Interdiffusion Data Research Articles

High-throughput studies and machine learning for design of β titanium alloys with optimum properties

Based on experimental data, machine learning (ML) models for Young’s modulus, hardness, and hot-working ability of Ti-based alloys were constructed. In the models, the interdiffusion and mechanical property data were high-throughput re-evaluated from composition variations and nanoindentation data of diffusion couples. Then, the Ti−(22±0.5)at.%Nb−(30±0.5)at.%Zr−(4±0.5)at.%Cr (TNZC) alloy with a single body-centered cubic (BCC) phase was screened in an interactive loop. The experimental results exhibited a relatively low Young’s modulus of (58±4) GPa, high nanohardness of (3.4±0.2) GPa, high microhardness of HV (520±5), high compressive yield strength of (1220±18) MPa, large plastic strain greater than 30%, and superior dry- and wet-wear resistance. This work demonstrates that ML combined with high-throughput analytic approaches can offer a powerful tool to accelerate the design of multicomponent Ti alloys with desired properties. Moreover, it is indicated that TNZC alloy is an attractive candidate for biomedical applications.

Fe–Mg interdiffusion in wadsleyite and implications for water content of the transition zone

Fe–Mg interdiffusion rates in polycrystalline wadsleyite aggregates have been determined as a function of water content (up to ∼0.345 wt.% H2O) at 16 GPa and 1373–1773 K in a Kawai-type multi-anvil apparatus. Pre-synthesized water-poor and -rich polycrystalline wadsleyite were used as starting materials. Diffusion profiles were obtained across the interface between Fe-free and -bearing diffusion couples, namely, Mg2SiO4 and (Mg0.9Fe0.1)2SiO4 aggregates by electron microprobe. Fe–Mg interdiffusivities by experiments yield DFe−Mg(m2/s)=D0XFenCH2Orexp⁡[−(E+αXFe+βCH2O)/RT], where D0 = 1.33−0.23+0.20× 10−11 m2/s, n = 0.19 ± 0.04, r = 0.29 ± 0.12, E = 92 ± 2 kJ/mol, α = −45 ± 12, and β = −134 ± 2. Our results indicate that water significantly enhances the rates of Fe–Mg interdiffusion in wadsleyite (a factor of 2.4 for fixed temperature and Fe concentration) compared to that in ringwoodite. Although under hydrous condition the transition zone shows the maximum Fe–Mg mixing efficiency as revealed by diffusivity-depth profile in the mantle, homogenization of existing chemical heterogeneity is still very limited at geological time scale only through solid-state diffusion. Combined with the Nernst–Einstein relation, the results suggest that the contribution of water to the electrical conductivity of wadsleyite or ringwoodite may be overestimated from Fe–Mg interdiffusion data at high water content. Further calculation demonstrates that ∼0.1–0.5 wt.% H2O is sufficient to account for the high conductivity values in the upper part (410–520 km) of the mantle transition zone as observed by electromagnetic induction studies.

Interdiffusion during film formation of ionically cross‐linked acrylics investigated with Förster resonance energy transfer (FRET)

ABSTRACTPolymer interdiffusion is crucial to obtain continuous films from aqueous polymer dispersions. Here, interdiffusion in films from dispersions of acrylates which were ionically cross‐linked prior to film formation was studied by Förster resonance energy transfer analysis. Dispersions of copolymers of n‐butyl acrylate, methacrylic acid, and zinc dimethacrylate (ZnDMA) were investigated. ZnDMA was used as a co‐monomer to ionically cross link the polymers during the synthesis. Ionic cross‐linking does not prevent interdiffusion even at high gel contents. Interdiffusion data were compared with results of tensile tests on final films. Films of ionically cross‐linked polymers fracture at both higher stress and strain than films of covalently cross‐linked polymers. Further interdiffusion studies addressed effects of temperature and humidity. Both increased temperature and humidity accelerate interdiffusion of ionically cross‐linked polymers. Thus, using ZnDMA allows for preparing dispersions which can form continuous films. Also, no volatile organic compounds are released during the film formation. © 2020 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48972.

