Optimization of Blended-Elemental Powder-Based Titanium Alloy Extrusions for Aerospace Applications

The process of canless extrusion in ambient environment, using cold isostatic pressed, and vacuum-sintered, direct-consolidated blended-elemental hydrided ADMA titanium powder, mixed with master alloy powder for the Ti-6Al-4V composition, has been successfully demonstrated. However, these initially processed unoptimized powder-based extrusions also exhibited oxygen content of about 3000 ppm, within the ASTM B817 Standard, but exceeding the AMS Specification 4935 maximum limit of 2000 ppm, and with pre-extrusion residual hydrogen within 300-500 ppm resulting in post-extrusion void nucleation aligned with the extrusion direction. Additional optimization of extrusion billets during the CIP-and-sintering steps has been successfully demonstrated reducing both oxygen and hydrogen contents to levels at or below the AMS Specification limits for Ti-6Al-4V composition (oxygen content of 2000 ppm maximum, and hydrogen content of 125 ppm maximum). Processing-microstructure-property correlations of the optimized, AMS-4935-Specification-conformant, Ti-6Al-4V blended-elemental powder-based product form exhibited an overall mechanical property balance matching that of double-arc-remelted ingot-based extrusions. Property matching was not only in terms of static mechanical properties (room-temperature tensile properties, and monotonic fracture toughness K (IC) (K (Q)) values), but also in terms of dynamic fatigue properties (combined S/N plus da/dN properties), as well as stress-corrosion resistance, as measured in terms of K (ISCC) threshold values.