PhD Dissertation Proposal Presentation

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Project overview of powder processing and sintering studies on Ti-6Al-4V materials for orthopedic implant applications.

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PhD Dissertation Proposal Presentation

  1. 1. Ti-6Al-4V for Functionally Graded Orthopedic Implant Applications PhD Dissertation Proposal Kyle Crosby University of Connecticut - IMS 4/2/2013
  2. 2.  Motivation ◦ Biomedical implant issues Ti-6Al-4V Background ◦ Properties, processing and applications Proposed Research Objective ◦ Functionally graded orthopedic implant Proposed Methodology ◦ Powder processing and sintering techniques Preliminary Results and What’s Left To Do ◦ Characterization of powders and sintered bodies Conclusion ◦ Viability as an artificial biological component University of Connecticut - IMS 4/2/2013
  3. 3.  Biomedical implant ◦ Femoral stem, cup and ball socket Invasive operation ◦ Long, painfull rehab and recovery time Secondary surgery within 5-25 years to repair or replace implant ◦ Fracture of metallic implants due to stress concentration sites and contaminates (i.e. pores and composition gradients) ◦ Implant loosening due to poor mechanical bonding between metallic implant and native bone University of Connecticut - IMS 4/2/2013
  4. 4.  Metallic components ◦ Stainless steel, pure titanium, titanium alloys, Co- Cr alloys Surface structures ◦ Porous surface network to allow for bone ingrowth and improved mechanical interlocking ◦ Pores act as stress amplifiers Bioactive coatings ◦ Hydroxyapatite ceramic mimics natural bone because HA is composed of mainly calcium phosphate University of Connecticut - IMS 4/2/2013
  5. 5.  Ti-6Al-4V vitals ◦ Lightweight  D = 4.45 g/cm3 ◦ High strength  σYS = 924 MPa ◦ Cheaper than pure Ti ◦ Corrosion resistant ◦ Biocompatible ◦ HCP @ R.T. University of Connecticut - IMS 4/2/2013
  6. 6.  Cast ◦ Sheet, barstock, ingot from a melt  High cost to maintain melt temperature continuously  Contamination of gases during melting and from crucible/mold during pouring Forged ◦ Better mechanical properties ◦ Additional processing step = additional cost Machining ◦ Difficult due to high hardness Powder Metallurgy (PREP) ◦ Tight geometrical tolerances ◦ Sintering process is less expensive than casting with equivalent mechanical properties University of Connecticut - IMS 4/2/2013
  7. 7.  Grade 5 α/β Alloy ◦ Aerospace  Engine components  Fasteners ◦ Marine  Structural components ◦ Sporting goods  Golf clubs, bicycles ◦ Jewelry  Earrings, studs ◦ Biomedical  Orthodontics  Screws, pins, staples  Total joint replacements University of Connecticut - IMS 4/2/2013
  8. 8.  Development of improved hip implant devices Ti-6Al-4V through functionally graded Ti-6Al-4V + rich core Hydroxyapatite composite components. ◦ Avoid implant loosening ◦ Avoid bioceramic spallation ◦ Avoid infection and secondary surgery Currently, co-sintering of Ti-6Al-4V +HA leads to formation of oxide and phosphate phases which have poor mechanical properties and show adverse bioactivity Powder metallurgy and sintering studies are HA rich conducted to reduce sintering temperature surface below threshold where undesirable phases form Slurry preparation and co-sintering of Ti+HA Current Ti Functionally using solid freeform fabrication technique hip joint graded Ti/HA hip joint University of Connecticut - IMS 4/2/2013
