A literature survey of aluminium powder metallurgy (PM) for high-strength applications was undertaken. Improvements in aluminium-base alloys made via ingot metallurgy (IM) are reaching the point of diminishing returns. PM offers an alternative technology, capable of producing alloys having improved fatigue, corrosion, and stress-corrosion resistance, as well as improved strength and toughness at room or elevated temperatures. The steps involved in powder metallurgy: powder manufacture, powder processing, de-gassing, and consolidation, are described. The merits and deficiencies of the various processes for each step are compared. The key to successful application of AI powder metallurgy alloys appears to be the de-gassing and consolidation of the powder. The properties of several new PM alloys are compared, with particular emphasis on highstrength, corrosion-resistant alloys and alloys developed for use at elevated temperatures.
HSLA-65 (ASTM A945) is a new structural steel of interest to the Navy shipbuilding community. The feasibility of joining the alloy by the friction stir welding (FSW) process was assessed. Single-pass weldments in 6.4-mm plates and two-pass weldments in 12.7-mm plates were successfully made. The FS weldments were evaluated by performing transverse tensile and bend tests; hardness, Charpy V-notch toughness, and salt spray corrosion testing; and metallographic evaluations. The weldments exhibited satisfactory transverse weld tensile strength, ductility, Charpy Vnotch toughness, and hardness. Visual examination revealed no difference in salt spray corrosion rates between the stir zone, the heat-affected zone, and the parent material. The results indicate that FSW does indeed have potential for joining ferrous alloys in shipbuilding, which should promote further efforts in this area.
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