Abstract: A submicron grain (SMG) microstructure, with an average grain size of about 0.4 μm was produced by equal channel angular extrusion (ECAE). Samples were examined at various scales using the transmission electron microscope (TEM), the scanning electron microscope (SEM) and the field emission gun (FEG/SEM) with electron-backscattered diffraction (EBSD) and also the neutron diffraction. After 8 passes into the channel, which corresponds to a total strain of about 8, the SMG microstructure was composed of large dynamic recrystallized grains within a poorly recovered matrix. A quantitative study of microstructural parameters, such as average low and high boundary spacings, grain and subgrain aspect ratios and crystallographic orientations, shows in particular that the area fraction of low angle boundaries is still very high (60%) and as a consequence the microstructure is not a true submicron grain structure required to resist recrystallization during annealing. Indeed, annealing at 200 °C in oil leads to a stable but not submicron structure, with a grain size of about 2 μm. [Copyright &y& Elsevier]

The Monte Carlo method is used to simulate primary recrystallization in a fcc nickel iron sheet deformed by cold rolling. Experimental data, such as the microstructure, the microtexture characterized by TEM and the stored energy estimated by neutron diffraction, constitute the input values for the calculation. This approach allows to reproduce experimental observations i.e. the bulging of cube cells during annealing. [Copyright &y& Elsevier]

Electrochemical experiments on titanium electrodes were coupled with electron backscattered diffraction (EBSD) experiments. The substrates were thermally treated and electropolished in order to have flat and reproducible polycrystalline surfaces, leading to EBSD orientation mapping. Afterwards, the samples were anodised by a galvanostatic procedure. It was shown that electrodeposition of PbO2 from a 0.5 M Pb(NO3)2+2.5 M HNO3 solution occurs selectively on the near {0 0 0 1} grains, whereas lead electrodeposition occurs on all the grains, whatever their orientation. These results are discussed, taking into account the fact that on {0 0 0 1} grains, the oxide layers are thinner than on other grains. It was concluded that electrodeposition is observed locally on Ti/TiO2 electrodes for (i) cathodic electrodeposition of metals at low overvoltage; (ii) anodic electrodeposition of PbO2, in potentiostatic or galvanostatic conditions. [Copyright &y& Elsevier]

Abnormal Goss grain growth in a conventional grain oriented Fe–3%Si steel is analysed using orientation imaging microscopy after several annealing times. Misorientation of boundaries surrounding the growing Goss grains is characterised. It appears that boundaries misoriented by 20–45° are not specially mobile during the secondary recrystallisation. [Copyright &y& Elsevier]

An improved Monte Carlo approach for simulation of recrystallization from experimental data is presented. The orientation and stored energy maps derived by orientation imaging microscopy and the X-ray bulk texture of a Fe–50%Ni alloy are used as input data. A realistic description of the dependence of grain boundary properties on misorientation is used to simulate the nucleation and growth of the new recrystallized grains. [Copyright &y& Elsevier]

Excellent mechanical properties of oxide-dispersion-strengthened (ODS) alloys arise from a high density of Y-Ti nano-oxides finely dispersed in the matrix. Characteristics of this precipitation can strongly be influenced by oxygen contamination during milling. We studied an as-received and annealed (1 h 1150 °C) oxygen-enriched ferritic ODS alloy by High Resolution Transmission Electron Microscopy. The as-received sample has unknown b.c.c nano-oxides, while the annealed one has orthorhombic nanoparticles. We propose a phase relaxation during the annealing, confirmed by the observation of a particle where both cubic and orthorhombic structures coexist. The influence of oxygen on the particle structure is also discussed. [ABSTRACT FROM AUTHOR]

Electron Backscatter Diffraction technique is used to characterize the microstructure of 316L steel generated by Surface Mechanical Attrition Treatment (SMAT) before and after low cycle fatigue tests. A grain size gradient is generated from the top surface to the interior of the samples after SMAT so that three main regions can be distinguished below the treated surface: (i) the ultra-fine grain area within 5 μm under the top surface with preferably oriented grains, (ii) the intermediate area where the original grains are partially transformed, and (iii) the edge periphery area where the original grains are just mechanically deformed with the presence of plastic slips. Fatigue tests show that cyclic loading does not change the grain orientation spread and does not activate any plastic slip in the ultra-fine grain top surface area induced by SMAT. On the opposite, in the plastically SMAT affected region including the intermediate area and the edge periphery area, new slip systems are activated by low cycle fatigue while the grain orientation spread is increased. These results represent a first very interesting step towards the characterization and understanding of mechanical mechanisms involved during the fatigue of a grain size gradient material. [ABSTRACT FROM AUTHOR]

