Formation of the gamma phase by a peritectoid reaction in the zirconium-hydrogen system

Abstract

Studies on the zirconium-hydrogen system have indicated that a peritectoid reaction occurs at about 255°C between the α and δ phases to give the γ phase. This reaction is dependent upon the interfacial contact and hence is sluggish if the two phases are in massive form. The γ is a stable phase of composition ZrH below 255°C and decomposes rapidly if heated above this temperature to give α and δ phases. Quenched α with saturated hydrogen, or δ of hightemperature composition, precipitate the γ phase at room temperature and require a long time for completion of the process. Non-equilibrium δ phase in a 49 at% hydrogen alloy, on β quenching and roomtemperature ageing, may transform fully to γ phase by a shear type of mechanism quite similar to the δ to ε transformation.