1Titanium Titanium Titanium Titanium
Alloys IAlloys I
General properties of TiGeneral properties of Ti
It has a HEX lattice at low temperature (
2Page 3
OutlineOutline
Ti primary production Ti primary production
CP Ti and applications
-Ti alloying, alloy design
near- alloy microstructures, forging
and heat treatment
/ alloys, Ti-6Al-4V
defects
Ti Primary Production Ti Primary Production
Kroll ProcessKroll Process Ti common in Earths crust
Energy to separate ~125 MWhr/tonne (7/kg just in Energy to separate ~125 MWhr/tonne (7/kg just in
power)
Batch process over 5 days:
Produce TiCl4 from TiO2 and Cl2
TiCl4 + 2 Mg 2 MgCl2 + Ti
chip out Ti sponge (5-8 t) from reactor chip out Ti sponge (5-8 t) from reactor
cost 8/kg
Chlorides corrosive, nasty
World annual capacity ~100,000 t, demand ~60,000t
Need a cheaper process that is direct
3Production of TiProduction of Ti
Obtained from minerals:Obtained from minerals:
rutilerutile (TiO(TiO22))
ilmeniteilmenite (FeO(FeO--TiOTiO22) approx 97) approx 97--98% TiO98% TiO22
Chemically converted to pure TiClChemically converted to pure TiCl44
Kroll Process:Kroll Process:
TiClTiCl44 reactesreactes with liquid Mg at ~773with liquid Mg at ~773--873873C in a C in a
closed stainlessclosed stainless--steel vessel (retort)steel vessel (retort)closed stainlessclosed stainless--steel vessel (retort)steel vessel (retort)
4TiCl4TiCl44 (gas) + 2Mg (liquid) (gas) + 2Mg (liquid) Ti (solid) + 2MgClTi (solid) + 2MgCl22 (liquid)(liquid)
Ti spongeTi sponge
Preparation of Ti IngotsPreparation of Ti Ingots
Molten Ti Molten Ti reactsreacts with oxygen & nitrogenwith oxygen & nitrogen Molten Ti Molten Ti reactsreacts with oxygen & nitrogenwith oxygen & nitrogen
Ti sponge crushed & compacted into electrode Ti sponge crushed & compacted into electrode
compactscompacts
these welded togetherthese welded together
form consumable electrodeform consumable electrode
for vacuum arc meltingfor vacuum arc melting for vacuum arc meltingfor vacuum arc melting
For alloy ingots the alloying materials are mixed For alloy ingots the alloying materials are mixed
with the crushed Ti sponge before compactingwith the crushed Ti sponge before compacting
4Page 7Subsequent ProcessingSubsequent Processing
harvey fig p11
Production of TitaniumProduction of Titanium
5Page 9
CastingCasting Use skull melting (EBHCR) instead of VIM/VAR/ESR for final melting
stage in triple melting process
Titanium AlloysTitanium Alloys Relatively new engineering metalsRelatively new engineering metals
Been in use as structural materials only since 1952Been in use as structural materials only since 1952
Ti alloys attractive because:Ti alloys attractive because: Ti alloys attractive because:Ti alloys attractive because:
High strength/weight ratioHigh strength/weight ratio
High elevated temperature properties (i.e., ~550High elevated temperature properties (i.e., ~550C)C)
Excellent corrosion resistance (particularly in Excellent corrosion resistance (particularly in
oxidizing acids and chloride media and in most natural oxidizing acids and chloride media and in most natural
environments)environments)
Disadvantage is cost i.e., Ti ~8x cost of aluminum and Disadvantage is cost i.e., Ti ~8x cost of aluminum and Disadvantage is cost i.e., Ti ~8x cost of aluminum and Disadvantage is cost i.e., Ti ~8x cost of aluminum and
5x cost of stainless steel5x cost of stainless steel
However they do compete effectively in areas where However they do compete effectively in areas where
strength/weight and highstrength/weight and high--elevated temperature elevated temperature
properties are of prime importance (i.e. aerospace)properties are of prime importance (i.e. aerospace)
6Commercially attractive propertiesCommercially attractive properties
and applicationsand applications
resistance to corrosion:resistance to corrosion:
chemical processing, the pulp and paper industry, chemical processing, the pulp and paper industry, chemical processing, the pulp and paper industry, chemical processing, the pulp and paper industry,
marine applications, and energy production and marine applications, and energy production and
storagestorage
inertness in the human body:inertness in the human body:
biomedical, surgical implants and prosthetic devicesbiomedical, surgical implants and prosthetic devices
high specific strength:high specific strength: high specific strength:high specific strength:
automotive industryautomotive industry
cameras, jewellery, frames for glasses musical cameras, jewellery, frames for glasses musical
instruments, and sports equipmentinstruments, and sports equipment
Ti Ti PourbaixPourbaix
Diagram:Diagram:
good corrosiongood corrosion
resistanceresistanceresistanceresistance
7Susceptibility to crevice corrosionSusceptibility to crevice corrosion
Crevice corrosion of
Ti0.3Mo0.8Ni and grade
2 unalloyed Ti in
saturated NaCl solution.
