titanium beneifit

8/8/2019 Titanium Beneifit

1/39

The Benefits of Titanium

High strength-to-weight ratio

Good mechanical properties to ~550C

Corrosion resistant

Unitized manufacturing techniques (SPF/DB)

- F-15E dual role fighter


2/39

Representative Material Usage in a Modern

Turbine Engine


3/39

Processing Steps in the Formation of Titanium

Sponge (Hunter Process)

Natural mineral form is titanium dioxide Chemically converted to titanium tetrachloride

Reacted with magnesium or sodium to produce titanium

William F. Smith. Structure and Properties of Engineering Alloys. McGraw-Hill Publishing Co. 1981


4/39

Properties and Typical Applications of

Selected Wrought Titanium Alloys

Format: Titanium alloyed with 6% Aluminum, 4% Vanadium ==> Ti-6Al-4V

Serope Kalpakjian. Manufacturing Engineering and Technology, 3rd Edition. Addison-Wesley Publishing Co. 1995


5/39

Strength (ksi) 150 60 220 35

Specific Properties:

Titanium Aluminum Iron Mg

E/p (inx106) 102 92 100 102Ftu/p (inx103) 915 615 775 550


Selected Properties of Titanium as Compared

to Aluminum, Iron and Magnesium

*

* Titanium has a very high melting point

Mg

1.77

6.5


6/39

? -Stabilized Systems

Phase Diagram for the

Titanium Aluminum

System

Almost all Ti contains aluminum

ductility

reduced density

Many slip systems in ? -titanium

high ductility

room temperature cold-rolling to>90% reduction in thickness

BCC

HCP

William F. Smith. Structure and Properties of

Engineering Alloys. McGraw-Hill Publishing Co.

1981


7/39

? -Stabilized Systems (Isomorphous)

Phase Diagram for the Titanium-Vanadium System


Alloying elements

miscible in ?phase,

decomposition of

? phase to ? plus

other does not

occur


8/39

? -Stabilized Systems (Isomorphous)Phase Diagram for the Titanium-Molybdenum System



9/39


? -Stabilized Systems (eutectoid)

Slow cooling allows ? phase to

transform to ? plus others

The most important alloying

elements of this system are

chromium, iron and silicon


10/39

? -Stabilized Systems (eutectoid)Phase Diagram for the Titanium-Chromium System



11/39

? -Stabilized Systems -- Other Alloys

Phase Diagram for the Titanium-Zirconium System


Zirconium

and Tin

contribute tosolid solution

strengthening


12/39

Classification of Titanium Alloys


? : primarily ? phase

near-? : ? phase with small amounts of? stabilizing elements

? ? ? : mixtures of? and ? phases

? : ? stabilized at room temperature after cooling from solution heat treatment


13/39


Chemical Compositions and Typical

Applications of Unalloyed Titanium

Pure titanium is lower strength, but more corrosion resistant and less expensive

Oxygen content determines strength

Iron is a ? stabilizer

Hydrogen is always bad (causes embrittlement)

Low levels of N good for interstitial strengthening


14/39


Unalloyed Titanium Microstructure -- ?

Grains with Small Spheroidal ? Particles


15/39


Effect of Oxygen, Nitrogen and Carbon Additions on

Mechanical Properties of Iodide Titanium

Tensile strength is governed by oxygen and nitrogen (somewhat by carbon)


16/39


Mechanical Properties of Commercially Pure

Titanium and Low Alloyed Titanium

Interstitial elements improve strength, but are detrimental to toughness


17/39


Chemical Compositions and typical

Applications of? Titanium Alloys

(Ti-5Al-2.5Sn)

Al: Solid solution strengthening, reduced densitySn: Solid solution strengthening

