THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Metal matrix composites – From science to technological significance

Friction stir processing (FSP), developed based on the basic principles of friction stir welding (FSW), a solid-state joining process originally developed for aluminum alloys, is an emerging metalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed.

Friction stir processing technology: A review

Mechanically alloyed nanocomposites

Microstructurally inhomogeneous composites: Is a homogeneous reinforcement distribution optimal?

Copper–tungsten exhibits total absence of solubility in both solid and liquid state. Mechanical alloying (MA) as a solid state, non-equilibrium process can be beneficial to the processing of such an immiscible system with the added features of refinement of structure. A study was undertaken to synthesise various Cu–W alloys and develop an ultrafine microcomposite structure of tungsten in copper matrix by mechanical alloying. Elemental powders of copper and tungsten were milled in high energy ball mills. The milling behaviour was found to depend on the composition, milling time and milling atmosphere. The milled powders were characterised for their particle size, microstructure and lattice parameters. Metastable mutual solid solubility in the system was confirmed. Crystallite sizes were found to be in the nanocrystalline regime. The conversion of milling energy effectively to generate deformed surfaces, which in turn led to metastable solid solubility and nanocrystalline structure, was aided by the presence of oxygen in the milling atmosphere.

Synthesis of nanocrystalline copper–tungsten alloys by mechanical alloying

Metal matrix composites made by a powder metallurgy route often exhibit clustering of the reinforcements due to geometrical reasons. The clustering tendency was studied in 2124 Al/30 v/o SiCp composites as a function of relative particle size ratio between the matrix and reinforcement particles. Dry blended composite powders, with different RPS ratios, were vacuum hot-pressed and microstructures were examined to assess the uniformity of the microstructure by measuring the local area fraction of the constituents. It was found that a decrease in RPS ratio resulted in an increase in strength as well as ductility, as a result of improved distribution of the SiCp. The improved response to the homogenisation treatment, observed in the composite with lower RPS ratio, is attributed to the smaller diffusion path length for the alloying element.

Structure–property correlation in discontinuously reinforced aluminium matrix composites as a function of relative particle size ratio

Attempts have been made to ascertain the mechanism of mass transport through the evaluation of the activation energies for different temperature ranges and through the sintering diagram approach of Ashby during sintering of microcrystalline titanium powders (average particle size of ∼3 μm). Present studies reveal that the sintering in the alpha range is controlled by lattice diffusion with source of matter at grain boundaries and the sintering in beta region appears to be controlled by lattice diffusion along with some kind of grain boundary rotation mechanism.

Sintering kinetics of micrometric titanium powder

Analysis of chip breaking during orthogonal machining of Al/SiCp composites

Discontinuously Reinforced Aluminum (DRA) Composites form unique case from the research in metal cutting point of view. Reinforcement in these materials acts as macroscopic and isolated discontinuities in the path of the tool. The mechanism of chip formation for such materials is yet to be evolved completely. In this paper, the mechanism of chip formation during machining of Al/SiCp composites based on the micro-structural analysis of chips and chip roots is presented. It was evident that the mechanism involves initiation of a gross fracture on the chip free surface and its propagation toward the tool nose. The extent of propagation of gross fracture depends upon the cutting speed and volume of reinforcement in composites. A model of deformation of the material along the shear plane is presented in terms of a ratio of length of flow-type deformation on the shear plane to the total length of shear plane. Influence of volume of reinforcement in composites and cutting speed on the ratio was verified experimentally.

P. Ramakrishnan

Papers

Synthesis of nanocrystalline copper–tungsten alloys by mechanical alloying

Structure–property correlation in discontinuously reinforced aluminium matrix composites as a function of relative particle size ratio

Sintering kinetics of micrometric titanium powder

Analysis of chip breaking during orthogonal machining of Al/SiCp composites

Micro-Structural Analysis of Chip Formation During Orthogonal Machining of Al/SiCp Composites