ti_col.pdf

1Titanium Titanium Titanium Titanium

Alloys IAlloys I

Titanium Titanium

Alloys IAlloys IAlloys IAlloys I

2General properties of TiGeneral properties of TiGeneral properties of TiGeneral properties of Ti

It has a HEX lattice at low temperature (

3Page 3

OutlineOutlineOutlineOutline

Ti primary production Ti primary production

CP Ti and applications

-Ti alloying, alloy design

near- alloy microstructures, forging near- alloy microstructures, forging

and heat treatment

/ alloys, Ti-6Al-4V / alloys, Ti-6Al-4V

defects

4Ti Primary Production Ti Primary Production

Kroll ProcessKroll Process

Ti Primary Production Ti Primary Production

Kroll ProcessKroll Process Ti common in Earths crust Ti common in Earths crust

Energy to separate ~125 MWhr/tonne (7/kg just in

power)

Batch process over 5 days:

Produce TiCl4 from TiO2 and Cl2

TiCl + 2 Mg 2 MgCl + Ti TiCl4 + 2 Mg 2 MgCl2 + Ti

chip out Ti sponge (5-8 t) from reactor

cost 8/kg cost 8/kg

Chlorides corrosive, nasty

World annual capacity ~100,000 t, demand ~60,000t World annual capacity ~100,000 t, demand ~60,000t

Need a cheaper process that is direct

5Production of TiProduction of Ti

Obtained from minerals:Obtained from minerals:

rutilerutile (TiO(TiO )) rutilerutile (TiO(TiO22))

ilmeniteilmenite (FeO(FeO--TiOTiO22) approx 97) approx 97--98% TiO98% TiO22

Chemically converted to pure TiClChemically converted to pure TiCl Chemically converted to pure TiClChemically converted to pure TiCl44

Kroll Process:Kroll Process:

TiClTiCl reactesreactes with liquid Mg at ~773with liquid Mg at ~773--873873C in a C in a 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)

4TiCl4TiCl (gas) + 2Mg (liquid) (gas) + 2Mg (liquid) Ti (solid) + 2MgClTi (solid) + 2MgCl (liquid)(liquid) 4TiCl4TiCl44 (gas) + 2Mg (liquid) (gas) + 2Mg (liquid) Ti (solid) + 2MgClTi (solid) + 2MgCl22 (liquid)(liquid)

Ti spongeTi spongeTi spongeTi sponge

6Preparation of Ti IngotsPreparation of Ti Ingots

Molten Ti Molten Ti reactsreacts with oxygen & nitrogenwith oxygen & nitrogen

Ti sponge crushed & compacted into electrode Ti sponge crushed & compacted into electrode

compactscompactscompactscompacts

these welded togetherthese welded together

form consumable electrodeform consumable electrode

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

7Page 7

Subsequent ProcessingSubsequent ProcessingSubsequent ProcessingSubsequent Processing

harvey fig p11

8Production of TitaniumProduction of Titanium

9Page 9

CastingCastingCastingCasting Use skull melting (EBHCR) instead of VIM/VAR/ESR for final melting

stage in triple melting process

10

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:

High strength/weight ratioHigh strength/weight ratio

High elevated temperature properties (i.e., ~550High elevated temperature properties (i.e., ~550C)C) 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 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

5x cost of stainless steel5x cost of stainless steel5x 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 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)

11

Commercially attractive propertiesCommercially attractive properties

and applicationsand applicationsand applicationsand applications

resistance to corrosion:resistance to corrosion: resistance to corrosion:resistance to corrosion:

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 biomedical, surgical implants and prosthetic devicesbiomedical, surgical implants and prosthetic devices

high specific strength:high specific strength:

automotive industryautomotive industry automotive industryautomotive industry

cameras, jewellery, frames for glasses musical cameras, jewellery, frames for glasses musical

instruments, and sports equipmentinstruments, and sports equipment

12

Ti Ti PourbaixPourbaix

Diagram:Diagram:Diagram:Diagram:

good corrosiongood corrosion

resistanceresistanceresistanceresistance

13

Susceptibility to crevice corrosionSusceptibility to crevice corrosion

Crevice corrosion of Grade 2Crevice corrosion of

Ti0.3Mo0.8Ni and grade

2 unalloyed Ti in

saturated NaCl solution.

