Novel fabrication of bulk Al with gradient grain size distributions via powder metallurgy

We describe a novel approach to synthesize gradient microstructures, defined hereafter as containing a broad but continuous distribution of grain sizes. These microstructures extend the concept of a bimodal grain size distribution and the ability to design with multiple length scales. We demonstrate the proposed approach via experiments involving cryogenic ball milling of Al–4.5Mg–0.4Mn–0.05Fe and Al–50Mg powder followed by subsequent consolidation. Our results reveal that the grains in the consolidated powder present a gradient size distribution ranging from <100 nm to >3 μm. Moreover, phase composition analysis revealed a unique “interfingered” structure where the two starting phases were intermixed in a complex three-dimensional mesh. Hardness studies of this gradient microstructure show average Vickers hardness values of 200 ± 2.6, 204 ± 4.3 and 266 ± 50 for macrohardness, microhardness and nanoindentation, respectively. The standard deviation values highlight that the gradient microstructure is disordered locally, but homogenous macroscopically.     

Materials analogue of zero-stiffness structures

Anglepoise lamps and certain tensegrities are examples of zero-stiffness structures. These structures are in a state of neutral equilibrium with respect to changes in configuration of the system. Using Eshelby's example of an edge dislocation in a thin plate that can bend, we report the discovery of a non-trivial new class of material structures as an analogue to zero-stiffness structures. For extended positions of the edge dislocation in these structures, the dislocation experiences a zero image force. Salient features of these material structures along with the key differences from conventional zero-stiffness structures are pointed out.     

Kinetic study of static recrystallization in an Fe–Al–O ultra-fine-grained nanocomposite

A nearly abrupt coarsening of grains is observed in a newly developed Fe–Al–O ultra-fine-grained nanocomposite with a significant volume fraction (4%) of alumina nano-precipitates. The microstructure of the alloy was analysed in different states (as-received and annealed) by means of scanning electron microscopy, transmission electron microscopy (TEM) and hardness. The initial grain size 150–200 nm increases up to 50 μm during annealing 1000 °C/8 h and thereafter demonstrates saturation. A linear correlation between volume fraction of coarse grains and hardness was found. It was identified by TEM that alumina nano-precipitates stabilize the dislocation microstructure against recovery very effectively and the grain coarsening is due to fast growth of very few dislocation free grains. Thus, the observed grain coarsening has the attributes of static recrystallization.     

A criterion for determining the optimum value of twist in the topological model

In previous works, in which the topological model has been applied to martensitic phase transformations, the value of twist angle ω was determined based on the habit plane-(HP) matching method, where the physical realization of the so-predicted interfacial defect networks may require reorientations of defect line directions by short-range diffusion, though no long-range diffusion was needed. In the present work, a novel criterion for determining the optimum value of twist is proposed so that the predicted interface defects are not only able to fulfil the function of fully accommodating the coherency strains arising on the terrace plane, but also capable of reaching the required position at the HP without long- or short-range diffusions. A numerical analysis for an Fe–20Ni–5Mn alloy is demonstrated based on the newly proposed criterion, and the predictions so obtained are in good agreement with the results provided by the phenomenological theory and experimental measurements.     

Core structure of a〈100〉 superdislocations in a single-crystal superalloy during high-temperature and low-stress creep

A thorough TEM analysis has been carried out to study the dislocations cutting into γ′ phase in a single-crystal superalloy during uniaxial tensile creep under high-temperature and low-stress conditions. It is proved that the a〈100〉 edge superdislocation originates from the interfacial a〈100〉 dislocations and moves into the γ′ phase by pure climbing. And the dissociation of the a〈100〉 superdislocation core into two a/2〈101〉 superpartial dislocations during uniaxial tensile creep has been identified by HRTEM method for the first time.     

Integrating covariates into circumplex structures: an extension procedure for Browne’s circular stochastic process model

Circumplex structures are elements of various psychological domains. Most work focuses on assessing the circular ordering of circumplex indicators and their relationships with covariates. In this article, an extension procedure for Browne’s circumplex model is presented. Our approach models the relationships among circumplex indicators and the relationships of covariates with a latent circumplex simultaneously without affecting the circumplex indicators’ positions on the circumplex. The approach builds upon Browne’s Fourier series parameterization of a correlation function, which is used to model the latent circumplex correlation structure. It extends the shape of the correlation function to the profile of each covariate’s correlations with the circumplex. The model is specified in the framework of structural equation modeling, thereby making it possible to test various hypotheses. Procedures are presented for deriving interval estimates for the parameters that relate the covariates to the circumplex. The model is compared to other approaches for assessing the relationships of a circumplex with covariates. The results of the exemplary applications and a simulation study were in favor of the suggested model. The approach is furthermore illustrated with a real-data example, focusing on the relationships between the interpersonal circumplex and the rivalry and admiration aspects of narcissism.     

