CRYSTALLINE-AMORPHOUS TRANSITION OF NIZR2, NIZR AND NI3ZR BY ELECTRON-IRRADIATION

Three intermetallic compounds in the Ni-Zr system were irradiated with 1 MeV electrons in a high-voltage electron microscope over the temper ature range 10-200 K. All three compounds were amorphized by the elect ron irradiation with varying degrees of amorphization tendency and dif ferent critical temperatures. The critical dose at 10 K and the critic al temperature for amorphization were 0.22 displacements per atom (d.p .a.) and 200 K, 0.37 d.p.a and 100 K and 3.18 d.p.a. and 50 K for NiZr 2, NiZr and Ni3Zr respectively. The critical dose increases from NiZr2 to. Ni3Zr at all the irradiation temperatures investigated. The diffe rence in enthalpy between the amorphous and crystalline states of thes e compounds, which was estimated from the Debye temperature ratio betw een the amorphous and crystalline states of each compound, also increa ses from NiZr2 to Ni3Zr. The large difference in the critical temperat ure of the three compounds is noteworthy, suggesting that the mobility of the point defects which are responsible for restoring the chemical order is substantially different for these compounds.