METALS AND ALLOYS

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Mind Map by , created over 5 years ago

Dental materials Mind Map on METALS AND ALLOYS, created by aahughes on 03/24/2014.

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Created by aahughes over 5 years ago
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METALS AND ALLOYS 2
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METALS AND ALLOYS
1 METAL: opaque, closely packed crystalline structure,
1.1 Conductors of heat and electricity
2 ALLOYS: Mix of 2 or more metals
2.1 2 metals - BINARY
2.2 3 metals - TERNARY
3 Composed of many small crystals
3.1 Form from molten metal
3.2 As it cools impurities enable metal atoms to deposit upon them
3.3 These Nucleat crystal growth
4 METALS
5 ALLOYS
6 Crystals termed GRAINS
6.1 Grow until all melt metal is consumed
6.2 where crystals abut their neighbour termed = GRAIN BOUNDARIES
7 NUCLEATION may be
7.1 HETEROGENOUS- many sites of nucleation
7.2 HOMOGENOUS- single site, metal is pure so requires 4 metal atoms
7.3 to come together and requires specfial equipment
8 GRAIN SIZE
8.1 Influences physical properties
8.2 TEMP OF MOULD - if similar to melt = slow cool and large grain size
8.3 If different = rapid cooling and small grain size
8.4 SHAPE OF MOULD - walls of mould intiate and influence crystal growth
9 VISUALISING GRAIN BOUNDARIES
9.1 Light reflecting microscope
9.2 Polished metal surface - irregularities scatter light
9.3 app of suitable etching chemical
10 AMALGAMATION - MIX WITH Hg(mercury)
10.1 plastic mass, hardening chemical reaction, Crystallisation
11 DUCTILITY - max degree of extensionin response to tensile force
11.1 MALLEABILITY - max degree of compression in response to an applied compressive force
12 On cooling from molten metals may :
12.1 remain SOLUBLE in each other=SOLID SOLUTION
12.2 be completely INSOLUBLE in each other
12.3 be PARTIALLY SOLUBLE in each other
12.4 form INTERMETALLIC COMPOUNDS if the metals have an AFFINITY for each other
12.5 eg. Ag3Sn
13 SOLID SOLUTIONS
13.1 3 TYPES - ORDERED SOLID SOLUTION:
13.1.1 metal atoms have specific site in common lattice
13.2 If radii differ distortions of lattice
13.3 RANDOM SOLID SOLUTION: Random sites in crystal lattice
13.4 INTERSTITIAL SOLID SOLUTION: atoms of one lie within primarylattice

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