Chapter 9 Flashcards
What does solution mean?
Solid, liquid, or gas solutions, single phase
What is a mixture?
More than one phase
What is the solubility limit?
The maximum concentration for which only a single phase solution exists.
What are components?
The elements or compounds which are present in the alloy
What are phases?
The physically and chemically distinct material regions that form.
What are some characteristics of binary phase diagrams?
- Just two components
- T,C,P are used (P often is 1 atm)
- Two phases
- Three phase fields
- Isomorphous (complete liquid and solid solubility)
What is a liquidus line?
On a binary phase diagram, the line or boundary separating liquid and liquid + solid-phase regions.
What is a solidus line?
On a binary phase diagram, the line or boundary separating solid and liquid + solid-phase regions.
How is phase composition determined?
If single phase: Co = Cp
If two phases: CL = Cliquidus, Cα = Csolidus
What is the lever rule?
A mathematical expression by which the relative phase amounts in a two-phase alloy at equilibrium may be computed.
How is the weight fraction of the L (liquid) phase determined?
WL = (Cα - Co) / (Cα - CL)
How is the weight fraction of the α (solid) phase determined?
Wα = (Co - CL) / (Cα - CL)
What is a tie line (isotherm)?
A horizontal line that connects the phases in equilibrium with each other
How does cooling affect structure?
Slow: equilibrium structure (composition is equal)
Fast: cored structure (composition is layered, highest composition in center/core)
What is a binary-eutectic system?
It has two components and a special composition with a minimum melting point
What is an eutectic structure?
It is a lamellar structure (alternating layers) of solid phases
What is an intermetallic compound?
A compound of two metals that has a distinct chemical formula. On a phase diagram it appears as an intermediate phase that exists over a very narrow range of compositions.
What does eutectic mean?
Liquid transforms into two solid phases
What does eutectoid mean?
One solid phase transforms into two other solid phases
What does peritectic mean?
Liquid and one solid phase transform to a second solid phase
What is austenite?
Face-centered cubic iron; also iron and steel alloys that have the FCC crystal structure.
What is cementite?
Iron carbide (Fe3C).
What is ferrite?
Ceramic oxide materials composed of both divalent and trivalent cations (e.g., Fe2+ and Fe3+), some of which are ferrimagnetic.
What is pearlite?
A two-phase microstructure found in some steels and cast irons; it results from the transformation of austenite of eutectoid composition and consists of alternating layers (or Lamellae) of Α-ferrite and cementite.
What does hypoeutectoid mean?
Before the
What does monotectic mean?
Liquid transforms into a second liquid phase and a solid phase
What does peritectoid mean?
Two solid phases turn into a third solid phase
What is a congruent transformation?
A transformation of one phase to another while maintaining the same composition.
What does hypoeutectoid mean?
Before the eutectoid composition
What does hypereutectoid mean?
After the eutectoid composition