Grade 2

saturated NaCl solution.

Shaded band represents

transition zone between

active and passive active and passive

behavior.

Ti0.3Mo0.8Ni

14

Selected physical properties ofSelected physical properties of

titanium as compared to those of titanium as compared to those 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 1,537Melting point [C] 1,668 660 1,537

Crystal structure at room

temperature

HCP FCC BCC

15

ConsiderConsider pure Tipure TiConsiderConsider pure Tipure Ti

Purity ranges from 99.5Purity ranges from 99.5--99.099.0% Ti% 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 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 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)interstitials interstitials (ELI)(ELI)

16

Miller indices of hexagonal Miller indices of hexagonal

crystal planescrystal planescrystal planescrystal planes

(a) Basal planes (b) Prism planes (a) Basal planes (b) Prism planes (c) (c) Pyramidal planesPyramidal planes

17

Deformation 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>90% without >90% without crackingcracking

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 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

the basal planesthe basal planesthe 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 CdCdin Ti than in Mg, Zn and in Ti than in Mg, Zn and CdCd

18

Lattice parameters of HCP metalsLattice parameters of HCP metals

Metal a c c/a*

Beryllium 2.2840 3.5841 1.5692Beryllium 2.2840 3.5841 1.5692

Cadmium 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 1.5873Titanium 2.9504 4.6833 1.5873

Zinc 2.6640 4.9450 1.8562

Zirconium 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:

PyramidalPyramidal

Prismatic (primary is Basal plane)

19

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 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 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 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 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

Grade 11 Pure Titanium + 0,120,25% Pd, low oxygen

Grade 26 Pure Titanium + 0,080,14% Ru oxygen

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

22/03/2010 Prof. G. Ubertalli

Ru

Grade 15 Alloy (Ni 0,5%, Ru 0,05%) standard oxygen

Grade 30 Pure Titanium + Co 0,200,80%, 0,040,08% Pd

20

Influence of interstitial elementsInfluence of interstitial elementsInfluence of interstitial elementsInfluence of interstitial elements

800

1000

R

e

s

i

s

t

e

n

z

a

[

M

P

a

]

20

30

R

o

t

t

u

r

a

a

f

l

e

s

s

i

o

n

e

(

s

a

l

d

a

t

u

r

a

)

,

%

Azoto

Ossigeno

600

800

R

e

s

i

s

t

e

n

z

a

[

M

P

a

]

Azoto

Ossigeno

10

20

R

o

t

t

u

r

a

a

f

l

e

s

s

i

o

n

e

(

s

a

l

d

a

t

u

r

a

)

,

%

Ossigeno

Carbonio

400

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

Contenuto di interstiziali, %

Ossigeno

Carbonio

0

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

Contenuto di interstiziali, %R

o

t

t

u

r

a

a

f

l

e

s

s

i

o

n

e

(

s

a

l

d

a

t

u

r

a

)

,

%

The graphs evidence the strength and elongation as a The graphs evidence the strength and elongation as a The graphs evidence the strength and elongation as a The graphs evidence the strength and elongation as a

Contenuto di interstiziali, % Contenuto di interstiziali, %


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).

21

Impact propertiesImpact propertiesImpact propertiesImpact properties200

grado 2

grado 3

100

150

R

e

s

i

l

i

e

n

z

a

[

J

]

grado 3

grado 4

50

100

R

e

s

i

l

i

e

n

z

a

[

J

]

0

-200 -100 0 100 200 300 400

Trend of impact energy Trend of impact energy of of three three different titanium alloysdifferent titanium alloys

