Microstructural Studies on Lattice Imperfections in Deformed Zirconium-Base Alloys by X-Ray Diffraction P. MUKHERJEE, S.K. CHATTOPADHYAY, S.K. CHATTERJEE, A.K. MEIKAP, P. BARAT, S.K. BANDYOPADHYAY, PINTU SEN, and M.K. MITRA X-ray diffraction intensity data from three compositions of zirconium-base alloys, viz. ZIRCALOY- 2, ZIRLO, and Zr-25 pct Nb, having extensive application in nuclear industry were recorded using a PHILIPS PW 1730 X-ray diffractometer. Detailed studies using the recorded diffractometer data, keeping in view the recent trends in the powder diffraction analysis, were carried out with a view to evaluating the microstructural paramaters, including domain size, microstrain, faulting probability, and dislocation density. While faulting appears to be absent in all alloys, the average domain size and root-mean-square (rms) strain appear to be smaller compared to pure zirconium. However, both of these parameters, i.e., average domain size and rms strain tend to increase with the addition of Nb, as in ZIRLO, but display a diminishing trend with higher content of Nb, as is evident in the Zr- 2.5 pct Nb alloy. I. INTRODUCTION the detailed Fourier line shape analysis of various fault- unaffected and fault-affected reflections. The results have ZIRCONIUM alloys are used extensively in nuclear been compared with the earlier observations on pure zirco- industry because of their much lower neutron absorption nium. The observations made from these analyses are also cross section than other commercially available structural compared with the mechanical properties of these materials materials. [1] Among these alloys, ZIRCALOY-2* and Zr-2.5 and a correlation has been sought. *ZIRCALOY-2 and ZIRLO are trademarks of Westinghouse Electric Company, Pittsburgh, PA. II. EXPERIMENTAL PROCEDURE AND pct Nb find extensive use as fuel cladding tubes and coolant METHOD OF ANALYSIS tubes, respectively, in power reactors. Another zirconium- The alloy ingots were prepared by double vacuum arc base tin, niobium, iron alloy, commonly known as ZIRLO,* melting followed by  quenching. The ingots were hot developed as a candidate material for fuel cladding tube has extruded at 800 °C and then air cooled. The flat diffracto- also been included in this study. These materials are used meter samples from the powders obtained by careful handfi- inside the reactor in cold-worked and heat-treated condi- ling of the homogenized alloy ingots have been prepared tions. [2] The initial microstructure of the cladding and coolant by making briquettes in standard sample holders using solu- tubes are of great concern from the point of view of irradia- tion of canada balsam in xylene as binder. [11,12] X-ray diffrac- tion-induced creep and irradiation-induced growth in these tion profiles have been recorded using a PHILIPS* PW alloys used inside the reactors. [3,4,5] It is well known that irradiation-induced dimensional changes can impose signifi- *PHILIPS is a trademark of Philips Electronic Instruments Corp., Mah- wah, NJ. cant design limitations and can limit the life expectancy of the reactor. The preirradiation dislocation network is thought 1730 X-ray diffractometer. The diffraction profiles of fault- to contribute to irradiation growth at high fluences. [6] The unaffected reflections, namely, 10.0, 00.2, 11.0, 11.2, and irradiation growth increases as the degree of cold work 00.4, and fault-affected reflections, namely, 10.1, 10.3, 20.1, increases [7,8] and has been reported to vary with the disloca- 10.2, 10.4, 20.2, and 20.3, were recorded at room tempera- tion density. ture at a step width of 0.02 deg using CuK a radiation. A X-ray diffraction line profile analysis has been widely separate portion of the powdered samples obtained from the applied for the evaluation of microstructural parameters in homogenized alloys by hand filing was annealed at 750 °C different deformed metals and alloy system. [9,10] In the pres- for 5 hours under vacuum in quartz capsules and cooled in ent investigation, the microstructural parameters such as furnace at the rate of 5 °C per hour. The diffractometer coherently scattering domain size, microstrains within the samples prepared from annealed powders were used as the domains, stacking faults, and dislocation densities of these standard for the correction of instrumental aberrations by deformed zirconium-base alloys have been determined from Stokes’ method. [9–13,15–18] The diffraction profiles for zirco- nium 2.5 pct Nb (annealed) are shown in Figure 1. The detailed Fourier analyses on the diffraction profiles have P. MUKHERJEE, P. BARAT, S.K. BANDYOPADHYAY, and PINTU been performed for these hexagonal-base alloys in the way SEN, Scientists, are with the Variable Energy Cyclotron Centre, Calcutta 700 064, India. S.K. CHATTOPADHYAY, Lecturer in Metallurgy, S.K. described earlier. [12,13,15–17] The Stokes’ corrected Fourier CHATTERJEE, Assistant Professor in Physics, and A.K. MEIKAP, Lecturer coefficients [18] (A L ) for various values of L (A ˚ ) have been in Physics, are with R.E. College, Durgapur 713 209, India. M.K. MITRA, calculated and are shown in Figures 2(a), 3(a), and 4(a) for Professor in Metallurgy, is with Jadavpur University, Calcutta 700 032, ZIRCALOY-2, ZIRLO, AND Zr-2.5 pct Nb alloys for fault- India. Manuscript submitted March 8, 1999. unaffected and Figures 2(b), 3(b), and 4(b) for fault-affected METALLURGICAL AND MATERIALS TRANSACTIONS A VOLUME 31A, OCTOBER 2000—2405