  9. 9.  Co-sintering of Ti-6Al-4V + HA components requires the temperature to be reduced below 1000°C ◦ Thermodynamic alteration  Diffusion mode shifted via particle size refinement and increased defect concentration  bulk lattice limited → grain boundary limited ◦ Kinetic alteration  Rate of thermal energy application (°C/min)  Tube furnace, MWS, and SPS densification methods University of Connecticut - IMS 4/2/2013
  10. 10.  Powder processing ◦ Particle size reduction ◦ Crystallite/grain size reduction ◦ Particle morphology changes Green body formation ◦ Uniaxial pressure effect ◦ Uniaxial pressing of as rec, 1 hr and 4 hr SPEX powders Sintering conditions ◦ Heat generation method, ramp rate, holding time ◦ Crystallite/grain size after sintering ◦ Relative density after sintering University of Connecticut - IMS 4/2/2013
  11. 11. ½” stainless steel ¼” stainless steel Ti-6Al-4V Stearic acid *Not to scaleUniversity of Connecticut - IMS 4/2/2013
  12. 12. 200 µm 250 µm 100 µm As received PREP 1 hr SPEX milled 4 hr SPEX milledAvg. Dia. = 110 µm Avg. Dia. = 150 µm Avg. Dia. = 25 µm University of Connecticut - IMS 4/2/2013
  13. 13. 10000 9000 8000 Ti 6-4 as rec powder 7000Relative Intensity (a.u.) Ti 6-4 SPEX 2wt%/1hr 6000 Ti 6-4 SPEX 3wt%/1hr Ti 6-4 SPEX 3wt%/4hr 5000 Ti 6-4 SPEX 4wt%/1hr 4000 Ti 6-4 SPEX 4wt%/2hr Ti 6-4 SPEX 4wt%/3hr 3000 Ti 6-4 SPEX 4wt%/4hr Ti 6-4 SPEX 5wt%/1hr 2000 Ti 6-4 SPEX 5wt%/4hr 1000 20 30 40 50 60 70 80 90 2 Theta (°) University of Connecticut - IMS 4/2/2013
  14. 14. 120 (1011) c 100 Ti 6-4 (002) Ti 6-4 (101) (0002) Crystallite Size (nm) 80 60 40 a2 20 0 0 1 2 3 4 5 Milling Time (hr)a3 a1 University of Connecticut - IMS 4/2/2013
  15. 15. (1011) c 45 Ti 6-4 (002) 40 (0002) Ti 6-4 (101) 35 Crystallite Size (nm) 30 25 20 a2 15 10 5 0 2 3 4 5 6a3 PCA Concentration (wt%) a1 University of Connecticut - IMS 4/2/2013
  16. 16. As received Ti-6Al-4V PREP powder 4 hr SPEX milled Ti-6Al-4V powder University of Connecticut - IMS 4/2/2013
  17. 17. 300 MPaAs received PREP powder 1 hr SPEX milled 4 hr SPEX milled 5 wt% PEG binder no binder no binder Dtheor = 50% Dtheor = 46% Dtheor = 58% University of Connecticut - IMS 4/2/2013
  18. 18. NO YESHeavily oxided Light surfacethroughout oxidationLow mechanical Polishes to mirrorstrength finishUseless for load High densitybearing University of Connecticut - IMS 4/2/2013
  19. 19.  Tube furnace sintering (RHS) ◦ Radiant heating of green body, from outside inward, through furnace atmosphere by electrical resistance through molybdenum heating elements Spark plasma sintering ◦ Electrical resistance heating at contact point between each powder particle in the green body Microwave sintering ◦ Dipole interaction of particle-pores within green body with microwave radiation University of Connecticut - IMS 4/2/2013
  20. 20. HOT COLDV University of Connecticut - IMS 4/2/2013
  21. 21.  Sintering chamber ◦ Inert atmosphere ◦ Microwave transparent crucible (good dielectric) ◦ Particle-pore dipole interaction within green body COLD HOT University of Connecticut - IMS 4/2/2013
  22. 22. University of Connecticut - IMS 4/2/2013
  23. 23. As received Sintered 2 hr Sintered 2 hr300 MPa uniaxial @ 1100°C @ 1250°C Dtheor = 50% Dtheor = 75% Dtheor = >97% University of Connecticut - IMS 4/2/2013
