The effect of low-temperature toughness degradation on damage tolerance and life analysis methodology is discussed. Spectrum fatigue and fatigue crack growth tests were conducted and life predictions made on 7475-T761 aluminum. The retardation behavior was determined by conducting constant K single overload fatigue crack growth tests. The low-temperature environment (−54°C[−65°F]) improved the life of fatigue and fatigue crack growth tests subjected to several loading spectra. This may be partially attributable to stronger retardation effects at low temperatures. It is concluded that low temperature may be a factor in damage tolerance and life analysis only under certain conditions.

Characterization of Al-Fe-Ce alloys has been conducted in the areas of static and fatigue mechanical property behavior, corrosion behavior, and joining and fabrication methods. Evaluation of the elevated-temperature powder metallurgy materials, which were fabricated by the Aluminum Company of America (Alcoa) under Air Force Contract No. F33615-81-C-5096, was performed on both extruded and sheet products. The constant-amplitude fatigue and crack growth properties of these alloys are similar to those of 7091-T7E69 aluminum; however, no effect of R-ratio on fatigue crack growth was observed in the Al-Fe-Ce alloys. The corrosion resistance of the Al-Fe-Ce alloys is superior to that of other aluminum alloys, such as Alloys 7075, 2024, and 6061, under all conditions evaluated to date. Adhesive bonding, ultrasonic weldbonding, and spot welding have been demonstrated to be viable joining techniques. This research has helped to establish an initial data base on the Al-Fe-Ce alloys. Continuation of these studies will lead to application of these alloys, primarily as replacements for titanium.

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