Effect of quenching rate on the β-to-α phase transformation structure in zirconium alloy

Crystallographic measurement of the β to α phase transformation and δ-hydride precipitation in a laser-welded Zircaloy-2 tube by electron backscattering diffraction

“…At very fast cooling rates of >1600-2000°C/s, the martensitic acicular structure is formed. Though the accurate temperature transient in the fusion zone is unknown, the cooling rate may be inferred to be above several 10's of°C/s from the existence of the basketweave structure and the lath width of about 0.5-1.0 lm in the fusion zone, based on the reported correlation between cooling rate and lath width [3]. Fig.…”

“…a 0 phase transformations occur. There have been many reported microstructural investigations by optical and scanning electron microscopy which focused on the metallographic morphology of the transformed phases [3][4][5][6][7][8]. However, there have been few crystallographic examinations reported.…”

Transformation kinetics of zirconium alloys under non-isothermal conditions

“…[12]. Quenching Zircaloy from b-phase in moderate cooling rates produces two variants of Widmanstätten structure, namely, the basketweave and the parallel-plate structure [13,3]. However, at cooling rates greater than 1000 K s À1 a martensite structure is observed, while for very low cooling rates, 60.5 K s À1 , the needle-shaped structure is rarely seen [14].…”

“…Fabrication of fuel cladding tube commonly comprises heat treatments (temperature range of roughly 300-1300 K) that involve time-dependent phase transformation of Zr alloy from hexagonal (a-phase) to cubic (b-phase) crystal structure [3,4]. Similarly, under extreme in-service conditions, e.g., during a postulated loss-of-coolant accident (LOCA), fuel cladding will be subjected to a rapid increase in temperature (up to 1000-1500 K) in steam environment, which not only induces a ?…”

Effect of heat treatment and Nb and H contents on the phase transformation of N18 and N36 zirconium alloys

“…Simultaneity, it was also found that the ␤-Zr phase usually nucleated and grew up in grain corners when the heating temperature for quenching test was near the transformation temperature of ␣ to (␣ + ␤) of the alloys, and which induced gradual disappearance of the defects. The Gibbs energy for the disappearance of the defects would provide drive force for subsequent nucleation [14].…”