Structure, properties and fracture of friction stir welds in a high-temperature Al-8.5Fe-1.3V–1.7Si alloy (AA-8009)

Friction stir welds produced in a rapidly-solidified, powder metallurgy Al-8.5Fe-1.3 V-1.7 Si (wt.%) alloy were characterized in order to investigate the effects of deformation during welding on the weld zone microstructure, hardness, tensile properties, and fracture behavior. A weld produced using a tool rotational speed of 1200 rpm and a traversing rate of 4.3 mm/s exhibited a repetitive pattern of dispersoid-depleted bands that were attributed to the intense deformation that occurred in the vicinity of the tool. The significant softening associated with these regions, and the presence of occasional, irregularly-shaped voids near the boundary between the base metal and the weld zone on the advancing side of the weld, promoted a weld tensile strength of 60–70% of the base metal. The application of a lower tool rotational speed of 428 rpm and a lower traversing rate of 1.9 mm/s promoted fewer bands and a more uniform dispersoid distribution throughout the weld zone, and an absence of defects along the weld zone/base metal interface. Tensile strength of these welds approached 90% of the base metal. Fracture of the transverse-weld oriented tensile specimens for both weld types consistently occurred near the boundary between the weld zone and the base metal on the advancing side of the weld zone, with tensile specimen ductilities appreciably lower than that of the base metal. C 2006 Springer Science + Business Media, Inc.