fei yang

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


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


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):


Rapid

Consolidation

Schematic flowchart for Powder compact extrusion (PCE)


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


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







Oxygen picking-up


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







Oxygen picking-up


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


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


Effect of Deformation amount on Microstructure

Extrusion temperature: 1300ºC, holding time 2min

Layer 1

Layer 2

Layer 3

Layer 4

Layer 5


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


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


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%)


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)


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


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


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


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


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

Acknowledgement


Thank you very much

for your

attention

fei yang

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