Ultrafine grained titanium andmagnesium alloys for permanent andbioresorbable medical implants
Yuri Estrin
Centre for Advanced Hybrid Materials, Department of Materials
Engineering,Monash University, Australia
andNational University of Science & Technology “MISIS”
Moscow, Russia
E-mail: yuri.estrin@monash.edu

ALMA Meeting, Kyoto, 6 August 2016

Aims of Research• Determine the effect of grain refinement by severe plastic
deformation on mechanical properties and biocompatibility oftitanium and magnesium alloys• Identify the effect of grain refinement on surface properties(roughness) of the materials with polished and modified surfaces• Assess the effect of surface modification on mechanicalproperties and cell response of titanium and magnesium alloys
with different structure2

CopperAFTERBEFORE

Frequency

Property profile of ECAP-processed Cu

STRENGTH

Pass number

Conductivity

Strength

Grain size

THERMAL CONDUCTIVITY

Pass number

Possible marketplace applicationsof SPD processing
Transportation•Lighter weight•Longer lifetime•Higher performance•New products

Aerospace

BiomedicalSports

Courtesy: Dr Terry Lowe, Manhattan
Scientifics, Inc.

Enhanced Strength and Biocompatibilityof Titanium(Permanent Implant Applications)

Grain refinement and mechanical property
improvement of Grade 2 CP Titanium

Grain structure of ECAPmodified titanium

Tensile curves of coarse-grained(CG) and ultrafine-grained (UFG)titaniumCorrelation between fatigue strength and UTS
Endurance (fatigue) limit,f0 / MPa

700
600
500
400
300200Non-heat Treatable Al-alloys
Heat Treatable Al-alloys
Ti

10000200

400

600

800

1000

1200

1400

Tensile Strength, UTS / MPa

Estrin & Vinogradov, Intl. J. Fatigue 2010

Surface topography

Coarse-GrainedUFG

Proliferation of fibroblast cells on Ti CP4UFG

CG

I. Semenova, R. Valiev, H. Rack, T. Lowe et al., 2008

Nanostructured Ti Shows Distinctly Greater Preosteoblastic
Cell Growth in vitro
MC3T3-E1 cells from mice embryos

Y. Estrin et al. J. Biomed. Materials Res., 2008

Stem cell attachment and growth

Y. Estrin et al., Acta Biomater. (2010)

Bacteria adhesion: S. aureus (left)
and P. aeruginosa (right)

EPS production (stained green)and viable cells (stained red)Animal test
proximal

4 week implantation
Rabbit tibia

Rabbit tibia

2mm

distal3mmJi-Hoon Jo, Hyon-Ee Kim, SNU

2D image (Histology)

Conventional Ti

ECAP Ti

2D image (Micro CT)
New boneGap

3D image (Bone in Volume of Interest)

Bone volume %BIC (Bone‐to‐Implant contact) %Microstructure
Average grain size

200nm

Grain size, µm

Gr2AsR

20

Gr4AsR30

Gr2ECAP (I)

0.25

Gr4ECAP (I)

0.23

Gr4ECAP (II)0.1

Gr2ECAP (I)Gr2AsR

200nm

Gr4AsR

Condition

200nm

Gr4ECAP (I)

Gr4ECAP (II)Alex Medvedev, PhD thesis, 2016 Monash University22

Mechanical propertiesCondition
Gr2AR
Gr2ECAP (I)
Gr4AR
Gr4ECAP (I)
Gr4ECAP (II)Ti‐6Al‐4VAR^

Average grain size, µm200.25300.230.1
3‐4 (α‐grains)ˣ

UTS*, MPa
480
850
7651030
1275940‐970

YS*, MPa
350
750620940
1130
840‐900

Elongation**, %291821.5
18.5
1316‐20

Statistical error does not exceed: * 5‐7MPa ** 1‐2%; Statistical analysis is not applicable to Ti‐6Al‐4V data

