Effects of casting parameters on microstructure and dendrite morphology of ZA27 zinc based alloy

Abstract

The effects of several casting parameters on microstructure and dendrite morphology of ZA27 alloy have been investigated. The results indicate that rising pouring temperature, solidifying in the mould with large chilling ability or with small diameter cavity may change the primary phase from the normal equiaxed dendrites to feathery grains. Four lines of secondary dendrite arms may form around the primary trunk of a feathery grain. Two of them exist in the twin plane (111) and the other two have an angle of 70?5u with the twin plane. All of them have an angle of 60u with the trunk. The former two lines are easier to grow up than the other two lines. Therefore, the feathery grains overlapped by laminar dendrites are the most common. The formation of the feathery grains can be divided into three stages, nucleation and growth, variation of growth direction and formation of laminar feathery grains.