Sheer sliding-off fracture of bulk amorphous Zr-based alloys containing nanoscale compound particles

By annealing a bulk amorphous Zr60Al10Cu20Pd10 alloy in the supercooled liq uid region between the glass transition temperature (T-g) and the crystalli zation temperature (T-x), a nanoscale mixed structure consisting of Zr-2(Cu , Pd) particles with a size of about 5 nm embedded in an amorphous matrix i s formed and the nanocrystalline amorphous alloy exhibits a high compressiv e yield strength of 1800 MPa and large plastic elongation over 4% at room t emperature. The plastic elongation is at least six times larger than that f or the corresponding bulk amorphous single phase alloy. The large elongatio n of the nanocrystalline amorphous alloy results from an increase in the sh ear sliding deformability along the maximum shear plane, leading to the fra cture only by sliding-off. The dramatic increase in the shear sliding for t he nanocrystalline bulk amorphous alloy is presumably due to the following three factors: (1) softening of the intergranular amorphous phase region ca used by the increase in temperature resulting from the localization of defo rmation into the intergranular amorphous phase, (2) change into a complex m ultiaxes-type stress condition in the amorphous phase region around nanocry stalline particles, and (3) introduction of free volumes caused by water qu enching from the supercooled liquid region corresponding to the annealing t emperature to maintain good ductility in the remaining amorphous phase.