Relations between interdiffusivities and intrinsic diffusivities in ternary and quaternary alloys

It is known that a reduction in the number of independent interdiffusivities and intrinsic diffusivities is possible if thermodynamic ideality of the (ternary) alloy is assumed or if the off-diagonal phenomenological coefficients are ignored. In the present letter we present a new analysis which shows generally, and exactly, that a reduction in the number of independent interdiffusivities and intrinsic diffusivities is always possible for ternary and higher alloys. In the general case, thermodynamic activities are also required.     

Kinetics of diffusion via divacancies in a concentrated random fcc alloy

The diffusion kinetics in a concentrated fcc alloy are described by means of divacancies. The model chosen is the random alloy model with bound divacancies. We show that for the fcc structure the Manning formalism developed originally for monovacancies can be used intact to describe diffusion via divacancies. Monte Carlo simulation results for both tracer and collective correlation factors are in good agreement with the results of the formalism for a wide range of the component atom exchange frequencies with the divacancy except for the slower-moving component.     

Atomic diffusion by the dumb-bell mechanism in a concentrated random bcc alloy

Matter transport by <110> dumb-bell interstitials in the bcc random alloy is considered in an analytical treatment based on linear response theory. Four different jump mechanisms of the dumb-bell are dealt with. It was found that at a low level of approximation relations can be deduced which give two of the three phenomenological coefficients in terms of the third one. (These relations are analogous to exact ones deduced for vacancy diffusion in the random alloy by Moleko, L. K., and Allnatt, A. R., 1998, Phil. Mag. A, 58, 666). Monte Carlo simulation shows that the relations are quite accurate, suggesting that they may well be exact.     

Limiting relations for atomic transport in lattice-gas models of solids

Abstract

The computer simulation of lattice-gas models of solids by Monte Carlo methods is significant for the theory of atomic migration and transport in alloys, solid solutions of hydrogen in metals, fast-ion conductors, etc. This paper presents certain exact limiting relations which provide useful checks on such simulations on complex models. These relations specify the way macroscopic transport coefficients and associated quantities (‘correlation factors’) depend upon isotopic ratios and vacancy fraction.     

Communal and exchange relationship perceptions as separate constructs and their role in motivations to donate

Researchers have operationalized communal and exchange relationship perceptions as either mutually exclusive categories or opposite ends of a continuum. This research conceptualizes these relationships as distinct constructs that should be measured separately. We develop multi-item measures of communal and exchange relationship perceptions and find that they are actually positively correlated. We also examine the way communal and exchange relationship perceptions combine to influence intrinsic, extrinsic, and social motivations to donate, a category stipulated in economics, but not in psychology. We find that both relationship perceptions influence consumer attitudes toward donating through a mix of intrinsic, extrinsic, and social motivations.     

Dislocation dissociation and stacking-fault energies in Ge1-xSix alloys

Dislocations in deformed Ge_1-xSi_x alloys in the whole range 0 < x < 1 have been investigated by means of weak-beam transmission electron microscopy. They are dissociated into Shockley partial dislocations bounding intrinsic stacking-faults. The intrinsic stacking-fault energy in the alloys decreases from 61 +/- 10 to 55 +/- 10 mJm^-2 with increasing Si content.     

Who Abuses Their Coworkers? An Examination of Personality and Situational Variables

ABSTRACT

This study examines predictors of abusive employee behavior toward coworkers. We examined two personality variables, negative affectivity and political skill, and two situational relationship variables—team member exchange and coworker relationship conflict. We tested our hypotheses with data obtained from a sample of 232 working employees. We found that political skill and team member exchange were negatively related to coworker abuse, whereas negative affectivity and relationship conflict were positively related. Additionally, we found statistical support for the negative affectivity-relationship conflict, political skill-team member exchange, and political skill-relationship conflict interactions. Practical implications and directions for future research are provided.     

