S. M. El-Soudani, The Boeing Company, Huntington Beach, CA; K. O. (. Yu, F. Sun, RTI International Metals Inc., Niles, OH; M. Campbell, J. Phillips, T. Esposito, Plymouth Engineered Shapes, Hopkinsville, KY; V. S. Moxson, V. Duz, ADMA Products, Twinsburg, OH
The feasibility of canless extrusion in ambient environment using blended-elemental hydrided titanium powder, ADMA-processed by phase-blending with master alloy powder for Ti-6AL-4V composition, then direct-consolidated by cold isostatic pressing (CIP), and vacuum sintering has been demonstrated. Extensive measurements of tensile properties of such blended-elemental ADMA powder-based extrusions conforming to Ti-6AL-4V composition processed both in the beta or alpha-beta ranges of extrusion temperatures showed equivalent or superior tensile properties as compared to identically processed wrought, ingot-based and extruded Ti-6AL-4V billet materials. Additionally, in the blended-elemental powder-based extrusions both nitrogen and carbon contents were within specification limits for Ti-6AL-4V alloy, while any excessive residual hydrogen was successfully vacuum-degassed after extrusion to within AMS specification limits for Ti-6AL-4V alloy. In such extruded billets with relatively high oxygen content (2700 to 2900 ppm) the high cycle fatigue S/N properties showed equivalence with ingot-based same-product-form behavior, but with a significant reduction in fracture toughness, ASTM-E399-KIC(KQ), and stress-corrosion resistance as measured by the NACE-KISCC test. Further optimization for fracture toughness, stress-corrosion resistance, and fatigue crack growth (da/dN) properties is continuing, and will build on the encouraging static and dynamic (S/N-fatigue) results, while seeking the best overall property balance for meeting Aerospace Material Specifications (AMS). This is to be achieved by monitoring and controlling oxygen uptake during pre-extrusion powder-consolidation processing steps. Reducing oxygen content to a maximum of 2000 ppm is recommended, and will be verified for final optimized powder-based titanium Ti-6AL-4V property balance for aerospace applications.
Summary: The feasibility of canless extrusion in ambient environment using blended-elemental hydrided titanium powder, ADMA-processed by phase-blending with master alloy powder for Ti-6AL-4V composition, then direct-consolidated by cold isostatic pressing (CIP), and vacuum sintering has been demonstrated. Extensive measurements of tensile properties of such blended-elemental ADMA powder-based extrusions conforming to Ti-6AL-4V composition processed both in the beta or alpha-beta ranges of extrusion temperatures showed equivalent or superior tensile properties as compared to identically processed wrought, ingot-based and extruded Ti-6AL-4V billet materials. Additionally, in the blended-elemental powder-based extrusions both nitrogen and carbon contents were within specification limits for Ti-6AL-4V alloy, while any excessive residual hydrogen was successfully vacuum-degassed after extrusion to within AMS specification limits for Ti-6AL-4V alloy. In such extruded billets with relatively high oxygen content (2700 to 2900 ppm) the high cycle fatigue S/N properties showed equivalence with ingot-based same-product-form behavior, but with a significant reduction in fracture toughness, ASTM-E399-KIC(KQ), and stress-corrosion resistance as measured by the NACE-KISCC test. Further optimization for fracture toughness, stress-corrosion resistance, and fatigue crack growth (da/dN) properties is continuing, and will build on the encouraging static and dynamic (S/N-fatigue) results, while seeking the best overall property balance for meeting Aerospace Material Specifications (AMS). This is to be achieved by monitoring and controlling oxygen uptake during pre-extrusion powder-consolidation processing steps. Reducing oxygen content to a maximum of 2000 ppm is recommended, and will be verified for final optimized powder-based titanium Ti-6AL-4V property balance for aerospace applications.
