Stability of Hume-Rothery phases in Cu–Zn alloys at pressures up to 50 GPa

Abstract

The crystal structure of the γ-brass phase Cu5Zn8 is confirmed with single-crystal x-ray diffraction and CCD detector to be cubic with 52atoms in the unit cell, space group , and the refined atomic positions are in good agreement with previously reported data. The structuralbehaviour of α-(fcc), β-(bcc), and γ-brass (cI52) phases of the Cu–Zn alloy system has been studied under pressureusing diamond anvil cells and powder x-ray diffraction with synchrotronradiation. The appearance of additional peaks in the diffraction patterns ofα- andβ-phases indicates the beginning of transitions to new phases at 17 and 37 GPa, respectively. The complexcubic γ-brass phase is observed to be stable up to at least 50 GPa. The bulk modulusK0 was determinedas 140(4) GPa for α-, 139(5) GPa for β-,and 121(2) GPa for γ-phase assuming K0′ = 4. The structural stability of brass phases of the Cu–Zn system under pressure is discussedin terms of a Hume-Rothery mechanism.