Pre- to Post-Season Changes in the Intrinsic Motivation of First Year College Athletes: Relationships with Coaching Behavior and Scholarship Status

This study examined whether the intrinsic motivation levels of first-year college athletes changed from pre- to post-season as a function of their scholarship status or their perceptions of their coaches' behavior. Division I college athletes ( N = 72) completed questionnaires assessing their intrinsic motivation at the beginning and end of their first year of participation. They also reported their scholarship status and their perceptions of their coaches' behaviors over the season. Contrary to predictions, results revealed that neither scholarship status nor time affected the athletes' level of intrinsic motivation. Strong support for the relationship between athletes' perceptions of their coaches' behavior and changes in athletes' level of intrinsic motivation over the season, however, emerged. Increases in athletes' level of intrinsic motivation were associated with athletes' perceptions that their coaches exhibited high frequencies of training and instruction behavior, and low frequencies of autocratic behavior and social support. Results are discussed in relation to cognitive evaluation theory and previous research on intrinsic motivation.     

site determination of dilute Cu in beta-phase NiAl by 63Cu nuclear magnetic resonance and X-ray emission channelling patterns

A sharply bimodal lattice site distribution of dilute Cu in both Ni-deficient and Al-deficient beta-phase Ni-Al alloys has been observed in the 63Cu nuclear magnetic resonance (NMR) spectra. These NMR results are correlated with results derived from incoherent channelling patterns (ICPs) formed by variations in characteristic X-ray emission as a function of incident fast electron orientation. Statistical analysis of ICP data, generated near a 210 zone axis, indicates that Cu occupies substitutional sites; Cu is exclusively on the Al sublattice sites in the Al-deficient alloy, whilst the partition ratio of Ni : Al sublattice sites for Cu in the Ni-deficient alloy is about 80 : 20. Comparison of ICP contrast from Cu X-ray emission with ICPs from the host lattice enables the two peaks in the 63Cu NMR spectrum to be individually identified as originating from Cu on Ni sublattice sites, and from Cu on Al sublattice sites. The respective NMR line intensities from the Ni-deficient alloy yields a Ni : Al sublattice site occupancy ratio which is in good agreement with the partitioning ratios derived from channelling patterns     

Thermal aging effects on magnetisation reversals in a pre-deformed Fe-1wt%Cu alloy studied via first-order reversal curves

Abstract

The ability of amorphous metallic alloys to resist irradiation-induced structural changes will depend on the composition of the alloy and the particle fluences used. In this paper we show that a fast neutron fluence of 10²⁰ cm^?2 can induce local crystallization in a refractory NiTi glass. For specimens irradiated with lower fluences, the mode of crystallization of the amorphous matrix is changed from that of a primary process to a eutectic mechanism.     

Cross-sectional transmission electron microscopy of electrodeposited Ni-P alloys

Abstract

Ultramicrotoming has been employed to prepare thin cross-sections of Ni-P alloys electrodeposited on to a copper substrate. The sections, as thin as 10nm or even less, can be prepared readily with negligible damage to the alloys. Subsequent examination of the ultramicrotomed sections in an analytical transmission electron microscope has revealed that Ni-P alloys of low P content consist of fine layers of different composition and crystallinity. High-resolution transmission electron microscopy of ultramicrotomed sections has also revealed the presence of ordered regions, a few nanometres in size, in the Ni₇₇P₂₃ alloy which has been thought previously to be amorphous.     

Severe-to-mild wear transition at higher temperatures in Al-17Si-5Cu alloy after short-duration isothermal heat treatment

ABSTRACT

The wear behaviour of hypereutectic Al–Si alloys, which are suitable for use in automobile engines as a replacement for cast iron, has not been explored at higher temperatures. In the present study, the wear behaviour of Al-17Si-5Cu alloy (AR alloy) has been studied in as-received condition as well as after applying a short-duration isothermal heat treatment developed by the present research team. It was found that AR alloy exhibits severe wear, whereas heat-treated alloy (HT alloy) shows mild wear at higher temperatures (up to 300°C) at all applied loads. This severe-to-mild wear transition is addressed here.     

Effects of crystallization on corrosion resistance and electron work function of Zr65Al7.5Cu17.5Ni10 amorphous alloys

The effects of crystallization on the electron work function and corrosion resistance of Zr₆₅Al_7.5Cu_17.5Ni₁₀ amorphous alloys have been studied. The single-phase amorphous alloy exhibits a better corrosion resistance and has a higher work function than the partially and fully crystallized alloys with the same composition. The close relationship between corrosion resistance and work function indicates that the Kelvin probe technique can be a powerful tool for characterizing the corrosion behaviour of amorphous alloy on an electronic level.     

