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Friction stir welding (FSW) is rapidly becoming accepted as a viable manufacturing process for aerospace applications. One potential area of concern, however, is the corrosion resistance of some FSW joints. While the corrosion resistance of friction stir welded 7075 aluminum has been investigated, and attempts made to enhance its corrosion resistance through different combinations of starting temper and post-weld artificial aging (PWAA) treatments, a clear approach for selecting pre-temper conditions and PWAA processing has not emerged. For this investigation, FSW butt-welds in sheets of 0.125-inch 7075-T73 and 7075-T6 were given a variety of PWAA treatments, some of which were developed previously by other authors. Thermal treatments were evaluated using optical microscopy, exfoliation, electrical conductivity, microhardness, tensile, and fatigue crack propagation testing. An important conclusion drawn from this work is that 7075-T73 can be friction stir welded and post-weld aged in a manner that produces superior exfoliation resistance and good mechanical properties without invalidating the bulk parent material temper specified in AMS 2770G.

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The use of poly methyl methacrylate (PMMA) based bone cement as a grouting agent for the fixation of orthopaedic implants has been in practice for nearly fifty years. Fatigue fracture has been identified as the primary cause of cement failure. Implant loosening due to the failure of the cement is one of the major factors necessitating revision surgery. The need for a more fatigue resistant bone cement is well documented in literature, and one method of producing a more fatigue tolerant bone cement is to reinforce it with short fibers.The fundamental objective of this work was to investigate the possible improvement of the fatigue characteristics of bone cement by incorporating two types of fiber reinforcement; short flexible fiber Polyethylene Terephalate (PET) fibers and stiff milled carbon fibers. The effects of the fiber reinforcement on the bone cement were determined experimentally. Since fatigue characteristics are known to have considerable scatter, the experimental data were analyzed statistically, the effect of the fiber reinforcement was also analyzed using a theoretical model coupled with extensive scanning electron microscopy of the fractured surfaces. The results of the research indicate that the fiber reinforcement improved the fatigue resistance of the bone cement. This could potentially lead to a more fatigue tolerant bone cement, which would delay implant loosening and the need for revision surgery.

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