Shaded band represents
transition zone between
Grade 2
transition zone between
active and passive
behavior.
Ti0.3Mo0.8Ni
Selected physical properties ofSelected physical properties of
titanium as compared to those of titanium as compared to those of
aluminium and ironaluminium and iron
Titanium Aluminium Iron
Density gm/cm3 4.54 2.70 7.87
Modulus of elasticity, x103 MPa 113 70 208
Melting point [C] 1,668 660 1,537
Crystal structure at room
temperature
HCP FCC BCC
temperature
8ConsiderConsider pure Tipure Ti
Purity ranges from 99.5Purity ranges from 99.5--99.099.0% Ti% Ti
Main alloying elements: Fe, C, O, N (interstitials)Main alloying elements: Fe, C, O, N (interstitials)
Can be considered an Can be considered an --phase alloy in which oxygen phase alloy in which oxygen
content determines the grade and strength content determines the grade and strength %O equivalent %O equivalent
= %O + 2%N + 0.67%C= %O + 2%N + 0.67%C
Each 0.1%O equivalent of interstitial elements in pure Ti increases Each 0.1%O equivalent of interstitial elements in pure Ti increases
strength by ~120 strength by ~120 MPaMPa
Although interstitials increase strength they decrease toughnessAlthough interstitials increase strength they decrease toughness
Therefore if high toughness is desired (especially at low Therefore if high toughness is desired (especially at low
temperatures), an alloy will be produced with extratemperatures), an alloy will be produced with extra--low low
interstitials interstitials (ELI)(ELI)
Miller indices of hexagonal Miller indices of hexagonal
crystal planescrystal planes
(a) Basal planes (b) Prism planes (a) Basal planes (b) Prism planes (c) (c) Pyramidal planesPyramidal planes
9Deformation properties of pure TiDeformation properties of pure Ti
Can be coldCan be cold--rolled at room temperature to rolled at room temperature to
>90% without >90% without crackingcracking
Unusual for HCP metals due to low c/a ratioUnusual for HCP metals due to low c/a ratio Unusual for HCP metals due to low c/a ratioUnusual for HCP metals due to low c/a ratio
Relatively high ductility of HCP Ti is attributed Relatively high ductility of HCP Ti is attributed
to the many operative slip systems and to the many operative slip systems and
available twinning planes in the crystal latticeavailable twinning planes in the crystal lattice
i.e. slip occurs on the {1010} prism planes i.e. slip occurs on the {1010} prism planes
and the {1011} pyramidal plans as well as on and the {1011} pyramidal plans as well as on and the {1011} pyramidal plans as well as on and the {1011} pyramidal plans as well as on
the basal planesthe basal planes
Twinning in plastic deformation more important Twinning in plastic deformation more important
in Ti than in Mg, Zn and in Ti than in Mg, Zn and CdCd
Lattice parameters of HCP metalsLattice parameters of HCP metals
Metal a c c/a*
Beryllium 2.2840 3.5841 1.5692
Cadmium 2.9787 5.6170 1.8857Cadmium 2.9787 5.6170 1.8857
Cobalt 2.5070 4.0690 1.6230
Hafnium 3.2060 5.0870 1.5867
Magnesium 3.2092 5.2103 1.6235
Titanium 2.9504 4.6833 1.5873
Zinc 2.6640 4.9450 1.8562
Zirconium 3.2300 5.1330 1.5892Zirconium 3.2300 5.1330 1.5892
*High c/a ratio leads to primary slip system on basal planes
Note: c/a affects tendency towards 2 secondary slip systems:
Pyramidal
Prismatic (primary is Basal plane)
10
Alloys DesignationAlloys Designation
CATEGORY CATEGORY
Grade 1 Pure Titanium, low oxygen Grade 16 Pure Titanium + 0,040,08% Pd, standard oxygen
Grade 2 Pure Titanium, standard oxygen Grade17 Pure Titanium + 0,040,08% Pd, low oxygen
Grade 3 Pure Titanium, high oxygen Grade 18 Alloy (Al 3%, V 2,5%) + 0,040,08% Pd Grade 3 Pure Titanium, high oxygen Grade 18 Alloy (Al 3%, V 2,5%) + 0,040,08% Pd
