Metals in mouth Flashcards
What type of bonding gives crystalline structure
Metallic
Name 2 properties a metal should have for human use
corrosion resistant, biologically inert
Name 4 issues we must compensate for in lost wax technique
- Shrinkage of wax
- Shrinkage of metal cast
- Setting expansion of investment metal
- Thermal expansion of metal
Define phase
Structurally homegonous part of system with CLEAR PHYSICAL BOUNDARIES
What is the latent heat of fusion
When crystallisation of metals happen and there is heat and energy released
What do crystals grow from?
nuclei grow to form crystals
What do crystals make?
Grain
What is the smallest atom in a crystal?
Unit cell
What is the pattern of atomic arrangement in crystals?
Atomic arrangement is repeated at regular intervals in 3D
How are the various crystalline systems arranged
Axially
How many axes does each lattice system have
3
What are the 7 types of lattice systems?
Cubic, Tetragonal, Orthorhombic, Rhombohedral, Hexagonal, Monoclinic and tri clinic
What is packing factor?
Volume of atoms inside cube/Volume of cube
What has a higher packing factor: Simple cubic or Face Centred
Face centred packs more atoms: 0.74 and Simple= 0.52
How can we visulaise grains
Etch
What does faster cooling of metal lead to/
Finer grains
What does electron beam heating do?
Resolidifies metal and grain GROWTH
How to investigate properties of alloys?
Phase diagrams
How is the temperature in crystallisation of a pure metal after heating?
Temperature is constant in crystallisation
How is the temperature in crystallisation of an alloy?
Temperature varies as the metals crystallise at different temps
What happens when we reheat an alloy?
There is diffusion of grains as there is homogenisation of grains
Name 3 types of alloys?
Solid, Intermetallic,Eutectic
What are the 2 types of solid solutions?
Substitutional and Interstitial
What happens to metals in a solid solution
They completely mix
What happens to metals in intermetallic?
There are specific sites for each atom within the lattice
What are properties of solid solution?
Enhance ductility
What are properties of intermetallic?
Increased hardness and brittle
Properties of eutectic?
Weak and corrodes
Why are there 2 types of solid solutions?
As it depends on size of solute particles
When do we get substitutional solids?
Solute particle DIRECTLY substitutes solvent particle.
- Atoms have similar valency
- Atom size within 15% of each other
- Atoms have similar crystal structure
Gimme example of substitutional solid?
Gold and copper
When do we get intestitial solid solutions
When solute atoms take small space between solvent atoms
-Solute atoms must be 60% smaller than solvent atoms
Gimme example of Interstitial solid
Steel+Carbon
How do we get intermetallic compound
2 metals react to form a new component at a stoichiometric ratio
Give example of intermetallic compound
Amalgam
What state of matter do intermetallic compounds form in
Can happen in solids as we get diffusion in metals
What happens in Diffusion of metals
Exchange of position of atoms in lattice
Why do eutectic alloys form?
As some metals are completely insoluble in metal phase.
How is eutectic alloy similar to a pure metal?
Crystallises at a specific temperature as opposed to over a range of temperatures
What can rapid cooling of alloys give?
Separation of metals
What does homogenous annealing do?
Uniform microstructure
What type of structure is formed when metals resolidify?
Dendritic
How do we get deformation of grains?
- Distort lattice
2. Slip
Define slip
Movement of vacacines, imperfections to the edge of structure
What happens when we deform metal?
Increased yield strength
increased hardness
-Th crystals will WARP
Name 3 types of imperfections in a ALLOY lattice?
- Substitutional atom
- Interstitial atom
- Vacancy
What happens when we beat out imperfections in slip?
The imperfections move through metal one plane at a time. The force applied does not cause fracture/failure of lattice
What happens to the lattice structure when we make a wrought alloy?
It gets DEFORMED
-We exceed elastic limit of metal
What is residual stress? (Strain hardening)
Occurs in the grains when we have distorted the lattice and caused grain deformation
What type of lattice in a wrought allow
Deformed
What happens when we heat wrought structure? (Annealing)
Grain Growth
Grain relaxation
Diffusion of atoms
How much stress is there in an extensively wrought structure?
More residual stress as more deformation to the lattice
Temperature or recrystallization in an extensively wrought structure?
Lower
Japanese Katana sword.
Fast cool of steel gives?
Slow cool of steel gives?
Fast=Martinsite
Slow= Pearlite
What steel in sword is softer and tougher
Pearlite
What material controls the cooling rate of the steel in the sword?
Clay