  24. 24. 15000 Ti 6-4 as rec tube - 1250C/2hr 14000 Ti 6-4 as rec tube - 1100C/2hr 13000 Ti 6-4 as rec SPS - 1000C/3min 12000 Ti 6-4 SPEX 4/4 tube - 1250C/2hrRelative Intensity (a.u.) 11000 Ti 6-4 SPEX 4/4 tube - 1100C/2hr 10000 Ti 6-4 SPEX 4/4 SPS - 1000C/3min 9000 Ti 6-4 SPEX 4/4 SPS - 600C/5min 8000 Ti 6-4 SPEX 4/4 MWS - 1250C/30min Ti 6-4 SPEX 4/4 MWS - 900C/1hr 7000 Ti 6-4 SPEX 4/1 tube - 1250C/2hr 6000 20 30 40 50 60 70 80 90 2 Theta (°) Ti 6-4 SPEX 4/1 tube - 1100C/2hr University of Connecticut - IMS 4/2/2013
  25. 25. 250 Ti 6-4 (002) (1011) c 200 Ti 6-4 (101) (0002) Crystallite Size (nm) 150 100 a2 50 0 500 600 700 800 900 1000 1100 1200 1300 Sinteirng Temperature (C)a3 a1 University of Connecticut - IMS 4/2/2013
  26. 26. Ti 6Al-4V as rec. Ti 6Al-4V as SPEX (1hr/4wt%) Ti 6Al-4V as SPEX (4hr/4wt%)1250°C/2hr → 90% dense 1250°C/2hr → 75% dense 1250°C/2hr → 97% dense 500 µm 500 µm 500 µm 500 µm 500 µm 500 µm Ti 6Al-4V as rec. Ti 6Al-4V as SPEX Ti 6Al-4V as SPEX (4hr/4wt%)1100°C/2hr → 78% dense (1hr/4wt%) 1100°C/2hr → 1100°C/2hr → 83% dense 60% dense University of Connecticut - IMS 4/2/2013
  27. 27. Ti-6Al-4V 4 hr SPEX, MWS at 900C Ti-6Al-4V 4 hr SPEX, MWS at 1250Cfor 1 hr (95% center, 80% edge) for 30 min (98% center, 81% edge) University of Connecticut - IMS 4/2/2013
  28. 28. 3 Ti 6Al-4V as Rec 2.5 Ti 6Al-4V as SPEX 1000°C 2 Displacement (mm) 1.5 1 0.5 0 0 100 200 300 400 500 600 700 800 900 1000 Temperature (°C) Pressure Max Displacement Displacement Density Sample ID Decrease Onset Displacement Plateau Temp Onset Temp (°C) (g/cm3) Temp (°C) Temp (°C) (°C)Ti 6Al-4V as 550 620 800 880 4.31 recTi 6Al-4V as 350 350 600 750 4.27 SPEX 1000 University of Connecticut - IMS 4/2/2013
  29. 29. (a) Ti-6Al-4V as (b) Ti-6Al-4V 4 hr SPEX (c) Ti-6Al-4V 4 hrreceived, SPS @ 1000C as SPS @ 1000C for 3 SPEX as SPS @ 600Cfor 3 min, 99% min, 99% for 5 min, 96% University of Connecticut - IMS 4/2/2013
  30. 30.  SPEX milled powder sinters @ lower temp than as received PREP powder ◦ Smaller particle size = shorter diffusion distance = shorter diffusion time ◦ Increase grain boundary area = rate limiting diffusion mechanism shift DL → Dg.b. Dg.b. >> DL RHS to full theoretical density is possible ◦ Requires strict atmospheric control ◦ Heat penetration lag = longer sintering dwell times MWS offers lower temperature, faster sintering than RHS ◦ Pressureless sintering = complex geometry retention is possible ◦ Heat emination lag = porous surface regions SPS offers low temperature, rapid sintering ◦ Very high heating rates = rapid diffusion ◦ Uniaxial pressure from conductive die = complex geometry retention is difficult University of Connecticut - IMS 4/2/2013
  31. 31.  Activation energy measurement ◦ Track density as a function of sintering conditions Grain size analysis ◦ Monitor grain size as a function of sintering temperature Mechanical properties ◦ Compressive and tensile strengths ◦ Rockwell C and microhardness Biological properties ◦ Cell attachment (# per unit area) ◦ Cell spreading (lateral area coverage as a function of time in simulated body fluid) Composite Ti-HA co-sintering studies ◦ SPS parameter optimization University of Connecticut - IMS 4/2/2013
  32. 32. 2C/min 4C/min 8C/min 2C/min 700 700 700 800 800 800 150 Quench Temp (C)Relative Density (%) 100 900 900 900 50 1000 1000 1000 0 1100 1100 1100 600 800 1000 1200 1250 1250 1250 Quench Temperature (C) 4C/min 8C/min 150 150Relative Density (%) Relative Density (%) 100 100 50 50 0 0 600 800 1000 1200 600 800 1000 1200 Quench Temperature (C) Quench Temperature (C) University of Connecticut - IMS 4/2/2013
