Studies of lattice imperfections in deformed aluminum-based lithium alloys by X-ray diffraction
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I. INTRODUCTION
ALUMINUM-LITHIUM alloys, extensively used in aircraft industries, are known for their higher strength, higher elastic moduli, and lower density. The drawback of having low fracture toughness and poor ductility can, however, be greatly reduced by the addition of alloying elements like Mg and Zr.[1,2] Considering these properties, five different compositions of Al-based zirconium-lithium and magnesium-lithium alloys, prepared and supplied by Hindustan Aircraft Industry (Bangalore, India), were chosen for investigation. The main aim of this investigation was to correlate the results with available X-ray diffraction (XRD) studies on aluminum-based alloy systems. This investigation of lattice imperfection is also a continuation of our work on the series of Al-based alloys.[3–6] The X-ray line-profile analysis used in the present analysis is an established technique and is widely applied[7,8,9] for the investigation of lattice imperfections by XRD. The five different Al-based alloys in the fcc phase taken under investigation have nominal compositions, in wt pct, of Al-0.1Zr0.1Li (alloy I), Al-0.1Zr-0.5Li (alloy II), Al-0.1Zr-1.0Li (alloy III), Al-4.5Mg-1.5Li (alloy IV), and Al-1.1Mg-1.8Li-1.8Cu0.15Zr (alloy V). The X-ray Fourier line-profile analysis[9,10] has been done on the alloys in the deformed (cold-worked) state, considering multiple reflections, and the results obtained were compared with other Al-based alloys[3,4,11] so as to investigate the role of solutes in the deformed matrix. II. EXPERIMENTAL PROCEDURE AND METHOD OF ANALYSIS The homogenized alloy ingots supplied by M/s. Hindustan Aeronautics (Bangalore, India) were deformed by hand filing
J. GHOSH, Lecturer, is with the Dr. B.C. Roy Engineering College, Durgapur–713 206, India. P. MUKHERJEE and P. BARAT, Scientists, are with VECC, Kolkata 700 064, India. S.K. CHATTOPADHAYAY, Assistant Professor, Department of Metallurgical Engineering, and S.K. CHATTERJEE, Professor, and A.K. MEIKAP, Assistant Professor, Department of Physics, are with the National Institute of Technology, Durgapur–713 209, India. Contact e-mail: [email protected] Manuscript submitted April 5, 2002. METALLURGICAL AND MATERIALS TRANSACTIONS A
using a jeweler’s file. The hand filing, which is an historically established technique, may introduce extreme shear deformation within the lattice. The flat diffractometer samples from the filings of both the cold-worked and annealed states for each composition were prepared from the filing after sieving through a 250-mesh screen and by making briquettes of sizes suitable for diffractometry, as was done earlier.[3–6] The XRD profiles of both the cold-worked and the annealed samples were recorded from 30 to 105 deg by a PHILIPS* *PHILIPS is a trademark of Philips Electronic Instruments Corp., Mahwah, NJ.
PW 1730 X-ray diffractometer. The annealed samples (annealed at 450 °C for 5 hours and quenched in ice-cooled water) from each alloy were taken as standard. The X-ray profile recording was done in step-scanning mode of 0.0
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