Dynamic Processing Characteristics for Melt Spinning
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DYNAMIC PROCESSING CHARACTERISTICS FOR MELT SPINNING R.P.I. ADLER AND S.C. HSU GTE Laboratories Incorporated, 40 Sylvan Road, Waltham, MA 02254 ABSTRACT Although during melt spinning the ongoing interactive thermal and mass transfer processes are affected by both materials properties and process variables, a simplified resolution for this complex system can be obtained by first identifying and characterizing those substrate and melt material combinations that provide useful, steady state production performance. A previously described standardized falling droplet/inclined plane test procedure that simulates the dynamic wetting and solidification behavior during melt spinning is being used to generate a range of phenomenological information for combination of melt (droplet) and substrate (plane). Real differences in dynamic wetting/solidification patterns are being correlated with melt spinning performance. Phenomenological and process characteristics from some melt spinning experiments for representative material combinations have been analyzed to verify the validity of these projected correlations as well as to provide complementary information about the interrelation of melt puddle/substrate dynamics with product dimensions and quality. INTRODUCTION As the potential advantages of using rapidly solidified materials become more apparent and applications more numerous, it will be more incumbent on materials suppliers to develop higher capacity processes for consistently producing a wide range of high quality crystalline and amorphous alloys with uniformly reproducible metallurgical and dimensional characteristics. Melt spinning is one rapid solidification processing method that has already shown much commercial promise for a specific group of alloys. However, further progress to generate a more universal processing capability for a greater range of materials requires a better understanding of this continuous solidification phenomenon to allow control and optimization of processing practices. In its simplest elements, melt spinning involves the dynamic interaction of a bounded molten metal form undergoing unidirectional shearing contact with a flat heat absorbing solid metal substrate. However, the superpositioning of motion, thermal gradients, and the possibility of concurrent solidification complicates the analysis of dynamic wetting compared to classical sessile drop wetting experiments 11, 2]. Thus the characterization of the dynamic wetting and solidification phenomena occurring during rapid solidification has important scientific and technological implications. With melt spinning additional dynamic complexities influencing the spreading flow of the melt are introduced by: (1)the boundary layer of gas attached to the moving substrate surface; (2) the effectively steady state but geometrically transient coupled mass and heat flow patterns within the melt puddle; (3) the possible temporal changes in the thermal, morphological and chemical parameters of the substrate surface during operation; and (4) the systematica
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