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 #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 #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 #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