No abstract

The effect of heating temperature and holding time on the phase transformation from (Fe, Mn)Al 6 to α-Al 12 (Fe, Mn) 3 Si in AA3104 aluminum alloy during homogenization was studied by BSE and EDS in SEM. The 3D morphology of the eutectic phases heated at 600 ª for different holding times was reconstructed by a novel serial sectioning method. Evolution of the microstructure could be revealed in 3D for the first time. Al spots were observed within the α-Al 12 (Fe, Mn) 3 Si phase and counted during different transformation stages. Large number of Al spots disappeared by diffusing into the neighboring matrix after extended heating times, while the volume of the α phase was also decreased at the same time. The microstructure of the α phase after transformation was analyzed, showing ¢duplex interfaces¤created by partly transformed particles. The dense holes within α phase particles are believed to promote particle break up during hot rolling of the homogenized material.

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,

Zirconium alloys are widely used as fuel cladding and structural materials for nuclear reactors due to the low neutron absorption cross-section, good corrosion resistance and acceptable mechanical properties. These properties are greatly dependent on microstructural and textural features, such as grain morphology, grain size, crystallographic texture and distribution of precipitates. It is necessary to understand microstructure and texture evolution during fabrication in order to optimize the manufacturing process and to improve the service performance. In this work, microstructure and texture evolution during fabrication of Zr-Sn-Nb new zirconium alloy sheets are investigated using XRD, SEM-ECC, TEM and EBSD. The results show that the random texture formed by β quenching transforms into tilt basal texture after hot rolling. The basal texture keeps stable during the following