Growth Temperature Measurements and Solidification Microstructure Selection of Primary Al 3Ni and Eutectic in the αAl-Al 3Ni System

Abstract

Competition between growth of contending primary phases and their eutectics is a key consideration in determining the solidification microstructure of a material that results from particular conditions. Application of the principle that solidification is led by the constituent which grows at the highest temperature under the prevailing conditions gives predictions that are in good accord with experimental fact. The necessary growth temperatures and their dependence on materials composition and solidification conditions have been measured, however, for rather few constituents in relatively few systems as yet. The present purpose is to extend to primary Al{sub 3}Ni and the Al-Al{sub 3}Ni eutectic in the Al-Ni system the measurements made earlier during Bridgman growth, for primary Al{sub 3}Fe(Al{sub 13}Fe{sub 4}) and for the Al-Al{sub 3}Fe and Al-Al{sub 6}Fe eutectics in the Al-Fe system. These measurements will be compared with predictions of dendrite and eutectic growth theory and related to the relevant boundary of the reported Al-Al{sub 3}Ni solidification microstructure selection diagram. Some preliminary results together with other findings were reported earlier in a cited reference.