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INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
INTERMETALLICS
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INTERMETALLICS

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METALLIC MATERIALS - INTERMETALLICS

METALLIC MATERIALS - INTERMETALLICS

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  • 1. METALLIC MATERIALS - INTERMETALLICS INTERMETALLICS N PRAKASAN ME METALLURGY 2
  • 2. METALLIC MATERIALS - INTERMETALLICS INTRODUCTION  Intermediate Phases:  Most of the alloy system do not show complete solid solubility. When the amount of solute element is more than the limit of solid solubility, a second phase also appears apart from the primary solid solution. The second phase which forms is an intermediate phase.  It is a phase formed at intermediate composition between the two primary components (pure metals).  The crystal structure of the intermediate phase is different from the both primary components.  Some of these intermediate phases have a fixed composition and are called Intermetallic compounds. 2
  • 3. METALLIC MATERIALS - INTERMETALLICS INTRODUCTION  Intermediate Phases:  Intermetallics are similar to alloys, but the bonding between the different types of atoms is partly ionic, leading to different properties than traditional alloys.  In general, the larger the electro negativity difference between the host atom and the impurity, the greater the tendency to form compounds and the less solubility there is.  So, elements with similar electro negativities tend to form alloy, whereas elements with large electro negativity difference tend to have more ionic bonds. 3
  • 4. METALLIC MATERIALS - INTERMETALLICS INTRODUCTION  Intermediate Phases:  An intermetallic compound contains two or more metallic elements, producing a new phase with its own composition, crystal structure, and properties.  Intermetallic compounds are almost always very hard and brittle.  Intermetallics or intermetallic compounds are similar to ceramic materials in terms of their mechanical properties.  Often dispersion-strengthened alloys contain intermetallic compound as the dispersed phase an 4
  • 5. METALLIC MATERIALS - INTERMETALLICS Intermetallics:  Classification:  Stoichiometric intermetallic compounds have a fixed composition. They are represented in the phase diagram by a vertical line.  Examples: • • • • • • Au2Pb in Au-Pb system, AlSb in Al-Sb system, MoSi2 in Mo-Si system, Fe3C in Steels, Mg2Pb in Mg-Pb system, MgNi2, Mg2Ni in Mg-Ni system 5
  • 6. METALLIC MATERIALS - INTERMETALLICS Intermetallics:  Classification:  Nonstoichiometric intermetallic compounds have a range of compositions and are sometimes called intermediate solid solutions.  Examples: • γ phase in Mo-Rh system, • β’phase in brass, • CuAl2 in Al-Cu system, • Mg2Al3 in Al-Mg system, • TiAl3 in Al-Ti system. 6
  • 7. METALLIC MATERIALS - INTERMETALLICS  Stoichiometric intermetallic compounds: Aluminum-antimony phase diagram includes a stoichiometric intermetallic compound γ. 7
  • 8. METALLIC MATERIALS - INTERMETALLICS  Stoichiometric intermetallic compounds: 19 wt% Mg-81 wt% Pb Mg2Pb Magnesium - Lead phase diagram includes a stoichiometric intermetallic compound γ. 8
  • 9. METALLIC MATERIALS - INTERMETALLICS  Stoichiometric intermetallic compounds: Magnesium–Nickel binary phase diagram includes Mg2Ni, MgNi2 stoichiometric intermetallic compounds. 9
  • 10. METALLIC MATERIALS - INTERMETALLICS  Stoichiometric intermetallic compounds: Proeutectoid cementite pearlite Hypereuctoid steel (1.2%C) contains metastable proeutectoid and eutectoid Fe3C, which has a fixed ratio of three iron atoms to one carbon atom (Interstitial compound). 10
  • 11. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric intermetallic compounds: The molybdenum-rhodium phase diagram nonstoichiometric intermetallic compound γ. includes a 11
  • 12. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric intermetallic compounds: The Copper - Zinc Phase diagram, containing more than 30% Zn, a second phase β’ forms because of the limited solubility of zinc in copper. 12
  • 13. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric Cartridge brass: 70% Cu + 30% Zn intermetallic compounds: Yellow brass: 65% Cu + 35% Zn Muntz Metal 60% Cu + 40% Zn β’ Brass alloy: More than 30% Zn addition provides complex structure of α and β’ (CuZn) phases. The β phase makes this alloy heat treatable. 13
  • 14. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric intermetallic compounds: The Aluminium – Copper (Eutectic) Phase diagram, θ (CuAl2) phase precipitates out during age hardening. 14