Grade 4 Pure Titanium, very high oxygen Grade 19 Alloy (Al 3%, V 8%, Cr 6%, Zr 4%, Mo 4%)
Grade 5 Alloy (Al 6%, V 4%) Grade 20 Alloy (Al 3%, V 8%, Cr 6%, Zr 4%, Mo 4%) + 0,040,08% Pd
Grade 6 Alloy (Al 5%, Sn 2,5%) Grade 21 Alloy (Mo 15%, Al 3%, Nb 2,7%, Si 0,25%)
Grade 7 Pure Titanium + 0,120,25% Pd, standard oxygen
Grade 22 - - - - - - -
Grade 8 - - - - - - Grade 23 Alloy (Al 6%, V 4%) ELI
Grade 9 Alloy (Al 3%, V 2,5%) Grade 24 Alloy (Al 6%, V 4%) + 0,040,08% Pd
Grade 10 - - - - - - Grade 25 Alloy (Al 6%, V 4%) + Ni 0,30,8%, 0,040,08% Pd
22/03/2010 Prof. G. Ubertalli
0,040,08% Pd
Grade 11 Pure Titanium + 0,120,25% Pd, low oxygen
Grade 26 Pure Titanium + 0,080,14% Ru
Grade 12 Alloy (Mo 0,3%, Ni 0,8%) Grade 27 Pure Titanium + 0,080,14% Ru
Grade 13 Alloy (Ni 0,5%, Ru 0,05%), very low oxygen
Grade 28 Alloy (Al 3%, V 2,5%) + 0,080,14% Ru
Grade 14 Alloy (Ni 0,5%, Ru 0,05%) low oxygen Grade 29 Alloy (Al 6%, V 4%) ELI + 0,080,14%
Ru
Grade 15 Alloy (Ni 0,5%, Ru 0,05%) standard oxygen
Grade 30 Pure Titanium + Co 0,200,80%, 0,040,08% Pd
Influence of interstitial elementsInfluence of interstitial elements
1000 30
Ro
ttu
ra a
fle
ssio
ne
(sa
lda
tura
), %
400
600
800
Re
sist
en
za
[M
Pa
]
Azoto
Ossigeno
Carbonio
0
10
20
Ro
ttu
ra a
fle
ssio
ne
(sa
lda
tura
), %
Azoto
Ossigeno
Carbonio
22/03/2010 Prof. G. Ubertalli
The graphs evidence the strength and elongation as a The graphs evidence the strength and elongation as a function of interstitial elements amount (N, function of interstitial elements amount (N, O, C).O, C).The graphs evidence the strength and elongation as a The graphs evidence the strength and elongation as a function of interstitial elements amount (N, function of interstitial elements amount (N, O, C).O, C).
400
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8
Contenuto di interstiziali, %
0
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8
Contenuto di interstiziali, %
11
Impact propertiesImpact properties
150
200
grado 2
grado 3
grado 4
0
50
100
150
Re
silie
nza
[J
]
grado 4
22/03/2010 Prof. G. Ubertalli
Trend of impact energy Trend of impact energy of of three three different titanium alloysdifferent titanium alloys
0
-200 -100 0 100 200 300 400
Temperatura [C]
Corrosion ResistanceCorrosion Resistance
0,6
0,8
Ve
loc
it
di c
orr
os
ion
e,
Ti-0,3Mo-0,8Ni
Grado 2
Ti-0,2Pd
0
0,2
0,4
0,6
0 20 40 60 80
Ve
loc
it
di c
orr
os
ion
e,
mm
/an
no
22/03/2010 Prof. G. Ubertalli
CCorrosion orrosion resistance as a function of nitric acid resistance as a function of nitric acid
concentration concentration of of three titanium alloysthree titanium alloys
0 20 40 60 80
Concentrazione di HNO3, %
12
Phase Diagram IPhase Diagram I
22/03/2010 Prof. G. Ubertalli
TiTi-- AlAl
Phase Diagram Phase Diagram IIII
22/03/2010 Prof. G. Ubertalli
TiTi-- VV
13
Phase Diagram Phase Diagram IIIIII
22/03/2010 Prof. G. Ubertalli
TiTi-- ZrZr
Influence of alloying elementsInfluence of alloying elements
Alloying Element Range weight % Effect on structure
Aluminium 2 7 stabilizing
Tin 2 6 stabilizingTin 2 6 stabilizing
Vanadium 2 20 stabilizingMolibdenum 2 20 stabilizingChromium 2 12 stabilizingCopper 2 6 stabilizing - e hardeningZirconium 2 8 -
Silicon 0,05 1 Increase creep resistance
22/03/2010 Prof. G. Ubertalli
A very important A very important property property of the alloying elements is of the alloying elements is their influence on the stabilization the their influence on the stabilization the phase (low phase (low
temperature) or the temperature) or the phase (high temperature).phase (high temperature).Carbon, oxygen and nitrogen are Carbon, oxygen and nitrogen are stabilizing.stabilizing.
