A combinatorial approach for efficient mapping of phase diagrams and properties
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A methodology is developed which extends the combinatorial approaches to structural materials research and development. This high-efficiency methodology employs diffusion couples and “diffusion multiples” to create large variations (libraries) of compositions in bulk samples for fast and systematic surveys of bulk properties. These composition libraries coupled with microanalytical techniques such as electron probe microanalysis, electron backscatter diffraction analysis, and nanoindentation tests can be used for efficient surveys of phases, equilibria, diffusion coefficients, precipitation kinetics, properties, and composition–phase–property relations (such as solution hardening and strengthening effect) for accelerated design of multicomponent alloys.
I. INTRODUCTION
Compared to the conventional one-alloy-at-a-time approach, the combinatorial approaches dramatically increase the efficiency of materials discovery by coupling parallel syntheses of large libraries of compositions with an effective screening for desired properties.1–6 The combinatorial approaches are being aggressively pursued to develop new functional materials with novel physical and chemical properties.1–6 These approaches using thinfilm deposition, however, have yet to find applications in developing structural materials for improved mechanical properties. Since the approaches usually generate only a very small volume of thin film for each composition, it is difficult to evaluate properties critical to structural materials design. For instance, the properties of structural materials are microstructure dependent, and desired microstructures can be difficult to achieve in thin films, especially when the scale of the microstructure is larger than the film thickness. In addition, phase precipitation kinetics, which is also critical for structural materials design, is usually very different in bulk samples than in thin films; thus, the kinetic information obtained from thin-film samples cannot be used for bulk structural materials design. To overcome the thin-film limitations, a different combinatorial approach has been developed which creates composition libraries in bulk diffusion couples and “diffusion multiples” by thermal interdiffusion.7 Diffusion multiple is an assembly of three or more different metal blocks, in intimate interfacial contact, arranged as a triple, quadruple, etc., and subjected to a high temperature J. Mater. Res., Vol. 16, No. 6, Jun 2001
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to allow thermal interdiffusion. The concept is an extension of a diffusion triple method introduced by Hasebe and Nishizawa8 for simple ternary systems and demonstrated by Jin et al.9–11 for complex ternary systems with intermetallic compounds. The coupling of the composition libraries generated in diffusion multiples with microscale composition, structure, and property evaluation techniques constitutes an efficient methodology for mapping phase diagrams and properties. The idea of this combinatorial approach can be illustrated using
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