2.5 Basic Material Properties Flashcards
What is plasticity?
Permanent shape change (through atom bonds breaking and reforming)
Why is it easy for metallically bonded materials to deform plastically?
1) Their bonds are non-directional
2) They have no charge constraints.
Which is more important and why: Shear and tensile forces
Shear’s more important!
Tensile forces pull things apart, but shear allows bonds to break and reform.
Why is it hard for ionically bonded materials to deform plastically?
Shear the ions once and they repel! It’s difficult.
What is plastic deformation like in metal alloys?
Oh, just the same as metal alloys. Because alloys are all metallically bonded and so there’s no real difference (unless sizes are different)
BONDING FORCES AND ENERGY
Yay!
There are min energy diagrams that I don’t feel like stopping on. See notebook.
Okay. Basically there are repulsive forces from similarly charted ions, and attractive forces from oppositely-charged pairs. Combining the two gives a diagram with a hump in it.
What is Stiffness?
Deformation per load
How would you find the stiffness of a material from it’s attractive and repulsive forces?
From the slope of the graph!
Why are there two atomic separations for any given energy level?
Because you can store energy in kinetic and potential energy!
How can you change the thermal expansion of a material?
Change the strength of its bonds!
Stronger bonds result in a higher or lower thermal expansion? Why?
Lower expansion
What is INVAR used for?
Absolute standards of length measurement! Clock and watch mechanisms, bimetallic strips.
What does high conductivity depend on?
Mobility of carriers, as well as number of carriers per unit volume.
BASIC MATERIAL PROPERTIES
Yay!
