Morphology and crystallography of unidirectionally solidified Zn-Al eutectic

• Published in: Journal of crystal growth Vol. 37; no. 3; pp. 301 - 308
• Main Authors: Singh, B., Smith, I.O., Chadwick, G.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1977
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/0022-0248(77)90124-5

The morphology and crystallography of unidirectionally solidified Zn-Al eutectic has been studied by optical and electron metallography and Laue back-reflection X-ray analysis. A preferred orientation relationship between the Zn-rich and Al-rich phases has been determined from analysis of Kikuchi line patterns obtained simultaneously from both phases and found to be: (0001)Zn // (111)Al // habit plane, <1 2 10>Zn // <1 1 0>Al ≃ // growth direction. Eutectic grains were found to rotate at rates of up to 4° per mm and both left and right hand rotations were observed. The interface plane in both left handed and right handed rotating lamellar grains lies on <5 1 4 0> zones and does not contain the growth direction which is very close to . Current ideas of rotation mechanisms are reviewed, no theory being found satisfactory. The precipitation of Zn in the Al-rich lamellae due to the monotectoid reaction has also been investigated by electron metallography.