The intermetallic precipitate particles Zr-2(Ni, Fe) in Zircaloy-2 and Zr(Cr, Fe)(2) in Zircaloy-4, dissolve and amorphize under irradiation. Pursuing a previous analysis by Motta and Lemaignan, we have studied those effects on the basis of the metastable free-energy diagram of the reference system Zr-Fe (calculated using Miedema’s model) and considering some aspects of the modification of this free-energy diagram by irradiation. We then can explain why both phases Zr-2(Ni, Fe) and Zr(Cr, Fe)(2) can be amorphized at low temperatures (below 350 K) without composition changes if sufficient energy can be accumulated by irradiation-produced defects and chemical disorder, and also that at intermediate temperatures (about 580 K) a driving force exists for particle amorphization at the matrix-particle interface for Zr(Cr, Fe)(2) but not for Zr(Ni, Fe)(2).