Microstructure refinement

The role of Cu in FINEMET has been discussed almost solely from the viewpoint of microstructural refinement. However, it is equally important to discuss the effect of Cu in suppressing the formation of magnetically hard compounds upon crystallization of the amorphous precursors. Prevention of the magnetically harder compounds from forming upon crystallization is surely the primary role of Cu in NANOPERM. 

Gradual mechanochemical reaction systems have generally been found to exhibit sigmoidal reaction kinetics. The reaction rate initially increases with milling due to increasing activation and microstructural refinement of the reactants. The reaction rate then reaches a maximum at an intermediate milling time before decreasing as the reaction approaches completion due to dilution of the reactants by the product phases. ... 

All in all, the WPPM approach can provide a simultaneous structure and microstructure refinement, based on physical models of the phases under study, without using any arbitrary profile function. Considering the terms of Equation (26), refinement parameters to be optimized in a least-squares analysis are relatively few, namely, mean (p) and variance (cr) of a suitable distribution of coherent domain sizes, dislocation density (p), effective outer cut-off radius (R ) and character (/e, effective fraction of edge dislocations), twin fault (P), deformation fault (a) and APB (y) probabilities. 

Herein, the two-dimensional version of the higher-order theory [6-7], briefly outlined below, is employed to investigate the effect of different levels of microstructural refinement on the internal stress field in a functionally graded TBC subjected to cyclic thermal loading in the presence of creep of the ceramic phase. 

HPT has been successfully applied for microstructure refinement in metals, alloys and not long ago in composites and in semiconductors [17,18], as well as consolidation of nanopowders [7], Among new developments in HPT processing we would like to emphasize also the observation of SPD-induced nanocrystallization in initially amorphous alloys producing nanocrystalline materials with a grain size of 10-15 nm [19],... 

One-step processing for superplasticity from cast sheet or hot-pressed powder metallurgy sheet A conventionally cast microstructure can be converted to a superplastic microstructure in many steps. The present process of microstructural refinement can be used directly on cast sheets. This leads to very economical manufacturing. Ma et al. (Ref 46)... 

Addition of second-phase particles and microstructural refinement can enhance wear properties. 

K. Oh-Ishi, A.P. Zhilyaev, and T.R. McNelley, Enhancement of Ductility and Strength through Microstructural Refinement by FSP of Nickel Aluminum Bronze, Mater. Sci. Forum, Vol 503-504,... 

Recommendation 4. The key areas of investigation recommended for non-oxide fibers are recently developed amorphous non-oxide fibers, such as Si-B-N-C fibers, to verity their stability and creep resistance and the utility of the reported in-situ coatings, and microstructural refinements to improve performanee in erystalline non-oxide fibers. 

The microstructure refinement from the modified thermomechanical treatment is responsible for enhancement of tensile strength and ductility by 18% and 25% respectively. Simultaneously, the stress rupture life as well as ductility is enhanced by virtue of controlled grain size and uniform carbide distribution brought about by the thermo-mechanical treatment. 

The laser surface melting can be combined with a simultaneous controlled addition of alloying elements. These alloying elements diffuse rapidly into the melt pool, and the desired depth of alloying can be obtained in a short period of time. By this means, a desired alloy chemistry and microstructure can be generated on the sample surface and the degree of microstructural refinement will depend on the sohdification rate. The smfaoe of a low-cost alloy, such as low carbon steels, can be selectively alloyed to enhance properties, such as resistance to wear and corrosion (Davis, 2001). 

Chemical formula. Common eompositions are Ni94Co3Zn3 (wt%) where cobalt is coprecipitated for the purpose of eonductivity enhancement and both cobalt and zinc have the funetion of oxygen overvoltage adjustment and microstructure refinement. 

This chapter starts with a brief overview about Mg-based BMGs and describes principal strategies and challenges for the achievement of maximum amorphous sample thickness. Characteristic thermal data and mechanical properties are summarized. Some fundamental considerations about the effect of microstructural refinements up to the adjustment of single-phase amorphous states on the corrosion reactivity of Mg-based alloys are made. 

Zinc additions can also lead to corrosion problems. In fact, zinc coatings are often used as sacrificial anodes, to avoid corrosion of the objects which are coated with zinc for that purpose. However, the corrosion potential of Zn is greatly reduced if it is combined, i.e., not present as a separate and distinct phase. For example, when Zn is combined with corrosion-resistant Ag within the Ag3Sn IMC phase, then the beneficial effect of Zn (i.e., microstructural refinement) can be used with minimal corrosion concern [16]. 

Betrabet, H.S. McGee, S.M. McKinlay, J.K. Processing dispersion-strengthened Sn-Pb solders to achieve microstructural refinement and stability. Scr. Metall. Mater. 1991, 25, 2323-2328. 

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