material science Flashcards
a regular repeating arrangement of atoms or molecules
crystal
regular repeating atomic arrangement
crystalline lattice
simplest crystalline structure, easy to distort, packing one of top of another to represent a cube of eight
simple cubic SC
central atom surrounded by 8 other atoms in the surrounding planes harder and less malleable than hcp structures
body centered cubic BCC
atoms at each corner and center of each cubic face, malleable good conductor
face centered cubic FCC
atoms from one layer nest in the empty space between atoms of adjacent layer. Three layers of atoms mallable and good conductor
hexagonal close packed HCP
what two basic structures are malleable and good conductors
Face centered cubic FCC and Hexagonal close packed HCP
what the differences in FCC/HCP?
HCP is less ductile than FCC and they stack different
what’s the moment a crystal begins to grow (liquid to solid)
Nucleation
point in which crystals meet
grain boundaries
what causes crystal growth
at solidification temperature
crystal growth size depends on
nucleation points
how to control grain size
fast and slow cooling
fast cooling causes
more nucleation points and smaller grain/fine grain
slow cooling causes
less nucleation points and larger grains
grain impact on metal properties (larger grains)
lower strength, lower hardness, higher ductility
all crystals have
some defect
Two types of defects
natural and engineered -alloy
______ ______ during production used to create materials with specific mechanical properties
manipulating defects
three types of crystal defects
point defect, line or linear defect, planar defect
whats the relationship between defects and plastic deformation
depends on dislocations for movement and plastic deformation during material forming operations increases the number of dislocations
an atom is missing or in an irregular place in the crystalline lattice
point defects
types of point defects
self-interstitial, interstitial impurity, substitutional, vacancies
areas where atoms are out of position in a crystal, generated and move when stress is applied
linear/ line defects
two types of dislocations
edge and screw
____ dislocation with extra half plane of atoms
edge
—– dislocation result of shear stress on a crystal structure
screw
a distortion/disruption in the long range stacking sequence of a crystalline structrure
planar defects
what are the three types of planar defects
stacking faults, twin boundaries, grain boundaries
Two types of voids
Pores
Cavitation
Voids due to air bubbles trapped during solidification process
Pores
Voids created due to shrinkage of material as it solidifies
Cavitation
Small, homogenous region of impurity atoms clustered within the crystalline structure of a metal
Precipitates
Materials change in shape due to applied load/stress
Deformation
Temporary change in shape, self reveres when force is removed
Elastic deformation
Permanent deformation of metal structure
Plastic deformation
A metal made by combining it with one more different elements
An Alloy
Purpose of an alloy
Increase strength and corrosion resistance
Type of alloy
Reactor vessel
Recirc piping
Stainless steel
Type of alloy
Steam generator tubes
Control rods drive
Inconel
Type of alloy
Pressure vessel
Condensate feed water
Steel alloy
Carbon and mild steel
Type of alloy
Fuel cladding
Zirconium
Type of alloy
Heat exchanger
Copper alloys
Brass
Bronze
A measure of materials reaction to a applied force (compressive or tension)
Stress
A measure of a materials deformation due to applied stress
Strain
A measure of a materials ability to withstand applied load/stress without fracture/failure
Strength
A measure of tensile stress (measure of materials ability to stretch)
Ductility
An amount of energy per unit volume that a material can absorb before fracturing
Toughness
An ability to resist deformation, penetration, indentation, and scratching
Hardness
Types of stress that pulls a metal apart
Plastic deformation by elongation
Tensile stress
Force/stress that pushes a metal from both ends
Plastic deformation by compression
Compressive stress
Force or stress applied tangentially to the surface of the material in opposite directions
Sheer stress
Angular displacement or twisting about the centerline/axis of the structure/material
Torque stress
Prevent material failure
Create uniformity of attachment
Allow for thermal expansion and contraction without failure/ fracture
Torque limits
Maximum compressive stress that, under gradually applied load, a material can sustain without failure
Compressive strength
Maximum amount of tensile stress/force that a material can take before failure
Tensile strength
The maximum force that can be applied to a clamping device without failure
Torque limits for clamping devices
A drive function that put maximum values on the torque that a motor can deliver to prevent damaging the motor of motor failure
Torque limits for a motor
Sudden break or cleavage of a metal without prior plastic deformation
Brittle fracture
Characteristics of brittle fracture
No gross, permanent or plastic deformation of the metal in the region of the brittle fracture
Used to alter physical and mechanical properties of metal without changing its shape
Heat treating
Heat treating methods
Annealing
Tempering
Heat treatment process which alters the microstructure of a metal to change its mechanical properties
Reduces hardness
Increase ductility
Eliminates internal stresses
Annealing
Soften a metal for cold working
Annealing
A heat treatment process that involves slow heating a metal to precise temperature below the critical point and slowly cooling to room temperature
Tempering
Reduce hardness, improve ductility, increase toughness and strength thereby reducing brittleness
Tempering
Common causes of material failure
Fatigue
Corrosion
Radiation induced embrittlement
Chemical
Work Harding
Repetitive and redistribution of forces acting on a material will cause
Fatigue
Combination of localized corrosion and fatigue failure
Surface defects caused by localized corrosion like pitting
Corrosion fatigue
Three factor that are necessary for stress corrosion cracking
Tensile stress
Susceptible material
Corrosion agent (oxygen/ chlorides)
What two ways can neutron radiation impact crystals
Elastic interaction
Inelastic interaction
When the Atom decays and becomes a new element
Neutron inelastic interaction
Radiation induced embrittlement increases and decreases what
Hardness -
Embrittlement -
Ductility-
Increase
Increase
Decrease
A sudden, extreme variation in temperature which causes tension/excessive stress in a material due to unequal expansion or contraction within the material
Thermal shock/ stress
Susceptible materials to thermal shock
Reactor vessel in Bwr
Reactor vessel, pressurize and steam generator for pwr
Form of erosion caused by implosion of gas bubbles on a metal surface
Cavitation
Chemical dissolution of surface oxides and metal accelerated by high velocity fluid and or flow impingement
Flow accelerated corrosion FAC
Causes of flow accelerated corrosion
Dissolution of the oxide film
Inadequate oxygen concentration/ph to sustain passive oxide film
