On structure and mechanical properties of ultrasonically cast Al–2% Al2O3 nanocomposite

Microstructure evolution and mechanical properties of Al-Zn-Mg-Cu alloy reprocessed by spray-forming and heat treated at peak aged condition

Attempts have been made to prepare highly dense bulk Al-based nanocomposite consisting of evenly distributed nano-intermetallic particles and amorphous phase by consolidating mechanically alloyed amorphous Al88Ni6Ti6 powder using spark plasma sintering (SPS), hot-pressing and pressure-less sintering techniques. SPS technique has been most effective in comparison to other two processes in getting better homogeneity of microstructural features, densification and mechanical properties due to lower sintering temperature and time, hindering excessive crystallization of amorphous phase and grain growth of formed nanocrystals. This helps in producing optimum microstructure consisting of homogeneous distribution of nanocrystalline intermetallic phase and remaining amorphous phase as revealed by detailed electron microscopy and nano-indentation tests.

Structure and mechanical properties of Al–Ni–Ti amorphous powder consolidated by pressure-less, pressure-assisted and spark plasma sintering

The microstructures and properties of Al-based alloys produced by severe plastic deformation under high pressure torsion straining were compared with alloys of the same compositions consolidated by hot extrusion and spray-forming processing. Partially amorphous alloy powders of two systems were studied; Al 90 Fe 7 Z 3 alloy powders were prepared by high-energy ball milling and Al 84 Y 3 Ni 8 Co 4 Zr 1 +SiC composite powder was prepared by gas atomisation. The alloy powders have been cold consolidated by high-pressure torsion straining under a stress of 5 GPa resulting in refined and uniform microstructures, with hardness values well above the measured values for the hot-extruded Al 90 Fe 7 Z 3 alloy and for the spray-deposited Al 84 Y 3 Ni 8 Co 4 Zr 1 +SiC composite alloy.

Consolidation of partially amorphous aluminium-alloy powders by severe plastic deformation

The microstructure and the tensile properties of an Al–8.9 wt.% Si–3.2 wt.% Cu–0.9 wt.% Fe–0.8% Zn alloy processed by spray forming was investigated. The alloy was gas atomized with argon and deposited onto a copper substrate. The microstructure was evaluated by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Small faceted dispersoids observed surrounding equiaxial α-Al matrix were identified by SEM–EDS as silicon particles. Sand cast samples with the same composition showed a columnar dendritic α-Al matrix, Al–Si eutectic, polyhedric α-AlFeSi and needle-like β-AlFeSi intermetallics. In the spray formed material the formation of the Al–Si eutetic was suppressed, and the formation of the α-AlFeSi and β-AlFeSi intermetallics was strongly reduced. The fine and homogeneous microstructure showed an aluminium matrix with grain size ranging from 30 to 40 μm, and particle size of the silicon dispersoids having a mean size of 12 μm. Room temperature tensile tests of the spray formed alloy showed relative increasing of strength and elongation when compared with the values observed for the conventionally cast counterparts. These results can be ascribed to the refined microstructure and the scarce presence of intermetallics of the spray formed material.

Microstructure and mechanical properties of spray deposited hypoeutectic Al-Si alloy

Amorphous phase formation in spray deposited AlYNiCo and AlYNiCoZr alloys

In this investigation the Al84Y3Ni8Co4Zr1 alloy has been processed by spray forming to investigate the potential of achieving substantial fractions of the amorphous phase in the billet. The alloy was prepared by spray metal forming using the ratio of volumetric gas flow rate to mass of metal flow rate of 8.7 m 3 / kg . The resulting billet, weighting 2.1 kg, as well as the powders produced by the particles that had not hit the growing billet (overspray), were characterized by using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The powders had particles with spherical morphology in the size range of few microns to 100 μm with the median particle diameters about 20±1 μ m. The resulting billet contained only crystalline phases nevertheless the powder was composed of about 40% volume fraction of amorphous phase. This result indicates that the heating of the billet, by the heat release during solidification of the liquid and semi-solid particles was at temperature and for time enough for crystallization.

M.F Amateau

Papers

Amorphous phase formation in spray deposited AlYNiCo and AlYNiCoZr alloys

Amorphous phase formation during spray forming of Al84Y3Ni8Co4Zr1 alloy

Challenges in the development of aluminium-based bulk amorphous alloys