The effect of hot-rolling on chill-cast AI-AI 3 Ni, chill-cast AI-AI 2 Cu, and Unidirectionally Solidified AI-AI 3 Ni Eu
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I.
INTRODUCTION
SEVERAL authors have reported hot-working aligned eutectic alloys; ~-5 however, there have been no detailed investigations of the effect of hot-working on the eutectic microstructure and mechanical properties. Rohatgi and Prabhakar ~have described how chill-cast A1-A13Ni eutectic can be wire drawn to produce a reduction in thickness of greater than 95 pct; this is surprising when the unidirectionally solidified AI-A13Ni eutectic has been shown to fail in tension with a fracture strain no greater than 1 pct even at temperatures just below the eutectic temperature. 6 The solidification behavior and the room temperature mechanical properties of the chill-cast A1-AI3Ni and AI-AlzCu eutectic alloys have been reported previously by the present authors. 7 From this work, where the chill-cast eutectic alloys were produced by casting into preheated mild steels molds (heated to 50 or 150 K above the respective eutectic temperatures) placed on either a water-cooled or plain copper chill, it was shown that the different casting conditions had little effect on the resulting mechanical properties. The object of the present work was to investigate the effect of hot-rolling on the microstructure and room temperature mechanical properties of unidirectionally solidified AI-AI3Ni eutectic, chill-cast A1-AI3Ni eutectic, and chillcast A1-A12Cu eutectic alloys. E S. J. JARDINE and B. CANTOR, formerly with the Department of Engineering and Applied Sciences, Sussex University, Falmer, Brighton, BN1 9QT, Sussex, United Kingdom, are, respectively, Director/Secretary of Smethwick Shopfitters Ltd., 246 Wharfdale Road, Tyseley, Birmingham, B11 2EG, United Kingdom, and Lecturer, Department of Physical Metallurgy and Science of Materials, Oxford University, Oxford, United Kingdom. Manuscript submitted August 11, 1981.
METALLURGICALTRANSACTIONSA
II.
EXPERIMENTAL M E T H O D
The AI-A13Ni and AI-A12Cu eutectic alloys were prepared by induction melting 99.9 pct commercial purity AI with either 99.99 pct purity Ni or Cu, respectively, in recrystallized alumina crucibles under a dynamic argon atmosphere. Unidirectionally solidified A1-AI3Ni eutectic single crystals, typically 300 mm long, 20 mm wide, and 3 mm thick, were prepared in a conventional horizontal Bridgman crystal grower at a solidification rate R of 3 • 10-5 m 9 s -*, with a temperature gradient G of - 2 • 10-4 K 9 m -*. The unidirectionally solidified eutectic crystals consisted of an A1 matrix containing --10 vol pct A13Ni fibers fully aligned along the solidification direction, with an interfiber spacing of 1.2/~m. Chill-cast eutectic ingots, typically 100 mm long with a 10 mm cross-section, were produced by casting the eutectic alloys into preheated split-mild steel molds mounted on copper chills, as follows: (a) the A1-A13Ni eutectic alloy was cast onto a water-cooled chill with a mold temperature of 1073 K, and (b) the AI-A12Cu eutectic alloy was cast onto a plain chill with a mold temperature of 973 K. These conditions were selected as the variation of solidifica
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