14
Ti Allotropes, Phase Ti Allotropes, Phase
DiagramDiagram
Pure Ti:Pure Ti:
L (bcc) @ 1,668 C
(hcp) @ 882.5 C
=4.7 g/cc
highly protective TiO2 film
Diffusion in 100x slower
than in
origin of better creep
resistance
4 alloys to be considered4 alloys to be considered
Grades 1Grades 14 increase in O4 increase in O--CC--N N UsageUsage
A. Pure Ti (99.0 + A. Pure Ti (99.0 + %Ti%Ti) HCP 35%) HCP 35%A. Pure Ti (99.0 + A. Pure Ti (99.0 + %Ti%Ti) HCP 35%) HCP 35%
B. B. alloyalloy (Ti(Ti--5Al5Al--2.5Sn) 2.5Sn) GradeGrade 6 10%6 10%
-- phasephase stabiliserstabiliser
C. C. alloyalloy (Ti(Ti--13V13V--11Cr11Cr--3Al) BCC ~1%3Al) BCC ~1%
-- phasephase stabiliserstabiliser
D. D. + + alloyalloy TiTi--6Al6Al--4V 4V GradeGrade 5/23 55%5/23 55%
-- phasephase stabiliserstabiliser -- phasephase stabiliserstabiliser
15
Mechanical propertiesMechanical properties
Grade Y.S. (MPa) UTS (MPa) % ElongationGrade Y.S. (MPa) UTS (MPa) % Elongation
1. Pure Ti 241585 331661 3020
2. Ti-5Al-2.5Sn () 806 861 16
3. Ti-1V-11Cr-3Al () 1,205 (H.T.) 1,275 8
4. Ti-6Al-4V (+) 1,102 (H.T.) 1,171 10
(H.T.) = Solution anneal quench and aged
Alloys Alloys
Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) Designed for high strength and depth sections and uses at
intermediate temperatureTi-6Al-2Sn-4Zr-6Mo
Ti-6Al-2Sn-4Zr-6Mo (Ti-6242) Designed for creep resistance
Ti-6Al-2Nb-1Ta-1Mo Designed for stress corrosion cracking in acqueous salt solution
and for high fracture toughnessTi-6Al-4V-ELI
AlloyAlloy ,, suchsuch asas TiTi--55AlAl--22..55Sn,Sn, areare slightlyslightly lessless corrosioncorrosion resistantsresistants
butbut evidenceevidence aa higherhigher strengthstrength thanthan purepure titaniumtitanium..
and for high fracture toughnessTi-6Al-4V-ELI
Ti-5Al-2.5Sn Designed for weld ability
Ti-5Al-2.5Sn-ELI Adopted for cryogenic applications
Ti-6Al-4V - lega ( + )-the most usedTi-6Al-6V-2Sn
Ti-10V-2Fe-3Al
They evidence a poor quench-ability in case of high depth
Designed for high strength at room and intermediate temperature
22/03/2010 Prof. G. Ubertalli
butbut evidenceevidence aa higherhigher strengthstrength thanthan purepure titaniumtitanium..
AlloyAlloy areare generallygenerally ductileductile;; thethe ELIELI gradegrade maintainsmaintains thisthis propertyproperty
atat cryogeniccryogenic temperaturetemperature..
AlloyAlloy areare notnot hardenablehardenable byby heatheat treatmenttreatment becausebecause thesethese alloysalloys
areare stablestable.. TheseThese alloysalloys cancan bebe hardenedhardened byby graingrain sizesize reductionreduction.. TheThe
mostmost importantimportant alloyingalloying elementelement isis AlAl..
16
Microstructures Microstructures near near
alloysalloys stabilisers raise /
transustransus
stabilisers to widen /
field and allow hot working
heat treatable
~10% primary (grain boundary)
during h.t. @ > 900 C
oil quench intragranular
plates + retained plates + retained
age at ~ 625 C to form ,
spheroidise and stress relieve
Then >> 90%
Lightly deformed (~5%) Ti-834
Imperial College London
Page 32
Refined grain size
stronger stronger
better fatigue resistance
Predominantly few good slip systems
good creep resistance
Si segregates to dislocation cores inhibit glide/climb further
17
HeatingHeating TemperatureTemperature
TheThe heatingheating temperaturetemperature isis
fundamentalfundamental inin thethe workabilityworkability
andand inin thethe finalfinal obtainableobtainable 1050
1100
Regione beta 100 % beta
10 % alfaandand inin thethe finalfinal obtainableobtainable
propertiesproperties..
DifferentDifferent forgingforging and/orand/or
heatheat treatmenttreatment temperaturetemperature
areare adoptedadopted forfor thethe TiTi--66AlAl--44VV
alloyalloy alphaalpha--betabeta..
TheThe higherhigher thethe temperaturetemperature800
850
900
950
1000
1050
Te
mp
era
tura
, C
Regione
alfa + beta
10 % alfa
60 % alfa
90 % alfa
Regione alfa
22/03/2010 Prof. G. Ubertalli
TheThe higherhigher thethe temperaturetemperature
ofof treatment,treatment, thethe greatergreater isis thethe
amountamount ofof betabeta phasephase thatthat
cancan bebe transformedtransformed inin
quenchingquenching andand temperingtempering..