Vapor–liquid equilibria and inter-diffusion coefficients for working pairs for absorption refrigeration systems composed of [HMIM][BF4] and fluorinated propanes

Hydrofluorocarbon + Ionic liquid is a promising working pair for the absorption refrigeration system. The vapor–liquid equilibrium and inter-diffusion coefficient of hydrofluorocarbon + ionic liquid are two key parameters used to evaluate the performance of the working pair. In this work, the vapor–liquid equilibrium and inter-diffusion coefficients of 1-hexyl-3-methylimidazolium tetrafluoroborate and fluorinated propanes including R227ea, R236fa and R245fa were measured from 303 K to 343 K and up to 332 kPa. The mole fractions of the three fluorinated propanes in liquid phase at vapor–liquid equilibrium were found to increase in the order: R227ea < R236fa < R245fa; they also increased with decreasing temperature and increasing pressure, while the inter-diffusion coefficients were found to increase with increasing temperature. The non-random two-liquid (NRTL) model was used to correlate vapor–liquid equilibrium data, while the Arrhenius, Litovitz, and Vogel−Fulcher−Tammann equations were used to correlate the inter-diffusion coefficient data.

Interdiffusion and Atomic Mobilities in Co-rich fcc Co-Cr-V Alloys

Diffusion couples for Co-rich fcc Co-Cr-V alloys were prepared, all of which were annealed at 1473 K for 259 200 s. The interdiffusion coefficients in fcc Co-Cr-V ternary systems were investigated by means of Whittle and Green method with the help of electronic-probe microanalysis (EPMA). On the basis of the thermodynamic parameters available in the literature, the interdiffusion data were critically assessed to develop the atomic mobilities of the fcc Co-Cr-V alloys via the DICTRA software. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that the experimental data can be well reproduced by the atomic mobilities obtained in this work. And the validity of the diffusion mobilities was tested by simulating the concentration-distance profiles and diffusion paths in diffusion couples.

Interdiffusion and Atomic Mobilities in fcc Co-Ga and Co-V Alloys

On the basis of Co/Co-10Ga, Co/Co-12Ga, and Co/Co-10V (at.%) diffusion couples, interdiffusion coefficients in the face-centered cubic (fcc) phase of the Co-Ga and Co-V binary systems were investigated in the temperature range between 1273 and 1573 K by means of the den Broeder method. Based on available thermodynamic information, the interdiffusion data were assessed to develop the atomic mobilities for the fcc Co-Ga and Co-V alloys using the DICTRA software package, and their validity was tested by simulating concentration–distance profiles.

Diffusion in B2 NiAl and FeAl Intermetallics and Their Alloys

Both FeAl and NiAl with B2 crystal structure are envisaged for their usage in high temperature applications and hence, availability of diffusion data in these intermetallics is crucial in designing their alloys and processes as well as deciding their in-service performance. A comprehensive overview of diffusion data available in B2 FeAl and NiAl and their alloys is provided in this article. Nearest neighbor vacancy jumps in B2 intermetallic lead to a local disorder in the lattice and hence it is not necessarily the unit step of diffusion in these structures. Several mechanisms of diffusion proposed in the literature are discussed including nearest neighbor jumps, next nearest neighbor jumps, six-jump vacancy cycle, triple defect and antisite bridge. Relevance of these mechanisms in FeAl and NiAl is discussed. An overview is given on the self-and solute diffusion and interdiffusion data available in both binary FeAl and NiAl. Due to wide solubility range of both FeAl and NiAl as well as their alloying requirements for improved properties, it becomes pertinent to study the multicomponent diffusion in the alloys based on these B2 itnermetallics. Hence, in the latter part of the article, various methods used for determining multicomponent diffusion data are reviewed. A detail overview is also provided on the diffusion studies available in literature on ternary alloys based on FeAl and NiAl with an emphasis on highlighting the diffusional interactions observed in these systems.

Influence of cross correlations on interdiffusion in Al-rich Al-Ni melts

The relation of self- and interdiffusion in a liquid metal, particularly the influence of cross correlations at low concentrations, is studied experimentally. Accurate interdiffusion data are obtained by a combination of x-ray radiography with the shear-cell method on the ground and on the sounding rocket MAPHEUS under microgravity conditions. Self-diffusion coefficients, measured by quasielastic neutron scattering, increase with decreasing Ni concentration, whereas interdiffusion coefficients are about constant. We show that cross correlations influence interdiffusion even at concentrations as low as 2 at. % Ni. Consequently, Darken's equation is not valid in this case.

