Banding formation and eutectic lamellar growth in directional solidified Ni50Al20Fe30 alloy

Abstract

Banding formation and eutectic lamellar growth in a directionally solidified Ni~,AlzoFe3o alloy were investigated. It was found that the banding area consists of two layers. The first layer is a ~, layer, while the subsequent one is a [3 layer. The composition of various phases around the banding area changes with the solidification process. The banding is formed by two steps process and caused by factors such as the fractions during the sample growth process. It was found that the band was found at relatively low growth rate. Therefore, this study indicates that increasing the growth rate is an effective method to eliminate the band formation. Eutectic lamellae nucleate and grow again after the banding formation. During the initial transition lamellar growth, the relationship between the square lamellar spacing, 72, and the distance from, the banding, d, can be described by the following equation: yz = K [1-exp(A.d)] where K and A are constant.