Simultaneous Measurement of Isotope-Free Tracer Diffusion Coefficients and Interdiffusion Coefficients in the Cu-Ni System

Abstract

A new formalism recently developed by Belova et al., based on linear response theory combined with the Boltzmann-Matano method, allows determination of tracer and interdiffusion coefficients simultaneously from a single, isotope-free, traditional diffusion couple experiment. An experimental methodology with an analytical approach based on the new formalism has been carried out using the model Cu-Ni system to effectively determine tracer diffusion coefficients from an isotope-free diffusion couple experiment. Cu thin films were deposited in between several binary diffusion couples with varying terminal alloy compositions (Cu-25Ni, Cu-50Ni, Cu-75Ni, Ni). Diffusion couples were annealed at 800, 900 and 1000°C, and the superimposed concentration profiles of thin film and interdiffusion were analyzed for the simultaneous determination of tracer and interdiffusion coefficients. Processed concentration profiles obtained from the diffusion experiments were also fitted with simple Gaussian distribution function. Results were compared to existing literature data obtained independently by radiotracer experiments, and an excellent agreement has been observed.

Investigation of sluggish diffusion in FCC Al0.25CoCrFeNi high-entropy alloy

“…Determination of G 2 and a have been described by Belova et al [26]. Schulz et al [27] used this approach to demonstrate that the Gaussian distribution function can be utilized to determine tracer diffusion coefficient using full width at half maxima (FWHM) of the thin film diffusion profile as:…”

“…Interdiffusion coefficients were determined for individual elements using traditional diffusion couple approach using Dayananda-Sohn approach [25] in the temperature range from 900°C to 1200°C. Tracer diffusion coefficient of Ni in Al 0.25 CoCrFeNi alloy was determined, without the use of radioactive tracers, using a sandwich diffusion couple experiment, where concentration profiles are analyzed by a novel formalism, established by Belova et al [26], based on linear response theory coupled with Boltzmann-Matano approach and Gaussian distribution function [26,27]. Then, tracer diffusivity of Ni (D * Ni ) was compared with the diffusivities in other FCC alloys with varying configurational entropy of mixing ( S mix ) and corresponding potential energy fluctuations (PEF).…”

“…At one of the interfaces between the two alloys existed a sputter-deposited thin film of pure Ni ( ∼ 900 nm thickness). Details on the diffusion couple assembly in sandwich configuration with a thin film to measure the tracer diffusivity also have been reported elsewhere [26,27]. All diffusion couples were isothermally annealed at a predetermined temperature, and subsequently, water quenched.…”

“…The concentration profiles were acquired from the Thermo-Scientific TM X-ray energy dispersive spectroscopy (XEDS) equipped on Zeiss TM Ultra-55 field emission scanning electron microscope (FE-SEM). Experimental concentration profiles measured from XEDS in this study were curve fitted using Origin TM Pro 8.5 software, with non-linear curve fitting function given by [15,27]:…”

Measurement of Interdiffusion and Tracer Diffusion Coefficients in FCC Co-Cr-Fe-Ni Multi-Principal Element Alloy

“…[11] In this work, tracer diffusion coefficient of Ni in equiatomic CoCrFeNi alloy was experimentally determined using sandwich diffusion couple experiment, wherein concentration profiles were analyzed by a novel mathematical formalism, established by Belova et al [36] based on linear response theory coupled with Boltzmann-Matano approach and Gaussian distribution function. [36,37] . Average effective interdiffusion coefficients of individual elements were determined by analyzing the concentration profiles, from solid-to-solid diffusion couple experiments, using Dayananda and Sohn [38] method.…”