Chapter 1 Flashcards
To select appropriate materials and processing techniques for specific applications engineers must…
- Have knowledge of materials properties
- Understand the structure-property relationships
What’s an example of processing? What does it affect?
- Cooling rate of steel from high temperature
- Structure (microstructure)
What does structure affect?
Properties
What are three properties of metals?
- Strong and ductile
- High thermal & electrical conductivities
- Opaque and reflective
What are polymers made from? What are three properties of polymers/plastics?
Compounds of non-metallic elements
- Soft, ductile, low strengths, low densities
- Low thermal & electrical conductivities
- Opaque, translucent or transparent
What are ceramics made from? What are three properties of ceramics?
Compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides)
- Hard and brittle
- Low thermal & electrical conductivities
- Opaque, translucent, or transparent
What are the 6 material properties?
METMOD: Mechanical, electrical, thermal, magnetic, optical, deteriorative
What happens if you increase the carbon content of steel (iron)?
It increases the hardness of
What three factors increase the electrical resistivity for copper?
- Increasing temperature
- Increasing impurity content
- Deformations
What is thermal conductivity?
measure of the material’s ability to conduct heat
What does increasing the impurity content do to thermal conductivity?
Decreases thermal conductivity
Are highly porous materials good or poor conductors of heat?
Poor conductors
Why do ceramic fibers have low thermal conductivity?
Significant void space
What are the two magnetic properties?
Magnetic storage and magnetic permeability
What is magnetic storage?
Recording medium is magnetized by recording write heat
What is magnetic permeability?
Measure of magnetization produced in a material in response to an applied magnetic field.
What is magnetic storage?
Magnetic storage or magnetic recording is the storage of data on a magnetized medium.
How do you make iron a better recording medium?
Add 3 atomic % Si
What affects optical properties?
The light transmittance of some materials depend on their structural characteristics.
What does the aluminum oxide single crystal look like? why?
optically transparent because of a high degree of perfection
what does the aluminum oxide polycrystalline material look like? why?
optically translucent because it has many small grains
what does the aluminum oxide polycrystalline material look like?
it’s optically opaque since it has some porosity
What does it mean for a material to be a single crystal?
the arrangement is periodic in all of the space of any size
Why are some crystals translucent?
there are grain boundaries that separate each section of crystal (each section is a single crystal)
What would happen if a steel bar was stressed and immersed in sea water?
It would form stress- corrosion cracking
Why does stress-corrosion cracking form?
When you put stress into something it has high energy to it cracks to get back to low energy
What kind of material has the most deteriorative properties? why?
metals since they’re the most reactive with oxygen
What is the relationship between heat treating and stress-corrosion cracking?
Crack growth is diminished by heat treating
Why does heat treatment work?
If you have a deformed metal and you heat it, energy is high, so atoms can be moved without cracking a lot
What are the 4 material requirements for artificial joins?
- Biocompatible– minimum rejection by surrounding body tissue
- Chemically inert to body fluids
- Mechanical strength to support forces generated
- Good lubricity and high wear resistance between articulating surfaces
Parts of an artificial hip replacement
Femoral stem?
Head (ball)?
Shell?
Liner?
Femoral stem: inserted into the top of the hip bone (femur)
Head (ball): affixed to femoral step
Shell: attached to the pelvis
Liner: into which head fits
Materials for Artificial Hip Replacement
Femoral stem?
Head (ball)?
Shell?
Liner?
Femoral stem: titanium or CoCrMo alloy
Head (Ball): CoCrMo alloy or Al2O3 (ceramic)
Shell: titanium alloy
Liner: polyethylene (polymer) or Al2O3 (ceramic)
With regards to the design, production, and utilization of materials, what are the four elements to consider?
Processing, structure, properties, and performance
What elements are metals composed of? Ceramics? Polymers? Composites?
Metals: Metallic elements
Ceramics: Compounds between metallic and nonmetallic elements
Polymers: Compounds composed of carbon, hydrogen, and other nonmetallic elements.
Composites: Two different material types.
What is an important property of semiconductors?
Having electrical conductivities intermediate between those of conductors and insulators
What are smart materials?
those that sense and respond to changes in their environments in predetermined manners
What is the subatomic structure?
involves electrons within the individual atoms, their energies and interactions with the nuclei
What is atomic structure?
Relates to the organization of atoms to yield molecules or crystals
What is nanostructure?
Deals with aggregates of atoms that form particles (nanoparticles) that have nanoscale dimensions (less than 100 nm)
What is microstructure?
Those structural elements that are subject to direct observation using some type of microscope (structural features having dimensions between 100 nm and several millimeters)
What is macrostructure?
Structural elements that may be viewed with the naked eye (with scale range between several millimeters and on the order of a meter)
What is a property?
A material trait in terms of the kind and magnitude of response to a specific imposed stimulus
What is a mechanical property?
relate deformation to an applied load or force, examples include elastic modulus (stiffness), strength, and resistance to fracture
What is an electrical property?
A stimulus is an applied electric field; typical properties include electrical conductivity and dielectric constant
What is a thermal property?
Are related to changes in temperature or temperature gradients across a material; examples of thermal behavior include thermal expansion and heat capacity
What is a magnetic property?
The responses of a material to the application of a magnetic field; common magnetic properties include magnetic susceptibility and magnetization
What are optical properties?
The stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties
What are deteriorative characteristics?
Relate to the chemical reactivity of materials; for example, the corrosion resistance of metals
