Chapter 10 Flashcards
Alloy
A material made from multiple elements that exhibits properties of a metallic material
Binary phase diagram
A phase diagram for a system with two components
Copolymer
A polymer that is formed by combining two or more different types of monomers,
usually with the idea of blending the properties affiliated with individual polymers.
Coring
Chemical segregation in cast products, also known as microsegregation or interdendritic
segregation. The centers of the dendrites are rich in the higher melting point
element, whereas interdendritic regions, which solidify last, are rich in the lower melting point
element.
Dispersion strengthening
Strengthening, typically used in metallic materials, by the formation
of ultra-fine dispersions of a second phase. The interface between the newly formed phase and
the parent phase provides additional resistance to dislocation motion, thereby causing strengthening
of metallic materials (Chapter 11).
Freezing range
The temperature difference between the liquidus and solidus temperatures
Gibbs phase rule
Describes the number of degrees of freedom, or the number of variables
that must be fixed to specify the temperature and composition of a phase ( ,
where pressure and temperature can change, , where pressure or temperature is
constant).
Homogenization heat treatment
The heat treatment used to reduce the
microsegregation caused by nonequilibrium solidification. This heat treatment cannot eliminate
macrosegregation.
Hot isostatic pressing (HIP)
Sintering of metallic or ceramic powders, conducted under an isostatic
pressure.
Hot pressing (HP)
Sintering of metal or ceramic powders under a uniaxial pressure; used for production
of smaller components of materials that are difficult to sinter otherwise.
Hot shortness
Melting of the lower melting point nonequilibrium material that forms due to segregation,
even though the temperature is below the equilibrium solidus temperature.
Hume-Rothery rules
The conditions that an alloy or ceramic system must meet if the system is
to display unlimited solid solubility. The Hume-Rothery rules are necessary but are not sufficient for
materials to show unlimited solid solubility.
Interdendritic segregation
Coring
Isomorphous phase diagram
A phase diagram in which the components display unlimited
solid solubility.
Lever rule
A technique for determining the amount of each phase in a two-phase system.
Limited solubility
When only a certain amount of a solute material can be dissolved in a solvent
material.
Liquidus
Curves on phase diagrams that describe the liquidus temperatures of all possible
alloys.
Liquidus temperature
The temperature at which the first solid begins to form during solidification
Macrosegregation
The presence of composition differences in a material over large distances
caused by nonequilibrium solidification. The only way to remove this type of segregation is to break
down the cast structure by hot working.
Multiple-phase alloy
An alloy that consists of two or more phases.
Phase
Any portion, including the whole of a system, which is physically homogeneous within it
and bounded by a surface so that it is separate from any other portions.
Phase diagrams
Diagrams showing phases present under equilibrium conditions and the phase
compositions at each combination of temperature and overall composition. Sometimes phase diagrams
also indicate metastable phases
P-T diagram
A diagram describing thermodynamic stability of phases under different temperature
and pressure conditions (same as a unary phase diagram).
Segregation
The presence of composition differences in a material, often caused by insufficient
time for diffusion during solidification.
Single-phase alloy
An alloy consisting of one phase
Solid solution
A solid phase formed by combining multiple elements or compounds such that the
overall phase has a uniform composition and properties that are different from those of the elements
or compounds forming it.
Solid-solution strengthening
Increasing the strength of a metallic material via the formation
of a solid solution
Solidus
Curves on phase diagrams that describe the solidus temperature of all possible alloys
Solidus temperature
The temperature below which all liquid has completely solidified
Solubility
The amount of one material that will completely dissolve in a second material without
creating a second phase.
Tie line
A horizontal line drawn in a two-phase region of a phase diagram to assist in determining
the compositions of the two phases.
Triple point
A pressure and temperature at which three phases of a single material are in equilibrium
Unary phase diagram
A phase diagram in which there is only one component
Unlimited solubility
When the amount of one material that will dissolve in a second material
without creating a second phase is unlimited.
Gibbs Phase Rule
P + F = C + N
Gibbs Phase Rule - P =
of phases
Gibbs Phase Rule - F =
of deg of freedom (T, P & %x)
Gibbs Phase Rule - C =
of components
Gibbs Phase Rule - N =
non-compositional variables (T & P)
Conditions for Unlimited Solid Solubility (4 of them)
Size factor, Crystal structure, Valence, Electronegativity
Do two examples of the lever rule
DO THEM!
Solid-Solution Strengthening (alloying) is a primary …..
strengthening mechanism
strength increases with increasing difference between
solvent (host) and solute (guest) size
Phase diagrams are useful tools to determine (3 points)
- the number and types of phases present,
- the composition of each phase,
- and the weight fraction of each phase given the temperature and composition of the system
