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 a charge-coupled device (CCD) detector to be cubic with 52 atoms in the unit cell, space group \(I\overline 4 3m\), and the refined atomic positions are in good agreement with previously reported data. The structural behavior of α-(fcc), β-brass (cI52) phases of the Cu−Zn alloy system has been studied under pressure using diamond anvil cells and powder X-ray diffraction with synchrotron radiation. The appearance of additional peaks in the diffraction patterns of α- and β-phases indicates the beginning of transitions to new phases at 17 and 37 GPa, respectively. The complex cubic γ-brass phase (52 atoms in the unit cell, space group \(I\overline 4 3m\) is observed to be stable up to at least 50 GPa. The bulk modulus K0 was determined as 140(4) GPa for α-, 139(5) for β-, and 121(2) for γ-phase assuming K0′=4. The structural stability of brass phases of the Cu−Zn system under pressure is discussed in terms of the Hume-Rothery mechanism.