No abstract

The effect of pressure on the crystallization behavior of metallic glass Fe72P11C6Al5B4Ga2 alloy with a wide supercooled liquid region has been investigated by in situ high-pressure and high-temperature x-ray diffraction measurements using synchrotron radiation. In the pressure range from 0 to 2.4 GPa, the crystallization temperature, Tx, increases with pressure, p, having a slope of 30 K/GPa while a minimum in Tx was detected in the range from 2.4 to 3.9 GPa. With a further increase of p, Tx is independent of p. The Tx vs p behavior can be qualitatively explained by the suppression of atomic mobility and changes of the Gibbs free energy of various phases with pressure.

Amorphous Fe74−xAl5P11C6B4Gax (x=0 or 2) powders with a wide supercooled liquid region were prepared by high energy ball milling of rapidly quenched ribbons and subsequently hot pressed in the viscous state to receive bulk glasses. Almost complete coercivity relaxation of the ball milled powders was achieved by annealing. The coercivity Hc of as-milled ribbons drops drastically from more than 2200 Am−1 after 1 h of milling to 14.6 Am−1 after optimum annealing. The coercivity of this powder and that of the as-quenched ribbons (7 Am−1) differs only by the different contributions of surface irregularities Hcsurf to the total coercivity Hctot. Drastic coercivity relaxation was also achieved by consolidating the as-milled powders. A minimum coercivity Hc of 30 Am−1 was found for the bulk sample after compaction of 1 h ball milled powders. It is of the same order of magnitude as Hc of cast amorphous rods. The milling-induced coercivity increase as well as the coercivity relaxation are discussed in terms of the change of magnetic anisotropy and the creation and elimination of stress and shear bands in the amorphous phase.