EFFECT OF PRE-DEFORMATION ON GRAINS AND PRECIPITATES OF Zr-Sn-Nb ALLOY DURING AGING

Abstract

Zirconium-based alloys are being used as fuel cladding and structural materials for nuclear reactors since they have a good irradiation stability, corrosion resistance and acceptable mechanical properties in a reactor environment. Recently, more advanced zirconium-based alloys are required for enhanced operating conditions such as an increased burn-up and higher operation temperatures. Therefore, the development of advanced zirconium alloys for a fuel cladding is being progressed in various countries. Among the developed new zirconium alloys, a low Nb containing alloy series designed by China is a group of promising cladding material. For the new alloy system, optimum manufacturing processes are significant factors to improve properties and need urgently to be established. In this work, electron channeling contrast (ECC), secondary electron (SE) imaging and energy dispersive spectroscopy (EDS) analyzing techniques are employed to investigate the effect of pre-deformation following β-quenching on recrystallization and precipitating behavior of a new Zr-Sn-Nb alloy during aging. The results show that remarkable differences exist between the microstructure of specimens with and without pre-deformation prior to aging at the same temperature (650 ¤). Specimens aged without pre-deformation present extremely heterogeneous recrystallized grains that generally own irregular shape. The size discrepancy between the intragranularly fine Zr(Fe, Cr, Nb) 2 precipitates and the larger ones, which is Cu-containing Zr 3 Fe particles and distribute along the conserved prior β grain boundaries, are distinct. While for specimens aged following 20% pre-deformation, the recrystallized α-grains are evidently fined and homogenized. The size discrepancy between the two sorts of precipitates decrease as well and the larger ones change to distribute along recrystallized α-grain boundaries. Therefore,

Effect of Processing Techniques on Precipitation Behavior of Secondary Phase Particles in Zr-1Nb-0.01Cu Alloy

“…As a result, particles grow with the total annealing time increasing accordingly. Studies show that the precipitation behavior of SPPs is influenced seriously by the final cold rolling reduction before final annealing treatment in zirconium alloys [18][19][20][21] . In the present investigation, the final rolling reduction is 82%, 65%, and 53%.…”

“…It can be known from Fig.1 and Table. 1 that the alloy intermediate annealed at 640 °C was cold rolled for twice, and the other one final annealed at 640 °C was cold rolled for only once. Study has demonstrated by Chai et al that the pre-deformation before annealing is more effective than prolonging the annealing time in accelerating the phase precipitation [18] . So it may be the main reason that the amount of β-Zr intermediate annealed at 640 °C is larger than that of the alloy finally annealed at 640 °C.…”