MICROSTRUCTURES AND MECHANICAL-PROPERTIES OF DISPERSION-STRENGTHENED HIGH-TEMPERATURE AL-8.5FE-1.2V-1.7SI ALLOYS PRODUCED BY ATOMIZED MELT DEPOSITION PROCESS

Dispersion-strengthened high-temperature Al-8.5 pct Fe-pct Si-pct V alloys were produced by atomized melt deposition (AMD) process. The effects of process parameters on the evolution of microstructures were determined using optical metallography and scanning and transmission electron microscopy. The extent of undercooling and the rate of droplet solidification were correlated with process parameters, such as melt superheat, metal/gas flow rates, and melt stream diameter. The size distribution and morphology of silicide dispersoids were used to estimate the degree of undercooling and the cooling rate as functions of process parameters. The tensile properties at 25-degrees-C to 425-degrees-C and fracture toughness at 25-degrees-C of these alloys produced with wide variations in dispersoids size and grain size were determined. Under optimum conditions, the alloy has ultimate tensile strength of 281 MPa and 9.5 pct ductility in the as-deposited condition. Upon hot-isostatic pressing and extrusion, the ultimate tensile strength increased to 313 MPa and ductility increased to 18 pct.