Investigation of the Dislocation Activity and Texture Development in Magnesium Alloy Sheets Containing Zinc, Neodymium, and Calcium

In dieser Arbeit wurde der Zusammenhang zwischen der Textur, der Mikrostruktur und den Verformungsmechanismen (insbesondere der Aktivität der Versetzungsgleitung) von Mg-Legierungen untersucht, der nach thermomechanischen Behandlungen zu unterschiedlichen Texturentwicklung führt. Seltene Erdelemente (SE) sind allgemein als geeignete Elemente für eine Texturmodifizierung in Mg-Legierungen bekannt. Die Zugabe von Zn in Kombination mit den SE-Elementen zeigt eine ausgeprägte Texturmodifikation. Das Ca ist ein vielversprechendes Element, das RE-Elemente teilweise ersetzen könnte. Als Grund für die Texturabschwächung werden normalerweise verschiedene Rekristallisations-mechanismen benannt. Diese verschiedenen Rekristallisationsmechanismen erfordern eine Keimbildung mit Kornrotation in zufällige Ausrichtungen, welche in Beziehung zu den Verformungsmechanismen stehen. Es wurde eine systematische Untersuchung durchgeführt, um den Einfluss der Legierungselemente, der aktiven Verformungsmodi und deren Beitrag auf die Mikrostruktur- und Texturentwicklung zu verstehen, basierend auf der Tatsache, dass die Textur die Aktivität der Verformungsmechanismen widerspiegelt. Die Mg-Legierungen wurden in dieser Arbeit erfolgreich unter Verwendung von In-situ Experimenten am Synchrotron untersucht, um die Texturentwicklung und die Veränderung der Diffraktionsdiagramme unter mechanischen Tests bei verschiedenen Temperaturen zu verfolgen. Die erhaltenen Messergebnisse wurden unter Verwendung einer CMWP-Analyse und von EBSD-Messungen im Hinblick auf Texturentwicklung, Aktivität der Verformungsmodi und Mikrostrukturbewertungen ausgewertet. Die gegenseitigen Einflüsse zwischen aktiven Verformungsmodi und dem Rekristallisationsverhalten bei Umgebungs- und erhöhter Temperaturen wurden diskutiert. Die CMWP Analyse zeigte, dass in den Nd- oder Ca-haltigen Mg Legierungen eine höhere Aktivierung von nicht-basal und pyramidal Versetzung als in der MgZn Legierung stattfindet. Erstere wird durch Zugabe von Zn in Kombination mit Nd oder Ca verstärkt. IGMA-Verteilungen, die aus den EBSD-Messungen gewonnen wurden, bestätigen, dass die dominierende prismatische Gleitung zur höheren Aktivierung der nicht-basal Versetzung beiträgt. Die Texturentwicklung zeigt ein offensichtliches Charakteristikum für alle untersuchten Bleche, nämlich eine Verbreiterung des basalen Pols senkrecht zur Verformungsrichtung und eine Verstärkung des 〈101ത0〉 Pols in Verformungsrichtung. Die Zn-Zugabe in Kombination mit Nd oder Ca zeigt eine ausgeprägtere Texturentwicklung im Vergleich zu einer alleinigen Zugabe von Nd oder Ca. Die Zugabe von Zn ohne Nd oder Ca zeigt eine weniger ausgeprägte Texturentwicklung. Bei erhöhten Temperaturen wird bei dem bei 100°C deformierten ZK10 eine verstärkte Aktivierung nicht-basaler Versetzungen beobachtet. Gewölbte Korngrenzen und feinere Körner an den Korngrenzen, also der Beginn der dynamischen Rekristallisation, werden bei dem bei 200°C verformten ZK10 beobachtet. Im Gegensatz dazu werden die gleichmäßige Verformung und die Verzögerung der thermisch aktivierten Prozesse, z.B. eine dynamische Erholung und eine dynamische Rekristallisation, in den anderen Legierungen beobachtet. Diese Verzögerung ist durch die Zugabe von Zn mit Nd oder Ca stärker ausgeprägt.This work investigates the interrelationship among the crystallographic texture, microstructure, and deformation mechanisms, especially dislocation slip activities, in the Mg alloys accompanying the different texture formations after thermomechanical treatments. The rare-earth (RE) elements are generally known as a tailored element to texture modifying in Mg alloys. The addition of Zn combined with the RE elements exhibits a more pronounced texture modification. The Ca is regarded as a promising element that could partially replace RE elements. It has been usually noted that various recrystallization mechanisms ascribe to the texture weakening in the Mg alloys. The various recrystallization mechanisms require nucleation with grain rotation towards random orientations, which are relevantly correlated to the deformation mechanisms. A systematic investigation is emphasized to understand the influence of alloying elements, the active dislocation slip activities, and their contribution to the microstructure on the texture development based on the fact that the texture reflects the deformation mechanisms. In this work, the Mg alloys were successfully investigated by using in-situ experiments at a synchrotron for tracking texture development and change of diffraction patterns under mechanical testing at different temperatures. The obtained results were evaluated using convolutional multiple whole profiles (CMWP) analysis and electron backscattered diffraction (EBSD) measurement in terms of texture development, dislocation slip activities, and microstructure evaluations. The mutual influences between active deformation modes and recrystallization behavior at ambient and elevated temperatures were discussed. The higher activations of non-basal and pyramidal dislocations in the Nd or Ca containing Mg alloys compared to the Mg-Zn alloy were found in the CMWP analysis. The former is enhanced by the addition of Zn combined with Nd or Ca. In-grain misorientation axes (IGMA) distributions obtained from the EBSD measurement confirms that the predominant prismatic slip contributes to the higher activations of non-basal dislocation. The texture evolution shows an obvious feature for all examined sheets, which is a broadening of the basal pole perpendicular to the loading direction and a strengthening of the 〈101ത0〉 pole at the loading direction. The Zn addition in combination with the Nd or Ca shows a pronounced evolution of texture, compared to a sole addition of Nd or Ca. The Zn addition without Nd or Ca shows a less pronounced texture development. At elevated temperatures, the enhanced activation of non-basal dislocations is observed in the ZK10 deformed at 100°C. The serrated grain boundaries and fine grains at the grain boundaries, i.e. the onset of dynamic recrystallization, are observed in the ZK10 deformed at 200°C. In contrast, the uniform deformation and the retardation of the thermally activated processes, e.g. dynamic recovery and dynamic recrystallization, are observed in the other alloys. This retardation is more pronounced with the simultaneous addition of Zn with Nd or Ca

