TITANIUM ALLOYS - Universidad de Sevilla

TITANIUM ALLOYS

Master GSC & AIO 2011-2012

GLOBAL SUPPLY CHAIN & AERONATICAL INDUSTRIAL OPERATIONS

Module 2: Metallic materials in the manufacturing of aircraft

Titanium alloys were developed

in the early 50's due to their high

strength / density rate, for use in

aerospace applications. Today

are about 15% of the structure..

Slat of EF-2000

Titanium alloys are used in aerospace for its excellent

combination of features:

-good mechanical properties (up to 1400 MPa)

-low-density (are 40% lighter than steel and 60% heavier than

aluminum)

-excellent corrosion resistance and electrochemical compatibility

with CFRC

- can compete, at equal weight, with steel as high as 2100Mpa,

and its resistance to corrosion is much better

-compared with aluminum alloys, are much more resilient, have

better behavior at high temperatures and have better fatigue

resistance and toughness at these temperatures.

There are many other properties of titanium alloys that allow

specific applications: low coefficient of thermal expansion, good

oxidation resistance at intermediate temperatures, good

toughness, etc ...

TITANIUM ALLOYS




TITANIUM ALLOYS

The allotropic forms of titanium are two:

-alpha: hexagonal close-packed HCP crystal structure

-beta: body centered cubic BCC crystal structure




../../../../../Documents%20and%20Settings/Particular/Mis%20documentos/Laureano/Fundamentos%20CMM/abab_rectangular.html

TITANIUM ALLOYS

-The alpha crystal structure of hexagonal close-packed atoms (HCP)

is stable at room temperature in pure titanium to about 882 ° C, that is

transformed into a body centered cubic structure (BCC) called beta,

which is stable until the melting point (1670 ° C).

-The alloying elements stabilize one stage or another:

-alpha-stabilizers: Al, C, O, N (increasing the stability of

the alpha phase above the beta transformation point)

-beta-stabilizers: Cu, Cr, Fe, Mo, V (down their

transformation temperature, allowing the beta structure to

be stable at lower temperatures, even at room temperature)

-The mechanical properties of Ti alloys are closely related to these

allotropic forms, because the beta (BCC structure) is much stronger

but more brittle than the alpha (HCP).




TITANIUM ALLOYS




TITANIUM ALLOYS

Ti alloys are classified into three types according to the

predominant crystalline structure:

-alpha-alloys or "near" alpha

-beta-type alloys

-alpha-beta-alloys

The alpha type are employed in applications where corrosion

resistance is the most desired quality, the remainder being

developed for aerospace applications and are a mixture of

alpha and beta phases and in general to heat treatable

achieving high levels of mechanical strength.

The most used is the Ti6Al4V.




TITANIUM ALLOYS




TITANIUM ALLOYS

The new beta alloys type Ti-5553 or TIMETAL 555 (Ti-5Al-5V-

5Mo-0.6Fe-3CR) can be heat treated to levels similar to those of

high strength steels (1240 MPa) much higher than the typical

Ti6Al4V, with improved damage resistance but are difficult to

machine.




TITANIUM ALLOYS

Partial phase diagram of the Ti-6Al-

V system and the schematic

representación of microstructures

resulting from the fabrication of Ti-

6Al-V alloy at various temperatures.




TITANIUM ALLOYS

Titanium alloys most widely used in aircraft manufacture are the alpha-beta, particularly Ti6Al4V:

-is around 50% of total world production of Ti and Ti alloys

-more frequent used in the annealed condition (896 MPa)




TITANIUM ALLOYS

Ti-8AL-1Mo-1V microstructures.

β α -β




TITANIUM ALLOYS

β-Titanium Alloy Ti-555 microstructures




TITANIUM ALLOYS

Manufacturing characteristics of titanium alloys:

-electrochemical compatibility with CFRC

-improvement of fatigue strength by stress relief heat treatments

and surface shot-peening

-must be taken precautions during surface treatments to prevent

the absorption of hydrogen and chloride contamination

-forming must be conducted by hot-forming or superplastic

forming

-exist titanium based alloys with shape memory




TITANIUM ALLOYS

Shot peening




TITANIUM ALLOYS

Hydrogen and oxigen contamination




TITANIUM ALLOYS

Stress corrosion cracking




TITANIUM ALLOYS

Forming must be conducted by hot-forming or superplastic

D-NOSES HTP LEADING EDGE A330




TITANIUM ALLOYS

The shape memory alloys or SMA are a special class of alloys of titanium and nickel

showing the ability to return to a previously defined shape or size when subjected to the

appropriate thermal process. Generally, these materials can be plastically deformed at a

relatively low temperature and then exposing them to higher temperatures, they return to

their shape or size prior to deformation.




1.-Properties and Selection: Irons, Steels, and High-Performance

Alloys.ASM Handbook.volume 01, 1Oth Edition.

2.-Properties and Selection: Nonferrous Alloys and Special-Purpose

Materials.ASM Handbook.volume 02, 1Oth Edition.

3.-Airframe Structural Design.M.Chung.8th Edition.1995.Commilit

Press.

4.-MIT Open Course.Structural Mechanics.Aeronautics.2002.

5.-Structural Elements Design Manual.T.Draycot.1999.

REFERENCES




TITANIUM ALLOYS - Universidad de Sevilla

Documents

Transcript of TITANIUM ALLOYS - Universidad de Sevilla