Improved Properties of Lower-cost Titanium-alloy Materials for Aerospace Fastener Applications

摘要

A potentially lower-cost approach for the productionrnof advanced titanium and titanium-alloy materials hasrnbeen demonstrated using cryogenic technology. Nearnanornand nano-grained materials with high-anglernboundaries and finely-dispersed particulates have beenrnproduced through severe plastic deformation achievedrnwith high-energy ball-milling and subsequentrnconsolidation techniques. These materials offer thernpotential for significant improvements in materialrnproperties since the Hall-Petch relationship predicts thernstrengthening of materials by reducing the averagerncrystallite (grain) size. These features combine to impartrnexcellent strength levels, good ductility, and excellentrnmicrostructural thermal stability. Furthermore, thernstarting powders are macroscopically in the micrometerrnrange having pre-alloying capabilities that allow for easyrnhandling, cleaner surfaces, and no environmentalrndangers.rnThis paper summarizes the preliminary results of thernmacrostructures, microstructures, chemistries, andrnmechanical properties achieved via this cryogenicrnprocessing approach. Initial results for commerciallypurerntitanium material will be presented, that show nearnanometerrnsize nitride particles formed in-situ duringrnprocessing along with the resulting elevated temperaturernstability of the alloy. A comparison is made showing thernincreases achieved in certain mechanical properties ofrnthe cryomilled near-nano and nanocrystalline materialsrnover those of conventionally-produced materials.