J. Ogren

On identifying the most critical step in the sequence of heat treating operations in a 7249 aluminum alloy

Abstract The variables studied in the heat treatment processes of the 7249 aluminum alloy were 5 solution treatment temperatures (445–505xa0°C), 3 quenching media (water, 20% polyalkylene glycol, and air), 3 natural aging times (0, 4, and 168 h) and 3 artificial aging temperatures (111, 121, and 131xa0°C). The effect of varying these parameters on the mechanical strength was discussed. Quenching is identified to be the most critical step in this process.

Effect of Tempering and Baking on the Charpy Impact Energy of Hydrogen-Charged 4340 Steel

Tempered AISI 4340 steel was hydrogen charged and tested for impact energy. It was found that samples tempered above 468xa0°C (875xa0°F) and subjected to hydrogen charging exhibited lower impact energy values when compared to uncharged samples. No significant difference between charged and uncharged samples tempered below 468xa0°C (875xa0°F) was observed. Neither exposure nor bake time had any significant effect on impact energy within the tested ranges.

Evaluation of the Effects of Powder Coating Cure Temperatures on the Mechanical Properties of Aluminum Alloy Substrates

The effects of curing temperature, based on new, low-temperature powder coating methods and traditional high-temperature powder coating methods, were studied. Heat-sensitive aluminum alloys (2024-T3, 6061-T6, and 7075-T6) were subjected to two different heat-treatment cycles, which were based on temperatures of 121 and 204xa0°C. Findings indicate that although both cure temperatures achieved powder coatings adhesion and thickness appropriate for industrial uses, the high-temperature cure treatment negatively affected the mechanical properties.

Evaluation of Advanced Adhesives for Aerospace Structures

Polymer adhesives are finding increased use in panel joining applications in aircraft and aerospace structures where the applied stresses permit their use and where a uniform stress distribution is needed. One such adhesive, Hysol EA-9394™, was compared to three other formulations in this study. The new formulations were Hysol EA-9396, Hysol EA-9396 filled with nickel nanofibers and mixed by machine (Jamesbury Blender), and Hysol EA-9396 filled with nickel nanofibers and hand mixed in the laboratory. The comparison consisted of measuring shear lap strengths of aluminum test pieces bonded together with the candidate adhesives. The mechanical tests were supplemented by a Weibull analysis of the strength data and by a visual inspection of the failure mode (adhesive/cohesive). The lap shear strengths (fracture stress values) of all three Hysol EA-9396 adhesives were greater than that of the baseline Hysol EA-9394 polymer.