Effect of Hydriding Temperature and Strain Rate on the Ductile-Brittle Transition in β Treated Zircaloy-4

Abstract

In this paper, the effect of hydriding temperature and strain rate on the ductile-brittle transition in β treated Zircaloy-4 has been investigated. The hydriding temperature used is 700°C, strain rates being 4×10⁻⁴ s⁻¹ and 4×10⁻³ s⁻¹. The results show that at same conditions the ductility of hydrides decreases as the hydriding temperature decreases. There exists a critical temperature (transition temperature) of 250°C for hydriding at 700°C, below which the hydrided specimens (and so for the hydrides) are brittle, while above it they are ductile. This transition temperature is lower than the one mentioned by various authors obtained for hydriding at 400°C. For the same hydriding temperature of 700°C, the specimens tested at 4×10⁻³ s⁻¹ are less ductile than those tested at 4x10⁻⁴ s⁻¹. Furthermore, unlike at a strain rate of 4x10⁻⁴ s⁻¹, there is no more a clear ductile-brittle transition behaviour.

KEYWORDS:

• β treated Zircaloy-4
• hydriding temperature
• strain rate
• ductile-brittle transitions
• hydrides
• elongation
• ductility
• ductile fracture
• brittle fracture
• hydridation
• transition temperature
• embrittlement