750
800
0 2 4 6 8
Vanadio, % in peso
Ti + 6Al
Heating Temperature
18
AlloysAlloys + + The alloys + can be obtained with opportune composition; the percentage ranges from 10 to 50%. The heat treatment is solutionheat treatment, quench and tempering at temperature ranging from480 and 650 C. The microstructure is a fine mixture of + in ametallic matrix of residual or transformed phase.metallic matrix of residual or transformed phase.
Property Beta processed Alfa/beta processed
Strength Moderate Good
Creep Resistance Good Low
Fatigue Resistance Moderate Good
FractureToughness Good Low800
850
900
950
1000
1050
1100
Te
mp
era
tura
, C
Regione beta
Regione
alfa + beta
100 % beta
10 % alfa
60 % alfa
90 % alfa
Regione alfa
22/03/2010 Prof. G. Ubertalli
InIn thethe tabletable areare reportedreported thethe vantagesvantages andand disadvantagesdisadvantagesofof thethe twotwo treatmentstreatments..
FractureToughness Good Low
Rate of crack propagation Good Moderate
Grains size Coarse Fine
750
800
0 2 4 6 8
Vanadio, % in peso
Ti + 6Al
Microstructure Microstructure -- PropertiesPropertiesMicrostructure Properties
Equiaxed
Higher ductility and HT deformability.
Higher minimal strength in stress corrosion cracking phenomena in
hot salt baths.
Higher strength (for equivalent heat treatments).
Better fatigue resistance at low cycles (crack initiation)
Higher properties of creep resistance.
The properties of different alloys depend on their microstructures. The properties of different alloys depend on their microstructures.
The microstructure depends on chemical composition and heat The microstructure depends on chemical composition and heat
treatment. treatment.
Acicular
Higher properties of creep resistance.
High values of fracture toughness.
Slightly decrease in hardening (in case of the same heat treatment).
Higher stress corrosion cracking values.
Lower values of crack propagation.
22/03/2010 Prof. G. Ubertalli
The The microstructure microstructure can be:can be:
-- equiaxedequiaxed, obtained heating the alloy in the , obtained heating the alloy in the -- range and range and
annealed at lower temperatureannealed at lower temperature
-- acicular, obtained by mechanical working or heat treated over acicular, obtained by mechanical working or heat treated over
transustransus temperature with a following rapid cooling (quench).temperature with a following rapid cooling (quench).
19
Influence of treatment temperatureInfluence of treatment temperature
Forged at 900 C, below the
standard range. Equiaxed
alpha grains (light) and
Forged at 1005 C (standard
temperature range) air
cooled. Primary equiaxed
Forged at 1093 C, over the
beta transus temperature and
a b c
22/03/2010 Prof. G. Ubertalli
Figures a, b, c: Microstructures observed on the Ti-8Al-1Mo-1V
alloy after forging at the different temperature.
alpha grains (light) and
mixed alpha-beta
microstructure (dark).
cooled. Primary equiaxed
grains (white) in a beta
transformed matrix (dark)
containing acicular alpha.
beta transus temperature and
rapid cooling in air. Beta
transformed containing fine
and coarse acicular
microstructure.
Microstructure Microstructure Ti6Al4VTi6Al4V
22/03/2010 Prof. G. Ubertalli
Rolled alloy, annealed from Rolled alloy, annealed from + + range temperature.range temperature.
The microstructure is polygonal The microstructure is polygonal and and -- 500x500x
Alloy as produced, quenched from
+ range temperature.The microstructure is acicular and inside primary grains of -500x
20
MicrostructureMicrostructure Ti6Al4VTi6Al4V
22/03/2010 Prof. G. Ubertalli
Alloy as produced, quenched Alloy as produced, quenched
from from + + range temperature.range temperature.The microstructure is constituted The microstructure is constituted
from from acicular acicular surrounded from surrounded from fine lamellae of fine lamellae of -- 100x100x
Rolled alloy, annealed from + range temperature.
Microstructure is polygonal and - 500x.
