J. Laakmann, MICROSTRUCTURE DEVELOPMENT AND ULTRAMICROHARDNESS OF ALFECE SOLIDIFIED UNDER FREE-FALL CONDITIONS, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 173(1-2), 1993, pp. 165-168
Small droplets of Al96Fe3Ce1 were solidified without a crucible under
free fall. The microstructure reveals three features: a segregation-fr
ee zone (zone A), followed by a cellular structure which subsequently
refines (zone B). The cellular structure consists of an aluminium soli
d solution matrix containing small (d < 100 nm) spherical AlFeCe preci
pitates surrounded by a lamellar eutectic wall of Al-Al3Fe. The ultra
microhardness of the segregation-free zone is approximately 2 GPa. Thi
s is 15% higher than the corresponding value of the coarse cellular zo
ne, which in turn is about 15% higher than the fine structure. While t
he hardness of zone A is equal to the values found for this zone in bi
nary Al-8at.%Fe alloys, the addition of cerium increases the hardness
of zone B by a factor of up to 1.5-1.7 as a result of dispersion harde
ning.