Real-time detection of metastable phases in Zr-based bulk glasses during fast heating in a synchrotron beam

We have studied in situ crystallization from the glassy state and solidific ation from the liquid state in Zr-based bulk glass-forming alloy. The exper iments were performed with a high intensity, high-energy monochromatic sync hrotron beam. Samples of amorphous Zr55CU20Al10Ni10Pd5 alloy with rectangul ar section and 2 mm thickness, sealed under vacuum in specially designed qu artz tubes were studied. Diffraction in transmission was used to minimize s urface crystallization effects. The choice of the sample thickness and the monochromatic beam energy allow an acquisition time of 2 s per full pattern . The heating rate was around 20 K/s nearly 20 times greater than that usua lly used in DSC calorimetry and close to those of cooling rates for glass f ormation. In Zr55CU30Al10Ni5, crystallization occurs via initial nucleation of a metastable phase that remains only a few seconds before transformatio n to the equilibrium phase, tetragonal Zr2Cu. The increase of Zr content to 69% increases the stability of the metastable phase, which remains until m elting. It was found that the Pd addition to the quaternary alloy with Zr 5 5 at.% also makes the metastable phase stable up to a temperature near melt ing. We have also found that, contrary to the Zr addition, the I'd addition eliminates the formation of bcc or hexagonal solid solution phase at high temperatures.