Temperatura [C]


different titanium alloysdifferent titanium alloys

22

Corrosion ResistanceCorrosion Resistance

0,8V

e

l

o

c

i

t

d

i

c

o

r

r

o

s

i

o

n

e

,

Ti-0,3Mo-0,8Ni

Grado 2

Ti-0,2Pd

0,4

0,6

V

e

l

o

c

i

t

d

i

c

o

r

r

o

s

i

o

n

e

,

m

m

/

a

n

n

o

Ti-0,2Pd

0,2

0,4

V

e

l

o

c

i

t

d

i

c

o

r

r

o

s

i

o

n

e

,

m

m

/

a

n

n

o

0

0 20 40 60 80

Concentrazione di HNO3, %

V

e

l

o

c

i

t

d

i

c

o

r

r

o

s

i

o

n

e

,

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

Concentrazione di HNO3, %


concentration concentration of of three titanium alloysthree titanium alloys

23

Phase Diagram IPhase Diagram I


TiTi-- AlAl

24

Phase Diagram Phase Diagram IIII


TiTi-- VV

25

Phase Diagram Phase Diagram IIIIII


TiTi-- ZrZr

26

Influence of alloying elementsInfluence of alloying elementsInfluence of alloying elementsInfluence of alloying elements

Alloying Element Range weight % Effect on structure

Aluminium 2 7 stabilizingAluminium 2 7 stabilizing

Tin 2 6 stabilizing

Vanadium 2 20 stabilizingMolibdenum 2 20 stabilizing

Chromium 2 12 stabilizingCopper 2 6 stabilizing - e hardening

A very important A very important property property of the alloying elements is of the alloying elements is

Zirconium 2 8 -

Silicon 0,05 1 Increase creep resistance

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.

27

Ti Allotropes, Phase Ti Allotropes, Phase

DiagramDiagram

Ti Allotropes, Phase Ti Allotropes, Phase

DiagramDiagram

Pure Ti:

L (bcc) @ 1,668 C

(hcp) @ 882.5 C (hcp) @ 882.5 C

=4.7 g/cc

highly protective TiO2 film2

Diffusion in 100x slower

than in

origin of better creep origin of better creep

resistance

28

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%

B. B. alloyalloy (Ti(Ti--5Al5Al--2.5Sn) 2.5Sn) GradeGrade 6 10%6 10%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%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%D. D. + + alloyalloy TiTi--6Al6Al--4V 4V GradeGrade 5/23 55%5/23 55%

-- phasephase stabiliserstabiliser -- phasephase stabiliserstabiliser

29

Mechanical propertiesMechanical propertiesMechanical propertiesMechanical properties

Grade Y.S. (MPa) UTS (MPa) % Elongation

1. Pure Ti 241585 331661 30201. 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

30

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

Ti-5Al-2.5Sn Designed for weld ability

Ti-5Al-2.5Sn-ELI Adopted for cryogenic applicationsTi-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

AlloyAlloy ,, suchsuch asas TiTi--55AlAl--22..55Sn,Sn, areare slightlyslightly lessless corrosioncorrosion resistantsresistants

butbut evidenceevidence aa higherhigher strengthstrength thanthan purepure titaniumtitanium..

AlloyAlloy areare generallygenerally ductileductile;; thethe ELIELI gradegrade maintainsmaintains thisthis propertyproperty 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


areare stablestable.. TheseThese alloysalloys cancan bebe hardenedhardened byby graingrain sizesize reductionreduction.. TheThe

mostmost importantimportant alloyingalloying elementelement isis AlAl..

31

Microstructures Microstructures near near

alloysalloys

Microstructures Microstructures near near

alloysalloys stabilisers raise / stabilisers raise /

transus

stabilisers to widen /

field and allow hot workingfield and allow hot working

heat treatable

~10% primary (grain boundary)

during h.t. @ > 900 Cduring h.t. @ > 900 C

oil quench intragranular

plates + retained

age at ~ 625 C to form , age at ~ 625 C to form ,

spheroidise and stress relieve

Then >> 90%

Lightly deformed (~5%) Ti-834

32

Imperial College London

Page 32

Refined grain size

stronger

better fatigue resistance better fatigue resistance

Predominantly few good slip systems

good creep resistance

Si segregates to dislocation cores inhibit glide/climb further Si segregates to dislocation cores inhibit glide/climb further

33

HeatingHeating TemperatureTemperature

TheThe heatingheating temperaturetemperature isis

fundamentalfundamental inin thethe workabilityworkability 1100fundamentalfundamental inin thethe workabilityworkability

andand inin thethe finalfinal obtainableobtainable

propertiesproperties..