++ alloys: alloys:
Microstructures Microstructures Contain significant
stabilisers to enable to be
retained to RTretained to RT
Classic Ti alloy: Ti-6Al-4V
>50% of all Ti used
Classically
1065 C all
forge @ 955C acicular
on grain boundaries to
inhibit coarseninginhibit coarsening
Air cool produce
lamellae colonies formed
in prior grains (minimise
strain), w/ in between
(think at the pearlite)
21
Mechanical propertiesMechanical properties
22/03/2010 Prof. G. Ubertalli
TiTi--66--4: properties4: properties
N.B. Must avoid Ti Al formation N.B. Must avoid Ti3Al formation
Al equivalent: Al+0.33 Sn + 0.16 Zr + 10 (O+C+2N) < 9 wt%
Precipitation
hardening
+ grain size
22
Imperial College London
Page 43
TiTi--66--4: 4:
heat treatheat treat
--Ti Alloy designTi Alloy designHard to completely stabilize
w.r.t. hexagonal phases
stabilisers: O, Al (N,C) stabilisers: O, Al (N,C)
stabilisers: V,Mo,Nb,Si,Fe
neutral: Sn, Zr
Strengthen near- alloys by
solid solution Fe,Nb,V
Hall-Petch
cold work
Uses: highly formable
Landing gear
Auto bodies
23
--AlloysAlloys
Highest strength Ti alloys Highest strength Ti alloys used in specialized used in specialized
applicationsapplications
Higher density because of Mo, V, Fe additionsHigher density because of Mo, V, Fe additions Higher density because of Mo, V, Fe additionsHigher density because of Mo, V, Fe additions
Add Al to lower density and give solid solution strength Add Al to lower density and give solid solution strength
and high temperature oxidation resistanceand high temperature oxidation resistance
Easy to cold work (BCC) in solution treated and Easy to cold work (BCC) in solution treated and
quenchedquenched conditioncondition
Can be subsequently aged to very high strengthsCan be subsequently aged to very high strengths
--AlloysAlloys
-- omega omega transition phase is brittletransition phase is brittle
TiTi--13%V13%V--11%Cr11%Cr--3%Al 3%Al onlyonly --alloyalloy producedproduced TiTi--13%V13%V--11%Cr11%Cr--3%Al 3%Al onlyonly --alloyalloy producedproduced
in in largelarge quantitiesquantities
LimitedLimited useuse becausebecause ofof::
Relatively high density because of V, MoRelatively high density because of V, Mo
Low ductility in high strength conditionLow ductility in high strength condition
In thick sections In thick sections chemical segregation; chemical segregation;
large grain size therefore low tensile ductility large grain size therefore low tensile ductility
and poor fatigue performanceand poor fatigue performance
24
MicrostructureMicrostructure forfor
TiTi--13%V13%V--11%Cr11%Cr--3%Al3%Al
SolutionSolution treatedtreated at at SolutionSolution treatedtreated at at
788788C C forfor 30min 30min
Water Water quenchedquenched
Metastable
phase (BCC)
--Ti Alloys: SurveyTi Alloys: Survey
Strength and Selection of -Ti alloys
y/y E
Low Cost Beta (LCB)250-290110950-1400Ti 4.5Fe 6.8Mo 1.5Al
Springs163-21970-103780-1050Ti 15V 3Cr 3Al 3Sn
Springs (Beta C)17188
825Ti 3Al 8V 6Cr 4Mo 4Zr
Landing Gear210-250105970-1170Ti 10 V 2Fe 3Al
Low Cost Beta (LCB)
Development of Beta C
250-290110950-1400Ti 4.5Fe 6.8Mo 1.5Al
25
ApplicationsApplications in in medicalmedical fieldsfields
HipHip prosthesisprosthesis HipHip prosthesisprosthesis
AorticAortic ValvesValves
PeacemakerPeacemaker
DentalDental applicationsapplications
Dental prosthesisDental prosthesis Dental prosthesisDental prosthesis
Dental plantsDental plants Dental plantsDental plants
26
AutomotiveAutomotive applicationsapplications
ValvesValves ValvesValves
ConnectingConnecting rodsrods
Exhaust gas systemExhaust gas system
Shock absorbersShock absorbersSpring mass calculationSpring mass calculation::
C
FGm
maz
f
2
2
2
ApplicationsApplications
Year Components Material Company Type Use/Year
1998
1998
1998
1999
1999
Brake pin
Flat washers
Knob of the gearbox
Connecting rod
Valves
Grade 2
Grade 1s
Grade 1
Ti-6Al-4V
Ti-6Al-4V
Mercedes-Benz
Volkswagen
Honda
Porsche
Mercedes-Benz
S-class
All
S2000 Roadster
GT3
Heigth 6-cil.
~ 8 t/yr
~ 40 t/yr
n/a
~ 1 t/yr
n/a1999
1999
2000
2000
2000
2001
2002
Valves
Rotor for turbocharger
Absorber springs
Sump valve
Rotor for turbocharger
Exhaust gas system
Valves
Ti-6Al-4V
Ti-6Al-4V
LCB
Alloy
TiAl
Grade 2
Ti-6Al-4V
Mercedes-Benz
Volkswagen
Mitsubishi
Mitsubishi
General Motors
Nissan
Heigth 6-cil.
Truck
Lupo FSI
All 1.8l-4 cil.
