Microstructural features and heat flow analysis of atomized and spray-formed Al-Fe-V-Si alloy
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I.
INTRODUCTION
The benefit of rapid solidification processing is well established in synthesizing aluminum alloys for high-temperature applications in aerospace structures. The alloy design for high-temperature service necessitates addition of alloying elements which form thermally stable dispersoids in the aluminum matrix. Among these, Al-Fe-V-Si alloy produced by rapid solidification planar-flow casting method has attracted considerable interest.[1,2] A commercial alloy 8009 (FVS0812: Al-8Fe-1.4V-1.7Si by wt pct) developed by Allied Signal (New Jersey, USA) has excellent room-temperature and high-temperature properties.[3,4] The microstructure of Al-Fe-V-Si alloy is characterized by a fine dispersion of silicide Al12(Fe, V)3Si phase with the bcc structure.[5,6] It was reported by Munson[7] and Skinner et al.[8] that the addition of V in ternary Al-Fe-Si alloy stabilizes the cubic phase. The cubic phase has practically no tendency to transform and has minimal coarsening rate even when held for 100 hours at temperatures up to 480 7C.[8,9,10] This structure is closely related to that of quasicrystals.[11–16] Blank et al.[17] employed laser surface modification technique to synthesize metastable intermetallic phases in AlFe-V-Si alloys. Srivastava et al.[18] discussed the effect of processing methods on the microstructural development in a rapidly solidified Al-Fe-V-Si alloy. A.K. SRIVASTAVA, formerly Research Associate with the Centre for Advanced Study, Department of Metallurgy, Indian Institute of Science, is Scientist, Metals and Alloys Group, National Physical Laboratory, New Delhi-110 012, India. S.N. OJHA, Professor, is with the Centre for Advanced Study, Department of Metallurgical Engineering, Banaras Hindu University, Varanasi-221 005, India. S. RANGANATHAN, Professor, is with the Centre for Advanced Study, Department of Metallurgy, Indian Institute of Science, Bangalore-560 012, India. Manuscript submitted October 27, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
The Al-Fe-V-Si alloy processed by the planar flow casting or inert gas atomization process requires further consolidation by hot rolling or hot extrusion methods.[4] Consequently, several processing steps involved in this route necessitate careful process control to improve the overall yield of the finished product. Alternatively, the spray forming process offers to synthesize the alloy, eliminating several intermediate steps used with powder metallurgy methods of materials consolidation. The spray forming process refers to the energetic disintegration of molten material by high-energy inert gas jets into micronsize droplets and the subsequent deposition of the mixture of solid, liquid, and partially solidified droplets on a substrate.[19,20] The capability of the process in producing nearnet-shape components employing a minimum number of processing steps is an attractive proposition.[21,22,23] In addition, rapid solidification inherent in spray deposition provides fine-grained microstructures, increased solid solubilities, nonequilibrium p
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