Effects of Microstructure on Ductility and Fracture Resistance of Zr-1.2Sn-1 Nb-0.4Fe Alloy

Abstract

The effect of microstructure on the ductility and fracture resistance of Zr-1.2Sn-1Nb-(0.2–0.5)Fe alloy has been studied. Different structural states of the alloy were attained by varying the iron content and working/heat treatment schedules, which comprised quenching, cold work, and anneal. The results of the tests for uniaxial tension, impact toughness, and static crack resistance as well as the electron microscope analysis of the microstructure revealed that the main structural factors governing the level of the as-recrystallized alloy ductility and fracture resistance are the sizes and uniformity of distribution of intermetallic particles of different types in the matrix. The highest ductility and impact toughness are reached when fine intermetallic particles from 0.03 to 0.20 μm are distributed uniformly within the structure. The impact toughness and critical crack opening grow linearly with an increase of particle distribution density and a decrease in interparticle spacing. Changes in the alloy microstructure and mechanical properties were investigated upon its anneal after β-quenching. It is demonstrated that the highest values of ductility and impact toughness are reached with the formation of a polygonized matrix structure without intermetallic particle precipitation.

Micro-focussed XAFS spectroscopy to study Ni-bearing precipitates in the metal of corroded Zircaloy-2

“…A large number of studies have been published on the evolution of precipitates during oxidation of the zirconium alloys [3,[7][8][9][10][11][12][13]. The microstructure of the alloys was predominantly observed by various analytical methods, e.g., conventional optical microscopy, transmitted light optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).…”

“…It has been observed that oxidation of precipitates is delayed compared to the zirconium matrix [14]. The effect of SPP on metallurgical properties and corrosion has been also reported [10]. The properties of these intermetallics under irradiation environment in reactor up to a high burn-up have been the subject of several investigations [15][16][17][18][19].…”

Structure Evolution of Zirconium Alloys during Deformation/Heat Treatment

“…The microstructure evolution and variations in the tensile properties of Zr alloys E110 and E125 were dealt with in detail in [1,3] where it was demonstrated that the tensile properties of these alloys (also impact strength and crack resistance) are primarily governed by the degree of matrix recrystallization and texture. As distinct from zirconium binary alloys, the fracture resistance of a multicomponent alloy of the E635 type is governed by intermetallic particles [3,4]. This work deals with studying the evolution of the microstructure and tensile properties of the multicomponent alloy E635 subjected to deformation/heat treatment.…”

“…The processability of the alloy as deformation/heat treated involving hot and cold work as well as anneals and tensile properties and performance of its finished products are in many respects governed by the microstructure that is formed at different stages of working. One of the routes to increase the toughness and ductility of the alloy finished product is to apply β -quenching from 950-1000 0 C immediately preceding the cold work operations which provides for the structure having uniformly distributed finely dispersed intermetallic particles in the recrystallized zirconium matrix [3][4][5]. The reduction schemas involving high reduction ratios used in the fabrication of thin -walled items also require a higher toughness margin of the alloy.…”

“…The reduction schemas involving high reduction ratios used in the fabrication of thin -walled items also require a higher toughness margin of the alloy. The anneal at 580-630 0 C close to the upper boundary of the α-region of the phase diagram usually applied for the sake of recrystallization at the final stage of processing the cold worked alloy after quenching fails to provide the high toughness and workability [5].…”