The microstructural and texture evolutions of as-cast AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) have been investigated in the course of thermomechanical processing at the temperature range of ...25–500 °C. Interestingly, compared with other conventional casting structures, significant strength-ductility ratio has been achieved at room temperature. In addition, the volume fractions of the constituent phases: soft FCC (face-centered cubic), and the hard BCC (body-centered cubic) phases, do not significantly change from room to elevated deformation temperatures. In fact, the strength and ductility have not been decreased at higher temperatures which represent the mechanical stability of the alloy in the examined temperature range. From room temperature up to 300 °C, the dendrites have been stretched and broken with a slight deviation from the load direction, whereas at higher temperature of 500 °C the dendrites have been rotated relative to the direction of load before fracture. Texture examination reveals the formation of a random texture in the initial and deformed states due to simultaneous contribution of different influencing factors such as stretching of dendrites during deformation, the dendrite morphology changes, and the presence of hard and soft phases and their interaction with each other.
The Li+ ion conductor Li7La3Zr2O12 was synthesized by solid state reaction as a ceramic with tetragonal and cubic crystal structure. The synthesis parameters were varied for these polycrystalline ...samples, e.g. the starting materials for Li and Zr, the crucible materials and the thermal treatments. Product formation is sensitive to the ZrO2 starting powder as well as the crucible material due to reactions between the powder mixture and the crucible wall. In this study, only the use of an alumina crucible or the addition of alumina resulted in the successful preparation of cubic Li7La3Zr2O12.
For single-crystal preparation, flux growth experiments were carried out at 1000 and 1200°C either in alumina crucibles lined with a gold foil or in magnesia crucibles and using Li2CO3 (Li2O) as flux. The small crystals were separated from the solidified flux by washing larger lumps in water. Irrespective of the additions of alumina, only tetragonal micro-crystals of Li7La3Zr2O12 were obtained.
These micro-crystals were studied by micro-Raman scattering spectroscopy. Polarized Raman spectra were recorded either in nearly backscattering or 90° geometry. The majority of Raman modes expected for the tetragonal phase (space group I41/acd, Z=8) were satisfactorily displayed. So far, it has not been possible to make unambiguous symmetry assignments of the observed peaks because of the unknown orientation of the micro-crystals.
► Li-ion conductor Li7La3Zr2O12 with tetragonal and cubic garnet-like structure ► Impact of impurities and impurity concentrations on phase formation ► Single-crystal preparation by flux growth method ► Vibrational study by polarized micro-Raman spectroscopy
•Fatigue properties are improved due to ϰ-carbide formation at low strain amplitudes.•Plastic deformation leads to shearing of the ϰ-carbides at high strain amplitudes.•Interaction of several ...elementary mechanisms contributes to LCF fatigue response.•Coffin–Manson and Basquin equations reveal a change of mechanisms in the LCF regime.•Fractography revealed fatigue crack initiation from the surface of the specimen.
High-manganese light-weight steels offer a great potential for structural purposes in the mobility sector due to their reduced density combined with outstanding mechanical properties. As many of the envisaged applications of these materials will suffer from cyclic loading during their service life, the fundamentals of their fatigue behavior must be studied extensively. In the present work, the low-cycle fatigue (LCF) properties of an austenitic Fe-29.8Mn-7.65Al-1.11C light-weight steel were investigated. Two microstructurally different conditions are directly compared: a homogenized, fully austenitic condition and an aged, austenitic, ϰ-carbide-containing condition. Results elaborated by total strain-controlled fatigue tests are discussed considering microstructural insights revealed by scanning electron microscopy and synchrotron diffraction analysis. Although fatigue properties are improved upon aging due to ϰ-carbide formation for lower strain amplitudes as compared to homogenized counterparts, the cyclic deformation behavior is characterized by cyclic softening at increased strain levels. Shearing of the ϰ-carbides and their mechanical dissolution due to the onset of plastic deformation are found to be the underlying mechanisms. Determination of LCF parameters for both conditions was realized by evaluation of the fatigue life based on the Coffin-Manson law and Basquin equation, eventually providing explanations for the Masing and non-Masing behavior of the aged and homogenized condition, respectively, deduced from analysis of half-life hysteresis loops.
•Deep rolling (DR) leads to increased YS, UTS and an increased hardness.•Compressive residual stresses are induced with a maximum of −850 MPa after DR.•Twin bands evolve in the near surface area ...after DR at cryogenic temperature.•Fatigue properties can be improved by means of DR between 103 and 106 cycles.•S-N curves (initial state vs. DR) reveal a point of intersection for Nf > 106.
High-cycle fatigue tests were performed on differently deep rolled conditions of the equiatomic high-entropy alloy (HEA) CoCrFeMnNi. Twinning in the near-surface layer of specimens deep rolled at cryogenic temperature is revealed by electron-backscatter diffraction. As internal failure mode and similar fatigue lives are found irrespective of the deep rolling temperature, these twins are not expected to significantly contribute to the fatigue properties of the surface treated HEA. S-N curves of the initial state and deep rolled conditions revealed a point of intersection at low stress amplitudes. This unexpected behaviour is explained based on the interplay of several characteristics of the near-surface layers.