Texture and lattice strain evolution during tensile loading of Mg–Zn alloys measured by synchrotron diffraction

To explore the effect of neodymium (Nd) on the deformation mechanisms of Mg–Zn alloys, texture and lattice strain developments of hot-rolled Mg–Zn (Z1) and Mg–Zn–Nd (ZN10) alloys were investigated using in situ synchrotron diffraction and compared with elasto-viscoplastic self-consistent simulation under tensile loading. The Nd-containing ZN10 alloys show much weaker texture after hot rolling than the Nd-free Z1 alloy. To investigate the influence of the initial texture on the texture and lattice strain evolution, the tensile tests were carried out in the rolling and transverse direction. During tension, the {002} texture components develop fast in Z1, which was not seen for ZN10. On the other hand, fiber // loading direction (LD) developed in both alloys, although it was faster in ZN10 than in Z1. Lattice strain investigation showed that // LD-oriented grains experienced plastic deformation first during tension, which can be related to basal slip activity. This was more apparent for ZN10 than for Z1. The simulation results show that the prismatic slip plays a vital role in the plastic deformation of Z1 directly from the beginning. In contrast, ZN10 plastic deformation starts with dominant basal slip but during deformation prismatic slip becomes increasingly important

Patch-Mix Contrastive Learning with Audio Spectrogram Transformer on Respiratory Sound Classification

