Using high-pressure torsion for metal processing: Fundamentals and applications

Surface integrity in material removal processes: Recent advances

Fabrication of a gradient nano-micro-structured surface layer on bulk copper by means of a surface mechanical grinding treatment

Methods of deforming metals to large strains are reviewed and the process of equal channel angular extrusion is analysed in detail. The development of microstructure during large strain deformation is discussed, and it is concluded that the main criterion for the formation of a sub–micron grain structure is the generation of a sufficiently large fraction (> 0.7) of high–angle grain boundary during the deformation process. For aluminium alloys, it is found that a low–temperature anneal is required to convert the deformed microstructure into an equi–axed grain structure. The material, microstructural and processing factors that influence the formation of such fine–grain microstructures are discussed, and the stability of these microstructures at elevated temperatures is considered.

Developing stable fine-grain microstructures by large strain deformation - Discussion

Cutting edge geometries

A study of the interactive effects of strain, strain rate and temperature in severe plastic deformation of copper

Characteristics of the deformation fields associated with chip formation in plane strain machining are described. The ability to impose very large strain deformation in a controlled manner is highlighted. The creation of nano- and ultra-fine grained structures by machining is demonstrated in a variety of metals and alloys. These results indicate that machining not only offers a simple method for large scale manufacturing of nanostructured materials, but also provides a unique experimental configuration for studying large strain deformation phenomena.

Large strain deformation and ultra-fine grained materials by machining

In spite of their interesting properties, nanostructured materials have found limited uses because of the cost of preparation and the limited range of materials that can be synthesized. It has been shown that most of these limitations can be overcome by subjecting a material to large-scale deformation, as occurs during common machining operations. The chips produced during lathe machining of a variety of pure metals, steels, and other alloys are shown to be nanostructured with grain (crystal) sizes between 100 and 800 nm. The hardness of the chips is found to be significantly greater than that of the bulk material.

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Low-cost manufacturing process for nanostructured metals and alloys

Severe plastic deformation of copper by machining: Microstructure refinement and nanostructure evolution with strain

A class of deformation processing applications based on the severe plastic deformation (SPD) inherent to chip formation in machining is described. The SPD can be controlled, in situ, to access a range of strains, strain rates, and temperatures. These parameters are tuned to engineer nanoscale microstructures (e.g., nanocrystalline, nanotwinned, and bimodal) by in situ control of the deformation rate. By constraining the chip formation, bulk forms (e.g., foil, sheet, and rod) with nanocrystalline and ultrafine grained microstructures are produced. Scaling down of the chip formation in the presence of a superimposed modulation enables production of nanostructured particulate with controlled particle shapes, including fiber, equiaxed, and platelet types. The SPD conditions also determine the deformation history of the machined surface, enabling microstructural engineering of surfaces. Application of the machining-based SPD to obtain deformation-microstructure maps is illustrated for a model material system-99.999% pure copper. Seemingly diverse, these unusual applications of machining are united by their common origins in the SPD phenomena prevailing in the deformation zone. Implications for large-scale manufacturing of nanostructured materials and optimization of SPD microstructures are briefly discussed.

Travis L. Brown

Papers

A study of the interactive effects of strain, strain rate and temperature in severe plastic deformation of copper

Large strain deformation and ultra-fine grained materials by machining

Low-cost manufacturing process for nanostructured metals and alloys

Severe plastic deformation of copper by machining: Microstructure refinement and nanostructure evolution with strain

Unusual Applications of Machining: Controlled Nanostructuring of Materials and Surfaces