Stoichiometric selectivity in Mackay icosahedra

Abstract

We present a discussion of the effect of chemical substitution on the stability of Mackay icosahedra in Al-Mn alloys based on a microscopic model of the total energy of metallic alloys. In particular, we demonstrate why the addition of Si stabilizes both the crystalline α-(Al-Mn-Si) structure and the icosahedral phase of Al-Mn-Si. We predict specific A1 sites which are favourable for Si substitution.     

Local order description of an icosahedral Al–Cu–Fe quasicrystal

Abstract

A rapidly solidified Al₆₅Cu₂₀Fe₁₅ icosahedral alloy has been studied by extended X-ray absorption he structure above the Cu and Fe K absorption edges. The local order has been determined around Cu and Fe atoms and compared with results obtained previously in other icosahedral alloys     

Formation of a 'splitting pattern' associated with L1 2 precipitates in Ir-Nb alloys

A cuboidal L1 2 phase forms in the fcc matrix of an Ir-Nb alloy. Under some conditions, a rod- or plate-like fcc structure can be observed in this phase. This is similar to the 'splitting pattern' observed in some Ni-based alloys. To understand the formation mechanism of this structure, samples were heated under different conditions. Microstructure evolution during ageing was observed by transmission electron microscopy. We observed a splitting pattern only when the L1 2 precipitates were already formed in the as-cast condition after additional heat treatment at the ageing temperature. In this case, the composition of the L1 2 phase was not equilibrated. We conclude that the splitting pattern appears owing to a kinetic phenomenon when the L1 2 phase changes to the equilibrium composition.     

Stability in ordered and icosahedral aluminium–transition metal alloys

Abstract

We present calculated electron state densities for A1T (T is a transition metal) compounds and icosahedral Al₈₆T₁₄ alloys which suggest that the relative stability of different short-range atomic arrangements varies inversely with the electron state density at the Fermi level. Using this argument, we show that the absence ofstable highly coordinated configurations is a necessary, but not sufficient, condition for the existence of icosahedral Al₈₆T₁₄ alloys.     

Energy contributions in the martensitic transformation of shape-memory alloys

Abstract

The thermoelastic martensitic transformation in shape-memory alloys is studied thermodynamically. Calorimetric experiments on the Cu─Zn─A1 alloy system reveal that the transformation takes place with a practically negligible entropy production. The usual hysteretic subloop behaviour during partial cycling is obtained for the first time by calorimetry. An analysis of the measurements gives the quantitative behaviour of elastic and dissipative energies with the volume fraction of martensite.     

Intrinsic motivation and individual deliberate practice are reciprocally related: Evidence from a longitudinal study of adolescent team sport athletes

ObjectiveThere is limited understanding of how sport motivation is associated with deliberate practice in youth team sport athletes. Therefore, the aim of this study was to examine prospective associations between intrinsic motivation and individual deliberate practice in specializing team sport athletes.DesignLongitudinal.MethodEstonian adolescent team sport athletes (N = 163; M_age – 13.6 years at the beginning of study) completed the Sport Motivation Scale and training diary across a 12-month period.ResultsBoth individual deliberate practice and intrinsic motivation increased over the 1-year period. Greater baseline intrinsic motivation predicted subsequent individual deliberate practice and greater initial individual deliberate practice predicted greater subsequent intrinsic motivation. The bidirectional relationship between athletes intrinsic motivation and individual deliberate practice were replicated across both time lags.ConclusionThe findings have significant implications for the importance placed on intrinsic motivation as a means of increasing of individual deliberate practice as well being an important outcome variable in specializing team sport athletes.     

A structural model for surface-enhanced stabilization in some metallic glass formers

A structural model for surface-enhanced stabilization in some metallic glass formers is proposed. In this model, the alloy surface structure is represented by five-layer Kagomé-net-based lateral ordering. Such surface structure has intrinsic abilities to stabilize icosahedral-like short-range order in the bulk, acting as ‘a cloak of liquidity’. In particular, recent experimental observations of surface-induced lateral ordering and a very high glass forming ability of the liquid alloy Au₄₉Ag_5.5Pd_2.3Cu_26.9Si_16.3 can be united using this structural model. This model may be useful for the interpretation of surface structure of other liquid alloys with a high glass forming ability. In addition, it suggests the possibility of guiding the design of the surface coating of solid containers for the stabilization of undercooled liquids.