An investigation of strain softening phenomenon in Al-0.1% Mg alloy during high-pressure torsion processing

An Al-0.1% Mg alloy was processed by high-pressure torsion (HPT) at room temperature. The Al-0.1% Mg alloy displays strain softening phenomenon through hardness evolution: the hardness values in the disc centre area are higher than at the disc edge area after 1/2, 1 and 3 turns, and the size of the hard region in the disc centre gradually reduces as the numbers of turns increases from 1/2 to 3 turns. The hardness values evolve towards homogeneity along the disc diameters after 5 and 10 turns. Electron backscatter diffraction (EBSD) and X-ray line profile analysis suggest that the lower hardness values at the disc edge area in the Al-0.1% Mg alloy are related to a recovery / recrystallization mechanism where the material is subjected to heavy straining

Comparisons of self-annealing behaviour of HPT-processed high purity Cu and a Pb–Sn alloy.

Early published results have demonstrated that high purity Cu and a Pb–62% Sn alloy exhibit very different behaviour during high-pressure torsion (HPT) processing at room temperature and subsequent room temperature storage. High purity Cu showed strain hardening behaviour with a refined grain structure during HPT processing whereas a Pb–62% Sn alloy displayed a strain weakening behaviour because the hardness values after HPT processing were significantly lower than in the initial as-cast condition even though the grain size was reduced. During room temperature storage after HPT processing, high purity Cu with lower numbers of rotations softened with the time of storage due to local recrystallization and abnormal grain growth whereas the Pb–62% Sn alloy hardened with the time of storage accompanied by grain growth. Through comparisons and analysis, it is shown that the low absolute melting point and the high homologous temperature at room temperature in the Pb–62% Sn alloy contribute to the increase in hardness with coarsening grain size during room temperature storage

An examination of microstructural evolution in a Pb-Sn eutectic alloy processed by high-pressure torsion and subsequent self-annealing.

The Pb-Sn alloy has a wide use in the electronic, energy storage and nuclear industries and a fine-grained Pb-Sn alloy may open up new possibilities for applications in these industries. In order to understand the behavior of grain refinement, a Pb-62% Sn eutectic alloy was processed by high-pressure torsion (HPT), stored at room temperature (RT) and then the microstructures of the alloy after HPT were repeatedly investigated during the course of self-annealing using electron backscatter diffraction, scanning electron microscopy and transmission electron microscopy. It is demonstrated that there is a large fraction of twin boundaries with a twin relationship of 62.8° in the microstructure of the initial as-cast condition. Due to the presence of the high imposed pressure, the mobility of Ʃ21 boundaries at 71° is greatly favoured during processing by HPT. After the high pressure is removed, the mobility of dislocation-twin boundaries near 62.8° is then favoured. Processing by HPT significantly increases the solubility of Sn in the Pb phase. The supersaturated state of Sn in Pb is not stable during self-annealing at RT and instead a decomposition of Sn from the Pb-rich phase is observed after storage for 16 days. The main mechanism for this decomposition is lattice diffusion

The moderation effect of personality on healthcare utilization in Chinese people living with HIV

There is evidence that Type D personality can predict impaired quality of life and health status in various chronic conditions. The evidence is conflicting as to whether Type D is associated with increased healthcare services, and no study has reported on the healthcare utilization of people living with HIV (PLWH) who have a Type D personality. This study investigated the impact of Type D personality on healthcare utilization in a sample of Chinese PLWH and examined physical and emotional symptoms as possible mechanisms of healthcare utilization. This was a cross-sectional study of 199 PLWH in rural China. Participants completed a survey on physical symptoms, emotional symptoms, healthcare utilization, and Type D personality. Those PLWH with a Type D personality reported more physical and emotional symptoms and healthcare utilization than patients without this personality. Among PLWH who had a Type D personality, physical symptoms had a direct effect on healthcare utilization, and emotional symptoms did not significantly mediate this association. However, among PLWH without a Type D personality, emotional symptoms significantly mediated the effects of physical symptoms on healthcare utilization. PLWH with a Type D personality reported more healthcare utilization, which was attributed to their high physical symptoms rather than their emotional symptoms. These findings suggest that PLWH with a Type D personality might be bothered by intensified emotional symptoms, which might be too severe to be associated with physical symptoms and healthcare utilization. New prospective studies should focus on the pattern of healthcare utilization among patients with a Type D personality and their intensified physical and emotional symptoms

Herbivores avoid host plants previously exposed to their omnivorous predator Macrolophus pygmaeus

Herbivorous arthropods use various cues to choose suitable host plants. We investigated whether three species of herbivores use cues associated with their omnivorous predator Macrolophus pygmaeus to select host plants. Earlier, we found that this omnivore induces plant defences which decreased the performance of two of the herbivores, i.e. the spider mite Tetranychus urticae and the western flower thrips Frankliniella occidentalis, whereas the green peach aphid Myzus persicae was not affected. Hence, the spider mite and thrips were expected to avoid plants that were previously exposed to M. pygmaeus because of their lower quality, and the aphid was not expected to avoid exposed plants because they were of equal quality as unexposed plants. However, the cues left behind by M. pygmaeus may also be indicative of predation risk, in which case all three herbivores were expected to avoid exposed plants. Spider mites and western flower thrips preferred clean plants over plants that had previously been exposed to M. pygmaeus, but no longer harboured this omnivore. Aphids showed no preference, in agreement with their performance, but not in agreement with reducing predation risk. We furthermore showed that the preference of spider mites and thrips for clean plants increased through time. Higher proportions of aphids left plants previously exposed to M. pygmaeus than clean plants through time. Hence, omnivorous predators can decrease herbivore densities on plants not only by killing them but also by indirectly affecting herbivore host plant selection