Respiratory sound contains crucial information for the early diagnosis of fatal lung diseases. Since the COVID-19 pandemic, there has been a growing interest in contact-free medical care based on electronic stethoscopes. To this end, cutting-edge deep learning models have been developed to diagnose lung diseases; however, it is still challenging due to the scarcity of medical data. In this study, we demonstrate that the pretrained model on large-scale visual and audio datasets can be generalized to the respiratory sound classification task. In addition, we introduce a straightforward Patch-Mix augmentation, which randomly mixes patches between different samples, with Audio Spectrogram Transformer (AST). We further propose a novel and effective Patch-Mix Contrastive Learning to distinguish the mixed representations in the latent space. Our method achieves state-of-the-art performance on the ICBHI dataset, outperforming the prior leading score by an improvement of 4.08%.Comment: INTERSPEECH 2023, Code URL: https://github.com/raymin0223/patch-mix_contrastive_learnin

Майер Василий (Вильгельм) Евгеньевич : к 85-летию со дня рождения : биоблиогр. указ.

To explore the effect of neodymium (Nd) on the deformation mechanisms of Mg–Zn alloys,texture and lattice strain developments of hot‐rolled Mg–Zn (Z1) and Mg–Zn–Nd (ZN10) alloyswere investigated using in situ synchrotron diffraction and compared with elasto‐viscoplastic selfconsistentsimulation under tensile loading. The Nd‐containing ZN10 alloys show much weakertexture after hot rolling than the Nd‐free Z1 alloy. To investigate the influence of the initial textureon the texture and lattice strain evolution, the tensile tests were carried out in the rolling andtransverse direction. During tension, the {002} texture components develop fast in Z1, whichwas not seen for ZN10. On the other hand, fiber // loading direction (LD) developed in bothalloys, although it was faster in ZN10 than in Z1. Lattice strain investigation showed that //LD‐oriented grains experienced plastic deformation first during tension, which can be related tobasal slip activity. This was more apparent for ZN10 than for Z1. The simulation results show that theprismatic slip plays a vital role in the plastic deformation of Z1 directly from the beginning. In contrast,ZN10 plastic deformation starts with dominant basal slip but during deformation prismatic slipbecomes increasingly important

Analysis of the dislocation activity of Mg–Zn–Y alloy using synchrotron radiation under tensile loading

An understanding of deformation behavior and texture development is crucial for the formability improvement of Mg alloys. X-ray line profile analysis using the convolutional multiple whole profile (CMWP) fitting method allows the experimental determination of dislocation densities separately for different Burgers vectors up to a high deformation degree. A wider use of this technique still requires exploration and testing of various materials. In this regard, the reliability of the CMWP fitting method for Mg–Zn–Y alloys, in terms of the dislocation activity during tensile deformation, was verified in the present study by the combined analysis of electron backscatter diffraction (EBSD) investigation and visco-plastic self-consistent (VPSC) simulation. The predominant activity of non-basal 〈a〉 dislocation slip was revealed by CMWP analysis, and Schmid factor analysis from the EBSD results supported the higher potential of non-basal dislocation slip in comparison with basal 〈a〉 dislocation slip. Moreover, the relative slip activities obtained by the VPSC simulation also show a similar trend to those obtained from the CMWP evaluation

Influence of Nd or Ca addition on the dislocation activity and texture changes of Mg–Zn alloy sheets under uniaxial tensile loading

n situ hard X-ray diffraction experiments were carried out to investigate the dislocation slip activity of Mg-1 wt.% Zn-based alloys containing Nd or Ca during tensile loading. Diffraction patterns collected during tensile loading at 3 temperatures were analyzed using a convolutional multiple whole profile fitting procedure. High activation of nonbasal and pyramidal dislocations was found in the Nd- and Ca-containing alloys. The microstructure evolution after 10% deformation was examined by complementary EBSD measurements. The microstructure evolution was related to the differences in the initial texture and active deformation modes, according to the alloying and temperature. In-grain misorientation axes analysis obtained from the EBSD measurements confirms that the addition of Nd or Ca contributes to the higher activity of prismatic slip. The high activity of prismatic slip leads to a broadening of the basal poles perpendicular to the loading direction and a strengthening of the $$ pole along the loading direction. The overall dislocation density evolution at elevated temperatures is controlled by dynamic recovery and dynamic recrystallization. These thermally activated mechanisms are retarded in the Nd- or Ca-containing alloys

