Effects of Aging Heat Treatment on the

Microstructure of Ti-Nb and

Ti-Nb-Sn Alloys Employed as Biomaterials

E.S.N. Lopes, A. Cremasco, R. Contieri and R. Caram

Mediterranean Conference on Innovative Materials and Applications

15 – 17 March 2011

Beirut - Lebanon

University of Campinas, Brazil

CIMA 2011 #2

University of Campinas, Brazil

University of Campinas

Campinas, Brazil

CIMA 2011 #3

Outline

Introduction

Orthopedic Implants

Total Hip Replacement Requiriments

Bone Elastic Deformation

Ti Alloys Phase Transformations

Objectives

Experiments

Results

DSC

High Temperature X-Ray Diffraction

Aging Heat Treatment and Mechanical Behavior

Cold Forged Femoral Stem

Conclusions

CIMA 2011 #4

Introduction

Concept of implanting materials in the human body

is not new

Ancient Egypt

mummified foot with an artificial wooden toe

Ancient Egypt

dental implant

in mummies

Ancient mediterranean civilization

dental bridge

CIMA 2011 #5

Total Joint Replacement

TJR is a surgical

procedure in which

certain parts of a

damaged joint, are

removed and replaced

with a plastic or metal

device called a prosthesis

Prosthesis is designed to

enable the artificial joint

to move just like a healthy

joint

Total Elbow

Replacement

Total Shoulder

Replacement

Total Knee

Replacement

Total Hip

Replacement

CIMA 2011 #6

Total Hip Replacement

Hip joints and

adjacent skeletal

components

Implant after

surgery

Total hip

replacement

CIMA 2011 #7

Adapted from Orlin & Cohen Orthopedic Group

R. Caram - 7

Total Hip Replacement

CIMA 2011 #8

Implant material must simulate bone elastic behavior

Wolff’s Law: Bone modifies its internal architecture and external

shape as a result of mechanical stress

Insufficient load transfer from the implant to the bone causes

bone mass loss and osteoporosis

Stainless

steel

E=200 GPa

Bone fracture

Healthy bone

Bone with osteoporosis

Bone Elastic Deformation

CIMA 2011 #9

Femoral Stem Requirements

High mechanical strength

Low prices

High biocompatibility

High corrosion resistance

Low elastic modulus

Ebone: 10 - 30 GPa

Estainless steel: 200 GPa

ETi-6Al-4V: 106 GPa

“Necessary development of

low elastic modulus Ti Alloys”

R. Caram - 9

Total Hip Replacement Requirements

CIMA 2011 #10

Objectives

To discuss phase transformations in Ti-Nb-Sn

alloys:

phase precipitation during aging heat

treatment of metastable microstructures

Correlation between microstructure and

mechanical behavior

Application of phase transformations

knowledge in Ti-based femoral stem

manufacturing

CIMA 2011 #11

Titanium Metallurgy

T

883 oC BCC ()

HCP ()

Titanium shows two allotropic forms:

HCP and BCC

Addition of alloying elements may

change the phase stability and hence,

the microstructure and mechanical

behavior

HCP ()

BCC ()

CIMA 2011 #12

Titanium Alloy

HIGH STRENGTH-TO-DENSITY RATIO

LOW ELASTIC MODULUS

HIGH STRENGTH

HIGH TOUGHNESS

BIOCOMPATIBILITY

EASY TO HEAT TREAT

EXCELLENT CORROSION RESISTANCE

LOW FORGING TEMPERATURE

Ti alloys

Stabilizer elements:

Cr, Nb, V, Ta, Mo

CIMA 2011 #13

Ms(’)

Ms(’) = ’ martensite start temperature

Ms(”)

Ms(”) = ” martensite start temperature

β + ω β + ωiso ωath β + β’

ωath = athermal ω phase

ωiso = isothermal ω phase

+

Stabilizer Content

Te

mp

era

ture

Ti Alloys Phase Transformations

Ti

100 wt%

metastable alloys

MECHANICAL

PROPERTIES OF Ti

ALLOYS

CHEMICAL

COMPOSITION AND

HEAT TREATMENTS

CIMA 2011 #14

Processing Route

Melting

> 2000ºC

Homogenization

12 h / 1000ºC Hot Forging

850ºC

Time

FC AC

Te

mp

era

ture

Aging: 0 - 2 h

260ºC and 400ºC

FC – FURNACE COOLED

AC – AIR COOLED

WQ – WATER QUENCHED

WQ

AC

Solution

1h / 1000ºC Mart

en

sit

e

Deco

mp

osit

ion

Alloy Compositions: Ti-30Nb and Ti-30Nb-2Sn (wt. %)

CIMA 2011 #15

Effect of Sn on ” Amount

150 µm

Ti-30Nb Ti-30Nb-2Sn

Effect of Sn addition on the amount of martensite

Water Quenched Samples

Microstructure = orthorhombic martensite (α”) and phase.

Small amount of nanometric precipitates of in Ti-30Nb.

