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A new study investigates the solid state reactions caused by mechanical alloying of elemental blends of Ni and Si.

A bcc-fcc allotropic transformation in Nb was induced by mechanical alloying of Bn80A120.

Abstract: Workability and mechanical properties of the ultrasonically cast Al–X wt% Al2O3 (X=2, 3.57 and 4.69) metal matrix nanocomposites were reported in the present investigation. The Al–Al2O3 (average size ∼10nm) composites showed maximum reduction ratios of 2, 1.75 and 1.41 at room temperature, and 8, 7 and 6 at 300°C. The elastic modulus, nanoindentation hardness, microhardness and Vickers hardness were measured on the as-cast, cold and hot rolled specimens. The tensile properties were also evaluated for the as-cast composites for different wt% of reinforcement. The microstructural examination was done by optical, scanning and transmission electron microscopy. The strength and workability of the nanocomposites were discussed in the light of dislocation/particle interaction, particle size and its concentration, inter-particle spacing and working temperature. 2wt% of Al2O3 reinforcement showed better combination of workability and mechanical properties possibly due to better distribution of particulates in the matrix. [Copyright &y& Elsevier]

Abstract: We report here successful synthesis of Al-based nanocomposites with L12–Al3Ti particles in binary Al–Ti (4.1, 5, 8.3, 10, 15 and 20% Ti) and ternary Al-1.6Ti-0.5Cr, Al-3.2Ti-1.0Cr and Al-6.3Ti-2.0Cr alloys, by rapid solidification processing. The microstructure of all the alloys consists of uniform distribution of nanocrystalline L12–Al3Ti intermetallic in ultra-fine α-Al matrix. The volume fraction of L12–Al3Ti phase in the as-spun ribbons was found to increase with the Ti content in the binary alloys with exception of Al-20% Ti alloy, which formed equilibrium DO22–Al3Ti. The α-Al grains were measured to be in the size range 0.5–1.0μm embedded with L12–Al3Ti particles of ∼50nm diameter. Nanoindentation as well as microhardness of nanocomposites in binary Al–Ti alloys measure hardness value of 3.75GPa (367 VHN). The nanocomposites formed by rapid solidification processing retain about 70–85% of its room temperature hardness even at 500°C for 100h, while the hardness of conventional Al alloys such as 2017 is almost lost at 350°C in 30min. [Copyright &y& Elsevier]

Abstract: The present paper reports the formation of nanocomposites containing α-Al and L12–Al3Ti in binary Al–Ti alloys containing 5, 10, 15, and 20at.% Ti. Supersaturated solid solution of Ti in Al was observed after 20h of mechanical alloying irrespective of the Ti content. Nanocomposites formed after mechanical alloying and subsequent annealing at 673K for 2h showed a high hardness (3.4GPa), modulus (106.4GPa) and density (95%). Hardness values of Al–(L12)Al3Ti nanocomposites obtained by nanoindentation were similar to hardness measured with microhardness. High strength of the nanocomposites was attributed to the formation of large volume fraction of nanocrystalline L12–Al3Ti particles and the ultrafine grain size of α-Al matrix. [Copyright &y& Elsevier]

Abstract: Nanocrystalline L12-Al3(Ti,Zr) intermetallic has been synthesized directly by mechanical alloying of elemental blends of the nominal composition Al75(Ti25−x Zr x ) for x =0, 5, 10, 15, 20 and 25. The long range order parameter is found to increase with the Zr content. The lattice parameter difference between the L12-Al3(Ti,Zr) and Al was minimum for the alloy with 10% Zr. A very high hardness of 3.23GPa was achieved for the L12 phase in the Al75Ti15Zr10 composition in the green compact condition with a relative density of 77.6%. [Copyright &y& Elsevier]

Abstract Nanofluids are a new group of materials with potentially broad applications in the industry, especially in the process of heat transfer. Recently, a new class of nanofluids called hybrid nanofluids are being used to enhance the heat transfer rate. In the present study, an experimental investigation on heat transfer characteristics of aqueous Al 2 O 3 /Ag hybrid nanofluids is presented. The main idea in producing hybrid nanofluids was to obtain better heat transfer rate compared to nanofluids dispersed with either of the dispersoids. The detailed surface properties of Ag and Al 2 O 3 nanoparticles were performed by X-ray diffraction and transmission electron microscopy. Polyvinylpyrrolidone used to stabilize the nanoparticles (Al 2 O 3 /Ag) in water. Dynamic light scattering and zetapotential measurements measured the particle size distribution of the nanoparticles in the nanofluid and the surface charge formed on the surface of the nanoparticle by the polyvinylpyrrolidone. The hybrid nanofluid was prepared by dispersing Al 2 O 3 /Ag (50,50) in distilled water, and the thermal conductivity measurements were conducted for particle loading varying from 0.005 vol% to 0.1 vol% using transient hot-wire method. The results indicate that Al 2 O 3 /Ag hybrid nanofluids exhibit higher thermal conductivity enhancement compared to Al 2 O 3 nanofluids alone. Based on the experimental data, a new correlation for predicting the thermal conductivity of aqueous Al 2 O 3 /Ag has been proposed. Graphical abstract Unlabelled Image Highlights • Two-step method has been employed to prepare aqueous Al2O3/Ag hybrid nanofluid. • Al2O3/Ag nanofluids exhibited higher thermal conductivity compared to Al2O3 nanofluid. • Proposed new correlation to predict the thermal conductivity of Al2O3/Ag nanofluids. [ABSTRACT FROM AUTHOR]

Transient hot-wire and laser flash methods are the two commonly used techniques for measuring the thermal conductivity of nanofluids. However, a comparative study of these two techniques considering identical nanofluids has not been carried out. In this regard, the current study aims at comparison of two methods with identical distribution of Al 2 O 3 and Ag nanoparticles in water. The study also accounts quantitatively for the wide difference in the measured thermal conductivities on the basis of the flux of nanoparticles across the thermal boundary layer resulting from the Brownian movement. It has been observed that the collision flux of the nanoparticle increases with increase in the initial perpendicular distance of the nanoparticle from the heat source wall. Such an increase results in higher thermal conductivity in case of transient hot-wire compared to laser flash method. [ABSTRACT FROM AUTHOR]