Lancer
Corvette Z06
Infinity Q 45
n/a
n/a
3-4 t/yr
n/a
n/a
> 150 t/yr
n/a
27
SeaSea applicationsapplications
Rotary Rotary drillingdrilling systemssystems Rotary Rotary drillingdrilling systemssystems
Submarine coatingsSubmarine coatings Submarine coatingsSubmarine coatings
AerospaceAerospace SectorSector
FigthersFigthers airplanesairplanes FigthersFigthers airplanesairplanes
Gas compressor deviceGas compressor device Gas compressor deviceGas compressor device
28
Page 55
Fan Blade TechnologyFan Blade Technology
+ 4% efficiency+ 4% efficiencyClappered Wide-chord fan
Page 56WideWide--chord Fan Technologychord Fan Technology
1st generation:
1984
2nd generation:
1995
Honeycomb
construction
DB/SPF
construction
29
Page 57Fan SectionFan Section
Page 58
Swept FansSwept Fans
30
Tank of ShuttleTank of Shuttle
Retractable undercarriage of Boeing 747Retractable undercarriage of Boeing 747
At 570 At 570 C it is preferred to substitute C it is preferred to substitute
the Ti alloys with Ni base alloys for the the Ti alloys with Ni base alloys for the
following reasons:following reasons:
Temperature too high for their properties.Temperature too high for their properties.
The cares that titanium could evidenced The cares that titanium could evidenced
some burning or flash phenomena.some burning or flash phenomena.
Oxidation problems for titanium, consequent Oxidation problems for titanium, consequent Oxidation problems for titanium, consequent Oxidation problems for titanium, consequent
oxygen enrichment of phase and lose of oxygen enrichment of phase and lose of
some properties (ductility).some properties (ductility).
31
EnergyEnergy
Heat exchangers, radiatorsHeat exchangers, radiators
Fan vapor turbinesFan vapor turbines Fan vapor turbinesFan vapor turbines
TitaniumTitanium in in tankstanks
M1 M1 AbramsAbrams
Armor plating propertiesArmor plating properties STEEL
PHA MIL-A-12560
ALUMI#IUM 5083
MIL-A-46026 Ti-6Al-4V
MIL-A-46077 PHA MIL-A-12560 MIL-A-46026 MIL-A-46077
Tensile strength (MPa) 1170 350 970
Density (g/cm3) 7.86 2.70 4.50
Specific strength
(MPa / cm3/g)
150 130 220
Mass efficiency (Em) 1 1.0-1.2 1.5
32
Building Building applicationsapplications
The properties of titanium in architecture are:The properties of titanium in architecture are:
ThermalThermal dilatationdilatation:: TitaniumTitanium hashas aa coefficientcoefficient veryvery lowlow ThermalThermal dilatationdilatation:: TitaniumTitanium hashas aa coefficientcoefficient veryvery lowlowandand thereforetherefore isis lessless influencedinfluenced fromfrom thethe seasonseasonchangechange ofof temperaturetemperature andand aa consequentconsequent higherhigherdimensionaldimensional andand geometricalgeometrical stabilitystability..
TitaniumTitanium dodo notnot changechange colourcolour asas aa consequenceconsequence ofofultravioletultraviolet raysrays andand dodo notnot evidenceevidence pittingpitting corrosioncorrosioninducedinduced fromfrom seawaterseawater environmentenvironment oror fromfrom acidacid rainsrains..
GoodGood resistanceresistance atat thethe environmentenvironment:: thethe changechange ofof GoodGood resistanceresistance atat thethe environmentenvironment:: thethe changechange ofoftemperaturetemperature andand thethe presencepresence ofof pollutionpollution dodo notnotinfluenceinfluence thethe corrosioncorrosion resistanceresistance ofof titanium,titanium, thatthat ininveryvery highhigh..
Guggenheim Guggenheim MuseumMuseum in in BilbaoBilbao
Van Van GoghGogh MuseumMuseum
National Center National Center ofof Science Science in in ScotlandScotland
33
The The titaniumtitanium in sportin sport
GolfGolfGolfGolf
CyclingCycling
DivingDiving
TrekkingTrekking
Winter SportWinter Sport
OtherOther applicationsapplications
Jewellery and fashionJewellery and fashion
SafetySafety
NanotechnologyNanotechnology
34
ComponentsComponents II
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CastCast technologytechnology..
ComponentsComponents IIII
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CastCast technologytechnology..
35
High temperature High temperature propertiesproperties asas
comparedcompared toto steelssteels
22/03/2010 Prof. G. Ubertalli
Tensile strength of different Tensile strength of different
metallic alloys at different metallic alloys at different
temperature.temperature.
Specific tensile strength of different
metallic alloys at different
temperature.
Ti Creep RatesTi Creep Rates
36
ComparisonComparison 2 2
High High
temperaturetemperature
TheThe mechanicalmechanical propertiesproperties atat highhightemperaturetemperature ofof titaniumtitanium alloysalloys arearemainlymainly thatthat ofof alphaalpha oror nearnearalphaalpha alloysalloys.. WheneverWhenever thethe creepcreepphenomenaphenomena isis notnot soso importantimportant atathighhigh temperature,temperature, thethe tensiletensilestrengthstrength ofof betabeta alloys,alloys, atat highhightemperaturetemperature forfor shortshort time,time, isishigherhigher..higherhigher..
