Phase transformations induced by irradiation with ions in β Cu-Zn=Al single crystals

Single crystals of beta Cu-Zn-Al alloys were irradiated with 30 keV Ar ions at room temperature to fluences in the range of 1 to 6 displacements per atom (dpa). The microstructural changes induced by the,irradiation were investigated with transmission electron microscopy. Specimens with two different surface orientations, (100)(beta) and (011)(beta), were studied. In specimens.with (100)(beta) surface orientation a new phase with a hexagonal close packed structure was formed due to the ion irradiation. The orientation relationship with the matrix was of the type: (0001)Hex parallel to (0 (1) over bar1)(beta); [1 (1) over bar 00](Hex) parallel to [011](beta). In specimens with (011)(beta) surface orientation, the hexagonal structure was not observed: Instead, small precipitates of the gamma phase with a mean size of 8 nm were found. The results are discussed in comparison with previous ion irradiation experiments and with similar, phase transformations occurring in beta Cu-Zn-Al alloys.