LI 2 Phases of Particular Interest

Ni3pe is one of the ductile LI 2 phases, as mentioned in the preceding section. It shows an order-disorder transition at intermediate temperatures which has been studied in detail with respect to energetics and kinetics (Marty etal., 1990 Cahn, 1992 see also the chapter by Inden and Pitsch in Volume 5 of MST). The mechanical behavior is well known and the characteristics have been discussed with re- 

The LI 2 phase ZrjAl, which forms peri-tectically from ZrjAl and Zr, was studied extensively for use as the cladding material for water-cooled, nuclear power reactors since it has a low cross section for the absorption of thermal neutrons (Schulson, 1984 Liu et al., 1990 Parameswaran et al., 1990). In particular, the mechanical behavior was the subject of detailed studies (Schulson, 1984) according to which the strength is high with an anomalous temperature dependence for the flow stress. The work hardening rate exceeds that for any disordered or ordered f.c.c. alloy. ZrjAl, with polished surfaces, has a ductil- 

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