Increase in strengthby 70-80 %Alex Medvedev, PhD thesis, 2016 Monash University23Surface after SLA treatment
Magnification
x1,00020 µm

Gr2AsR

Gr2ECAP(I)Gr4AsR

Gr4ECAP(I)Gr4ECAP(II)Alex Medvedev, PhD thesis, 2016 Monash University24

Surface after SLA treatment
Magnification
x25,000
1 µm

Gr2AsR

Gr2ECAP(I)Gr4AsR

Gr4ECAP(I)Gr4ECAP(II)Alex Medvedev, PhD thesis, 2016 Monash University25

Fatigue properties
T = 25°C, Air, R = ‐1

Polished surface

SLA‐treated surface

Arrowsindicate an increase of fatigue life of titanium after
ECAP‐processing compared to as‐received coarse‐grained counterparts

Alex Medvedev, PhD thesis, 2016 Monash University26

Surgical and dental implants from ultrafine‐grained Ti
Development of a new lightweight
structure for spine fixation“nano” Ti

Usual Ti

[Timplant Co. ,www.timplant.cz]
From I. Semenova et al., TMS 2008 Annual Meeting, New Orleans, USALightHigh SpecificStrength
Bioactive

Mg as an Implant Material

Elastic modulus

Biodegradable

Corrosion(Strength)

Alloying..
Coating..

Mg + 2 H2O = Mg(OH)2 (s) + 2 H2 (g)Mg‐based bone implants

Possible applications of Mg

Courtesy Prof. Hyoun-Ee Kim

Magnesium
Mg : Corrosion
Mg + 2 H2O = Mg(OH)2 (s) + 2 H2 (g)Alloying
Coating

Courtesy Prof. Hyoun-Ee Kim

AZ31, AZ91 . .
ZK60, ZM21. .

WE43

Strength retention

Coated-Mg

Bare Mg

Hyoun-Ee Kim, SNU
Calvarias of Rat for up to 12 weeks

BareHA coated6 weeks

8 weeks

Mg for temporary implants?
Degradation rate (m/day)

2.4
2.2

SC

2.0
1.8

ECAP

1.6
1.4

HR

1.2
1.0
0.8
0.6

0

24

68

10

1214

161820Time (day)Fatigue strength

Corrosion in Hank’s solution

Wang, Song, Estrin, Zuberova, Adv. Eng. Mater. 9 (11), 967-972 (2007)

22Research at Seoul National University, Prof. Hyoun-Ee Kim

Corrosion resistance of Mg – Role of coating

Research at Seoul National University, Prof. Hyoun-Ee Kim

Rabbit femoral shaft, 4 weeks

Magnesium alloys

Methods of SPD
High pressure torsion(HPT)

Mg-RE (WE43)
Mg-Ca
Mg-Zn-Ca

Equal Channel Angular
Pressing (ECAP)
Multiaxial Deformation(MD)

Mg-Li-Ca
Rotary swaging (RS)
Estrin, Dobatkin, Lukyanova,Anisimova (work in progress)

LX41: Processing schedule

Saurabh Nene, PhD Thesis 2016
(Monash-IITB)

Property profile of alloy LX41 after rolling
and annealing

Estrin et al., Mater. Lett. 173, 252 (2016))(Materials Today, April 2016)

cd

Specific Strength,
Cytocompatibility andTexture IntensityeObtaining porous Ti and Ti/Mg
Si400µm

Mg
100µm

Y. Qi, R. Lapovok,Y. Estrin, 2014

Porous titanium for medical implants

S.W. Kim et al.,“Fabrication of porous titanium scaffold with controlled porous structure andnet-shape using magnesium as spacer”, Mater. Sc. Eng.: C 33, 2808 (2013).

GENERAL CONCLUSION:
There is a lot of scope for researchand development in theburgeoning area of medicalimplants – both permanent andbioresorbableThank you for your attention!

yuri.estrin@monash.edu