The Hidden Stress in Superalloys: How Atomic Misfit Shapes Strength and Ductility
A comprehensive study of 14 different nickel-based single-crystal superalloys reveals a critical, and often overlooked, factor in their tensile performance: the lattice misfit between the γ and γ′ phases. Using high-resolution X-ray diffraction, researchers directly measured this misfit and linked it to microstructural deformation mechanisms at 650°C. They found that alloys with a large negative misfit, like TMS-238, develop high coherency stresses that promote early, homogeneous plastic deformation. This leads to strong work hardening but also reduces ductility and can paradoxically lower the yield strength. In contrast, alloys with a moderate misfit exhibit more localized deformation.
Why it might matter to you:
For researchers focused on age-hardening phenomena in complex alloys, this work underscores that mechanical properties are not dictated by composition and precipitate structure alone. The internal coherency stresses arising from atomic-scale misfit are a fundamental design variable. Understanding this relationship provides a more precise framework for predicting and tailoring the balance between strength, ductility, and work hardening in advanced metallic systems, which is central to optimizing performance in demanding applications.
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