Fractal growth of graphite nodules in iron

It has been found from a large number of statistical tests that graphite nodules in malleable iron grow with time according to a power law. The growth of the nodules and their fractal dimension have been investigated experimentally as a function of annealing time. Based on the assumption of carbon-diffusion-controlled growth in the initial stage, the growth equation is R _G = K ₁ t ^1/(D-1), where R _G is the radius of the graphite nodules, t the time, D the fractal dimension and K ₁ a constant. Assuming cementite-dissolution-controlled growth in the later stages of growth, the relation is R _G = K ₃ t ^3/D , where K ₃ is a constant. The fractal dimension, or the aggregate state of the graphite nodules, strongly influences the growth process.     

On elastic–viscoplastic modeling of nanotwinned metals based on coupled intra-twin and twin-boundary-mediated deformation mechanisms

An elastic–viscoplastic model has been developed for nanotwinned (nt) metals based on coupled intra-twin and twin-boundary-mediated (TBM) deformation mechanisms. The grain-size dependence of intra-twin plasticity was incorporated in the proposed model to determine the transitional twin thickness corresponding to the maximum strength. In addition, the joint distribution of grain size and twin thickness was also taken into account to simulate the microstructure of nt metals. The results obtained show that the TBM deformation mechanism dominated at low strain rate and small twin thickness, and that the grain-size and twin-thickness distributions had significant influence on the macroscopic behavior of nt metals. A linear relation between the transitional twin thickness and grain size is predicted by the proposed model, which is in good agreement with the results obtained from three-dimensional molecular dynamics simulations and experiments.     

New insights on tensile plasticity of ultrafine-grained metallic materials

ABSTRACT

The tensile properties of TiNi_43.5Fe_6.5 alloy samples having different grain sizes (0.16, 0.35, 1.7, 2.3, and 3.9?μm) and fabricated by severe plastic deformation and annealing were investigated. It was observed that both the strength and the elongation of the alloy increase with a decrease in the grain size until the average size reaches 1.7?μm. However, for average grain sizes smaller than 1.7?μm, the elongation decreases continuously with further grain refinement. On the other hand, the strain-hardening rate does not decrease with the decrease in plasticity but instead increases slightly. The poor ductility of the ultrafine-grained TiNi_43.5Fe_6.5 alloy is accompanied by a high degree of strain hardening. This newly observed ductility behaviour of the ultrafine-grained TiNi_43.5Fe_6.5 alloy is elucidated by characterising the intragranular and grain boundaries.     

High-pressure electrical resistivity behaviour of nanocrystalline perovskite (La,Sr)(Mn,Fe)O3

We report here the electrical resistivity of nanocrystalline perovskite-structured La–Sr manganites as a function of pressures up to 8?GPa, at room temperature. The nanocrystalline perovskite manganites were prepared by the sol–gel technique and found to have crystallite sizes of 12–18?nm. The pressure dependence of the electrical resistivity shows a first-order phase transition at 0.66(2)?GPa and a subtle phase transition between 3.5 and 3.8?GPa. The first-order transition at 0.66?GPa can be related to the transition from localized-electron to band magnetism.     

Observation of planar stacking faults in a Ti-rich two-phase Ti-Al alloy after deformation at elevated temperatures

It is a common observation that in two-phase Ti-Al-based binary alloys, deformation of the gamma phase occurs by 1/2<110]-type ordinary dis-location activity and twinning associated with 1/6<112] type partials. In the present study the microstructure of a new Ti-Al-based alloy (Ti-47at.% Al-2at.%Mn-2at.%Nb+ 0.8 vol.% TiB₂) with a duplex microstructure consisting of primary equiaxed gamma grains and lamellar alpha₂+ gamma colonies was studied by transmission electron microscopy (TEM) after deformation at elevated temperatures. Planar stacking faults were found in the gamma laths. A detailed contrast analysis by TEM shows that these planar stacking faults lying on {111} planes are bound by all the fcc variants of the Shockley partial dislocations of type 1/6<121>, in contrast with the observations in stoichiometric binary TiAl alloys, where only 1/6<112]-type Shockley partials are found to be associated with the true twins. It is proposed that the addition of ternary and quaternary elements such as Mn and Nb promotes the other variants of the fcc-like dissociations (not common in L1₀structure) in the present alloy.     

Negative affectivity,perceived occupational stress,and health during organisational restructuring: A follow-up study

Abstract

This paper presents a survey of the relationships among multiple indicators of perceived occupational stress, trait negative affectivity, and later mental and physical health symptoms, among 157 Australian public servants during organisational restructuring. It was hypothesised that individual differences in negative affectivity would inflate the relationships between perceived stress and later strain as assessed by health symptoms in the follow-up phase. The possible role of negative affectivity in moderating the stress-strain relationships was also investigated. Multiple regression analyses conducted with depressive and physical health outcomes separately indicate that the only significant predictors of depressive symptoms were negative affectivity and role insufficiency, whereas the significant predictors of physical health symptoms were role ambiguity, physical environment, and negative affectivity. None of the interaction terms involving occupational stress and negative affectivity was found to be significant Implications of the findings are discussed in the context of the research literature on work stress, particularly the role of negative affectivity in inflating the stress-strain relationship and indications for future research.     

Resource replacement and psychological well-being during unemployment: The role of family support

There is an established inverse relationship between unemployment and psychological wellbeing. However, little is known about the processes that underlie this relationship. Using latent deprivation, conservation of resources, and social capital to form a theoretical framework, this study explored the relationship between the latent benefits associated with employment, family support, and financial strain. In a sample of 174 unemployed individuals, latent benefits were shown to partially mediate the relationship between family support and psychological well-being. Additionally, this mediation was moderated by financial strain, with latent benefits being more related to psychological well-being in those with greater financial strain. These findings provide guidance in understanding how to better address the needs that contribute to psychological well-being in those who are unemployed.     

Are you tired? Spillover and crossover effects of emotional exhaustion on the family domain

This paper examines the spillover and crossover effects of emotional exhaustion on marital satisfaction for both employees and partners as well as on employee work–family conflict and partner family–work conflict. It investigates how the transmission of psychological strain from the workplace to the family domain mediates these relationships. In a sample of 226 employee–partner dyads from manufacturing, electronics, banking, service industries and public organizations, the results support the notion that employees' emotional exhaustion spawns negative strain in the home. More specifically, the results of spillover mediation analyses show the relationships between emotional exhaustion and employee marital satisfaction/work–family conflict in the home. In a crossover model, the results indicate that employee psychological strain mediates the relationships between emotional exhaustion and the marital satisfaction of partners/family–work conflict in partners. These findings provide supports for spillover and crossover models to investigate a direction for the effectiveness of emotional exhaustion on family issues. Theoretical and practical implications of the results are discussed, and directions for future research are offered.