* Oxygen strengthens Ti, but also reduces ductility, this specialty material

retains low temperature ductility

*


18/39

Microstructure of Ti-5Al-2.5Sn


HCP ? phase with small ? particles

Note: Al in excess of 5-6% would

allow formation of brittle Ti3Al ? 2phase


19/39


Mechanical Properties of? Titanium Alloys

8 ksi tensile strength reduction due to less oxygen


20/39


Chemical Composition and Typical

Applications of Near-? Titanium Alloys

Mo and V are b stabilizers, which allow some retention of b at room temperature

b stabilizing elements are often politically active (available in small quantities from troubled nations)

High modulus, susceptible to stress corrosion cracking

in salt environment


21/39


Microstructure of Near ? Titanium Alloys

(? Particles in an ? matrix)

Normally not heat treated, but annealed

Mill Anneal: 790C for 8hr., furnace cooled

Duplex Anneal: reheated to 790C for 15 minutes, air cooled(produces a more disorderd a phase with improved ductility and impact resistance)


22/39


Mechanical Properties of Near ? Titanium Alloys

Moderately high strength, with good ductility

Ti-8Al-1Mo-1V could be solution heat treated and aged to improve strength 25%

(but this makes it susceptible to stress corrosion cracking in salt environment)


23/39

Cooling From Above the ? Transus (~1066F)


Water quench from all ?

phase to all ? (titanium

martensite)

Ftu ~160 ksi


24/39


Strengthening by Grain Refinement with BCC to

HCP Transformation and Increased Dislocation

Density

Soft compared to

Martensite in steel


25/39


Aging or Tempering Titanium Martensites Increases

Strength by Allowing ? Phase Precipitates


26/39


Air Cool From 1066C

? transformed from ?

by nucleation and

growth (fine ? )


27/39


Chemical Composition and Typical

Applications of? ? ? Titanium Alloys

? ? ? Alloys:

retention of

significant ? phase at

room temperature

? ? ? alloys can besolution heat treated

and aged

Welded, forged or machined

Low hardenability (~1 depth)

Higher strength

High strength at temperature

More hardenable


28/39


Thermal Treatments to Ti-6AL-4V

Microstructure of? ? ? titanium

depends on chemical composition,

processing, thermal treatment

Very complex microstructure


29/39


Furnace Cooling From 1066C

Structure approaches equilibrium

- coarse ? formed from

nucleation and growth


30/39


*

Cooling From Below the ? Transus

Water quenching from 954C

- primary ? coexists with ? , and on rapid cooling ? transfoms to ? martensite

- ? embedded in ?


31/39


Air Cooling From 954C

Primary ? in matrix of

transformed ?


32/39


Furnace Cooling From 954C (Near

Equilibrium)

? and intergranular ?


33/39


Cooling From Just Above Martensitic

Temperature (843C)

*

Water quenched:

- less ? present than at higher temperature, but stabilized so ? retained

(thus ? and retained ? )


34/39


Mechanical Properties of? ? ? Titanium Alloys


35/39

Design, Mechanical and Physical Properties

of Ti-6Al-4V Sheet, Strip and Plate

MIL-HDBK-5F Table 5.4.1.0(b)


36/39

Effect of Temperature on Mechanical

Properties of Ti-6AL-4V

MIL-HDBK-5E Figure 5.4.1.1.1.1 (Ti-6Al-4V)

MIL-HDBK-5E Figure 2.3.1.1.1 (low alloy steel)

MIL-HDBK-5E Figure 5.4.1.1.6(b) (Ti-6Al-4V)

MIL-HDBK-5E Figure 5.4.1.1.6(c) (Ti-6Al-4V)


37/39

Fatigue Crack Propagation Data for Ti-6Al-

4V Plate

MIL-HDBK-5E Figure 5.4.1.1.9


38/39


Chemical Compositions and Typical

Applications of? Titanium Alloys

Sufficient ? stabilizers (vanadium, molybdenum, chromium, iron)

allow metastable ? at room temperature

? titanium is BCC, thus readily cold-worked

higher density due to high % heavy metals

low ductility and fatigue performance for high strength alloys

non-uniform microstructure in thick sections


39/39


Mechanical Properties of? Titanium Alloys

Highest strength titanium alloys

titanium beneifit

Documents