Solidification of Liquid Distributed in its Primary Matrix Phase of Al-10Cu-Fe Alloy and Their Tribological Characteristics

摘要

Solidification behavior of liquid phase entrained in its primary solid has been investigated. A hypoeutectic alloy based on Al-Cu-Fe system containing Fe and Si was thermal cycled between semisolid regions to low temperatures. The freezing characteristics of the liquid were recorded in inverse rate cooling curves. The continuous network of the liquid phase progressively changed into isolated droplets with their different size and size distribution. Such droplets revealed undercooling of the melt varying from 20 to 35 A degrees C below the eutectic temperature of the alloy. This behavior of melt undercooling is discussed in light of independent nucleation events associated with freezing of droplets. Solidification structure of droplets revealed particulate eutectic phases in contrast to lamellar eutectic microstructure in the interdendritic region of the as-cast alloy. The droplet distribution and their solidification structure resulted in an improvement in tribological characteristics of the alloy. This effect is correlated with features of wear surfaces generated on the matting surfaces.