The kinetics of infralow-frequency viscoelastic internal friction induced by irreversible structural relaxation of a metallic glass

This letter presents the results of internal-friction measurements of Co 70 Fe 5 Si 15 B10 metallic glass at temperatures 400K h T h 700K and frequencies 0.01 Hz h f h 0.05Hz. It is shown that Maxwellian viscoelastic damping is predominant in this case. The nature of this damping is determined by irreversible structural relaxation. The kinetic relaxation law is derived.     

A phase-field model for deformation twinning

We propose a phase-field model for modeling microstructure evolution during deformation twinning. The order parameters are proportional to the shear strains defined in terms of twin plane orientations and twinning directions. Using a face-centered cubic Al as an example, the deformation energy as a function of shear strain is obtained using first-principle calculations. The gradient energy coefficients are fitted to the twin boundary energies along the twinning planes and to the dislocation core energies along the directions that are perpendicular to the twinning planes. The elastic strain energy of a twinned structure is included using the Khachaturyan's elastic theory. We simulated the twinning process and microstructure evolution under a number of fixed deformations and predicted the twinning plane orientations and microstructures.     

General analytical solution for stress intensity factor of a hypocycloid hole with many cusps in an infinite plate

In this article, the problem for the determination of the displacement functions and the stress intensity factors (SIFs) around a boundary of a hypocycloid hole with cusps in an infinite elastic plate subject to normal and shear stresses are presented. A hole with cusps (hypocycloid) is mapped onto a unit circle and the modified complex potential is used for solving the relevant boundary value problems. An analytical solution for the SIF of a hypocycloid hole is obtained. For a special case, our results agree with others.     

Crystallization behaviour of Al-based amorphous alloy and nanocomposites by rapid quenching

The microstructure and crystallization behaviour of melt-spun Al₈₈Ni₉Ce₂Fe₁ amorphous alloy and nanophase composites have been studied by means of X-ray diffraction, transmission electron microscopy and scanning and isothermal calorimetry. The diffraction patterns from Al₈₈Ni₉Ce₂Fe₁ amorphous alloys are diffuse, indicating a basically amorphous structure but contain two rings presumed to be associated with quenched-in nuclei. In the cases of Al₈₈Ni₉Ce₂Fe₁ nanophase composites, nanoscale precipitated particles are homogeneously dispersed in an amorphous matrix, and the crystallite diameter and volume fraction are sensitive to quenching conditions. During thermal crystallization, a two-step phase transformation occurs in the amorphous alloy and nanocomposites, which is characterized by a diffusion-controlled precipitation of nanoscale Al particles and the growth of a Al₃(Ni, Fe) nanophase prior to a Al₁₁Ce₃ nanophase. This study gives insight into structure-control for obtaining nanophases dispersed in an amorphous matrix by rapid quenching.     

The Behavioral Genetics of Religiousness

Behavioral geneticists have sought to characterize the genetic and environmental contributions to individual differences in religiousness. Behavioral genetic methodology is described and twin and adoption studies of religiousness are reviewed. It is concluded that familial resemblance for religiousness is due largely to shared environmental factors in childhood and adolescence, but to genetic factors in adulthood. Additional evidence shows that there is a genetic correlation between religiousness and antisocial and altruistic behavior. Claims for the discovery of a “God gene” are premature and unlikely, as any genetic influence is likely to represent the aggregate effect of many genetic factors.     

A statistical model of cleavage fracture in structural steels with power-law distribution of microcrack size

Based on the well-accepted physical understanding that cleavage fracture of structural steels is preceded by plastic deformation, a critical flaw in the Beremin model and its modifications is proposed, and a new statistical model with the power-law distribution of microcracks is obtained to describe the cumulative probability of cleavage fracture. A set of cleavage fracture toughness data of a nuclear pressure vessel steel is used to highlight the difference between the new model and the Beremin model.     

Influencing surface plastic flow in metals using common chemical media

We demonstrate a unique mechanochemical effect – change in surface plastic flow by action of chemical media such as inks and glues – in large-strain deformation of metals. Unlike other well-known phenomena such as stress corrosion cracking and liquid metal embrittlement, the effect is not catastrophic and is largely material independent. High-speed in situ imaging shows that the media influence the flow by effecting a local ductile-to-brittle transition – from unsteady, large-amplitude, plastic folding, to repeated fracture and segmentation – with large decrease in deformation forces. The benign nature of the media offers opportunities for enhancing performance of metal cutting and deformation processes.     

Factor structure and aetiological architecture of the BRIEF: A twin study

Executive function is a broad construct that encompasses various processes involved in goal‐directed behaviour in non‐routine situations (Banich, 2009). The present study uses a sample of 560 5‐ to 16‐year‐old twin pairs (M = 11.14, SD = 2.53): 219 monozygotic twin pairs (114 female; 105 male) and 341 dizygotic twin pairs (136 female, 107 male; 98 opposite sex) to extend prior literature by providing information about the factor structure and the genetic and environmental architecture of the Behavior Rating Inventory of Executive Function (BRIEF; Gioia et al., 2000, Child Neuropsychol., 6, 235; Gioia et al., 2000, Behavior rating inventory of executive function, Lutz, FL: Psychological Assessment Resources), a multifaceted rating scale of everyday executive functions. Phenotypic results revealed a 9‐scale, 3‐factor model best represents the BRIEF structure within the current sample. Results of the genetically sensitive analyses indicated the presence of rater bias/contrast effects for the Initiate, Working Memory, and Task‐Monitor scales. Additive genetic and non‐shared environmental influences were present for the Initiate, Plan/Organize, Organization of Materials, Shift, and Monitor and Self‐Monitor scales. Influences on Emotional Control were solely environmental. Interestingly, the aetiological architecture observed was similar to that of performance‐based measures of executive function. This observed similarity provided additional evidence for the usefulness of the BRIEF as a measure of ‘everyday’ executive function.     

Influence of plastic strain localisation on the mechanical properties of metal matrix composites

The aim of the present study is to reveal the most critical underlying factor influencing the mechanical properties of metal matrix composites (MMCs). It is shown that the mechanical properties of MMCs are essentially governed by the degree of strain localisation during plastic deformation. In other words, the MMCs exhibit superior mechanical performance only if the strain localisation is obviously inhibited and the accumulated stresses can be effectively transferred out. The work provides a new perspective in guiding the design of next-generation high-performance MMCs by suppressing the strain localisation as far as possible.     

Distribution of Cr atoms in a strained and strain-relaxed Fe89.15Cr10.75 alloy: a Mössbauer effect study

An Fe_89.15Cr_10.75 alloy in a heavily strained (by cold rolling) state and in strain-relaxed states was studied by means of conversion electrons Mössbauer spectroscopy. Analysis of the spectra in terms of a two-shell model revealed significant differences between the studied samples, particularly in values of the hyperfine field and the distribution of Cr atoms within the first two neighbour shells. The latter is quantified in terms of short-range order parameters.