Silicon germanium interdiffusion in SiGe device fabrication: A calibrated TCAD model

SiGe alloys are used in many types of electronic devices. For upcoming FinFET technologies, there is interest in the use of SiGe heterostructures in the complete mole fraction range (0–100% Ge atoms). For high Ge mole fraction and small device dimensions, interdiffusion of Si and Ge atoms can lead to critical changes in the distribution of Si and Ge atoms, impacting channel strain and carrier mobility. A process model for Si–Ge interdiffusion has been developed which covers the needs for actual device fabrication processes. Interdiffusion is understood to be correlated with the diffusion of vacancies, self-interstitials, and dopant-defect pairs. We consider the impact of non-equilibrium point defect concentrations (such as interstitial super-saturation after ion implantation), the impact of compressive or tensile strain, and a twofold impact of doping: first, doping determines the local electron concentration and thereby the abundance of charged point defects, and second, the diffusion of dopant-defect pairs can contribute to the interdiffusion of Si and Ge atoms. The model covers the full range of possible Ge mole fractions (0–100%). For undoped SiGe, it has been calibrated against a broad range of published experimental data for radio-tracer diffusion in SiGe and for interdiffusion in biaxially strained SiGe heterostructures grown on Si, stress-relaxed SiGe, or Ge. The extensions for doped SiGe are presented with a reference to few interdiffusion data for heavily doped SiGe heterostructures. Finally, the model has been consistently integrated into a set of models for the continuum process simulation of point defects and dopants in pure Si, SiGe, and pure Ge, in Sentaurus Process.

On the atomic interdiffusion in Mg–{Ce, Nd, Zn} and Zn–{Ce, Nd} binary systems

Abstract

Study on Atomic Mobility and Molar Volume for FCC Fe-Co Phase

The diffusion-couple experiments have been performed at 1273 K and 1423 K in order to verify and bias the controversial interdiffusion data in the literature. In the meantime, the literature data on the lattice parameter have been assessed to obtain the molar volume of fcc Fe-Co phase, which was in turn fed into the Sauer-Freise equation to retrieve the interdiffusion coefficients from the EPMA (Electron Probe Micro-Analysis) measured diffusion profiles. The reliable experimental data on the diffusion coefficients for fcc Fe-Co phase have finally been used to assess the atomic mobility. A general agreement has been reached between the calculated and experimentally measured data.

Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order–disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

Interdiffusion and Phase Growth Kinetics in Magnesium-Aluminum Binary System

Binary interdiffusion data as functions of composition in the Mg-Al system are essential in modeling kinetics of phase transformations in multicomponent Mg and Al alloys. Interdiffusion and phase growth kinetics were studied in the binary Mg-Al system using multiphase diffusion couples assembled between pure Mg and pure Al at 380, 400 and 420 °C. Two phases, Al3Mg2 (β) and Mg17Al12 (γ) were formed between Al and Mg at the three temperatures studied. Both β and γ phases were observed to follow parabolic growth with time, which suggests that the growth of the two phases is controlled by bulk diffusion mechanisms. The activation energies for the growth of β and γ phases in the temperature range of 380-420 °C were found to be 37.3 ± 4.1 and 187.7 ± 1.9 kJ/mol, respectively. The interdiffusion coefficients were evaluated as functions of compositions in various phases at the three temperatures studied, which were further utilized for evaluating the activation energies and frequency factors for interdiffusion in each phase. The activation energy for interdiffusion in FCC-Al is found to increase with increasing Mg-content whereas the activation energies for interdiffusion in HCP-Mg and γ phases do not vary significantly with composition.

A unified interdiffusivity model and model verification for tensile and relaxed SiGe interdiffusion over the full germanium content range

An interdiffusivity model was established for SiGe interdiffusion under tensile or relaxed strain over the full Ge content (xGe) range (0 ≤ xGe ≤ 1), which is based on the correlations between self-diffusivity, intrinsic diffusivity, and interdiffusivity. It unifies available interdiffusivity models over the full Ge range and applies to a wider temperature range up to 1270 °C at the xGe = 0 end and to 900 °C at the high xGe = 1 end. Interdiffusion experiments under soak and spike rapid thermal annealing conditions were conducted to verify the model. Literature interdiffusion data under furnace annealing conditions were also used for the same purpose. The interdiffusivity model of this work has been implemented in major process simulation tools, and the simulation results showed good agreement with experimental data under furnace annealing and soak and spike rapid thermal annealing conditions. This work demonstrated a new approach in studying SiGe interdiffusion, which has the advantage of studying interdiffusion under non-isothermal annealing conditions.