150 µm

Ti-30Nb Ti-30Nb-2Sn

CIMA 2011 #16

0 20 40 60 80 100 120 140 160 180 200

-0,7

-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

0,1

0,2

0,3

0,4

0

100

200

300

400

500

600

700

800

900

1000Ti-30Nb

DSC

Temperature

exo

Tem

pera

ture

(ºC

)

Time (min.)

DS

C/(

uV

/mg

)

0 20 40 60 80 100 120 140 160 180 200

-0,8

-0,7

-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

0,1

100

200

300

400

500

600

700

800

900

1000

DS

C/(

uV

/mg

)

Time (min.)

Ti-30Nb-2Sn

DSC

Temperature

exo

Te

mp

era

ture

(ºC

)

Thermal Analysis – DSC

Martensite Decomposition

WQ Ti-30Nb and Ti-30Nb-2Sn samples with ” and phases

Peak 1: reverse transformation ”

Precipitation of in matrix (end of peak 1)

Peak 2: nucleation of - “ act as substrates”

Peak 3: transus

1

2

3

CIMA 2011 #17

Martensite Decomposition: Ti-30Nb

30 40 50 60 70 80 90

Ti-30Nb

400oC/0.9 ks

400oC/3.6 ks

400oC/7.2 ks

260oC/14.4 ks

260oC/7.2 ks

""

Pt

Pt

Pt

Pt

"

"/

""

"

"" "

Inte

ns

ity

(a

.u.)

2 (Degrees)

Pt

RT

Martensite

decomposition

occurred with the

aging time

Reverse

transformation of α”

into phase also took

place

Precipitation of and

phases is visible by

high temperature XRD

High Temperature X-Ray Diffraction

CIMA 2011 #18

30 40 50 60 70 80 90

Pt

Inte

ns

ity

(a

.u.)

2 (Degrees)

400oC/0.9 ks

400oC/3.6 ks

400oC/7.2 ks

260oC/14.4 ks

260oC/7.2 ks

Pt

Pt

Pt

Pt

"

"/

" ""

" " "

Pt

RT

Ti-30Nb-2Sn

Martensite Decomposition: Ti-30Nb-2Sn

Martensite

decomposition

occurred with the

aging time

Reverse

transformation of α”

into phase also took

place

No precipitation of

phase is observed by

high temperature XRD

High Temperature X-Ray Diffraction

CIMA 2011 #19

Mechanical Behavior: Ti-30Nb

WQ

260°C

/0.0

6 k

s260°C

/7.2

ks

260°C

/14.4

ks

400°C

/0.0

6 k

s400°C

/0.6

ks

400°C

/1.2

ks

400°C

/1.8

ks

400°C

/3.6

ks

400°C

/7.2

ks

60

70

80

90

100

110

120

200

250

300

350

400

450

500

Ela

sti

c M

od

ulu

s (

GP

a)

Ti-30Nb

Vic

ke

rs H

ard

ne

ss

(H

V)

CIMA 2011 #20

Mechanical Behavior: Ti-30Nb-2Sn

WQ

260°C

/0.0

6 k

s260°C

/7.2

ks

260°C

/14.4

ks

400°C

/0.0

6 k

s400°C

/0.6

ks

400°C

/1.2

ks

400°C

/1.8

ks

400°C

/3.6

ks

400°C

/7.2

ks

60

70

80

90

100

110

120

200

250

300

350

400

450

500

Ela

sti

c M

od

ulu

s (

GP

a)

Vic

ke

rs H

ard

ne

ss

(H

V)

Ti-30Nb-2Sn

CIMA 2011 #21

Alloy

Condition

Phases

(XRD)

UTS

(MPa)

Elong

(%)

E

(GPa)

Hardness

(VH)

Ti-30Nb ”++ 332 21 30 7 74 299 6

Ti-30Nb

Aged

++ 826 24 0.8 0.1

105 430 10

Ti-30Nb-2Sn ”+ 300 32 36 4.0 67 219 5

Ti-30Nb-2Sn

Aged

++** 800 22

3.0 0.2

85 390 15

Effect of aging on mechanical behavior

Tensile Test: Mechanical Properties

** - very small amount

CIMA 2011 #22

Cold Forged Femoral Stem using Ti-30Nb-2Sn alloy

Cold Forging

CIMA 2011 #23

Conclusions

Microstructure of WQ Ti-30Nb and Ti-30Nb-2Sn was formed by

and ” phase and the amount of ” decreases with increase of

Sn;

Aging caused ” decomposition and precipitation of , and

phases;

Results suggest that Sn may act as a suppressor of

precipitation, which allows the control of microstructure features

and hence, mechanical properties

WQ Ti-Nb-Sn sample showed yield strength near 300 MPa, which

makes easier cold forging process, whose aged sample value

increased up to 800 MPa

Aged Ti-Nb-Sn alloy showed elastic modulus of 85 GPa

These final values are very suitable in terms of orthopedic

biomaterial applications

CIMA 2011 #24

Questions??