Effect of Cooling Rates and Impurities on the Microstructure of β→α Transformation in Zr Alloys

Abstract:

This paper presents a comprehensive review about the effect of cooling rates and impurities on the microstructure of zirconium alloys during β→α transformation with the expectation to facilitate the development of high-performance zirconium-based cladding materials. For zirconium alloys, the diffusionless Martensitic transformation does not produce a surface rumpling after quenching the pre-polished specimens. The Ms temperature keeps independent of β quenching rates. When alloy composition is fixed, increasing of cooling rate causes microstructural change in the following sequence: lenticular α→Parallel plate α→Basketweave α→Martensitic α'. The impurities which can form insoluble second phase particles in β phase will promote the formation of Basketweave Widmanstatten structures. However, the impurities that might increase β phase transformation temperature will lead to more Parallel-plate Widmanstatten structures

Key words:zirconium alloys; cooling rates; Martensite; Wadmanstatten; impurity elements