Application of multireflection grazing incidence method for stress measurements in polished Al–Mg alloy and CrN coating

Multi-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al–Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al–Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin2 technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined

Investigation of plastic deformation heterogeneities in duplex steel by EBSD

An EBSD analysis of a duplex steel (austeno-ferritic) deformed in tension up to fracture is presented. The main purpose of the paper is to describe, qualitatively and quantitatively, the differences in the behavior of the two phases during plastic deformation. In order to do so, several topological maps are measured on the deformed state using the electron backscatter diffraction technique. Distributions of grain size, misorientation, image quality factor and texture are then analyzed in detail.International audienceAn EBSD analysis of a duplex steel (austeno-ferritic) deformed in tension up to fracture is presented. The main purpose of the paper is to describe, qualitatively and quantitatively, the differences in the behavior of the two phases during plastic deformation. In order to do so, several topological maps are measured on the deformed state using the electron backscatter diffraction technique. Distributions of grain size, misorientation, image quality factor and texture are then analyzed in detail

Correlation between microstructure and intergranular corrosion behavior of low delta-ferrite content AISI 316L aged in the range 550e700 C

The microstructure and the phase identification of austenitic stainless steel AISI 316L with low δ-ferrite content (δ ≤ 1%) and aged for up to 80 000 h at temperatures ranging from 550 to 700 °C were investigated by using an optical microscope (OM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Local changes of chromium content, resulting from nucleation and growth of chromium-rich phases during aging, were quantitatively assessed by energy dispersive X-ray spectroscopy (EDX) in the scanning transmission electron microscope (STEM). The intergranular corrosion behavior (IGC) of annealed and aged specimens was evaluated using the double loop electrochemical potentiokinetic reactivation (DL-EPR) and completed by IGC morphologies according to the ASTM A262 practice A standard. The results showed that δ-ferrite decomposed gradually into M23C6 at 550 °C and decomposed totally into intermetallic phases (σ, η, χ, and R) and into secondary austenite (γr) at temperatures equal to or higher than 650 °C. Similarly γ-austenite decomposed into M23C6 carbide at 550 °C and into intermetallic phases such as η and σ in addition to carbide, at higher temperatures. The time-temperature-sensitization diagram (TTS) was established and used to calculate the critical cooling rate (CCR) that prevents IGC sensitization. The analysis of IGC results leads to the conclusion that sensitization-desensitization is still controlled by the characteristics of chromium-depleted area surrounding austenite grain boundary regions. No significant effect of remained δ-ferrite and derived components on the corrosion behavior of AISI 316 L containing 1% of δ-ferrite

Valeur de l’examen extemporane en pathologie thyroïdienne

OBJECTIF : Etudier la valeur de l’examen extemporané dans la pathologie thyroidienne et identifier ses limitesMATERIELS ET METHODES : Notre étude est rétrospective incluant 800 examens extemporanés réalisés sur des pièces de résectionthyroïdienne colligés dans notre service sur une période de 12 ans (2000-2011).Les résultats ont été comparés à ceux del’examen anatomopathologique définitif.RESULTATS : Les résultats étaient concordants dans 96,5%, discordants dans 3,5 %. La sensibilité de l’examen extemporané toustypes confondus était de 78 % et la spécificité de 100 %CONCLUSION : Notre étude a montré une spécificité parfaite de l’examen extemporané cependant l’interprétation difficile des lésionsthyroïdiennes d’architecture vésiculaire expliquent une sensibilité de 78 %.Mots Clés : Thyroïdectomie, examen extemporanOBJECTIVE: To assess the value of frozen-section examination in thyroid surgery and evaluate its limitationsPATIENTS AND METHODES: This retrospective study examined the results of 800 frozen-sections of thyroid specimens analysedover the 12 –year period (2000-2011). Their results were compared with definitive anatomo-pathological examinationRESULTS :Frozen-section diagnosis was concordant with subsequent histopathological examination in 96,5% ,discordant in 3,5%.The global specificity of frozen section analysis for all histological subtypes was 100 % and its sensitivity was 78 %.CONCLUSION: This study shows the good specificity of frozen section .Discordances between frozen-section and definitive diagnosiswas associated with microfllicular lesions wich explain the sensibility of 78%Key Words: Thyroid surgery, frozen section examinatio

Application of multireflection grazing incidence method for stress measurements in polished Al–Mg alloy and CrN coating

Multi-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al–Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al–Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin2 technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined

Microstructure and texture evolution of the Al-20sn alloy processed by equal-channel angular pressing using route C

In this work, the microstructure and texture evolution of an Al-20Sn (mass%) alloy processed by Equal Channel Angular Pressing is presented. The evolution of dislocation cells into subgrains and the mechanical response of the deformed alloy have been emphasized. Samples were characterized by transmission electron microscopy, X-ray diffraction (for microstrain and texture measurements) and Vickers microhardness. It was found, that Al grains, suffered the highest degree of deformation during the ECAP process, however, the evidence showed that the deformation was largely heterogeneous, in terms of crystalline domain and feasibly in misorientation angles. The initial copper texture changes throughout the ECAP process forming an incipient shear texture component (111)[11-2]. The heterogeneity of the results obtained from the Vickers microhardness mapping could be associated to the microstructure resulted after the ECAP process. © 2014 The Japan Institute of Metals and Materials

Texture and Lattice Distortion Study of an Al-6061-T6 Alloy Produced by ECAP

Equal channel angular pressing (ECAP) is a severe plastic deformation (SPD) technique that produces nanostructured materials. Based on a remarkable grain size reduction, this process has led to improve mechanical properties, such as yield strength, fatigue, UTS, etc. In this work the characterization of the microstructure of the aluminum 6061-T6 alloy; plastically deformed up to ε ≈ 6, by the ECAP process, following route Bc, is presented. For this purpose, the ECAP processed samples were characterized by means of X-ray diffraction (for texture and line profile analysis) and transmission electron microscopy. The initial crystallographic texture vanished after one ECAP pass and a new, well defined, shear texture Cθ was generated. For the subsequent ECAP passes, more shear components: A1θ *, Bθ and \bar{B}θ were also developed. From the orientation distribution function analysis, a shift (generally less than 15°) between some experimental maxima and the reported ideal shear texture positions was observed. From these results, it was found that the microstructure generated with this process was stabilized after the 5th ECAP pass. Finally, the micro-strain analyses, in addition to the texture and transmission electron microscopy, contributed to the understanding of the effect of the physical and mechanical processes that were activated during the SPD-ECAP technique