DifferentDifferent forgingforging and/orand/or

1000

1050

T

e

m

p

e

r

a

t

u

r

a

,

C

Regione beta 100 % beta

10 % alfa

60 % alfa

90 % alfa

DifferentDifferent forgingforging and/orand/or

heatheat treatmenttreatment temperaturetemperature

areare adoptedadopted forfor thethe TiTi--66AlAl--44VV

alloyalloy alphaalpha--betabeta..900

950

T

e

m

p

e

r

a

t

u

r

a

,

C

Regione

alfa + betaRegione alfaalloyalloy alphaalpha--betabeta..

TheThe higherhigher thethe temperaturetemperature

ofof treatment,treatment, thethe greatergreater isis thethe800

850

T

e

m

p

e

r

a

t

u

r

a

,

C

Ti + 6Al

Regione alfa

ofof treatment,treatment, thethe greatergreater isis thethe

amountamount ofof betabeta phasephase thatthat

cancan bebe transformedtransformed inin

quenchingquenching andand temperingtempering..

750

0 2 4 6 8

Vanadio, % in peso

Ti + 6Al


34

Heating Temperature

35

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 fromheat 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.

Property Beta processed Alfa/beta processedProperty Beta processed Alfa/beta processed

Strength Moderate Good

Creep Resistance Good Low950

1000

1050

1100

T

e

m

p

e

r

a

t

u

r

a

,

C

Regione beta 100 % beta

10 % alfa

60 % alfa

90 % alfa

Creep Resistance Good Low

Fatigue Resistance Moderate Good

FractureToughness Good Low750

800

850

900

T

e

m

p

e

r

a

t

u

r

a

,

C

Regione

alfa + beta

Ti + 6Al

Regione alfa

InIn thethe tabletable areare reportedreported thethe vantagesvantages andand disadvantagesdisadvantages

Rate of crack propagation Good Moderate

Grains size Coarse Fine

750

0 2 4 6 8

Vanadio, % in peso


InIn thethe tabletable areare reportedreported thethe vantagesvantages andand disadvantagesdisadvantagesofof thethe twotwo treatmentstreatments..

36

Microstructure Microstructure -- PropertiesPropertiesMicrostructure PropertiesMicrostructure 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).Higher strength (for equivalent heat treatments).

Better fatigue resistance at low cycles (crack initiation)

Acicular

Higher properties of creep resistance.

High values of fracture toughness.

Slightly decrease in hardening (in case of the same heat treatment).

The properties of different alloys depend on their microstructures. The properties of different alloys depend on their microstructures.

Acicular Slightly decrease in hardening (in case of the same heat treatment).Higher stress corrosion cracking values.

Lower values of crack propagation.

The microstructure depends on chemical composition and heat The microstructure depends on chemical composition and heat

treatment. treatment.

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


-- 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).

37

Influence of treatment temperatureInfluence of treatment temperature

a b cForged at 900 C, below the

standard range. Equiaxed

alpha grains (light) and

mixed alpha-beta

Forged at 1005 C (standard

temperature range) air

cooled. Primary equiaxed

grains (white) in a beta

Forged at 1093 C, over the

beta transus temperature and

rapid cooling in air. Beta

transformed containing fine

a b c

Figures a, b, c: Microstructures observed on the Ti-8Al-1Mo-1V

mixed alpha-beta

microstructure (dark).grains (white) in a beta

transformed matrix (dark)

containing acicular alpha.

transformed containing fine

and coarse acicular

microstructure.


Figures a, b, c: Microstructures observed on the Ti-8Al-1Mo-1V

alloy after forging at the different temperature.

38

Microstructure Microstructure Ti6Al4VTi6Al4V

Rolled alloy, annealed from Rolled alloy, annealed from + + Alloy as produced, quenched from 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 -


and and -- 500x500x and inside primary grains of -500x

39

MicrostructureMicrostructure Ti6Al4VTi6Al4VMicrostructureMicrostructure Ti6Al4VTi6Al4V

Alloy as produced, quenched Alloy as produced, quenched Rolled alloy, annealed from + 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

Rolled alloy, annealed from + range temperature.

Microstructure is polygonal and - 500x.


from from acicular acicular surrounded from surrounded from fine lamellae of fine lamellae of -- 100x100x - 500x.

