Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Mechanical Alloying And Milling

http://nanomechanics.mit.edu/sites/default/files/documents/Kumar_03.pdf

Mechanical behavior of nanocrystalline metals and alloys

http://files.janapv.webnode.cz/200000097-8a03f8afdf/ex_bias_nano.pdf

Exchange bias in nanostructures

Understanding the correlation between magnetic properties and nanostructure involves collaborative efforts between chemists, physicists, and materials scientists to study both fundamental properties and potential applications. This article introduces a classification of nanostructure morphology according to the mechanism responsible for the magnetic properties. The fundamental magnetic properties of interest and the theoretical frameworks developed to model these properties are summarized. Common chemical and physical techniques for the fabrication of magnetic nanostructures are surveyed, followed by some examples of recent investigations of magnetic systems with structure on the nanometer scale. The article concludes with a brief discussion of some promising experimental techniques in synthesis and measurements.

Magnetic Properties of Nanostructured Materials

Consideration of Orowan strengthening effect in particulate-reinforced metal matrix nanocomposites: A model for predicting their yield strength

Deformation Mechanism of Nanocrystalline Magnesium in Compression

The evolution of microstructure during mechanical milling of magnesium powder has been studied. Commercially pure (99.6%, −325 mesh) magnesium powder was mechanically milled in a modified SPEX 8000 shaker mill in an inert atmosphere. The optical microscopy of the powder in the early stage of milling showed deformation by twinning and re-twinning within the grains developing sub-grain boundaries, which eventually defined nanometre-sized grains. The grain size reduction examined using XRD revealed a rapid decrease and then saturation of the grain size at approximately 42 nm. A relatively large final grain size compared to other mechanically milled metals was obtained due to the high recovery rate of magnesium. The corresponding internal strain was also observed to be low, confirming that enhanced recovery had occurred during milling. The internal strain during milling showed inverse grain size dependence. Moire fringe patterns of TEM micrographs showed absence of dislocations within the grains of as milled magnesium powder.

Mechanical milling of magnesium powder

Compressive Mechanical Properties of Mg-Ti-C Nanocomposite Synthesised by Mechanical Milling

Remanence enhancement in isotropic Sm-Co powders

Nanocrystalline Co0.5Fe2.5O4 has been prepared by mechanical alloying and subsequent vacuum annealing. Significant increase of coercivity was observed after a postannealing at low temperatures in air. Magnetic annealing resulted in anisotropic sample with a coercivity of 2.8 kOe and a remanence of 81% of the saturation magnetization, providing a theoretical maximum energy product of 4 MG Oe.

P.G. Mccormick

Papers

Deformation Mechanism of Nanocrystalline Magnesium in Compression

Mechanical milling of magnesium powder

Compressive Mechanical Properties of Mg-Ti-C Nanocomposite Synthesised by Mechanical Milling

Remanence enhancement in isotropic Sm-Co powders

High Magnetic Performance in Mechanically Alloyed Co Substituted Fe3O4