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Fei Yang

Preparation of Titanium rods with High Properties by Thermomechanical Processing of Titanium Powder Compact. Fei Yang. Waikato Centre for Advanced Materials Faculty of Science and Engineering The University of Waikato New Zealand. OUTLINE. Introduction

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Fei Yang

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  1. Preparation of Titanium rods with High Properties by Thermomechanical Processing of Titanium Powder Compact Fei Yang Waikato Centre for Advanced Materials Faculty of Science and Engineering The University of Waikato New Zealand

  2. OUTLINE • Introduction • Issues for Rapid Consolidation of Powder Mixtures using PCE • Ti Alloy Parts Manufactured by PCE of Powder Mixture and Its Properties • Conclusions • Acknowledgement

  3. Introduction Advantages: low density, high strength, good corrosion resistance, and excellent biocompatibility • Raw Materials Cost, 3-10 times higher than steel or Al alloys • Machining Cost • The buy-to-fly ratio is 20:1, 95% of material is wasted Blended Elemental Powder Metallurgy (BE-PM): • Near Net Shape Forming • Freedom in composition selection • Lower oxygen content

  4. Rapid Consolidation Schematic flowchart for Powder compact extrusion (PCE)

  5. Issues for Rapid Consolidation of Powder Mixture using PCE • Microstructure inhomogeneity • Elemental powder particles can not be completely dissolved • Master alloy powder particles can not be completely dissolved • Non-uniform element distribution • Oxygen picking-up

  6. Ti-4Al-4Sn-4Mo-0.5Si (IMI551) alloy extruded from powder mixture of elemental Ti, Al, Mo, Sn, and Si powders at 1250ºC-1300ºC Ti Al Si Mo Courtesy of Mr.Huiyang Lu

  7. Issues for Rapid Consolidation of Powder Mixture using PCE • Microstructure inhomogeneity • Elemental powder particles can not be completely dissolved • Master alloy powder particles can not be completely dissolved • Non-uniform element distribution • Oxygen picking-up

  8. Ti-6Al-4V (Ti-64) alloy extruded from powder mixture of elemental Ti, Al and 65Al35V master alloy powders at 1200ºC/2min

  9. Issues for Rapid Consolidation of Powder Mixture using PCE • Microstructure inhomogeneity • Elemental powder particles can not be completely dissolved • Master alloy powder particles can not be completely dissolved • Non-uniform element distribution • Oxygen picking-up

  10. Ti-6Al-4V (Ti-64) alloy extruded from powder mixture of elemental Ti, Al and 65Al35V master alloy powders at 1300ºC/2min +1 +2 2 1

  11. 1300ºC/5min 1300ºC/2min 1300ºC/10min SEM Images for Ti-64 alloy rods extruded at different conditions Tensile properties of Ti-64 rods extruded at 1300℃ with different holding time

  12. Effect of Deformation amount on Microstructure Layer 1 Extrusion temperature: 1300ºC, holding time 2min Layer 2 Layer 3 Layer 4 Layer 5

  13. Effect of Deformation amount on Microstructure • With an increasing amount of deformation, the master alloy particles are more rapidly dissolved into titanium matrix and much more uniform elemental distribution can be achieved during extrusion. Adjusting die entrance angle to improve deformation amount Promoting elemental powder and master alloy powder particles to completely dissolve into titanium matrix, and obtain homogeneous element distribution. Targets: Lower the extrusion temperature and shorten the holding time, to further reduce oxygen picking-up Powder Compact Extrusion Die

  14. Oxygen Picking-up Approach I Approach II As-extruded pure titanium rods under argon Oxygen content: 0.38% Starting Materials: HDH Ti: Oxygen content: 0.33% Oxygen content: 0.43wt.% Approach III As-vacuum sintered titanium billets

  15. Ti alloy parts manufactured by PCE Ti alloy rods Diameter: 20mm and 12mm Length: 150-550mm Alloy composition: Ti-64 alloy IMI551 (Ti-4Al-4Sn-4Mo-0.5Si) Ti-5553 (Ti-5Al-5V-5Mo-3Cr) (β alloy) Oxygen range: 0.37-0.42wt% (Starting materials: HDH Ti 0.33wt%)

  16. Pure Titanium (Grade 4) made through Approach III (900ºC extrusion) Optical microstructures of pure titanium: As-vacuum-sintered at 1300ºC for 2h: a- c), and as-extruded at 900ºC: d)-f)

  17. SEM microstructures of pure titanium: a) as-vacuum-sintered at 1300ºC for 2h, and b) and c) as-extruded at 900ºC Grain size: 15-65μm Stress-strain curves for pure titanium: curve 1: as-vacuum-sintered at 1300ºC for 2h, and curve 2: as-extruded at 900ºC

  18. Fracture surface of pure titanium after tensile test: a)-c): as-vacuum-sintered at 1300ºC for 2h, and b)-f): as-extruded at 900ºC

  19. Pure Titanium (Grade 4) made through Approach I (1300ºC extrusion) Microstructures of as-extruded pure titanium at 1300ºC and with a holding time of 1min (Grain size: 5-45μm) Mechanical properties of as-extruded pure titanium at different conditions

  20. Conclusions • Different titanium alloy rods are manufactured by TPC processes, such as Ti-6Al-4V, IMI551, Ti-5553 alloy, and the mechanical properties of as-extruded alloys are comparable with those of the alloys made by ingot metallurgy route. Different titanium alloy parts are produced, such as rod and knife, by TPC processes. • Pure titanium rods were produced by the extrusion of as-vacuum-sintered titanium billets at 900ºC in air and by titanium powder compact extrusion at 1300ºC after a 1 min holding time at temperature under an argon atmosphere. Both of the as-extruded titanium rods have higher levels of mechanical properties compared with the ASM standard for CP titanium (grade 4).

  21. Acknowledgement The funding from Ministry of Business, Innovation and Employment, New Zealand, to support this work is gratefully acknowledged.

  22. Thank you very much for your attention

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