Eutectic solidification processing via bulk melt undercooling

The control of eutectic microstructures is generally achieved via controlling the growth velocity, thermal gradients and the alloy composition. While current efforts in producing in-situ nanocomposites are centered on conventional rapid solidification processing (RSP), we describe here a more non-traditional processing of eutectics by RSP via bulk melt undercooling of near-eutectic compositions. It will be shown that a wide variety of microstructures can be produced in alloys with the same composition. These include the formation of metastable phases, growth of coupled eutectic compositions and the formation of mixed metastable/stable eutectics. These effects are discussed using examples of rapidly solidified Nb-Si alloys processed in a containerless environment. (C) 1997 Elsevier Science S.A.