Abstract
Nanoscale inhomogeneities are typical for numerous metallic alloys and crucially important for their practical applications. At the same time, stabilization mechanisms of such a state are poorly understood. We present a general overview of the problem, together with a more detailed discussion of the prototype example, namely, Guinier-Preston zones in Al-based alloys. It is shown that coherent strain due to a misfit between inclusion and host crystal lattices plays a decisive role in the emergence of the inhomogeneous state. We suggest a model explaining the formation of ultrathin plates (with the thickness of a few lattice constants) typical for Al-Cu alloys. Discreteness of the array of misfit dislocations and long-ranged elastic interactions between them are the key ingredients of the model. This opens a way for a general understanding of the nature of (meta)stable embedded nanoparticles in practically important systems.
Highlights
One of the basic concepts in physics and chemistry of solids and materials science is the formation of microstructures which a Institute of Quantum Materials Science, CJSC, Ekaterinburg 620075, Russia b Institute of Metal Physics, Russian Academy of Sciences—Ural Division, Ekaterinburg 620041, Russia c Ural Federal University, Theoretical Physics and Applied Mathematics Department, Mira str. 19, Ekaterinburg, 620002, Russia d Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, Nijmegen, 6525 AJ, Netherlands
Gornostyrev became a head of Institute of Quantum Materials Science in Ekaterinburg
His main scientific interests relate to ab initio based multiscale modeling of phase equilibrium and phase transformations in metals, crystal lattice defects, strength and plasticity of steel and alloys
Summary
We focus on the other class of materials, which attract increasing attention in the last few decades In this case, the microstructure contains stable or long-living metastable nanosized-scale precipitates embedded in a host.[31] Such a heterogeneous state is typical for the so called nanoscale granular materials[32] and was observed in many technologically important alloys. This situation is quite exclusive (it happens in elemental Ti, Zr and Hf under pressure), the incommensurate athermal omega phase is much more typical,[40] the omega– beta mismatch (that is, amplitude of displacements of the {111} planes) depends on the concentration of the dopant Such a conjugation is semi-coherent and includes appearance of domain boundaries or topological defects as suggested in ref. One can assume that the peculiar structural state of beta + omega titanium based alloys is responsible for their anomalous electronic properties such as negative temperature coefficient of resistivity[5] and provides an efficient mechanism of giant ultrasound attenuation[49] observed in these alloys.[50]
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