Interdiffusion and Atomic Mobility for Face-Centered-Cubic Co-Al Alloys

Interdiffusion in the face-centered-cubic (fcc) Co-Al binary alloys was studied by the diffusion-couple approach in the temperature range of 1173 K to 1573 K (900 °C to 1300 °C). Interdiffusion coefficients of the fcc Co-Al alloys were then evaluated by using the Sauer–Freise method. The effect of magnetic ordering on the Co-Al interdiffusion was observed at 1273 K (1000 °C) by examining the Arrhenius plots. The interdiffusion data were assessed to develop the atomic mobility for the fcc Co-Al alloys, and their validity was tested by simulating the diffusion-couple experiments.

Diffusion characteristics of surface-modified MK-40 mixed-cation ion-exchange membranes

Previously proposed approaches to determining diffusion parameters of mixed-cation membranes have been tested to describe ionic conductance and H+/M+ (M = Li, Na, K) interdiffusion data for asymmetric MK-40-based membranes modified with a thin layer of MF-4SK perfluorinated membrane material containing silica and zirconia additions. The diffusion coefficients, effective ion exchange constants, and asymmetry effects in the membranes are evaluated. The conclusion is made that there is an additional barrier to ion transport across the surface of MK-40 membranes.

Diffusion characteristics of mixed-cation ion-exchange membranes

Approaches are proposed for determining diffusion parameters of mixed-cation membranes. One of them is used to evaluate diffusion coefficients and effective ion-exchange constants in membranes containing both H+ and M+ (M = Li, Na, K, Rb) cations from ionic conductance and interdiffusion data for samples in equilibrium with solutions differing in the ratio of salt and acid concentrations.

Selected Analyses and Observations in Multicomponent Diffusion

Selected isothermal diffusion studies in ternary and quaternary systems are reviewed in order to present analytical and experimental approaches adopted for the determination of interdiffusion fluxes of components, interdiffusion coefficients, diffusional interactions among components, and internal consistency in the experimental data. Several interesting phenomena and observations including uphill diffusion, zero-flux planes and flux reversals, and double serpentine diffusion paths are illustrated with selected single phase Cu-Ni-Zn, Fe-Ni-Al and Cu-Ni-Zn-Mn diffusion couples. The main challenges involved in the experimental determination of interdiffusion data from multicomponent diffusion couples and in the application of such data are also addressed.

Interdiffusion Data in Multicomponent Alloys as a Source of Quantitative Fundamental Diffusion Information

Tracer diffusion experiments have historically furnished much of the information about fundamental diffusion processes as embodied in such quantities as tracer correlation factors and vacancy-atom exchange frequencies. As tracer diffusion experiments using radiotracers are rather less often performed nowadays, it is important to be able to process other diffusion data to provide similar fundamental information. New procedures that are primarily based around the random alloy model have been established recently for analyzing chemical diffusion data in binary and ternary alloy systems. These procedures are reviewed here. First, we review the random alloy model, the Sum-rule relating the phenomenological coefficients and three diffusion kinetics formalisms making use of the random alloy. Next, we show how atom-vacancy exchange frequency ratios and then component tracer correlation factors can be extracted from chemical diffusion data in alloy systems. Examples are taken from intrinsic diffusion and interdiffusion data in a number of binary and ternary alloys.

Analysis of interdiffusion data in multicomponent alloys to extract fundamental diffusion information

This paper reviews new procedures based around the random alloy model that have been established recently for analyzing chemical diffusion data in binary and ternary alloy systems. The authors show how atom-vacancy exchange frequency ratios, individual tracer correlation factors, and vacancy-wind factors can be extracted from the chemical diffusion data. Examples are taken from intrinsic diffusion data in the Ag-Cd and Ag-Cd-Zn alloy systems and from interdiffusion data in the Fe-Ni-Cr and Cu-Fe-Ni alloy systems.