Microstructure of binary Mg-Al eutectic alloy wires produced by the Ohno continuous casting process

Abstract

Directionally solidified binary Mg-Al eutectic alloy wires of approximately 5 mm in diameter were produced by the Ohno continuous casting (OCC) process and the mi-crostructure was examined. It was found that the wires possess obvious unidirectional growth characteristic along its axial direction. The micro structure consists of parallel columnar grains that resulted from the competitive growth of equiaxed grains solidified on the head of dummy bar. Each columnar grain comprises regular eutectic αa-Mg and β-Mg17Al12 phases, which grew along the axial direction of the wires. The morphology of the eutectic is mainly lamellar, meanwhile rod eutectic exists. The formation of rod eutectic was attributed to the “bridging effect” caused by incidental elements in the alloy.