Lattice Parameter Studies of Annealed, of Aged, and of Cold-Worked Alpha Brass

Abstract

On aging at 120°C two annealed alpha brasses containing 30 and 35% Zn, respectively, a small (about 0.0003 to 0.0006 A) reduction in the lattice parameter occurs. In the present work all diffraction lines in the spectrum were measured using monochromated CuKαi radiation, and all indicated the same change. Cold work induced by filing produced a measurable amount of stacking faults as detected by the shifts in the diffraction lines and in addition caused an apparent increase in lattice parameter of about 0.0008 A. On aging these cold-worked alloys for over 1000 hr at 120°C, the lattice parameter decreased. For the Cu-35Zn the decrease was 0.0037 A and was accompanied by the precipitation of a small but measurable amount of beta phase. Thereby the solubility limit of the alpha phase was placed between 33 and 34% Zn. The Cu-30Zn alloy also showed a decrease in the lattice parameter of 0.0029 A but, as expected, no beta phase. In neither case was there any observable change in the stacking fault density. These data are interpreted in terms of solute clustering, possibly to stacking faults, as considered by Suzuki. It is suggested that solute clustering may also be the cause of the decrease in lattice parameter for the annealed and aged alloys, rather than short-range ordering.