Moods and Quality of Life

In modern society, flow and stress are well-known terms in the theoretical discussions of the good life, subjective well-being and quality of life. The purpose of this article is to present the results of a phenomenological analysis of flow and stress experiences in everyday life. The analysis yielded a distinction between different phenomenological dimensions identified as arising in different combinations within concrete experience of flow and stress. These different dimensions were characterised by different feelings, different experiences of time and different experiences of the world. The results are discussed and interpreted in the light of Martin Heidegger's, Otto Friedrich Bollnow's and F.C.J. Buytendijk's theories of moods and feelings. Flow and stress experiences are phenomenologically interpreted as moods and classified as a modern version of basic polarities of moods as described by Bollnow and Buytendijk. Lastly, the concept of mood is emphasised as a specific entrance to the subjective and experienced dimensions involved in the complex concepts of quality of life, the good life and happiness.     

Presence of ε-martensite as an intermediate phase during the strain-induced transformation of SUS304 stainless steel

We have investigated the formation process of α′-martensite from the γ-phase induced by external strain using in situ synchrotron diffraction experiments, combined with Lorentz transmission electron microscopy (TEM) and high-resolution TEM observations. It is clearly demonstrated that ε-martensite with hexagonal symmetry appears as an intermediate structure during the plastic deformation of SUS304 stainless steel. In addition to stacking faults and dislocations, interfaces between the twin structures presumably play a key role in the formation of ε-martensite.     

Experimental observation of the dislocation walls in heterostructures with two interfaces: Ge/Ge0.5Si0.5 10 nm/Si(001) as an example

High-resolution electron microscopy (HREM) at the atomic scale has been applied to study the edge dislocation redistribution between interfaces in Ge/Ge_0.5Si_0.5/Si(0?0?1) heterostructures. Our results provide a direct explanation that plastic relaxation of the GeSi buffer layer proceeds owing to motion of Lomer-type dislocation complexes consisting of a pair of complementary 60° dislocations with the ends of the {1?1?1} extra planes being located at a distance of ~2–12 interplanar spacings from each other. It is demonstrated that edge dislocations belonging to the upper and lower interfaces become arranged one under the other and dislocation walls are formed. The distributions of tension and compression in the [0?0?1] direction between two edge dislocations, obtained by processing the HREM image, testify to superposition of strain fields.     

A model for 〈c+a〉 dislocation transmission across nano-spaced parallel basal stacking faults in a HCP alloy

We develop a model for recently observed 〈c + a〉 dislocation transmission across nano-spaced parallel basal stacking faults in hexagonal close-packed (HCP) Mg microcrystalline grains. The model theoretically predicts nanospace-dependent yield strength that is in good agreement with experimental data. Additionally, it theoretically predicts activation volume and strain rate sensitivity.     

Comparing the Effects of Loving-Kindness Meditation (LKM), Music and LKM Plus Music on Psychological Well-Being

Loving-kindness meditation (LKM), a meditative practice directing caring feelings toward self and others, is a popular, evidence-base approach to increasing well-being. Music listening is also a popular form of emotion regulation used to enhance well-being. This interdisciplinary study evaluated a novel intervention called Convergence—combining LKM with accompanying classical guitar music—and its effects on adults’ well-being, mindfulness, compassion and self-compassion outcomes. Convergence was compared to active control groups LKM-only and Music-only regarding their relative effectiveness in improving these outcomes. Participants (N?=?78; aged 18 to 69?years; 90% females; recruited from the general public) were assigned to either the Convergence, LKM-only, or Music-only condition. Each condition received a 2-hour workshop, involving psychoeducation, three prerecorded meditations, and group enquiry and discussion. Participants were assessed at pre-program, post-program, and 4-week follow-up. Findings revealed that Convergence, LKM-only and Music-only were equally effective interventions, producing improvements in dependent variables with small effect sizes. There was no additive effect of the components when delivered together as Convergence. Significant correlations were found between the amount of home practice, and mindfulness and self-compassion at follow-up. LKM, music listening and Convergence all provide brief, evidence-based alternatives for improving well-being. Practical and theoretical implications are provided, as well as recommendations for future research.