Evaluation of Solid-Solution Hardening in Several Binary Alloy Systems Using Diffusion Couples Combined with Nanoindenta
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THE plastic flow resistance of a metal can be enhanced through various strategies like work hardening, grain boundary strengthening, solid-solution hardening and precipitation strengthening. Among these, solid-solution hardening (SSH) is perhaps the simplest and the most widely used method. Together with the construct of equilibrium phase diagrams and the theory of diffusion kinetics, the understanding of SSH behavior and mechanisms is essential to the development of materials with improved properties. As a result, SSH in binary solid-solution alloys has been a widely studied topic.[1–4] Despite this, such studies have largely been limited to low-solute concentrations due to the requirement of only minor solute additions to strengthen structural alloys. However, with recent advances in the development of multiple-principle element alloys and
SOURABH B. KADAMBI is with the Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India, and also with the Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27695. V.D. DIVYA is with the Department of Materials Engineering, Indian Institute of Science, and also with Rolce-Royce India Private Limited, Manyata Embassy Business Park, Outer Ring Road, Bangalore 560045, India. U. RAMAMURTY is with the Department of Materials Engineering, Indian Institute of Science. Contact e-mail: [email protected] Manuscript submitted April 13, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
the realization of their potential for structural applications,[5] it has also become necessary to understand SSH at large solute concentrations. The conventional method of obtaining SSH data— strength or hardness as a function of solute concentration—is through the synthesis and testing of one alloy with a specific composition at a time. However, this approach is not effective as it is time consuming and cost intensive. In addition, such an approach will be impractical in studying SSH in multicomponent alloys like high-entropy alloys which will require synthesis and testing of thousands of alloy compositions. Therefore, alternative experimental approaches that facilitate rapid assessment of SSH are required. In this context, the diffusion couple (DC) approach combined with smallscale testing methods such as nanoindentation and/or micropillar compression holds great promise.[6–14] By means of the DC method, a library of compositions is generated in the interdiffusion zones, and the compositional analysis along these zones is performed with a high degree of accuracy by employing techniques such as electron probe microanalysis (EPMA). The interdiffusion zones are then probed for hardness, H, by employing nanoindentation (NI), and H as a function of solute concentration, c, is obtained. This approach is not only rapid but also requires possibly the minimum amount of material for synthesis and testing. The DC-NI approach pioneered by Zhao[6–8,13] has been used—for the determination of diffusion coefficients, to generate pha
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