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Rapidly solidified Al–Cr alloys: Crystalline and quasicrystalline phases

Swamy, VT and Ranganathan, S and Chattopadhyay, K (1989) Rapidly solidified Al–Cr alloys: Crystalline and quasicrystalline phases. In: Journal of Materials Research, 4 (3). pp. 539-551.

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Abstract

Rapidly solidified Al–Cr alloys up to 20 at. % Cr were studied to delineate the extent of crystalline and quasicrystalline phase formation in these alloys in comparison with as-cast alloys by using transmission electron microscopy and x-ray diffraction technique. The icosahedral quasicrystals are observed from 7 to 15 at. % Cr alloys, while equilibrium ?–Al11Cr2 phase is completely absent. Both rapid solidification and subsequent thermal decomposition studies indicate that the main competing phase is ?–Al2Cr up to 15 at. % Cr. Beyond this composition ?–Al4Cr is the dominant phase together with a small amount of ?4–Al7Cr3. We have shown that the electron diffraction patterns of Al–Cr quasicrystals are often associated with a diffuse intensity distribution, indicative of short-range order. The change in quasilattice constant with composition suggests the existence of structural vacancies. Further, a sudden change from coarse to ultrafine quasicrystalline grain structure in Al-7 at. % Cr alloy points to a change in nucleation mechanism from heterogeneous to homogeneous mode during the rapid solidification.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to The Materials Research Society.
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 25 Aug 2010 06:28
Last Modified: 19 Sep 2010 06:14
URI: http://eprints.iisc.ernet.in/id/eprint/31398

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