40

++ alloys: alloys:

Microstructures Microstructures Microstructures Microstructures Contain significant

stabilisers to enable to be stabilisers to enable to be

retained to RT

Classic Ti alloy: Ti-6Al-4V

>50% of all Ti used >50% of all Ti used

Classically

1065 C all

forge @ 955C acicular forge @ 955C acicular

on grain boundaries to

inhibit coarsening

Air cool produce Air cool produce

lamellae colonies formed

in prior grains (minimise

strain), w/ in between

(think at the pearlite)(think at the pearlite)

41

Mechanical propertiesMechanical properties


42

TiTi--66--4: properties4: propertiesTiTi--66--4: properties4: properties

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

43

Imperial College London

Page 43

TiTi--66--4: 4: TiTi--66--4: 4:

heat treatheat treat

44

--Ti Alloy designTi Alloy design--Ti Alloy designTi Alloy designHard to completely stabilize

w.r.t. hexagonal phases

stabilisers: O, Al (N,C)

stabilisers: V,Mo,Nb,Si,Fe

neutral: Sn, Zr neutral: Sn, Zr

Strengthen near- alloys by

solid solution Fe,Nb,V

Hall-Petch

cold work

Uses: highly formable

Landing gear Landing gear

Auto bodies

45

--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

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 resistanceand 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 conditionconditionquenchedquenched conditioncondition

Can be subsequently aged to very high strengthsCan be subsequently aged to very high strengths

46

--AlloysAlloys--AlloysAlloys

-- omega omega transition phase is brittletransition phase is brittle -- omega omega transition phase is brittletransition phase is brittle

TiTi--13%V13%V--11%Cr11%Cr--3%Al 3%Al onlyonly --alloyalloy producedproduced

in in largelarge quantitiesquantitiesin in largelarge quantitiesquantities

LimitedLimited useuse becausebecause ofof::

Relatively high density because of V, MoRelatively high density because of V, Mo 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; 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

47

MicrostructureMicrostructure forfor

TiTi--13%V13%V--11%Cr11%Cr--3%Al3%Al

MicrostructureMicrostructure forfor

TiTi--13%V13%V--11%Cr11%Cr--3%Al3%Al

SolutionSolution treatedtreated at at

788788C C forfor 30min 30min 788788C C forfor 30min 30min

Water Water quenchedquenched

Metastable Metastable

phase (BCC)

48

--Ti Alloys: SurveyTi Alloys: Survey

Strength and Selection of -Ti alloys

/ E

Landing Gear210-250105970-1170Ti 10 V 2Fe 3Al

y/y E

Springs163-21970-103780-1050Ti 15V 3Cr 3Al 3Sn

Springs (Beta C)17188

825Ti 3Al 8V 6Cr 4Mo 4Zr

Low Cost Beta (LCB)

Development of Beta C

250-290110950-1400Ti 4.5Fe 6.8Mo 1.5Al

Springs163-21970-103780-1050Ti 15V 3Cr 3Al 3Sn

Development of Beta C

49

ApplicationsApplications in in medicalmedical fieldsfields

HipHip prosthesisprosthesis

AorticAortic ValvesValves AorticAortic ValvesValves

PeacemakerPeacemaker PeacemakerPeacemaker

50

DentalDental applicationsapplicationsDentalDental applicationsapplications

Dental prosthesisDental prosthesis

Dental plantsDental plants

51

AutomotiveAutomotive applicationsapplicationsAutomotiveAutomotive applicationsapplications

ValvesValves ValvesValves

ConnectingConnecting rodsrods ConnectingConnecting rodsrods

Exhaust gas systemExhaust gas system Exhaust gas systemExhaust gas system

52

Shock absorbersShock absorbersShock absorbersShock absorbersSpring mass calculationSpring mass calculation::

C

FGm

maz

f

2

2

2

Applications

Year Components Material Company Type Use/Year

1998

1998

Brake pin

Flat washers

Grade 2

Grade 1s

Mercedes-Benz

Volkswagen

S-class

All

~ 8 t/yr

~ 40 t/yr1998

1998

1999

1999

1999

2000

Flat washers

Knob of the gearbox

Connecting rod

Valves

Rotor for turbocharger

Absorber springs

Grade 1s

Grade 1

Ti-6Al-4V

Ti-6Al-4V

Ti-6Al-4V

LCB

Volkswagen

Honda

Porsche

Mercedes-Benz

Volkswagen

Mitsubishi

All

S2000 Roadster

GT3

Heigth 6-cil.

