Shear Sliding-off Fracture of Bulk Amorphous Zr-Based Alloys Containing Nanoscale Compound Particles

Abstract

By annealing a bulk amorphous Zr 60 Al 10 Cu 20 Pd 10 alloy in the supercooled liquid region between the glass transition temperature (T g ) and the crystallization 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 is formed and the nanocrystalline amorphous alloy exhibits a high compressive yield strength of 1800 MPa and large plastic elongation over 4% at room temperature. The plastic elongation is at least six times larger than that for the corresponding bulk amorphous single phase alloy. The large elongation of the nanocrystalline amorphous alloy results from an increase in the shear sliding deformability along the maximum shear plane, leading to the fracture only by sliding-off. The dramatic increase in the shear sliding for the nanocrystalline bulk amorphous alloy is presumably due to the following three factors: (1) softening of the intergranular amorphous phase region caused by the increase in temperature resulting from the localization of deformation into the intergranular amorphous phase, (2) change into a complex multiaxes-type stress condition in the amorphous phase region around nanocrystalline particles, and (3) introduction of free volumes caused by water quenching from the supercooled liquid region corresponding to the annealing temperature to maintain good ductility in the remaining amorphous phase.