Noise abatement and internal vibration absorption in potential structural materials

Efforts have been directed toward achieving higher yield strengths in high damping cobalt-iron base alloys by adding nickel, aluminum and manganese. Substantial increases have been achieved through aluminum and manganese additions at low levels. The range of loss factors and yield strengths which are attainable exceed currently available commercial materials. Measurement of the temperature dependence of the loss factor of the cobalt-iron alloy for comparison with Nitinol and Incramute show that the cobalt-iron alloy retains a high loss factor up to 120 C while the latter materials exhibit a drop in loss factor well below 100 C. The effects of alloying additions of iron and manganese as well as reduction in grain size are being investigated as a means for reducing the brittleness of copper-aluminum-nickel alloys which exhibit thermoelastic martensitic transformations. These transformations provide high damping characteristics and high loss factors.