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Waikato Centre for Advanced Materials
Preparation of Titanium rods with High Properties by Thermomechanical Processing of Titanium
Powder Compact
Fei Yang
Waikato Centre for Advanced MaterialsFaculty of Science and Engineering
The University of WaikatoNew Zealand
Waikato Centre for Advanced Materials
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
Waikato Centre for Advanced Materials
IntroductionAdvantages:
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
low density, high strength, good corrosion resistance, and excellent biocompatibility
Near Net Shape Forming Freedom in composition selection Lower oxygen content
Blended Elemental Powder Metallurgy (BE-PM):
Waikato Centre for Advanced Materials
Rapid
Consolidation
Schematic flowchart for Powder compact extrusion (PCE)
Waikato Centre for Advanced Materials
Issues for Rapid Consolidation of Powder Mixture using PCE
Elemental powder particles can not be completely dissolved
Master alloy powder particles can not be completely dissolved
Non-uniform element distribution
Microstructure inhomogeneity
Oxygen picking-up
Waikato Centre for Advanced Materials
Ti-4Al-4Sn-4Mo-0.5Si (IMI551) alloy extruded from powder mixture of elemental Ti, Al, Mo, Sn, and Si powders at 1250ºC-1300ºC
Courtesy of Mr. Huiyang Lu
Ti
SiAl
Mo
Waikato Centre for Advanced Materials
Issues for Rapid Consolidation of Powder Mixture using PCE
Elemental powder particles can not be completely dissolved
Master alloy powder particles can not be completely dissolved
Non-uniform element distribution
Microstructure inhomogeneity
Oxygen picking-up
Waikato Centre for Advanced Materials
Ti-6Al-4V (Ti-64) alloy extruded from powder mixture of elemental Ti, Al and 65Al35V master alloy powders at 1200ºC/2min
Waikato Centre for Advanced Materials
Issues for Rapid Consolidation of Powder Mixture using PCE
Elemental powder particles can not be completely dissolved
Master alloy powder particles can not be completely dissolved
Non-uniform element distribution
Microstructure inhomogeneity
Oxygen picking-up
Waikato Centre for Advanced Materials
Ti-6Al-4V (Ti-64) alloy extruded from powder mixture of elemental Ti, Al and 65Al35V master alloy powders at 1300ºC/2min
Position Ti (wt.%)
Al (wt.%)
V (wt.%)
1 90.35 5.71
3.94
2 84.11 5.76 10.13
+2 +1
1 2
Waikato Centre for Advanced Materials
1300 ℃ 2min 1300℃ 5min 1300 ℃ 10minYield strength(MPa) 1255 1216 1180
Ultimate strength(MPa)
1300 1254 1215
Ductility (%) 7.0% 8.0% 10.0%
Tensile properties of Ti-64 rods extruded at 1300℃ with different holding time
SEM Images for Ti-64 alloy rods extruded at different conditions
1300ºC/2min 1300ºC/5min 1300ºC/10min
Waikato Centre for Advanced Materials
Effect of Deformation amount on Microstructure
Extrusion temperature: 1300ºC, holding time 2min
Layer 1
Layer 2
Layer 3
Layer 4
Layer 5
Waikato Centre for Advanced Materials
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.
Targets: Lower the extrusion temperature and shorten the holding time, to further reduce oxygen picking-up
Promoting elemental powder and master alloy powder particles to completely dissolve into titanium matrix, and obtain homogeneous element distribution.
Adjusting die entrance angle to improve deformation amount
Powder Compact Extrusion Die
Waikato Centre for Advanced Materials
Oxygen Picking-up
Oxygen content:
0.43wt.%
Starting Materials:HDH Ti:
Oxygen content: 0.33%
As-extruded pure titanium rods under argon
Oxygen content: 0.38%
As-vacuum sintered titanium billets
Approach IIApproach I
Approach III
Waikato Centre for Advanced Materials
Alloy composition:Ti-64 alloy IMI551 (Ti-4Al-4Sn-4Mo-0.5Si)Ti-5553 (Ti-5Al-5V-5Mo-3Cr) (β alloy)
Ti alloy parts manufactured by PCE
Ti alloy rods Diameter: 20mm and 12mmLength: 150-550mm
Alloy UTS(MPa) YS (MPa) Ductility (%)
Ti-64 1215-1300 1180-1255 7-13
IMI551 1230 1120 11
Ti-5553 (Aging 500ºC) 1600 (Aging) Hardness (HRC 50)
Oxygen range: 0.37-0.42wt% (Starting materials: HDH Ti 0.33wt%)
Waikato Centre for Advanced Materials
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)
Waikato Centre for Advanced Materials
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
Curve UTS(MPa) YS (MPa) Ductility (%)
1 602 570 4
2 705 650 20
Waikato Centre for Advanced Materials
Fracture surface of pure titanium after tensile test: a)-c): as-vacuum-sintered at 1300ºC for 2h, and b)-f): as-extruded at 900ºC
Waikato Centre for Advanced Materials
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
Waikato Centre for Advanced Materials
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).
Conclusions
Waikato Centre for Advanced Materials
The funding from Ministry of Business, Innovation and Employment, New Zealand, to support this work is gratefully acknowledged.
Acknowledgement
Waikato Centre for Advanced Materials
Thank you very much
for your
attention
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