T3 Flashcards
What is a component?
An element in an alloy
What is a phase?
A region of material having uniform physical and chemical characteristics
What is composition?
The mass of each component in an alloy or phase
What is constitution?
The sum of the phases, the mass of each phase and the composition
Difference between complete and limited solid solutions
Complete solid solubility is when solute atoms are completely soluble in a solvents atoms for any composition of each. This a 2nd phase doesn’t form if complete solid solubility exists. Limited solid solutions have a solute that isn’t completely soluble and so can precipitate out of the solvent.
What is a solvus line?
Solid solubility limit line separating A and B phases
What is a solidus line?
The lowest temp at which a liquid phase may exist
What is a liquidus line?
Temp at which all components are liquid
Name 2 main iron forms and their properties:
Ferrite: (A Fe)BCC structure forms at temps below 910’C, magnetic.
Austenite: (Y Fe)FCC crystal structure, exists between 910-1391’C, non magnetic
What is a eutectoid point?
Point in a phase diagram where a solid is at equilibrium with two other solid phases.
What is the eutectic point?
Point in a phase diagram indicating the chemical composition and temp corresponding to the lowest melting point of a mixture of components
What is hypo-eutectoid composition?
Compositions below the eutectoid composition
What is hyper-eutectoid composition?
Compositions above the eutectoid composition
Describe pearlite structure
A eutectoid structure, an equilibrium structure of ferrite then cementite layers or lamellar. An alloy of the eutectoid composition will transform entirely to pearlite when cooked from Y phase.
Gray iron
flakes of graphite with ferrite and pearlite around, weak and brittle in tension, high wear resistance, workshop equipment
