Optimizing superplastic response in lithium containing aluminum-magnesium alloys.

http://archive.org/details/optimizingsuperp00munrNAN

Surface engineering of corrosion, environmental fracture, cavitation & impingement resistant materials

There is a need for materials that are highly resistant to corrosion, environmental fracture, cavitation, and liquid droplet impingement, especially within the Navy. Several novel approaches to enhancing the cavitation and impingement resistance of ship and aircraft components are discussed. These approaches include: (1) new ultra-hard amorphous-metal coatings, applied with a hydrogen-fueled HVOF process; (2) coatings with extreme interfacial bond strength, produced with LLNL’s new laser-based HVLAD process; (3) nickel aluminide coatings with nano-diamond strengthening and hardening, applied with a combination of cold spray and post- deposition heat treatment with intense diode sources; (4) diode-assisted friction stir processing for the elimination of surface defects in large cast propellars; and (5) laser peening for the elimination of residual tensile stresses, and the associated fatigue and environmental cracking. This paper discusses several novel approaches to the development of such materials, through surface engineering, and the benefits that will be enjoyed if such a developmental effort is successful.Department of Energy (DOE)Contract DE-AC52-07NA2734

Peak Stir Zone Temperatures during Friction Stir Processing

The stir zone (SZ) temperature cycle was measured during the friction stir processing (FSP) of NiAl bronze plates. The FSP was conducted using a tool design with a smooth concave shoulder and a 12.7-mm step-spiral pin. Temperature sensing was accomplished using sheathed thermocouples embedded in the tool path within the plates, while simultaneous optical pyrometry measurements of surface temperatures were also obtained. Peak SZ temperatures were 990 ⁰Cto 1015 ⁰C (0.90 to 0.97 TMelt) and were not affected by preheating to 400⁰C, although the dwell time above 900 ⁰C was increased by the preheating. Thermocouple data suggested little variation in peak temperature across the SZ, although thermocouples initially located on the advancing sides and at the centerlines of the tool traverses were displaced to the retreating sides, precluding direct assessment of the temperature variation across the SZ. Microstructure-based estimates of local peak SZ temperatures have been made on these and on other similarly processed materials. Altogether, the peak-temperature determinations from these different measurement techniques are in close agreement

Friction stir processing / welding of NiAl bronzes

Friction stir processing (FSP) of as-cast NiAl bronzes converts the as-cast microstructure to a wrought condition in the volume of materials subjected to the process. This results in improved properties in the absence of component shape change. With the development of portable systems, friction stir processing may enable in situ repair of defective components such as propellers and thus avoid expensive procedures such as dry docking for such repairs.Approved for public release; distribution is unlimited

Friction stir processing / welding of NiAl bronzes

Research ProjectFriction stir processing (FSP) of as-cast NiAl bronzes converts the as-cast microstructure to a wrought condition in the volume of materials subjected to the process. This results in improved properties in the absence of component shape change. With the development of portable systems, friction stir processing may enable in situ repair of defective components such as propellers and thus avoid expensive procedures such as dry docking for such repairs

Materials research at NPS

Metals are useful partly because they can bend permanently before they break, i.e. they can deform plastically. Metal plasticity is usually evaluated by measurement of the percentage elongation during tensile testing and the result is referred to as the ductility of the material. Ductility of structural metals is typically 10-50% at ambient temperature and perhaps attains 100% at elevated temperatures

Thermomechanical processing of Al alloy 2090 for grain refinement and superplasticity.

http://archive.org/details/thermomechanical00spirNAN

Resume of Terry Robert McNelley, 1980

Naval Postgraduate School Faculty Resum

Resume of Terry Robert McNelley, 1976

Naval Postgraduate School Faculty Resum