  • 15. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric intermetallic compounds: Mg2Al3 Grain boundary particles The Aluminium – Magnesium Phase diagram, includes β phase (Mg2Al3) compound. 15
  • 16. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric intermetallic compounds: Petal-like TiAl3 particles in α-Al solid solution The Aluminium - Titanium (Peritectic)Phase diagram, Ti Al 3 act as a nuclei for grains to grow. Multiple nucleation of averagely eight sites 16 may occur on each particle.
  • 17. METALLIC MATERIALS - INTERMETALLICS  Nonstoichiometric intermetallic compounds: Ni3(Al,Ti) (γ’ prime) priciptate (FCC) Carbids (M23C6, M6C or MC) γ Matrix (FCC austenite) Nickel base superalloys, addition of small amount of Al, Ti, Nb forms precipitates with Cuboid shape. The elements C, Cr, Ta, Hf, Ti, Nb,W forms Carbides. The elements Co, Fe, Cr, Nb, Ta, Mo, W, V, Ti, B, Zr and Al strengthen the Matrix. 17
  • 18. METALLIC MATERIALS - INTERMETALLICS  Properties of some Intermetallic compounds * B2 – Binary compound structure having 1:1 stoichiometry, * L1 – Alloys. 18
  • 19. METALLIC MATERIALS - INTERMETALLICS  Properties of intermetallic compounds: Nickel-based superalloys The unit cells of two intermetallic compounds: (a) TiAl has an ordered tetragonal structure, and (b) Ni3Al has an ordered cubic structure. 19
  • 20. METALLIC MATERIALS - INTERMETALLICS  Properties of intermetallic compounds: The strength and ductility of the intermetallic compound Ti3Al compared with that of a conventional nickel superalloy. The Ti 3Al maintains strength to higher temperatures longer than does the nickel superalloy. 20
  • 21. METALLIC MATERIALS - INTERMETALLICS  Properties and Applications:  Molybdenum disilicide (MoSi2)  This material is used for making heating elements for high temperature furnaces.  At high temperatures (1000 to 1600°C), MoSi2 shows outstanding oxidation resistance.  At low temperatures (500°C and below), MoSi2 is brittle and shows catastrophic oxidation known as pesting. 21
  • 22. METALLIC MATERIALS - INTERMETALLICS  Properties and Applications:  Copper Aluminide (CuAl2)     Precipitation of the nonstoichiometric intermetallic copper aluminide CuAl2 causes strengthening in a number of important aluminium alloys. Precipitation hardening – by forming θ (CuAl2) phase in α matrix, gives high strength and toughness. Properties: • High strength (2119: σTS 505 - 520 MPa). • Good creep strength at high temp. • High toughness at cryogenic temp. • Good machinability. Applications: • Fuel Tanks (2119) • Pistons, rivets for aircraft constructions (2024-T4) : Al2CuMg 22
  • 23. METALLIC MATERIALS - INTERMETALLICS  Properties and Applications:  Al-Mg-Si Alloys (Mg2Si)  Mg and Si are added in balanced amount to form Mg2Si.  Mg + Si (0.8-1.2%) ; Mg + Si (> 1.4%) Properties: • Medium-strength structural alloys (most widely used 6063-T6, σy 215 MPa, σTS 245 Mpa).   • Readily extruded • Colour anodized. Applications : • Car bodies, Electric trains (6009) • Structural Components (6061) • Satellite dish (6005) • Large water pipes (6063) • Aircraft, Automotive (6013 – T6,T8) 23
  • 24. METALLIC MATERIALS - INTERMETALLICS  Properties and Applications:  Platinum silicide (PtSi2) :  Intermetallics based on silicon (e.g., platinum silicide) play a useful role in microelectronics.  Niobium family intermetallics:  Certain intermetallics such as NbTi, Nb3Sn, NbZr, Nb3Al,and Nb3Ge are used as superconductors. β’ Brasses (α + CuZn): 24
  • 25. METALLIC MATERIALS - INTERMETALLICS  Properties and Applications:  TiAl and Ni3Al (Nickel base superalloys)     Properties: TiAl and Ni3Al possess good combinations of high-temperature mechanical properties and oxidation resistance up to approximately 650 - 960°C. Good Toughness and Corrosion resistance. Applications: • Aircrafts, space vehicles, rocket engines • Industrial gas turbines (IN 738LC). • Nuclear reactors, submarines. • Steam power plants, petrochemical equipment. • Combustion Engine Exhaust Valves • Submarines 25
  • 26. METALLIC MATERIALS - INTERMETALLICS  Properties and Applications: Ni-Base Superalloys 26
  • 27. METALLIC MATERIALS - INTERMETALLICS  References :  Donald R. Askeland, Pradeep P. Fulay, Wendelin J. Wright, The Science and Engineering of Materials, Sixth Edition.  Robert Cahn, Peter Haasen, Physical metallurgy, Fourth edition.  William D.Callister, Fundamentals of Materials Science and Engineering, Fifth edition.  Brian S.Mitchell, An introduction to Materials engineering and science, John Wiley & Sons Inc.  Vijendra singh, Physical Metallurgy  Lecture 4, Copper and its alloys, Suranaree university of technology.  Lecture 6, Nickel and its alloys, Suranaree university of technology.  Loren A. Jacobson, Physical Metallurgy_class notes 27

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