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This paper presents a comparative study of the preparation and characterisation of Fe38.5Co38.5Nb7P15Cu1 alloy produced by mechanical alloying (MA) and rapid quenching (RQ) method. In order to obtain the starting mixture (SS) in the present study, we opted for the replacement of elemental Nb and P powders with ferroalloy powders of niobium and phosphorus. Benzene was used as a control agent of the process (PCA) for wet MA. The samples obtained (powders and ribbons) were characterised by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray microanalysis (EDX), magnetic measurements M(H) and thermomagnetic measurements M(T). After 40 h of wet MA, the alloy was partially amorphous, and the ribbons obtained by RQ do not show an amorphous state. Also, the magnetic measurements show the influence of the method used on the magnetic properties. [ABSTRACT FROM AUTHOR]

The soft magnetic nanocrystalline powders, alloys (Ni3Fe, 79Ni16Fe5Mo, 77Ni14Fe5Cu4Mo, wt. %) and zinc ferrite, were obtained by dry and wet mechanical alloying and reactive milling, followed by different heat treatments. The powders were characterised by X-ray diffraction, scanning electron microscopy, X-ray microanalysis, differential scanning calorimetry, thermomagnetic and magnetic measurements. The X-ray diffraction shown the progressive new phases formation. The crystallite size is between 18-7 nm depending on materials and milling conditions. The particle size is smaller for wet-mechanical alloying comparing with dry-milling. The thermomagnetic measurement shown the Curie temperature of the alloys. The spontaneous magnetisation of the wet-milled and annealed samples is higher than of the molten alloys. [ABSTRACT FROM AUTHOR]

Invar36 (FeNi) and Invar-Cu (FeNiCu) nanocrystalline compacts were successfully obtained by spark plasma sintering from mechanically alloyed powders. The coefficient of thermal expansion (CTE) was determined for both Invar36 and Invar-Cu compacts. For Invar36 powder, the lattice parameter value is constant up to 250 °C, while for the Invar-Cu powder, the value of lattice parameter changes for the temperatures that exceed 160 °C. Both Invar36 and Invar-Cu nanocrystalline compacts were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and dilatometry. The value of CTE is very low for both Invar36 compact ( α = 0.6 × 10/°C) and Invar-Cu ( α = 5.2 × 10/°C) up to Curie temperature ( T ), in agreement with in situ (high-temperature X-ray diffraction-HT-XRD) analyses of Invar-type powders. [ABSTRACT FROM AUTHOR]

This paper presents the effects of aqueous processing of WC-Co powders on their sinterability and mechanical properties. WC-Co powders have been milled in aqueous media (distilled water + corrosion inhibitor). The as-milled samples have been compacted and sintered in vacuum at 1380 °C. The investigations performed on the two components, carbide and binder, reveal different oxidation behaviour in water, with a further effect on the properties of the sintered product. The decrease of the saturation magnetisation of the compacts corroborated with the microstructure reveals the oxidation of the samples milled for a longer duration. The magnetic properties, hardness and microstructure suggest that the used corrosion inhibitor is effective for short milling durations. [ABSTRACT FROM AUTHOR]

Nanocrystalline magnetite - Fe3O4 has been synthesized in nanocrystalline state by mechanical milling of well crystallized magnetite samples obtained by heat treatment of a stoichiometric mixture of iron and hematite. Upon increasing the milling time, the mean crystallite size of magnetite is diminishing. After only 5 minutes of mechanical milling the crystallites are 110 nm. The milling up to 120 minutes leads to a continuous reduction of crystallites size up to 8 nm. The mechanical milling process induces strains into the lattice and the lattice strains increase drastically in the first 60 minutes of milling, after that a saturation of lattice strains is noticed. During milling a contamination of the powder with elemental iron occurs for milling times larger than 30 minutes. A decrease of the saturation magnetisation is noticed upon increasing the milling time and the decrease is associated with the structural disorder and defects that are induced into the material during milling. A tendency of the magnetisation to become unsaturated is also noticed and it is related to canted spins effect. [ABSTRACT FROM AUTHOR]