ti al intermetalics

7/29/2019 Ti Al Intermetalics

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BY

Sandeep Akki

Under the guidance of

Dr. E. Abhilash


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Continents

1. Introduction

2. Titanium alumindes

2.1. Properties of different types Titanium aluminides3. Applications

4. Conclusion

5. References


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Introduction Intermetallic compound : A compound of two metals that has a

distinct chemical formula on phase diagram, it appears as anintermediate phase that exist over a very narrow range ofcompositions.

Different classification of intermetalic compounds are:-Aluminides,

Nitrites,Silicades,Iron aluminides,Beryllides,

Nickel aluminides etc.


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Titanium Aluminides:

Types

1. Ti3Al (2)

2. TiAl ()

3. TiAl3()

Properties of these aluminides are

Improved levels of stiffness,

Higher values of elastic modulus than normal Ti alloys.

Resistance to oxidation with increase in %age of Al.

Enhanced creep resistance (strong bonding between two atomsat elevated temp.)

These alloys have limited capacity to undergo slip results in low

values of ambient temp ductility due to presence of impurityelements such as Oxygen & hydrogen. Formability at elevatedtemp is also restricted. It is these problem that have delayed theintroduction of these elements.


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1. Ti3Al (2):

Has a outstanding strength ;weightratios when compares with

conventional titanium alloys,although improvements in creepstrength have so far been relativelysmall

It undergoes an order/disorder

transition within the compositionrange 22-39% Al. to form anordered DO19 Hexagonal structure.

Low ductility at room temp.

It does not undergo deformation bytwinning.


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1. Ti3Al (2):

Attempts are being made to add alloying elements to improve low

temp ductility. Niobium has become widely used in this regard although

molybdenum in smaller quantities, also behaves in this way &provides the additional advantage of solid solution strengthening& improved creep strength.

Vanadium is also used instead of Niobium because of its lowerdensity although oxidation resistance is reduced.

Examples of alloys of recent developments Ti-24% Al- 11% & Nb,

Ti 25% Al-17% Nb-1% & Mo, Ti-25% Al-10% Nb-3% V-1% Mo,Densities ranges from 4.2 to 4.7 g cm-3 which compare with 4-5 for

titanium.


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2. TiAl ()

It is a recent development, this compound intrinsically, has even

less room temp ductility than Ti3Al. alloys have lower densities combined with superior values of

elastic modulus , oxidation resistance, thermal stability &plasticity at elevated temperatures.

TiAl has fc tetragonal structure. The composition may extend from 48.5 66% Al as per practical

interest.

Fracture is predominantly by cleavate at both Low & high temp.

It retains its tetragonality up to its melting point of 1460C They usually have aluminum contents within the range 46-49% ,

with 1-4% of other additional elements.

Density ranges from 3.9 to 4.1 gcm-3.


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3. TiAl3

Has DO22 Tetragonal crystal structure

Has highest specific stiffness & oxidation resistance of all thetitanium aluminides.

It exhibits compressive ductility above 620C

It is brittle at lower temp. at which deformation occurs solely by

twinning. To improve its ductility ternary additions of transition metals that

encourage formation of structurally related but more symmetriccubic structure.

Ex: Ti-65Al-10Ni in this Al & Ni atoms occupy the face centeredsites & Ti as cube corners.

Ternary addition of copper, manganese, zinc, iron & chromiumhave been made, but at low temp. they are still brittle & exhibit

cleavage fracture.


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4. Applications of Titanium aluminides.

Aerospace industry

Turbine engine components : discs, blades, valves & spacer rings

Contenders for use in structure of hypersonic transatmosphericaircraft

Motor car engines such as cast turbocharger rotors

Cost reduction can be achieved Automotive engine valves. Etc


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5. Conclusion

As per the required application different percentage of aluminum isadded to the alloy to get the desired properties & suit theapplication.

6.References Recent developments in light weight alloys

Google

Answer.com


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ti al intermetalics

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