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28 Cards in this Set
- Front
- Back
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Pure metals
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no use, limited
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Alloys
Types: |
Mixture of 2+ elements, 1 of which is a metal
Types: binary/teritary etc. Solid/Intermetallic |
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Solid Solution
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Mixture of elements at atomic level
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Solid Solution Properties
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Both metals completely soluble
Forms 1 type of crystal Stronger and harder, poor electrical conductivity but not as elastic |
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Types of solid solutions
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Substitutional solid solution
Interstitial solid solution |
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Substitutional Solid Solution
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Solute atom substitues directly for solvent atom in normal lattice site of crystal
atoms have similar size(within 15%) and valencyI |
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Interstitial Solid Solution
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Solute atom takes up space between solvent atom
Solute atom must be 60% smaller than solvent atom Ex: carbon in iron, hydrogen nitrogen, boron |
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Solid Solution Hardening(how to)
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Sub./ Interstitial defects-->pinning point which restrict motion of dislocations strengthening the material(tension/compression)
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Intermetallic Compounds
Properties |
2+ metals combine forming a specific stoich. ratio
Complex Crystal Structure -limited plastic deformation -hard, brittle |
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Cooling Curve
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Tm: transofrmaiton from a solid to a liquid at contstant temp
Latent Heat: the heat that is used up in transition from a solid to a liquid |
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Cooling curve for an alloy
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TM-increases
Melting range: solidification start/end at different points liquid + solid phase at different temps decrease in temp as melting |
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Critical Temperatures
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solidus/liquidus limitsw solubility
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Critical Temperatures Diagram
Properties |
Liquidus Line: Joins solidification start points(above = liquid)
Solidus Line-joins solidfication end points on phase diagram, below the line alloys are solid B/W solidus alloys are mixture of solid and liquid |
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Ratio of Phases
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Lever Law:
Ratio at 1268 for 60/40 Cu/Ni B= Percentage of alloy A= liquidus-line at that temperature C=solidus-line at that temp A-B/B-C = mass of solid/mass of liquid for Cu Liquid Composition A= 65-35 Solid Composition C=48-cu-52 |
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Partial Solid Solution
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atoms only partially soluble in one another, grain looks like layers-->eutectic alloy
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Eutectic Alloys
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components of materials are not sufficietly soluble to form complete solid solution
Liquidus/Solidus meet at a mid-range composition |
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Eutectuc Table
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table!
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Eutectic Point
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3 phases
temp/composition |
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Alloy at Eutectic Composition
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Eutectic phase at room temp
insolubility of Ag/Cu in solid condition Fine layered appearance |
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Alloy at other composition
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Alpha + eutectic, B+ eutectic
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Eutectic Temperature
Melting Point |
From liquid to two solid phases w/o going thorugh a liquid solid mixture state
Lower than either of pure componenets Solder materials with low melt temp. |
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Inter-metallic Compounds
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two metals form a new compound with a specific composition
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Ternary Phase Diagram
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A phase diagram for a alloy with 3 componenets(2d-3d)
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Solidification of a metal
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Aggregates of atoms regularly arranged in a crystalline structure
normal: material beings to solidify and multple crystals begin to grow in the liquid and polycrystalline solid forms |
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Nucleation
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The moment crystals begin
Many nuclei of crystallization scattered in molten metal Presence of impurity -->nucleation points |
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Solidfication of a metal
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Nucleation of crystals
Crystal Growth Irregular grains form as crystals grow together Grain boundaries |
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Grain Size influences
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Strength
Workability Corrosion suscpetibility |
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Fine grains
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Desirable
small grain -->more grain boundaries -->higher resistance to deformation Rapid cooling Addition of grain refiners in gold alloys Nucleation site increase --> increase number of grains--->decrease size of individual grain |