InIn factfact thesethese alloys,alloys, untiluntil aboutabout425425 C,C, havehave higherhigher specificspecifictensiletensile strengthstrength thanthan HH1111 tooltoolsteels,steels, whilewhile alphaalpha andand nearnear alphaalphaalloysalloys areare notnot inin advantageadvantage..
ForFor longlong timetime applicationsapplications thethealphaalpha andand nearnear alphaalpha alloysalloys havehavesubstitutedsubstituted thethe steelssteels ininaeronauticalaeronautical turbinesturbines..
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aeronauticalaeronautical turbinesturbines..
InIn figurefigure areare plottedplotted thethe curvescurves ofofspecificspecific tensiletensile strengthstrength ofof twotwotitaniumtitanium alloysalloys adad threethree steelssteelsadoptedadopted forfor aeronauticalaeronautical turbines,turbines,inin thethe averageaverage lowlow temperaturestemperaturesrangerange.. InIn comparisoncomparison withwith steels,steels,thethe titaniumtitanium alloysalloys havehave higherhigherpropertiesproperties untiluntil 540540 CC..
SuperSuper--plasticityplasticity
AtAt highhigh temperaturetemperature ((870870925925 C,C,withoutwithout exceedingexceeding thethe betabeta--transustransus)) somesome alloysalloys evidenceevidence thethe
1000
1200
transustransus)) somesome alloysalloys evidenceevidence thethesupersuper--plasticityplasticity phenomenaphenomena.. ToToinduceinduce thisthis behaviourbehaviour somesome wellwelldefinedefine conditionsconditions areare neededneeded::
VeryVery finefine graingrain dimensionsdimensions (about(about1010 mm size)size)..RelativelyRelatively highhigh temperaturetemperature (higher(higherthanthan 11//22 thethe meltingmelting temperaturetemperature K)K)..
AA controlledcontrolled deformationdeformation raterate(generally(generally fromfrom 00..00010001 toto 00..0101 ss--11))..
400
600
800
1000
All
un
ga
me
nto
, %
Ti-6Al-4V
22/03/2010 Prof. G. Ubertalli
(generally(generally fromfrom 00..00010001 toto 00..0101 ss--11))..
AA twotwo phasephase microstructuremicrostructure (( andand inin titanium)titanium)..
InIn figurefigure isis evidencedevidenced suchsuch influenceinfluence..
0
200
0 20 40 60 80 100
Contenuto di beta, vol.%
Ti-6Al-4V-2Ni
Ti-6Al-2Sn-4Zr-2Mo
Ti-8Mn
Valori minimi
Valori massimi
37
Fracture toughness of TitaniumFracture toughness of Titanium
TheThe fracturefracture toughnesstoughness valuesvaluescancan bebe improvedimproved byby aa factorfactor 22 oror
80
cancan bebe improvedimproved byby aa factorfactor 22 oror33 forfor TiTi alloys,alloys, ifif thethe appropriateappropriateheatheat treatmenttreatment andand chemicalchemicalcompositioncomposition areare chosenchosen(microstructure(microstructure andand preferredpreferredorientation)orientation)..
HoweverHowever OxygenOxygen mustmust bebemaintainedmaintained lowlow;; iitt isis alwaysalways ananimpurityimpurity..
20
40
60
Te
na
cit
a
fra
ttu
ra [
MP
a m
]
Ti-6Al-4V piastra
Ti-6Al-4V getto
Ti-17 (a-b) processato
Ti-17 b processato
Beta III
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impurityimpurity..
0
700 900 1100 1300
Snervamento [MPa]
Beta III
Valori minimi
Valori massimi
SSchemecheme ofof propertiesproperties
Ti 834 Ti-6Al-2Sn-4Zr- Ti-6Al-2Sn-4Zr-2Mo Ti 17
2Mo-0,8Si TA5E IMI 685 BetacezTi-6Al-4V
transus Deformability
Flusso
tensioniStrain rate sensitivity
Weldability Hardeability
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Leghe Leghe "near" Leghe + Leghe "near" Leghe
HighT strength Room T strength
38
P/M Ti alloys?P/M Ti alloys?
Have been produced: would be useful in Have been produced: would be useful in
e.g. controlling grain size in pure
forging
BUT: problem of avoiding oxide layer on BUT: problem of avoiding oxide layer on
powder particles and consequent TiO2
and inclusions
SinteredSintered components toughnesscomponents toughness
60
65
KQ
[Mp
a m
]
40
45
50
55
94 95 96 97 98 99 100
Fratt
ure to
ug
hn
ess
K
Density % of theoretical
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EffectEffect ofof density on density on fracturefracture toughnesstoughness ofof sinteredsintered
Ti6Al4V Ti6Al4V partsparts. .