Truck

Lupo FSI

~ 40 t/yr

n/a

~ 1 t/yr

n/a

n/a

3-4 t/yr2000

2000

2000

2001

2002

Absorber springs

Sump valve

Rotor for turbocharger

Exhaust gas system

Valves

LCB

Alloy

TiAl

Grade 2

Ti-6Al-4V

Mitsubishi

Mitsubishi

General Motors

Nissan

Lupo FSI

All 1.8l-4 cil.

Lancer

Corvette Z06

Infinity Q 45

3-4 t/yr

n/a

n/a

> 150 t/yr

n/a2002 Valves Ti-6Al-4V Infinity Q 45 n/a

53

SeaSea applicationsapplicationsSeaSea applicationsapplications

Rotary Rotary drillingdrilling systemssystems

Submarine coatingsSubmarine coatings

54

AerospaceAerospace SectorSectorAerospaceAerospace SectorSector

FigthersFigthers airplanesairplanes

Gas compressor deviceGas compressor device

55

Page 55

Fan Blade TechnologyFan Blade TechnologyFan Blade TechnologyFan Blade Technology

+ 4% efficiency+ 4% efficiencyClappered + 4% efficiency+ 4% efficiencyClappered Wide-chord fan

56

Page 56WideWide--chord Fan Technologychord Fan Technology

1st generation:

1984

2nd generation:

1995

Honeycomb

construction

DB/SPF

construction

57

Page 57Fan SectionFan Section

58

Page 58

Swept FansSwept FansSwept FansSwept Fans

59

Tank of ShuttleTank of Shuttle Tank of ShuttleTank of Shuttle

Retractable undercarriage of Boeing 747Retractable undercarriage of Boeing 747 Retractable undercarriage of Boeing 747Retractable undercarriage of Boeing 747

60

At 570 At 570 C it is preferred to substitute C it is preferred to substitute 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:following reasons:following reasons:

Temperature too high for their properties.Temperature too high for their properties. 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.some burning or flash phenomena.some burning or flash phenomena.

Oxidation problems for titanium, consequent Oxidation problems for titanium, consequent

oxygen enrichment of phase and lose of oxygen enrichment of phase and lose of oxygen enrichment of phase and lose of oxygen enrichment of phase and lose of

some properties (ductility).some properties (ductility).

61

EnergyEnergy

Heat exchangers, radiatorsHeat exchangers, radiators

Fan vapor turbinesFan vapor turbines

62

TitaniumTitanium in in tankstanksTitaniumTitanium in in tankstanks

M1 M1 AbramsAbrams M1 M1 AbramsAbrams

Armor plating propertiesArmor plating propertiesArmor plating propertiesArmor plating properties STEEL

PHA MIL-A-12560

ALUMI#IUM 5083

MIL-A-46026 Ti-6Al-4V

MIL-A-46077

Tensile strength (MPa) 1170 350 970 Tensile strength (MPa) 1170 350 970

Density (g/cm3) 7.86 2.70 4.50

Specific strength

(MPa / cm3/g)

150 130 220

(MPa / cm /g)

Mass efficiency (Em) 1 1.0-1.2 1.5

63

Building Building applicationsapplications

The properties of titanium in architecture are:The properties of titanium in architecture are:

ThermalThermal dilatationdilatation:: TitaniumTitanium hashas aa coefficientcoefficient veryvery lowlowandand thereforetherefore isis lessless influencedinfluenced fromfrom thethe seasonseasonchangechange ofof temperaturetemperature andand aa consequentconsequent higherhigherchangechange ofof temperaturetemperature andand aa consequentconsequent higherhigherdimensionaldimensional andand geometricalgeometrical stabilitystability..

