The atomic structure of Zr–Cu binary amorphous alloys was studied using real space pair distribution functions derived from x-ray diffraction. The structure can be modeled by an ideal solution approximation because of relatively weak Cu–Zr atomic interactions. Addition of Al to Zr–Cu metallic glasses modifies the atomic structure in the short and medium range order because of the strongly attractive interaction between Al and Zr atoms. These interactions generate strong deviations from the ideal solution behavior.

Without the availability of slip systems and dislocation glide as in crystalline materials, metallic glasses resist irreversible deformation to elastic strains of 2% or more before undergoing heterogeneous plastic flow via the formation of shear bands. Observation of crystallite formation under compressive load was previously obtained by transmission electron microscopy. In this Letter, we present results of nondestructive x-ray diffraction microprofiling of the section of a bent glassy ${\mathrm{Pd}}_{40}{\mathrm{Cu}}_{30}{\mathrm{Ni}}_{10}{\mathrm{P}}_{20}$ ribbon in transmission using a synchrotron microbeam. Crystallization was clearly detected but only on the compression side of the neutral fiber. The experimental results and crystal nucleation frequency analysis are consistent with massive nucleation in shear bands forming under compressive stress but mainly for metallic glasses that show a large supercooled liquid temperature range $\Delta T=T_x-T_g$ between glass transition at $T_g$ and crystallization at $T_x$. The phenomenon is sensitively dependent on the volume change that accompanies crystallization in the supercooled liquid temperature range where the much larger liquid-state thermal expansion coefficient significantly increases the specific volume difference between the liquid and crystalline states. The results are also consistent with the many reports of extensive strain to fracture of metallic glasses under compressive load but not under tension.