Abstract: Cathodic hydrogen charging was applied to low-carbon pipeline-steel samples produced using different thermomechanical paths. The samples developed similar microstructures but different crystallographic textures and grain–boundary distributions. This made it possible to investigate the resistance to hydrogen-induced cracking (HIC) of steels with strong {111}ND and {112}ND texture fibres, steels with a dominating {001}ND texture fibre, and steels with close-to-random textures; {h k l}ND representing grain orientations with {h k l} planes parallel to the steel rolling plane. The results show that strong {111}ND fibre textures produced by warm-rolling schedules significantly increase HIC-resistance of pipeline steels, whereas {001}ND and close-to-random textures make steels HIC-prone. [Copyright &y& Elsevier]

Abstract: The influence of the tool rotational speed, the probe plunge depth and the shoulder penetration depth on weld microstructure and on the weld strength have been studied. The shear tests showed that the friction stir spot welds fail by nugget pullout. Three microstructural factors play a determinant role on the weld''s strength: the size and location of the stir zone, and the unwelded interface tip slope. With increasing rotational speed, the shear strength increases because of the larger size of the stir zone. By changing the probe plunge depth the location of the stir zone can be controlled in order to maximize the bonded distance between the interface tip and the central hole left by the probe. The shoulder penetration depth must be sufficient to ensure a horizontal interface tip and therefore avoid fracture by the opening mode (mode I) during shear loading. [Copyright &y& Elsevier]

Abstract: The role of microtexture in hydrogen-induced crack interaction and coalescence is investigated in line pipe steels using electron backscatter diffraction. Experimental evidence shows that, depending on the local grain orientation, crack interaction and coalescence can depart from the conditions predicted by the mixed-mode fracture mechanics of isotropic linear elastic materials. Stress simulation and microtexture analysis are used to explain the experimental observations. [Copyright &y& Elsevier]

Abstract: The deformed microstructure of an IF-Ti steel has been characterized by TEM observations after 40% cold rolling. Different substructures can be distinguished: lamellar bands for the {111}〈112〉 grains belonging to the γ fibre ND∥〈111〉 and equiaxed cells for the {111}〈110〉 orientation that belong to both γ and α fibres (α fibre RD∥〈110〉). Whatever the initial dislocation structure, the first steps of nucleus formation is characterized by coalescence and growth of existing cells in the recovered matrix. Then, nucleus growth occurs by sub-boundary migration. Nucleation is mainly intragranular for the {111}〈112〉 grains and it is widely observed at the grain boundaries or at the vicinity of the grain boundaries for the {111}〈110〉 grains. Therefore, first steps of recrystallization mainly take place by continuous growth of subgrains followed quickly or not by bulging of grain boundaries. [Copyright &y& Elsevier]

Four events have been identified in the Tagragra d’Akka and Tafeltast–Kerdous inliers: (i) a middle Palæoproterozoic (Orosirian, ca. 2.047Ga) event corresponding to the emplacement of calc-alkaline and peraluminous granites containing older inherited zircon (2.07–2.15Ga), (ii) an upper Palæoproterozoic (Statherian) event corresponding to the emplacement of pegmatites and porphyritic microgranites (ca. 1.76Ga), intimately associated with numerous mafic dikes assumed to be, at least partly, of the same age, (iii) an upper Neoproterozoic event corresponding to dacite dikes (600±5Ma), (iv) a Variscan (301±7Ma) hydrothermal event corresponding to the crystallization of muscovites related to Au-quartz veins. A polycyclic magmatism (Eburnian-Birimian, Pan-African and Variscan) is now evidenced in these two inliers of the western Anti-Atlas. The Pan-African orogeny is very homogeneous all along the Anti-Atlas during Neoproterozoic time. No inherited Archæan component has been found in zircons from granites or dikes. It appears that the northern border of the West African craton is an important juvenile cratonic limit submitted to periodical continental growth since 2.05Ga at least. [Copyright &y& Elsevier]

The influence of the cold rolled reduction on stored energy was studied in Fe–53%Ni using neutron diffraction. Measurements of diffraction peak broadening were undertaken to study the influence of stored energy on mechanisms that govern the nucleation and growth of the cube texture in a heavily cold rolled Fe–Ni alloy. [Copyright &y& Elsevier]

Titanium Matrix Composites (TMC's) containing various volume fractions of (TiB+TiC) particles have been deposited from powder feedstocks consisting of a blend of pre-alloyed (Ti-6Al-4V+B 4 C) powders, using the direct metal deposition (DMD) laser process and the in-situ chemical reaction 5Ti+B 4 C→4TiB+TiC. Process optimization has allowed to obtain a homogeneous distribution of tiny TiB whiskers within the Ti-6Al-4V α/β matrix, with a full solubilization of C for low B 4 C contents (0.5 wt% and 1.5 wt%), and the formation of a small amount of globular TiC particles at higher B 4 C content (3%). Comparisons with Ti-6Al-4V DMD walls revealed a substantial grain refinement on TMC's due to enhanced grain nucleation on TiB whiskers, even for low B 4 C contents. Last, mechanical investigations indicated an increase of 10–15% of Vickers hardness, and a constant 10% increase of Young modulus on a large temperature range (20–600 °C) for all B 4 C content. [ABSTRACT FROM AUTHOR]

