Composition and mechanical properties of AlC, AlN and AlCN thin films obtained by r.f. magnetron sputtering

Aluminum carbide (Al-C), aluminum nitride (Al-N), and aluminum carbonitride (Al-C-N) thin films were grown onto Si [100] substrates by r.f. reactive magnetron sputtering at 400 °C. The Al-N coatings were obtained by sputtering of Al (99.9%) target in Ar/N₂ atmosphere and the Al-C and Al-C-N by co-sputtering of a binary (50% Al, 50% C) target in argon and in Ar/N₂ mixture, respectively. The d.c. bias voltage was varied between 0 and − 150 V. The films were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transformed infrared spectroscopy (FTIR) and the mechanical properties by nanoindentation. The structure of the films has been determined by XRD, which shows that amorphous films are formed in all cases. The variation of polarization bias voltage produced chemical differences in the films. As the bias voltage is increased, the Al content is reduced in all three materials. The nitrogen content also varied between 10 and 14 at.% for Al-N coatings, remaining practically constant (21 at.%) for the Al-C-N films. The Berkovich hardness results were 7.0, 17.2 and 9.2 GPa for Al-C, Al-N, and Al-C-N films, respectively.     

Strength and ductility of ultrafine grained aluminum and iron produced by ARB and annealing

Strength and ductility of ultrafine grained (UFG) aluminum and iron fabricated by ARB and annealing were clarified in the grain sizes ranging from 200 nm to 20 μm. Strength held Hall–Petch relationship, while uniform elongation of the UFG materials was limited below a few percents. The limited uniform elongation in the UFG materials could be explained in terms of plastic instability.     

Effects of forming conditions on homogeneity of microstructure and mechanical properties of A6061 aluminum alloy manufactured by time-dependent rheoforging on a mechanical servo press

The different forming behaviors of the solid and liquid phases in semisolid metal slurry during deformation result in products with inhomogeneous quality. A mechanical servo press with the capability of multistage compression was employed to forge A6061 aluminum alloy in the semisolid state. A time-dependent rheoforging strategy including mechanical stirring, a fast first compression, short holding, and a secondary compression was designed to improve the homogeneity of rheoforged samples. The distributions of the microstructure and mechanical properties, such as the solid fraction, hardness, and deformation resistance, of samples manufactured under various experimental conditions were investigated. When the stirred semisolid A6061 slurry was forged in the temperature range from 625 to 628 °C with a short holding time of 4 s and the upper die preheated to 300 °C, samples with a homogeneous microstructure and mechanical properties were manufactured. The homogeneity of rheoforged samples was attributed to the controllable free motion capability of the mechanical servo press and the adjustable fluidity and viscosity of the semisolid slurry.     

Effect of Cu, Ni on the property and microstructure of ultrafine WC-10Co alloys by sinter-hipping

Sub-micron size (0.4-0.6 μm) Co-Cu/Ni composite powders were synthesized by a co-precipitation method. The effects of minor Cu and Ni additions on the microstructure and the mechanical properties of ultrafine WC-10Co alloys were investigated using scanning electron microscope, X-ray diffraction and mechanical properties tests. The results show that Co-Cu binder phase refines the WC grains and increases the hardness of the base alloys. But the addition of Ni can't refine the WC grains and increase the hardness. The addition of minor Cu or Ni can improve transverse rupture strength of alloys through the solid solution strengthening. However, adding excess Cu can lead to the decrease in transverse rupture strength. With the partial substitution of Co by Cu and Ni, the hardness and transverse rupture strength of the alloys have a little change.