TitaniumTitanium dodo notnot changechange colourcolour asas aa consequenceconsequence ofofultravioletultraviolet raysrays andand dodo notnot evidenceevidence pittingpitting corrosioncorrosionultravioletultraviolet raysrays andand dodo notnot evidenceevidence pittingpitting corrosioncorrosioninducedinduced fromfrom seawaterseawater environmentenvironment oror fromfrom acidacid rainsrains..

GoodGood resistanceresistance atat thethe environmentenvironment:: thethe changechange ofoftemperaturetemperature andand thethe presencepresence ofof pollutionpollution dodo notnottemperaturetemperature andand thethe presencepresence ofof pollutionpollution dodo notnotinfluenceinfluence thethe corrosioncorrosion resistanceresistance ofof titanium,titanium, thatthat ininveryvery highhigh..

64

Guggenheim Guggenheim MuseumMuseum in in BilbaoBilbao Guggenheim Guggenheim MuseumMuseum in in BilbaoBilbao

Van Van GoghGogh MuseumMuseum Van Van GoghGogh MuseumMuseum

National Center National Center ofof Science Science in in ScotlandScotland National Center National Center ofof Science Science in in ScotlandScotland

65

The The titaniumtitanium in sportin sportThe The titaniumtitanium in sportin sport

GolfGolfGolfGolf

CyclingCyclingCyclingCycling

DivingDivingDivingDiving

TrekkingTrekkingTrekkingTrekking

Winter SportWinter SportWinter SportWinter Sport

66

OtherOther applicationsapplicationsOtherOther applicationsapplications

Jewellery and fashionJewellery and fashion Jewellery and fashionJewellery and fashion

SafetySafety SafetySafety

NanotechnologyNanotechnology

67

ComponentsComponents IIComponentsComponents II

CastCast technologytechnology..


68

ComponentsComponents IIIIComponentsComponents IIII

CastCast technologytechnology.. CastCast technologytechnology..


69

High temperature High temperature propertiesproperties asas

comparedcompared toto steelssteelscomparedcompared toto steelssteels

Tensile strength of different Tensile strength of different Specific tensile strength of different


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.

70

Ti Creep RatesTi Creep Rates

71

ComparisonComparison 2 2

High High

TheThe mechanicalmechanical propertiesproperties atat highhightemperaturetemperature ofof titaniumtitanium alloysalloys arearemainlymainly thatthat ofof alphaalpha oror nearnearalphaalpha alloysalloys.. WheneverWhenever thethe creepcreep High High

temperaturetemperature

alphaalpha alloysalloys.. WheneverWhenever thethe creepcreepphenomenaphenomena isis notnot soso importantimportant atathighhigh temperature,temperature, thethe tensiletensilestrengthstrength ofof betabeta alloys,alloys, atat highhightemperaturetemperature forfor shortshort time,time, isis

temperaturetemperaturetemperaturetemperature forfor shortshort time,time, isishigherhigher..

InIn factfact thesethese alloys,alloys, untiluntil aboutabout425425 C,C, havehave higherhigher specificspecifictensiletensile strengthstrength thanthan HH1111 tooltooltensiletensile strengthstrength thanthan HH1111 tooltoolsteels,steels, whilewhile alphaalpha andand nearnear alphaalphaalloysalloys areare notnot inin advantageadvantage..

ForFor longlong timetime applicationsapplications thethealphaalpha andand nearnear alphaalpha alloysalloys havehavealphaalpha andand nearnear alphaalpha alloysalloys havehavesubstitutedsubstituted thethe steelssteels ininaeronauticalaeronautical turbinesturbines..

InIn figurefigure areare plottedplotted thethe curvescurves ofofspecificspecific tensiletensile strengthstrength ofof twotwospecificspecific tensiletensile strengthstrength ofof twotwotitaniumtitanium alloysalloys adad threethree steelssteelsadoptedadopted forfor aeronauticalaeronautical turbines,turbines,inin thethe averageaverage lowlow temperaturestemperaturesrangerange.. InIn comparisoncomparison withwith steels,steels,


rangerange.. InIn comparisoncomparison withwith steels,steels,thethe titaniumtitanium alloysalloys havehave higherhigherpropertiesproperties untiluntil 540540 CC..