The Oisans Massif, located in the external zones of the western Alps, experienced significant shortening during the Alpine collision. While a series of major top-to-the west shear zones was recently described, the general low grade of the metamorphism has not attracted much petrological and geochronological studies. This paper provides combined temperature and age constraints on the evolution of the Oisans Massif. Temperature was estimated with the Raman Spectrometry of Carbonaceous Material (RSCM) method and chlorite geothermometry. Maximum temperature reached by the Mesozoic cover ( T max ) from Grenoble to the Galibier pass (E-W) and from Saint Jean de Maurienne to Embrun (N-S) yielded almost constant ca. 330 °C temperatures all through the Massif. Temperatures however strongly decrease either westward towards the top of the Vercors sedimentary sequence or eastward towards the Penninic Frontal Thrust. Age constraints were retrieved using 40 Ar/ 39 Ar in situ analyses performed on variously strained samples from Alpine shear zones. Over strain gradients, incipient Alpine recrystallizations progressively develop at the expense of former Variscan parageneses. A combined textural and EPMA approach permitted to identify newly formed chlorite and phengite that unequivocally grew in response to deformation or to low grade metamorphism. Chlorites recorded temperatures from ca. 350–150 °C during the activity of shear zones. In parallel, 40 Ar/ 39 Ar in situ experiments enabled dating deformation using both synkinematic phengites crystallized below the closure temperature of white-micas and former Variscan muscovite whose isotopic system have been, at least partially re-opened. Activity of top-to-the-west shear zones responsible for the shortening and thickening of the Oisans massif thus occurred between 34 and 33 and 25 Ma. Integrating these new age-constraints, T max estimates, and published geological data on the Oisans Massif and neighbouring areas allow proposing a new shortening scenario for the external zones. From ca. 34–33 Ma, the Oisans Massif was buried as a rigid block below more internal units and reached a temperature of ca. 330 °C. Shearing progressively localized along a series of top-to-the-W shear zones in the basement until 25 Ma. Deformation then localized along a major thrust at the base of the ECM massif and propagated along the basement-cover interface below the Vercors massif after 16 Ma. [ABSTRACT FROM AUTHOR]

The formation of annealing twins has been studied from the beginning of the 20th century and a variety of mechanisms have been suggested. Molecular dynamics simulations on the atomic scale have also been performed. This paper reports a microscale simulation of primary recrystallization and twinning of a nickel alloy based on the Monte Carlo approach. Different twin morphologies were simulated. A possible dependence of grain growth direction on twin formation during annealing was demonstrated. The formation of incoherent Σ3 and Σ9 boundaries is verified as the indirect outcome after coherent Σ3 formation. [ABSTRACT FROM AUTHOR]

Abstract: The glasses in the SrO-TiO2-P2O5 system were prepared by the conventional quenching route. The amorphous state of samples was verified by X-ray diffraction (XRD). Density, molar volume, micro-hardness, glass transition temperature (T g), and crystallization temperature (T c) parameters are determined for each glass. The results show that they depend strongly on the chemical compositions. The structure approach of the glasses is determined by using Infrared spectroscopy (IR). This investigation highlights that the glassy-matrix contains various phosphate structural units. The crystallization of the glasses by heat-treatments is performed and the crystallized phases Sr3P4O13, TiP2O7, Sr(PO3)2 are identified by XRD. The overall results are correlated to the glass structure and the nature of chemical bonds constituting the glass network. [Copyright &y& Elsevier]

A new approach based on the concept of curvature-driven migration of grain boundaries in the presence of particle distribution has been used to study the abnormal grain growth of Goss grains in silicon steels. The morphological aspect of the abnormal growth is considered by the introduction of the limit radius of neighbourhood. This critical radius is able to explain the presence of island grains observed inside the growing Goss grain. These island grains are formed as a result of large neighbouring grain resistance. [Copyright &y& Elsevier]

The spatial distribution of plastic deformation and grain orientation surrounding hydrogen-induced cracks (HIC) is investigated in samples of API-5L-X46 pipeline steel using scanning electron microscopy and electron backscattering diffraction (EBSD). This work shows direct experimental evidence of the influence of microstructure, microtexture and mesotexture on HIC crack path. [Copyright &y& Elsevier]