SEDL / STP / STP430-EB / STP41823S

Electron Microscopy Applied to a Unidirectionally Solidified Al-Al³Ni Eutectic Alloy

Tice, W. K.
Research engineer, research supervisor, and research engineerpersonal member ASTM, United Aircraft Research Laboratories, East Hartford, Conn

Lasko, W. R.
Research engineer, research supervisor, and research engineerpersonal member ASTM, United Aircraft Research Laboratories, East Hartford, Conn

Lemkey, F. D.
Research engineer, research supervisor, and research engineerpersonal member ASTM, United Aircraft Research Laboratories, East Hartford, Conn

Pages: 11    Published: Jan 1968

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Abstract

Optical methods, replicas, and thin foils prepared by both ultramicrotomy and electropolishing techniques, as well as direct surface analysis by emission microscopy, were evaluated in order to characterize the interfacial crystallography and morphology of unidirectionally solidified Al-Al³Ni eutectic specimens. Replicas gave somewhat limited data due to the presence of subtle artifacts created during metallographic preparation, while emission microscopy gave considerably more topographical definition than that obtained by optical methods. Microtomed sections also proved to be of little value due to the plastic deformation induced by cutting. On the other hand, thin foils prepared by electropolishing methods clearly resolved the morphology of the dispersed Al³Ni phase and permitted direct determination of the interfacial plane, as well as the cristallographic orientation relationships between Al-Al³Ni. The A³Ni rods were found to be bounded by prismatic facets which were coincident with low index planes of aluminum lying in the ⟨110⟩ zone axis.