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Hot Working of Metals
permanent deformation of metals and alloys above the temperature at which a strain-free microstructure is produced continuously
Cold Working of Metals
permanent deformation of metals and alloys below the temperature at which strain-free microstructure is produced continuously
Annealing
a heat treatment used on a metal to soften it
Extrusion
a plastic-forming process in which a material under high pressure is reduced in cross section by forcing it through an opening in a die
Forging
a primary-processing method for working metals into useful shapes in which the metal is hammered or pressed into shape
Wire Drawing
a process in which wire stock is drawn through one or more tapered dies to the desired cross section
Deep Drawing
a metal-forming process for shaping flat sheets of metal into cup-shaped articles
Elastic Deformation
if a metal deformed by a force returns to its original dimensions after the force is removed
Engineering Stress
average uniaxial force divided by the original length of sample
Engineering Strain
change in length of sample divided by the original length of sample
Shear Stress
shear force S divided by the area A over which the shear force acts
Shear Strain
shear displacement a divided by the distance h over which the shear acts
Engineering Stress-Strain Diagram
experimental plot of engineering stress versus engineering strain
Modulus of Elasticity, E
stress divided by strain in the elastic region of an engineering stress-strain diagram for a metal
Yield Strength
the stress at which a specific amount of strain occurs in the engineering tensile test
Ultimate Tensile Strength (UTS)
the maximum stress in the engineering stress-strain diagram
Hardness
a measure of the resistance of a material to permanent deformation
Slip
the process of atoms moving over each other during the permanent deformation of a metal
Slipbands
line markings on the surface of a metal due to slip caused by permanent deformation
Slip System
a combination of a slip plane and a slip direction
Deformation Twinning
A plastic deformation process that occurs in some metals and under certain conditions. In this process, a large group of atoms displaced to form a region of a metal crystal lattice that is a mirror image of a similar region along a twinning plane
Hall-Petch Relationship
an empirical equation that relates the strength of a metal to its grain size
Strain Hardening
the hardening of a metal or alloy by cold working. During cold working, dislocations multiply and interact, leading to an increase in the strength of the metal
Solid-Solution Hardening
strengthening a metal by alloying additions that form solid solutions. dislocations have more difficulty moving through a metal lattice when the atoms are different in size and electrical characteristics, as is the case with solid solutions
Recovery
the first stage in the annealing process that results in removal of residual stresses and formation of low-energy dislocation configurations
Recrystallization
the second stage of the annealing process in which new grains start to grow and dislocation density decreases significantly
Grain Growth
the third stage of the annealing process in which new grains start to grow in an equiaxed manner
Annealing
a heat-treatment process applied to a cold-worked metal to soften it
Superplasticity
the ability of some metals to deform plastically by 1000% to 2000% at high temperatures and low loading rates
Nanocrystalline Metals
metals with grain size smaller than 100 nm
Ductile Fracture
a mode of fracture characterized by slow crack propagation. ductile fracture surfaces of metals are usually dull with a fibrous appearance
Brittle Fracture
a mode of fracture characterized by rapid crack propagation. brittle fracture surfaces of metals are usually shiny and have a granular appearance
Transgranular Fracture
a type of brittle fracture in which the crack propagates across the grain
Intergranular Fracture
a type of brittle in which the crack propagates along the grain boundary
Ductile-To-Brittle Transition (DBT)
observed reduced ductility and fracture resistance of a material when temperature is low
Surface Energy per Unit Area
the energy associated with the surface created as a result of fracture
Theoretical Strength
fracture strength in a flawless body (without defects), determined by basic principles
Stress Concentration Factor
the amplification of stress influenced by the geometry of the component and the defect, represented by the ratio of maximum stress to far field or normal stress
Fracture Toughness
the critical value of stress intensity factor, a material property, at which a preexisting crack extends and the plate fails
Fatigue
the phenomenon leading to fracture under repeated stresses having a maximum value less than the ultimate strength of the material
Fatigue Failure
failure that occurs when a specimen undergoing fatigue fractures into two parts or otherwise has been significantly reduced in stiffness
Fatigue Life
the number of cycles of stress or strain of a specific character that a sample sustains before failure
Fatigue Crack Growth Rate
the rate of crack growth extension by constant amplitude fatigue loading
Creep
time-dependent deformation of a material when subjected to a constant load or stress
Creep Rate
the slope of the creep-time curve at a given time
Creep-Rupture Strength
the stress that will cause fracture in a creep test at a given time and in a specific environment at a particular temperature
LM Parameter
a time-temperature parameter used to predict stress rupture due to creep