Texture development and dislocation activities in Mg-Nd and Mg-Ca alloy sheets

Texture modification during sheet rolling appears differently in binary Mg-RE (rare-earth) or Mg-Ca alloy, compared to their ternary counterparts containing Zn. The differences in texture development and the active deformation mechanisms under tensile loading were investigated in the binary alloys. These analyses are based on in-situ synchrotron experiments and electron backscatter diffraction measurements to reveal direct experimental evidence of the texture development and the active deformation mechanisms. Higher activations of nonbasal and pyramidal dislocations were found in the Nd or Ca containing Mg alloys, compared to the Mg-Zn alloy. The texture development shows an obvious feature, which is a broadening of the basal pole intensity distribution perpendicular to the loading direction and a strengthening of the pole at the loading direction in all examined sheets. This texture development relates to the higher activation of prismatic slip. The addition of Zn in the Mg-RE or Mg-Ca alloys further promotes the activation of nonbasal and pyramidal dislocations. This enhanced prismatic slip in the Zn containing ternary alloys is confirmed by EBSD misorientation analysis

Deformation and Recrystallization Mechanisms and Their Influence on the Microstructure Development of Rare Earth Containing Magnesium Sheets

Many studies have shown that textures with less distinct alignment of basal planes and the related improvement of formability are found in alloys that contain rare-earth (RE) elements and zinc. However, the effect of the combination of these additional elements on the texture modification has not been yet clearly understood. In this work, sheet samples from Mg–Zn–RE alloys rolled at 400 °C were used for in situ synchrotron X-rays diffraction measurements under tensile loading at different temperatures, in order to track the development of diffraction profiles and textures during deformation. In Mg–Zn–RE alloys, a significantly retardation of recovery and dynamic recrystallization during the high temperature deformation is observed in comparison to the RE-free Mg–Zn alloy. The differences in the active deformation mechanisms as well as the dynamic recrystallization mechanisms are reviewed with respect to the texture alteration. For discussion of the impact of different mechanisms, EBSD observations reveal the microstructure development

An Herbal Medicine, Yukgunja-Tang is more Effective in a Type of Functional Dyspepsia Categorized by Facial Shape Diagnosis: A Placebo-Controlled, Double-Blind, Randomized Trial

Introduction. Functional dyspepsia (FD) is a functional gastrointestinal disorder characterized by persistent upper dyspeptic symptoms without organic lesions. There is no standard therapy for FD. Yukgunja-tang (YGJT) is an herbal medicine used for treating upper gastrointestinal symptoms in Asia. Studies on the effect of YGJT on FD have been conducted. However, the results were inconsistent. In Hyungsang medicine, traditional Korean medicine, FD patients are classified into bladder body (BB) or gallbladder body (GB) subtypes by the shape and angle of their faces. Each subtype may have different characteristics, physiology, and pathology of the same disease. YGJT is more effective for patients with BB subtype. The three-dimensional facial shape diagnostic system (3-FSDS) was shown to be effective in diagnosing BB or GB subtypes. This study aimed to investigate the effect of YGJT on FD patients classified using the 3-FSDS. Materials and Methods. The current study was a placebo-controlled, double-blinded, randomized, two-center trial. Eligible patients were diagnosed with either BB or GB FD subtype using the 3-FSDS. Ninety-six participants (48 BB and 48 GB subtypes) were randomly allocated to treatment or control groups in a 2:1 ratio. YGJT or placebo was administered for eight weeks. The primary outcome was assessed using the total dyspepsia symptom scale (TDS), while the secondary outcomes were assessed using the single dyspepsia symptom scale (SDS), proportion of responders, visual analog scale, Nepean dyspepsia index, functional dyspepsia-related quality of life, and spleen qi deficiency questionnaire. Results and Discussion. The result of TDS showed the superior effect of YGJT on BB over GB subtype. The subgroup analysis of TDS and SDS scores showed the superior effect of YGJT over placebo. Other outcome variables did not show any significant differences between groups. Conclusion. YGJT may be considered for FD patients diagnosed with BB subtype using 3-FSDS