Chapter 11 Flashcards
Age hardening
A strengthening mechanism that relies on a sequence of solid-state phase transformations
in generating a dispersion of ultra-fine particles of a second phase. Age hardening is a
form of dispersion strengthening. Also called precipitation hardening (Chapter 12).
Dispersed phase
A solid phase that forms from the original matrix phase when the solubility limit
is exceeded.
Dispersion strengthening
Increasing the strength of a material by forming more than one
phase. By proper control of the size, shape, amount, and individual properties of the phases, excellent
combinations of properties can be obtained.
Eutectic
A three-phase invariant reaction in which one liquid phase solidifies to produce two solid
phases.
Eutectic microconstituent
A characteristic mixture of two phases formed as a result of the
eutectic reaction.
Eutectoid
A three-phase invariant reaction in which one solid phase transforms to two different
solid phases.
Hyper-
A prefix indicating that the composition of an alloy is more than the composition at which
a three-phase reaction occurs.
Hypereutectic alloy
An alloy composition between that of the right-hand end of the tie line
defining the eutectic reaction and the eutectic composition.
Hypo-
A prefix indicating that the composition of an alloy is less than the composition at which a
three-phase reaction occurs
Hypoeutectic alloy
An alloy composition between that of the left-hand end of the tie line defining
the eutectic reaction and the eutectic composition.
Interlamellar spacing
Interlamellar spacing
Intermediate solid solution
A nonstoichiometric intermetallic compound displaying a range
of compositions.
Intermetallic compound
A compound formed of two or more metals that has its own unique
composition, structure, and properties.
Interphase interface
The boundary between two phases in a microstructure. In metallic materials,
this boundary resists dislocation motion and provides dispersion strengthening and precipitation
hardening.
Isopleth
IsoplethIsopleth
Intermediate solid solution
A nonstoichiometric intermetallic compound displaying a range
of compositions.
Intermetallic compound
A compound formed of two or more metals that has its own unique
composition, structure, and properties.
Interphase interface
The boundary between two phases in a microstructure. In metallic materials,
this boundary resists dislocation motion and provides dispersion strengthening and precipitation
hardening.
Isopleth
A line on a phase diagram that shows constant chemical composition
Isoplethal study
Determination of reactions and microstructural changes that are expected while
studying a particular chemical composition in a system
Lamella
A thin plate of a phase that forms during certain three-phase reactions, such as the eutectic
or eutectoid.
Matrix
The continuous solid phase in a complex microstructure. Solid dispersed phase particles
may form within the matrix.
Metastable miscibility gAP
A miscibility gap that extends below the liquidus or exists completely
below the liquidus. Two liquids that are immiscible continue to exist as liquids and remain
unmixed. These systems form the basis for Vycor™ and Pyrex® glasses.
Microconstituent
phase or mixture of phases in an alloy that has a distinct appearance.
Frequently, we describe a microstructure in terms of the microconstituents rather than the actual
phases.
Miscibility gap
A region in a phase diagram in which two phases, with essentially the same structure,
do not mix, or have no solubility in one another.
Modification
Addition of alloying elements, such as sodium or strontium, which change the
microstructure of the eutectic microconstituent in aluminum-silicon alloys.
Monotectic
A three-phase reaction in which one liquid transforms to a solid and a second liquid
on cooling.
Nanowires
are cylinders or “wires” of material with diameters on the order of 10 to 100 nm.
Nonstoichiometric intermetallic compound
A phase formed by the combination of two
components into a compound having a structure and properties different from either component.
The nonstoichiometric compound has a variable ratio of the components present in the compound
(see also intermediate solid solution).
Peritectic
A three-phase reaction in which a solid and a liquid combine to produce a second solid
on cooling.
Peritectoid
A three-phase reaction in which two solids combine to form a third solid on cooling
Precipitate
A solid phase that forms from the original matrix phase when the solubility limit is
exceeded. We often use the term precipitate, as opposed to dispersed phase particles, for alloys
formed by precipitation or age hardening. In most cases, we try to control the formation of the precipitate
second phase particles to produce the optimum dispersion strengthening or age hardening.
(Also called the dispersed phase.)
Precipitation hardening
A strengthening mechanism that relies on a sequence of solid-state
phase transformations in generating a dispersion of ultra-fine precipitates of a second phase
(Chapter 12). It is a form of dispersion strengthening. Also called age hardening.
Primary microconstituent
The microconstituent that forms before the start of a three-phase
reaction. Also called the proeutectic microconstituent
Solvus
A solubility curve that separates a single solid-phase region from a two solid-phase region
in the phase diagram
Stoichiometric intermetallic compound
A phase formed by the combination of two components
into a compound having a structure and properties different from either component.
The stoichiometric intermetallic compound has a fixed ratio of the components present in the
compound.
Strengthening mechanisms so far (3)
Cold work, Grain size strengthening, Solid Solutions
What happens if we exceed the solubility limit?
We have more than 1 phase
Intermetallic Compounds
Contains 2 or more metallic elements producing a
new phase and crystal structure.
Intermetallic Compounds Are almost always
hard and brittle and thermally
stable.
Eutectic
liquid transforms to two solid phases
Eutectoid
one solid phase transforms to two other
solid phases
Peritectic
liquid and one solid phase transform to a
second solid phase
Eutectics have relatively (2)
low melting points and no
freezing range.
Eutectics are _______ casting alloys
Effective
Eutectics are ____melting solders
Low
Nonequilibrium freezing can result in a _______
solidus curve
nonequilibrium
Dispersion strengthening can be obtained when ……
the
solubility limit is exceeded and 2 or more phases are
produced.
T / F - For optimum dispersion strengthening of a metal - a large number of small, hard, discrete particles in a soft, ductile
matrix will most effectively block dislocations
True
T / F - For optimum dispersion strengthening of a metal - round dispersed particles minimize stress concentrations
True
Intermetallic compounds are strong but _____
brittle
Phase diagrams for materials containing multiple
phases normally contain one or more ______ reactions
3-phase
The eutectic reaction permits _____ to solidify as an intimate mixtures of two phases
liquid
eutectic _________ can be controlled to generate a variety of
properties, including a balance of strength and ductility
microstructures
