Structural stability and compressibility of group IV transition metals-based bulk metallic glasses under high pressure

Abstract

High-pressure x-ray diffraction studies have been carried out on the two group IV transition metals-based bulk metallic glasses (BMGs) Zr57Cu15.4Ni12.6Al10Nb5 and Ti42Zr24Cu15.5Ni14.5Be4 to a pressure of 30 GPa at ambient temperature in a diamond anvil cell. Image plate x-ray diffraction studies under high pressure were carried out at a synchrotron source and the two BMG diffraction bands can be followed to the highest pressure using an internal copper pressure standard. The amorphous phase is observed to be stable to the highest static pressure of 30 GPa suggesting that the phase change observed in dynamical pressure experiments is related to an increase in temperature. The measured bulk modulus (B0) and its pressure derivative (B′) are 118 GPa and 3.11 for Zr-based BMG and 116 GPa and 2.84 for Ti-based BMG. The measured bulk modulus for BMG’s by x-ray diffraction technique is consistent with the ultrasonic measurements. The decompression data reveal an increase in density by 3%–4% at ambient condition after pressure cycling to 30 GPa indicating reduction in excess free volume.