defects, diffusion and slip
What are the 2 types of solid diffusion? Which are faster? and which are stronger? How does this impact the amount of remove for free atoms.
Interstitial: faster, weaker, and atoms can freely go jump in more easily due to bonds breaking apart.
Vacancy: Slower, stronger, and atoms cannot as easily freely jump in due to stronger bond forces
What are properties of metals, ceramics, and plastics?
Metals: Ductile, high density, conductive, hard, shiny
Ceramics: insulators, brittle
Plastic/Polymers: Brittle ish, lower density, insulator, translucent
What is plastic deformation and what are the 2 dislocation?
Plastic deformation is caused by dislocation motion. Edge and screw are the 2 dislocations. Edge dislocation are parallel motion and screw dislocations are perpendicular motion
What is BCC. what is the number of atoms in the unit cell, a value, APF and number of touching neighbours
What is FCC. what is the number of atoms in the unit cell, a value, APF and number of touching neighbours
What is SCC. what is the number of atoms in the unit cell, a value, APF and number of touching neighbours
Body centred cubic, n = 2, c = 8, a = 4/√3 R
Face centred cubic, n = 4, c = 12, a = 2√2 R
Simple centred cubic, n = 1, c = 6, a = 2R
Transgranual vs Intragranual Vs Intergranual Fracture
What is DBTT
Transgranual Fracture: on grains
Intragranual fracture: within grains, ductile or brittle
Intergranual fracture: between grains, brittle
DBTT = Ductile to Brittle Transition temperature. Temperature is lower when a material is brittle and increases as ductility and toughness increases.
What are the 3 types of defects and explain them.
Point Defects: Involves a single crystal. Hume Rothery Rules:
Degree of solution:
Similar electronegativity, Valence electrons (larger amount of valence electrons = higher dissolve rate), crystal orientation, atomic factor size
Area defects: Grain boundaries
Line Defects: Dislocations that cause slip (1D) --> Burgers vector, slip occurs along densest plane
What are the 4 bonding types, what is the order of bond energy, and what are the ways they bond
Ionic: losing and gaining, Covalent: sharing, Metallic: attractive and repulsive forces, Secondary: dipoles (fluctuating or permanent (van Der Waals))
(ordered highest to lowest)
What is annealing and what are the 3 treatment stages
Annealing is forming new crystals using high temperatures until reaching the recrystallization temperature. When annealing cold rolled materials, annealing is done below recrystallizaton temperature. When annealing hot rolled materials, annealing is done above recrystallizaton temperature
3 steps:
Recovery - Atoms recover from coldworking
Recrystillization - (must have seen cold work) Grains are heated until at recrystallization temperature
Grain growth - Grains grow due to a reduction of grain boundaries
What are the ways to determine miller indices of planes and directions when given a drawing
Find how far they are from an origin point. Ensure the plane points are each on separate axis, if not move the axis. Then write the distances from origin in ( ) and then reciprocate them for the final answer
Find how far they are from an origin point (tail of arrow) to the end point (where arrow tip/head is). Put the values in [ ]
If fractions, multiply to get whole numbers, negative values have bars on top
What is the definition of fatigue? What are the 3 stages of fatigue failure?
Lowering the strength/failure of a material below its yield point due to repetitive cyclic loading
3 stages: Crack initiation (surface), Crack propagation, Faster fracture when area is reduced
What are the interfacial defects and 3 other 3d defects
Twin boundary: Reflection of an atom across twin planes
Grain boundaries: Crystal orientation difference
Stacking vault: the order crystals are stacked
Phase boundary: Composition differences
Pores, Inclusions, Cracks
What is amorphous vs polymorphous vs single crystal vs polycrystalline
amorphous: random orientation of crystals that do not define a shape.
poly morphous: many different crystal orientations all in there own smaller regions that do not define shapes.
Single crystal: one crystal orientation, clear
Polycrystalline: many different crystal orientations in their own small regions that form one big arrangement, opaque and strong, and has more grain boundaries
What is fracture toughest, resilience, hardness, and the hardness tests
Fracture toughness is the tensile toughness which is energy required to break a unit volume of material
Resilience: ability to store energy
Hardness: Resistance to permanent indentation on a surface. High hardness is the resistance to plastic deformation or cracking.
Hardness tests: rockwell, knoop, vickers, Brinell
How to calculate grain size and what does the grain size say about the fineness of a grain.
A larger grain size number results in a finer grain. Grain size can be calculated using 2^n-1 at 100x mag and using a longer equation given on formula sheet that I don't want type of other magnification
What is creep and what are each of the 3 states of creep?
Creep is permanent deformation due to a high temperature over time. Primary creep is when the creep rate decelerates, Secondary creep is when the creep rate does not vary with time (steady state), tertiary creep is when the creep rate accelerates.
What is slip system (I believe this is lecture 7 but there isn't room on that one :))
A slip system is the sum of slip direction and slip plane. The slip planes is the plane with the highest planar density. The slip direction is the direction of movement and the line with the highest linear density.
What is electronegativity and what levels do electrons occupy?
Electrons occupy lower levels first. Electronegativity increases from left to right and from down to up
Metal dislocations vs ceramic dislocations vs ionic ceramics
Metal dislocations are non directional and closed packed direction for slip.
Covalent ceramic dislocations are directional and motion is hard
Ionic ceramics are when motion is difficult and + ions avoid + ions and - avoid -
What is anisotropic and what is isotropic
Anisotropic is directional for loading and isotropic has many directions for loading
Ductile vs Brittle Fracture
Ductile fracture has more plastic deformation (with warning) which leads to more energy absorption. Smaller cracks form leading to more grain boundaries. Dimples form.
Brittle fracture has a chevron pattern. The direction of crack motion is perpendicular to the applied stress direction. Brittle fracture has little to no plastic deformation and is catastrophic. This requires less energy absorption
What is diffusion, sintering and ticks first and second law
Diffusion is the material transport by atomic motion from high concentration to low concentration.
Sintering is the grain growth of alumina caused by forces and temperature.
Ficks first law states that diffusion is at steady state concentration but also varies over time. The diffusion flux is proportional to the concentration.
Ficks second law states that Diffusion coefficient is proportional to temperature. It is not steady state and therefore it varies with time and position. Prediction of change in concentration gradient with time due to diffusion
Which primary bonding types are directional and which are not
Ionic is non directional since charge is uniform in all directions and covalent is directional as atoms have to share electrons on one side. Metallic is also non directional
What are the 4 strengthening mechanisms
Precipitate hardening: Uses shear for harder precipitate. (more grain boundaries)
Coldwork/strain hardening: Cold work deforms grains reducing their size and increasing the number of grain boundaries and causing the dislocations at those boundaries which strengthens the material. If cold working is done at a high temperature effects may be reversed
Grain size reduction: preventing a material from growth and reducing its size. ncreasing the number of grain boundaries and causing the dislocations at those boundaries which strengthens the material. In addition there are then more barriers to slip.
Solid solutions: Reduces mobility increasing strength.
What is the equation for Number of atoms in a unit cell, Planar and linear density, theoretical density, APF and IPF
CHECK SLIDES lecture 3
Explain the process creep failure and how can you prevent it.
Internal cavities (impurity atoms) form, mostly along grain boundaries. Cavities then accumulate causing damage to occur at start of tertiary stage. To prevent creep failure you can choose a material with a higher temperature, alloying, no grain boundaries, or very little grain boundaries.