Abstract
Since the Cu–Be alloys have excellent age hardenability, many investigations have been carried out on their characteristics. The X-ray diffraction technique and electrical resistivity measurement were mainly used in earlier work, but recently the use of transmission electron microscopy has contributed greatly to clarify the mechanism of precipitation.
In this study, the Cu–Be alloys were aged for 2 hr at temperatures between 120° and 350°C and the mechanism of precipitation hardening was studied by hardness measurement, optical microscopy and transmission electron microscopy. The results show that the aging sequence of the Cu–Be alloys is α phase→G. P. (I) zone→G. P. (II) zone→γ′ phase→anomalous γ′ phase in the grains and α phase→dilute α phase plus γ phase at the grain boundaries. The γ phase at the grain boundary in both Cu-2%Be and Cu–Be 25 alloys initialy precipitates at the aging temperature of 250°C. Furthermore, the effect of Co on the precipitation hardening was studied by optical microscopy and X-ray microanalysis.
