Amorphous phase formation during spray forming of Al84Y3Ni8Co4Zr1 alloy

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 m3/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 μm. 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.