Intro Flashcards
Example of “materials nan limited design, with new processes and materials comes Nero opportunities but also new problems.”
Plastics lead to time release drugs, contacts, pep but it is also found as micro plastics in humans
Material science
Study of the relationship between structure and property in materials
How are materials engineers and mechanical engineer related
Materials take knowledge from materials scientist to create materials with specific properties
Mechanical desire performance from design, they select materials and processes based on data from materials engineers
How are the properties and structure of materials related
Materials →← processing → structure → properties → performance
Levels of material structure
Microstructure → crystal/molecular structure (atomic arrangement) → atomic structure → subatomic particle (proton, photon, electron, phones )
What is the micro structure of a material
The high level arrangerent of the structure,
Easy to manipulate→ GB discontinuities, second phase, impunities
Most impactful change to structure
How does heat treatment effect structure of a material
It changes / controls the microstructure
What properties does a change in structure effect
Physical (density), electrical, magnetic, thermal, optical
All levels of structure change effects these properties, some more them others
Forging process
Choice of steel + additional material → forging, shaping, folding → annealing → sharpening I hardening (quenching tempering)
What is annealing
Heating up a material at a pre-set temp for a pre-set time
What is a crystalline material
Crystalline → long-range order, typically structural metals or structural ceramics
What are non-crystatalline materials
Amorphous, no long range order, glasses, polymers, ceramics
(T/f) unit cells and lattice basis are native to the material
T
Ex of FCC
Cu
Al
Ni
Gamma-fe
Ex of bcc
Alpha-fe
Beta-ti
Ex HCP
Mg
2n
Alpha-ti
What are allotropes
Different crystal stators for the same material, can happen to materials at different temps
What is crystal structure
How atoms interact
What is band strength
Strength of a material, energy needed to break bonds (specifically, energy needed to break all bonds and reform them shifted over )→ represents the theoretical shear strength of the material
Hw does measured strength compare to theoretical strength
Measured is significantly lower since dislocations will take the path of least resistance
What are defects
Imperfections in now atoms are arranged, categorized by dimensions needed to describe the defect →o, 1,2,3
What are oD defects
Point defects
Vacancies: holes where atoms should be
Self-interstial: atoms that exist in the structure that got stuck in a wrong position
Solute items: impurities → can be interstitial, can replace atoms in structure
What are 1D defects
Line defects
Dislocations
What are 2D defects
Area/planar defects
Grain boundaries : separation between grains with different orientations
Stacking faults: angle created by the wrong orientation of grains
Domain boundaries
Free surface: no free surface for cell to repeat itself on →the surface of an object must have incomplete/ dangling bonds
What are 3D defects
Volume defects
Precipitates: 2nd phase particles
Voids: holes
What are 2nd phase particles
Something with a different chemical makeup and different crystal structure
Dislocations
Most common mechanism for plastic deformation
Edge, screw, mixed
Happens along a slip plane in a slip direction
One line of bands is broken at a time across a slip place later than breaking all bands at once
More via dislocation slip glide
Defects are used to slow dislocation movement (strengthering)
Yield strength
Ability of a material to resist plastic deformations ( governed by dislocation movement)→ energy needed to move a dislocation
R. Yield strength, strength of a material
Increase=increase
Slip system
A slip place and slip direction
Describes now a dislocation will move
Slip direction = most densely packed direction
Slip place = plane containing slip direction with largest inter-planner spacing
R. # of slip system, material strength, ductility
Increase= decrease = increase
Exception to more slip system = less strength
Bcc is stronger than FCC despite having more sip system due to have inherent resistance to dislocation movement → so many slip place that they interfere and block each others → strengthening
Bcc and FCC = ductile, hcp = brittle
