Correlation between ductility and work function in NiAl–Ce–Cr alloys

In spite of many superior high-temperature properties of intermetallics, it has been difficult to understand their intrinsic brittleness. To eliminate or improve the embrittlement, the conventional alloying technique based on the trial-and-error method is still the most effective and practical. However, it remains a main challenge for both physicists and materials scientists to provide either an alloying principle or a deep insight into its toughening mechanism at an atomic or electronic level. This letter reports a simple experimental approach that uses work function (WF) as a sensitive indicator of the role of alloying in changing mechanical behavior. NiAl is chosen as a typical example. It is found that with the addition of Cr and Ce, the ductility of NiAl increases significantly. Such an increase in ductility corresponds to a concomitant decrease in the WF, which is attributed to a change in the nature of the atomic bonding or in the electronic structure induced by the alloying. This fundamental understanding on the embrittlement nature of NiAl could provide some alloying guidelines or principles for other intermetallics.     

Tensile behaviour of submicrocrystalline ferritic steel processed by large-strain deformation

Mechanical tests have been carried out on Fe–15%Cr ferritic stainless steel with various microstructures. Ultrafine-grained microstructures with grain sizes of 0.2–0.3 µm were developed by large-strain cold-working and light annealing. The effects of severe deformation on the mechanical behaviour of as-processed and recovered steel were evaluated with reference to the same material having conventional work-hardened and recrystallised microstructures. Despite the low dislocation density in the fine grain interiors in the as-processed state, the samples with strain-induced submicrocrystalline structure were characterised by high internal stresses that resulted in a higher strength than could be expected from simple grain-size strengthening. These internal stresses were associated with a non-equilibrium state of strain-induced grain boundaries after severe deformation.     

Fracture mechanism of a coarse-grained magnesium alloy during fracture toughness testing

The fracture mechanism during fracture toughness testing has been investigated on a coarse-grained magnesium alloy, with an average grain size of ～50 µm, and a low fracture toughness. The results show that {1012}-type deformation twins are formed at the crack tip and many dislocations pile up on these boundaries. The accumulated strains at these boundaries become the origin of fracture; i.e. cracks propagate along these boundaries between the deformation twins and the matrix.     

New experimental test of strain-gradient plasticity theory: metal foil sandwich structures in flexure

Experimental tests of strain-gradient plasticity theory rely on studies of the size effect (smaller is stronger) in micromechanical testing. The plastic strain gradient is varied by varying the size of the specimen. This confounds the direct effects of the size and the effects of the strain gradient. We propose experiments on foil sandwich structures in which these parameters are separated. Preliminary results suggest that it is the foil thickness that determines the strength, not the strain gradient.     

Investigation of {111} stacking faults and nanotwins in epitaxial BaTiO3 thin films by high-resolution transmission electron microscopy

{111} stacking faults and nanotwins in epitaxial BaTiO₃ thin films on MgO substrates have been investigated by high-resolution transmission electron microscopy. In many cases, the stacking faults and nanotwins were found to be accompanied by partial dislocations. These partial dislocations can be classified as two different types, analogous to the situation in the fcc structure. One is of the Shockley type with the Burgers vector (a/3)<112>. The other is of the Frank type with the Burgers vector (a/3)<111>. The movements of both types of partial can lead to the {111} stacking faults and the {111} twins observed in these films.     

Tensile deformation behaviour of Zr-based glassy alloys

This paper presents a study of the deformation behaviour of a glassy phase in two Zr-based alloys, Zr₆₅Ni₁₀Cu₅Al_7.5Pd_12.5 and Zr₆₅Al_7.5Ni₁₀Pd_17.5, performed in situ in a transmission electron microscope. In contrast to the case of shear localisation and formation of 10–20 nm thick shear bands in deformed bulk glassy samples studied earlier, it is found that in thin (electron-transparent) samples the glassy phase in front of a crack deforms more homogeneously and no nanocrystallisation takes place. The reasons for such behaviour are discussed. According to the observed results, one can conclude that the studied metallic glasses can be intrinsically ductile in submicrometre-sized volumes.     

Deformation twins induced by multi-mode deformation in nanocrystalline copper

A multi-mode deformation model is used in a molecular dynamics simulation of nanocrystalline copper. Abundant deformation twin lamellae are developed by shearing the following compression to the elastic limit. Deformation twins (DTs) nucleate through two different mechanisms facilitated by Shockley partial slips. Interactions between DTs and Shockley partials are observed in this simulation.     

Genetic and Environmental Transmission of Political Orientations

This article reports results from the first twin study of adults in the United States that focuses exclusively and comprehensively on political traits. These data allow us to test whether a common set of genetic and environmental influences act upon a broad variety of values, personality traits, and political attitudes. In short, it allows us to empirically investigate whether there are a core set of predispositions that form the basis of our political orientations and, if so, whether these predispositions are shaped by the same environmental and innate forces. The key finding from our analysis is that there are core political predispositions that are rooted in common genetic and environmental influences and that these predispositions are empirically distinct from broader personality traits.     

Genetic and Environmental Influences on the Development and Stability of Executive Functions in Children of Preschool Age: A Longitudinal Study of Japanese Twins

Executive functions (EF) are an important predictor of later adaptive development. A number of environmental influences, such as parenting, have been suggested as important promoters of EF development. However, behavioural genetic research has demonstrated that many environmental influences could be affected by genetic influences. Therefore, it is important to consider genetic variations when investigating environmental influences on EF development in children. To date, few studies have used genetically informative designs to assess the etiology of EF development during the preschool years, a period of rapid development. As a result, it remains unclear how and to what extent the environmental influences that are not confounded by genetic influences affect EF development during this developmental period. The present study explored EF development during the preschool years using a longitudinal and genetically informative design and a non‐Western population. Japanese twins were visited at their homes and individually tested on EF measures at 24, 36, and 48 months of age. Phenotypic correlations and confirmatory factor analyses suggested that EF are less cohesive at 24 months of age and emerge as a common single factor at 36 and 48 months. Additionally, longitudinal and multivariate behavioural genetic analyses indicated that the EF developmental change during this period is promoted by both shared and nonshared environmental influences as well as genetic influences, while EF stability is brought about by shared environments. The present findings elucidated the etiology of EF development during the preschool years and confirmed that this period is an important transitional stage for EF development. Copyright © 2016 John Wiley & Sons, Ltd.