72

SuperSuper--plasticityplasticitySuperSuper--plasticityplasticity

AtAt highhigh temperaturetemperature ((870870925925 C,C,withoutwithout exceedingexceeding thethe betabeta--

1200

withoutwithout exceedingexceeding thethe betabeta--transustransus)) somesome alloysalloys evidenceevidence thethesupersuper--plasticityplasticity phenomenaphenomena.. ToToinduceinduce thisthis behaviourbehaviour somesome wellwelldefinedefine conditionsconditions areare neededneeded:: 800

1000

definedefine conditionsconditions areare neededneeded::

VeryVery finefine graingrain dimensionsdimensions (about(about1010 mm size)size)..RelativelyRelatively highhigh temperaturetemperature (higher(higher

600

800

A

l

l

u

n

g

a

m

e

n

t

o

,

%

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))..

AA twotwo phasephase microstructuremicrostructure (( andand 200

400

A

l

l

u

n

g

a

m

e

n

t

o

,

%

Ti-6Al-4V

Ti-6Al-4V-2NiAA twotwo phasephase microstructuremicrostructure (( andand inin titanium)titanium)..

0

200

0 20 40 60 80 100

Ti-6Al-4V-2Ni

Ti-6Al-2Sn-4Zr-2Mo

Ti-8Mn

Valori minimi

Valori massimi


InIn figurefigure isis evidencedevidenced suchsuch influenceinfluence..

0 20 40 60 80 100

Contenuto di beta, vol.%

73

Fracture toughness of TitaniumFracture toughness of TitaniumFracture toughness of TitaniumFracture toughness of Titanium

TheThe fracturefracture toughnesstoughness valuesvalues80

TheThe fracturefracture toughnesstoughness valuesvaluescancan bebe improvedimproved byby aa factorfactor 22 oror33 forfor TiTi alloys,alloys, ifif thethe appropriateappropriateheatheat treatmenttreatment andand chemicalchemicalcompositioncomposition areare chosenchosen

60

T

e

n

a

c

i

t

a

f

r

a

t

t

u

r

a

[

M

P

a

m

]

compositioncomposition areare chosenchosen(microstructure(microstructure andand preferredpreferredorientation)orientation).. 40

T

e

n

a

c

i

t

a

f

r

a

t

t

u

r

a

[

M

P

a

m

]

Ti-6Al-4V piastra

Ti-6Al-4V getto

HoweverHowever OxygenOxygen mustmust bebemaintainedmaintained lowlow;; iitt isis alwaysalways ananimpurityimpurity..

20Te

n

a

c

i

t

a

f

r

a

t

t

u

r

a

[

M

P

a

m

]

Ti-6Al-4V getto

Ti-17 (a-b) processato

Ti-17 b processato

Beta III

Valori minimi

0

700 900 1100 1300

Snervamento [MPa]

Valori massimi


74

SSchemecheme ofof propertiesproperties

Ti 834 Ti-6Al-2Sn-4Zr- Ti-6Al-2Sn-4Zr-2Mo Ti 17

2Mo-0,8Si 2Mo-0,8Si TA5E IMI 685 Betacez

transus

Ti-6Al-4V

Deformability

Flusso

tensioniStrain rate sensitivity

Weldability Hardeability

HighT strength Room T strength


Leghe Leghe "near" Leghe + Leghe "near" Leghe

75

P/M Ti alloys?P/M Ti alloys?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

powder particles and consequent TiOpowder particles and consequent TiO2

and inclusions

76

SinteredSintered components toughnesscomponents toughness

60

65

[

M

p

a

m

]

50

55

60F

r

a

t

t

u

r

e

t

o

u

g

h

n

e

s

s

K

Q

[

M

p

a

m

]

40

45

50

F

r

a

t

t

u

r

e

t

o

u

g

h

n

e

s

s

40

94 95 96 97 98 99 100

F

r

a

t

t

u

r

e

t

o

u

g

h

n

e

s

s

Density % of theoretical

EffectEffect ofof density on density on fracturefracture toughnesstoughness ofof sinteredsintered

Ti6Al4V Ti6Al4V partsparts. .


Ti6Al4V Ti6Al4V partsparts. .

ti_col.pdf

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