Consumer products are widely used as stimuli across several research fields. The use of consumer products as experimental stimuli lacks, however, the support of normative data regarding product ...features variability. In this work, we provide a first set of norms for people's perceptions of 150 consumer products regarding six relevant dimensions: product perceived complexity, quality objectivity, material/experiential nature, perceived price, familiarity and attitude. Products available in this normative database showed good overall distribution across the range of the dimensions evaluated. Obtained correlations between some of these dimensions provided evidence of how they can be confounded across products, further justifying the need to control for these dimensions. These norms should aid future research by allowing researchers to select products according to specific attributes and achieve appropriate experimental control. The norms here provided should also aid consumer behavior practitioners (such as marketers and advertisers) by providing insights as to how consumers perceive products along relevant dimensions.
To describe the prevalence of amputation-related pain; to ascertain the intensity and affective quality of phantom pain, residual limb pain, back pain, and nonamputated limb pain; and to identify the ...role that demographics, amputation-related factors, and depressed mood may contribute to the experience of pain in the amputee.
Cross-sectional survey.
A sample of persons who contacted the Amputee Coalition of America from 1998 to 2000 were interviewed by telephone.
A stratified sample by etiology of 914 persons with limb loss.
Not applicable.
Prevalence, intensity, and bothersomeness of residual, phantom, and back pain, depressed mood as measured by the Center for Epidemiologic Study Depression Scale, characteristics of the amputation, prosthetic use, and sociodemographic characteristics of the amputee.
Nearly all (95%) amputees surveyed reported experiencing 1 or more types of amputation-related pain in the previous 4 weeks. Phantom pain was reported most often (79.9%), with 67.7% reporting residual limb pain and 62.3% back pain. A large proportion of persons with phantom pain and stump pain reported experiencing severe pain (rating 7-10). Across all pain types, a quarter of those with pain reported their pain to be extremely bothersome. Identifiable risk factors for intensity and bothersomeness of amputation-related pain varied greatly by pain site. However, across all pain types, depressive symptoms were found to be a significant predictor of level of pain intensity and bothersomeness.
Chronic pain is highly prevalent among persons with limb loss, regardless of time since amputation. A common predictor of an increased level of intensity and bothersomeness among all pain sites was the presence of depressive symptoms. Further studies are needed to elucidate the relationship between pain and depressive symptoms among amputees.
Little is known about associations between perceived stress, psychosocial factors (social support, emotional coping, coping self-efficacy, and autonomous motivation), and depressive symptoms in ...low-income overweight or obese mothers of young children. Using baseline data of a lifestyle intervention study, this secondary analysis investigates whether perceived stress might mediate the associations between the psychosocial factors and depressive symptoms.
Convenience sampling was applied. Low-income overweight or obese mothers of young children were recruited from the Special Supplemental Nutrition Program for Women, Infants, and Children in Michigan, US. Survey data were collected through phone interviews. Participants (N = 740) responded to valid surveys measuring perceived stress, social support, emotional coping, coping self-efficacy, autonomous motivation, and depressive symptoms. Composite indicator structural equation modeling was performed to test for potential mediation.
When investigating the potential role of perceived stress as a mediator, the indirect effects of social support (b = - 2.10, p < 0.01), emotion coping (b = - 3.81, p < 0.05), and coping self-efficacy (b = - 7.53, p < 0.01) on depressive symptoms through perceived stress were significant, but the indirect effect of autonomous motivation was not.
Future intervention studies aiming to alleviate depressive symptoms in low-income overweight or obese mothers of young children might consider including practical strategies to promote social support, emotional coping, and coping self-efficacy to reduce perceived stress, which might potentially decrease depressive symptoms.
Clinical Trials NCT01839708 ; registered February 28, 2013.
The solid-state friction stir welding (FSW) process was used to join Al–Si12 parts fabricated via the selective laser melting (SLM) technique. The effect of the welding process on microstructural ...evolution and mechanical properties of the samples is investigated in present work. Microstructural studies demonstrate that FSW is capable of changing Si phase morphologies (i.e. shape and size) resulting in various mechanical properties. The stir zone of the welded joint shows significantly lower micro-hardness in comparison to the as-built SLM samples. Correspondingly, the friction stir welding process results in significant reduction of tensile strength, while ductility is strongly improved. The fully-reversed strain-controlled low-cycle fatigue (LCF) tests imply that at low strain amplitudes the FSW and SLM samples show almost the same fatigue life, while at the high strain amplitudes the SLM samples show superior LCF performance. Fracture analysis of fatigued samples reveals that the near-surface pores lead to the crack initiation in both SLM and FSW cases.
Despite the widespread use of exploratory factor analysis in
psychological research, researchers often make questionable decisions
when conducting these analyses. This article reviews the major ...design
and analytical decisions that must be made when conducting a factor analysis
and notes that each of these decisions has important consequences for the
obtained results. Recommendations that have been made in the
methodological literature are discussed. Analyses of 3 existing
empirical data sets are used to illustrate how questionable decisions in
conducting factor analyses can yield problematic results. The article
presents a survey of 2 prominent journals that suggests that researchers
routinely conduct analyses using such questionable methods. The
implications of these practices for psychological research are
discussed, and the reasons for current practices are
reviewed.
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