MECHANICAL-BEHAVIOR OF ION-IRRADIATED ORDERED INTERMETALLIC COMPOUNDS

The status of research on the mechanical behavior of ion-irradiated ordered intermetallic compounds is reviewed. The nature of displacement damage produced by charged particles is discussed and the miniaturized disk bend test, which is used extensively to evaluate mechanical properties of the ion-irradiated alloys studied, is described. The mechanical behavior of Zr3Al, Ni3Al and TiAl is then described, followed by a presentation and discussion of recent preliminary results on Ni3Si, Ni3Ge and Ti3Al. With few exceptions ion irradiation induces an increase in the yield strength or hardness of ordered intermetallic compounds. This is expected for the L1(2) and D0(19) alloys, because these alloys are stronger in the disordered condition than they are in the ordered state, but the increase in strength of TiAl is unexpected on this basis. However, it is noted that disordering is not the only consequence of ion irradiation and that several other factors can contribute to the measured increases in strength. For most ordered alloys an increase in ductility is also expected on disordering, but quantitative information from the mechanical tests is insufficient to support this finding. The extent of strengthening observed varies with the individual alloy, even among those sharing the same crystal structure. For example, the increase in yield stress is much larger for Ni3Si than for Ni3Al and the increase in the fracture stress of Ti3Al is much larger than that of Ni3Ge. The absence of microstructural information on most of the intermetallic compounds investigated has precluded an understanding of the interesting effects observed.