Phase transformations in alloys of the zirconium - molybdenum system

Conclusions

• 1. The eutectoid transformation β⇌α+ε occurs at 630°C in alloys of the Zr-Mo system.

• 2. In Zr-Mo alloys rich in zirconium, decomposition of the β phase occurs with formation of different structures in connection with changes in composition and cooling rate. One observes eutectoid decomposition with formation of a fine-grained eutectoid, oriented eutectoid decomposition with formation of an acicular structure, partial decomposition of β phase with formation of an acicular structure without precipitates of ε phase and considerable super-saturation of the α phase with molybdenum, and finally the cessation of β phase decomposition.

• 3. The heating rate has a substantial effect on the eutectoid transformation α+ε→β in Zr-Mo alloys.

• 4. By optimal alloying of zirconium with molybdenum (about 5%) and proper heat treatment (cooling from the β region with formation of a martensite-like structure without eutectoid decomposition) one can substantially increase the hardness of the Zr-Mo alloys.