Superplasticity in a bulk amorphous Pd-40Ni-20P alloy:a compression study

Compressive deformation behavior of a cast Pd40Ni40P20 bulk metallic glass in the supercooled liquid region (589–670 K) was investigated at strain rates ranging from 10−4 to 10−2 s−1. The material exhibited excellent mechanical formability in the supercooled liquid region. However, in contrast to a Newtonian behavior generally observed in oxide glasses, the present alloy also showed a non-Newtonian behavior, depending upon the temperature and applied strain rate. Specifically, the alloy is like a Newtonian fluid at high temperatures, but becomes non-Newtonian at low temperatures and high strain rates. Structures of the amorphous material, both before and after deformation, were examined using X-ray diffraction and high-resolution transmission electron microscopy. The non-Newtonian behavior is proposed to be associated with the glass instability during deformation.