Papers by Author: E. Sarath Menon

Abstract: FSP is an allied technology of friction stir welding (FSW). These processes are reviewed and the additional considerations such as processing pattern and step over distance in FSP are introduced. The application of FSP to cast metals including AA5083, Al-7Si and NiAl bronze is summarized. As-cast microstructures may be converted to a wrought condition in the absence of external shape change and the extent of grain refinement and homogenization of microstructure is documented. The FSP-induced superplastic response of AA5083, enhanced ductility of Al-7Si and surface hardening of NiAl bronze are summarized as examples of properties developed by FSP.

Abstract: Multi-pass FSP was conducted on continuously-cast (CC) AA5083 materials in the as-cast condition. Stir zone grains were refined to ~1.0 – 3.5μm in size and highly superplastic response was obtained during tension testing of the as-processed materials at 450°C (>1200 pct. elongation at 10-1 s-1). Current models of recrystallization do not predict adequately the highly refined grains and predominantly random textures that are observed in stir zones. Grain refinement during FSP is accompanied by refinement and redistribution of non-deforming constituents in the absence of particle fracture. The mechanics of the homogenization process remain to be established and requirements for redistribution mechanisms will be summarized. Comparison reveals that results from FSP of the as-cast material are superior to those attained in conventional processing.

Abstract: Parameters for multi-pass FSP include the pattern of tool traverse and step-over distance between successive passes. Multi-pass FSP was conducted on as-cast NiAl bronze and as-cast AA5083 in order to modify stir zone (SZ) microstructures and mechanical properties. Highly refined and homogeneous SZ microstructures may be produced by FSP. Refined and equiaxed grain structures reflect recrystallization during FSP; mechanisms leading to homogenization by redistribution of microstructure constituents remain to be determined. Refined microstructures exhibit enhanced ambient-temperature properties and superplasticity at elevated temperatures.