Fundamentals Of Metals (basic Metallurgy) Flashcards
Define a substitution alloy
Mixture of different type of atoms
Define an interstitial alloy
The atoms slip between each other
Define phase of a solid solution alloy
A homogenous portion of a system that has the same physical and chemical characteristics
Define solid solution
A homogenous crystalline phase that contains two or more chemical species
Define solubility limit
A specific temperature where there is a maximum concentration of solute atoms that may dissolve to form a solid solution.
Define equilibrium
When a systems free energy is at a minimum under some specified combination of temperature, pressure and composition
Give an example of a substitutional alloy
Brass
Name the stages of the solidification of materials
Liquid metal/ solid solution Embryo Nucleus (Dendrites) Grains
Define a grain
An individual crystal in a polycrystalline metal or ceramic
Define grain boundary
The interface separating two adjoining grains having different orientations
Define grain growth
The increase in average grain size of a polycrystalline material. Most materials need a temperature increase for this
What happens to an atomic structure when force is applied to it?
The Atomic bonds stretch and the attractive forces between the atoms opposes the applied force. When the stress is removed and if the metal has not yielded the inter atomic forces pull the metal back to its original shape
What are the two categories of nucleation and what are they?
Homogenous - the nuclei for solidification is provided by the liquid melt
Heterogenous - the nucleation occurs in a liquid on the surface of its container.
Define polymorphism
The existence of two or more different crystal structures for a substance ( generally an elemental solid)
Define allotropy
Allotropes have the same chemical properties but different physical properties
Name four categories of imperfections/ defects in materials
Point defects
Interfacial
Linear
Bulk or volume
Define an impurity point defect
Substitutional - the solute or impurity atoms replace the host atoms
What four factors determine the degree of the solvent atoms in the sub alloy
Atomic size factor
Crystal structure
Electronegativity
Valences
Define atomic size factor
One shouldn’t be bigger than the other or it’ll be fucked
Define Crystal structure in retaliation to imperfections in metal
Crystal structures for metals of both atom types must be the same
Define electronegativety
The more positive one element is compared to the other more negative one then the likelihood that they will form an intermetallic compound will increase rather than it forming a substitutional solid solution
Define valences
A metal with a higher valency will tend to dissolve a metal with a lower valency
Describe a dislocation in a material
A dislocation is a linear defect around which some of the atoms are mis aligned.
What is a twin boundary
A grain boundary where there is specific mirror lattice symmetry
What are the three types of microscopy?
Optical
Electronic ( scanning and transmission)
Scanning probe ( scanning, tunneling, atomic force)
Describe optical microscopy
The effect of etching into the surface of a metal to uncover th grain structure underneath
Describe a scanning electron microscope
A SEM produces an image by firing an electron beam at the surface of a specimen which are reflected to form an image
Describe a transmission electron microscope
An image is produced by a beam of electrons that pass through a specimen
Describe a scanning probe microscope
An SPM uses a very sharp probe Rasta scans across the specimen surface which form a topographical graph on a nano scale
