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Register a new userEffect of heavy ion irradiation on microstructure and electron density distribution of zirconium alloy characterised by X-ray diffraction technique
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Different techniques of the X-ray Diffraction Line Profile Analysis (XRDLPA) have been used to assess the microstructure of the irradiated Zr-1.0%Nb-1.0%Sn-0.1%Fe alloy. The domain size, microstrain, density of dislocation and the stacking fault probabilities of the irradiated alloy have been estimated as a function of dose by the Williamson-Hall Technique, Modified Rietveld Analysis and the Double Voigt Method. A clear signature in the increase in the density of dislocation with the dose of irradiated was revealed. The analysis also estimated the average density of dislocation in the major slip planes after irradiation. For the first time, we have established the changes in the electron density distribution due to irradiation by X-ray diffraction technique. We could estimate the average displacement of the atoms and the lattice strain caused due to irradiation from the changes in the electron density distribution as observed in the contour plots.
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Zirconium based alloys have been irradiated with 11 and 15 MeV proton and 116 MeV oxygen ions at different doses. The changes in the microstructure have been studied for the ion irradiated alloys as a function of dose using X-Ray Diffraction Line Profile Analysis (XRDLPA) based on the whole powder pattern fitting technique. It was observed that the microstructural parameters like domain size, microstrain within the domain, dislocation density did not change significantly with the increase in dose for proton irradiated samples. A clear change was noticed in these microstructural parameters as a function of dose for oxygen irradiated samples. There was a drastic decrease in domain size at a dose of 1x10^17 O5+/m2 but these values reached a plateau with increasing dose. The values of microstrain and dislocation density increased significantly with the dose of irradiation.
The high energy density of electronic excitations due to the impact of swift heavy ions can induce structural modifications in materials. We present a X-ray diffractometer called ALIX, which has been set up at the low-energy IRRSUD beamline of the GANIL facility, to allow the study of structural modification kinetics as a function of the ion fluence. The X-ray setup has been modified and optimized to enable irradiation by swift heavy ions simultaneously to X-ray pattern recording. We present the capability of ALIX to perform simultaneous irradiation - diffraction by using energy discrimination between X-rays from diffraction and from ion-target interaction. To illustrate its potential, results of sequential or simultaneous irradiation - diffraction are presented in this article to show radiation effects on the structural properties of ceramics. Phase transition kinetics have been studied during xenon ion irradiation of polycrystalline MgO and SrTiO3. We have observed that MgO oxide is radiation-resistant to high electronic excitations, contrary to the high sensitivity of SrTiO3, which exhibits transition from the crystalline to the amorphous state during irradiation. By interpreting the amorphization kinetics of SrTiO3, defect overlapping models are discussed as well as latent track characteristics. Together with a transmission electron microscopy study, we conclude that a single impact model describes the phase transition mechanism.
There is considerable controversy about swift heavy ion (SHI) irradiation induced displacive phase transitions in thermally insulating oxides. We present here unambiguous evidence for tetragonal to monoclinic and rhombohedral to monoclinic phase transitions in BaTiO3 under swift heavy ion irradiation (120MeV 108Ag+9 ions) using in-situ x-ray powder diffraction (XRPD) studies. The anomalous splitting/broadening of 111/222pc, 200pc and 220pc pseudocubic peaks for fluences greater than 3*1012 ions/cm2 reveal structural changes before amorphization at higher fluences. Lebail analysis of XRPD profiles confirm that the monoclinic phase is of MA type in the Cm space group. Shear stress for the structural phase transition is estimated to be ~ 430MPa, which we believe is generated as a result of stopping of the SHI.
The diffraction peaks of Zircaloy-2 and Zr-2.5%Nb alloys at various deformations are found to be asymmetric in nature. In order to characterize the microstructure from these asymmetric peaks of these deformed alloys, X-Ray Diffraction Line Profile Analysis like Williamson-Hall technique, Variance method based on second and fourth order restricted moments and Stephens model based on anisotropic strain distribution have been adopted. The domain size and dislocation density have been evaluated as a function of deformation for both these alloys. These techniques are useful where the dislocation structure is highly inhomogeneous inside the matrix causing asymmetry in the line profile, particularly for deformed polycrystalline materials.
The mechanism of the evolution of the deformed microstructure at the earliest stage of annealing where the existence of the lowest length scale substructure paves the way to the formation of the so-called subgrains, has been studied for the first time. The study has been performed at high temperature on heavily deformed Ti-modified austenitic stainless steel using X-ray diffraction technique. Significant changes were observed in the values of the domain size, both with time and temperature. Two different types of mechanism have been proposed to be involved during the microstructural evolution at the earliest stages of annealing. The nature of the growth of domains with time at different temperatures has been modelled using these mechanisms. High-resolution transmission electron microscopy has been used to view the microstructure of the deformed and annealed sample and the results have been corroborated successfully with those found from the X-ray diffraction techniques.
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