Rapid Solidification Processing and Powder Metallurgy of Al Alloys.

Abstract : Regarding work on the development of microstructure during rapid solidification, three areas have been addressed. The first of these involved a determination of the mechanism of formation of the so-called zones A and B in hyper-eutectic AL-transition metal alloys. The second area of work involving the development of microstructure concerns submerged phase transformations. In a study of AL-Be hyper-eutectic alloys, it was determined that solidification proceeded by a set of phase transformations that may be described by a monotectic reaction. The third area of study concerning microstructural development involves quasi-crystalline AL alloys. In fact, work done in this program has concentrated on the potentially beneficial aspects of quasi-crystalline phases in the microstructure of AL alloys. Work on the consolidation of particulate has concentrated on the use of conventional techniques (.e. extrusion) and novel processes (i.e. dynamic compaction). An estimate of the mechanical properties of rapidly solidified AL alloys has been obtained. As explained above, the effect of extrusion is to cause decomposition of the rapidly solidified microstructure. A comparison has been made, using the alloy AL-8Fe-2Mo, between the tensile properties of the decomposed microstructure (.e. extruded) and sub-scale test specimens produced by laser surface melting, consisting entirely of zone A.