Diffusion reaction in the zirconium-copper system
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Diffusion Reaction in the Zirconium-Copper System K. B H A N U M U R T H Y , G.B. KALE, and S.K. K H E R A Diffusion reaction occurring between two solids plays an important role in many metallurgical processes, such as cladding, carborizing, and diffusion bonding. Interdiffusion in the zirconium-copper system has been studied in a limited temperature range of 873 to 977 K to understand the compatibility between the two metals. The only earlier work t~ in this system refers to isothermal annealing at temperature in the vicinity of alpha-to-beta phase transformation of zirconium. These results confirmed the formation of C u a Z r and Cu3Zr in the diffusion zone. In the present studies, detailed investigations of the chemical diffusion in the zirconium-copper system are reported. Electron beam-melted zirconium (99.8 pct) ingots and high-purity copper (99.9 pct) plates were roiled to thin sheets of 3 - m m thickness. Diffusion couples of 10 x 5 • 3 m m were prepared from fully annealed (1173 K for 3 days) samples taken from these sheets. The mating surfaces of zirconium and copper were prepared by metallographic polishing up to 1-/xm diamond finish. The polished faces of zirconium and copper were
K. BHANUMURTHY, Scientific Officer, G.B. KALE, Scientific Officer, and S.K. KHERA, Research Coordinator, Diffusion Research Group, are with the Metallurgy Division, Bhabha Atomic Research Centre, Bombay 400 085, India. Ma)nuscript submitted July 18, 1991. METALLURGICAL TRANSACTIONS A
kept in contact with each other and were loaded in a specially made jig (at a pressure of 10 MPa) in order to ensure intimate contact between two surfaces. The entire assembly was placed in a vacuum furnace (10 -5 m m ) for diffusion bonding at 860 K for 10 minutes. The couples thus prepared were sealed under helium atmosphere and subsequently annealed in the temperature range of 873 to 977 K for periods between 0.5 and 20 hours in a preheated resistance furnace controlling the temperature within ___1 K with the help of a proportional controller. The concentration penetration profiles across the polished sections perpendicular to the diffusion direction were obtained on all of the couples. The electron probe microanalyses of the diffusion couples were carried out with a stabilized beam current of 80 nA at 15 KeV. These observed intensity ratios were corrected for atomic number, absorption, and fluorescence effects to get true concentrations, t21 Some of the diffusion couples were analyzed at the interface by X-ray diffraction to confirm the stoichiometry of the compound formed in the diffusion zone. Diffusion coefficients were evaluated by both the Boltzmann-Matano-Heumann and the Wagner methods from the concentration penetration profiles. The details of these two methods have been discussed elsewhere, t3m The typical back-scattered electron micrograph of the diffusion couple annealed at 977 K for 16 hours is shown in Figure 1. The micrograph clearly indicates the presence of two intermetallic compounds. The X-ray diffraction investigations of
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