  33. 33. 4 hr SPEX powder Sintering @ 900C Sintering @ 1250C Grain size vs. mechanical strength ? Grain size vs. activation energy barrier? Grain size vs. cell attachment and spreading? University of Connecticut - IMS 4/2/2013
  34. 34.  Compressive strength ◦ Quasi-static using cross-head speed of 1,10,100 mm/min ◦ High strain rate using Split-Hopkinson Pressure Bar at 300, 900 s-1 frequency Tensile strength ◦ Strain until failure ◦ σYS , σUTS , E Rockwell C and microhardness ◦ Compare to as received powder, commercially cast or forged products and between each other University of Connecticut - IMS 4/2/2013
  35. 35. (a) HA as SPS @ 1000C (b) Ti-6Al-4V 4 hr SPEX (c) Ti-6Al-4V 4 hr SPEX for 3 min, 99% (90 vol%) + HA (10 vol%) (75 vol%) + HA (25 vol%) as SPS @ 96% as SPS @ 1000C for 3 min, 83% University of Connecticut - IMS 4/2/2013
  36. 36. University of Connecticut - IMS 4/2/2013
  37. 37.  Funding ◦ United States National Science Foundation contract CBET- 0930365 Supervision ◦ Dr Leon Shaw Instrumentation ◦ Dr. Claude Estournes (SPS at CIRIMAT in France), Dr. Ashraf Imam (MWS at NRL in D.C.), Jack Gromek (XRD), Roger Ristau and Lichun Zhang (TEM/SEM), Bob Bouchard and Matt Bebee (SPEX vial and die fabrication) Support ◦ Monica & Ling (HA synthesis and biostudies) and Girije Marathe (quartz tube sealing) as well as the rest of my groupmates and fellow grad students in MSE/IMS University of Connecticut - IMS 4/2/2013
  38. 38.  [1] Hennig, R., Lenosky, T., Trinkle, D., Rudin, S., Wilkins, J. "Classical potential describes martensitic phase transformations between the alpha, beta, and omega titanium phases," Physical Review B, 78,054121, 2008. [2] Kubaschewski O., Wainwright C., and Kirby F.J., “The Heats of Formation in the Vanadium-Titanium- Aluminium System,” J. Inst. Met., 89, 1960, 139-144. [3] Honma BERES 7 Series Driver, honmagolf.com, 2010. [4] Solid Grade 5 Titanium, TNG Body Jewlery, 2012. [5] Deutsch, A., “Bike review: Merlin works CR 6/4,” Brooklyn Arches Cycling, 2012. [6] Titanium dental implants, Naomi Dental, 2011 [7] Total hip replacement, defectivejoints.com, 2011 [8] Shaw, L., “Rapid prototyping of functionally graded orthopedic implants via the slurry mixing and dispensing process,” NSF proposal submitted 2009. [9] What’s SPS, “Principles and mechanism of the SPS process,” Fuji Electronic Industrial Co. University of Connecticut - IMS 4/2/2013
  39. 39. ?University of Connecticut - IMS 4/2/2013
  40. 40.  Armstrong starting powder ◦ Low apparent density (~5%) ◦ Sponge morphology with high SSA Slurry preparation ◦ Stable suspension ◦ Proper pH and viscosity Freeform 3D printing ◦ Tip diameter = slurry droplet size  Lateral and layer thickness resolution Software development to allow for composition gradient from core to surface ◦ Must accommodate change in composition within each z-slice Mechanical and biological properties of functionally graded component ◦ Ti-HA composites via SPS Bioactivity as a function of surface roughness ◦ Cell # and lateral spreading as a function of SiC scratch width Surface functionalization ◦ Macropores filled with aerogel particles containing growth hormone or antibiotic University of Connecticut - IMS 4/2/2013
  41. 41. SiC paper vs.Ti-6Al-4V University of Connecticut - IMS 4/2/2013
  42. 42. Antibiotic or pain relieving aerogel capsulesUniversity of Connecticut - IMS 4/2/2013

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