Structure Flashcards
Why is there a stronger tendency to form glasses in oxides as compared to metals?
The crystallization rates of oxides are lower than those of metals.
How does higher APF affect the following properties?
- Close-packed ness
- Ductility
- Slipping
High APF = more close packed, therefore more ductile because it allows slipping of GB
What is the Crystal Structure and APF of Austenite phase of Iron?
FCC - 74%
What is the Crystal Structure and APF of Ferrite phase of Iron?
BCC - 68%
Why does the ductile to brittle transition temp exist in ferritics but not austenitics?
Crystal structure. Ferritic steel is BCC, which has APF of 68% which means it is ALMOST close packed. However, there is some amount of thermal energy that is required to enable GB slipping, hence why they are brittle at low temps but ductile at high temps
Why is austenitic SS FCC but ferritics are BCC?
High nickel content of austenitic SS maintains the FCC structure even at low temperatures
which crystal structures are close packed? what is their APF?
FCC and HCP. 74%
What are the first 5 Alkane chains of Hydrocarbons? and what is the pneumonic?
Methane, Ethane, Propane, Butane, Pentane
Many Elephants Prefer Blue Pineapples
What are the two types of polymeric structures? Describe the following properties of each: Melting point, transparency, chemical resistance, tensile strength, ductility, density, Mold Shrinkage.
Semicrystalline - distinct Tm; Opaque; Higher chem resistance, tensile strength, density; lower ductility. Higher Mold Shrinkage
Amorphous- softens over range of temps; transparent; lower chem resistance, tensile strength, density; higher ductility, better toughness
What do the following symbols represent with regard to planes and directions?
() {} [] <>
() - plane
{} - family of planes
[] - direction
<> - family of directions
Bar above number is negative
How do you find the name of a plane?
- Mark locations where plane crosses x,y,z axis (1, 1/2, infinity)
- Take inverse (1, 2, 0)
- Make plane (120)
How do you measure grain size? And convert to ASTM grain size #?
draw line across micrograph, count GB intersections, divide by line length. Do this a few times and take average
Use equation in reference book to convert to ASTM grain size
Eutetic System/Mixture
a homogeneous mixture of substances that melts or solidifies at a single temperature that is lower than the melting point of any of the constituents
What is the eutectic composition and temperature for steel? what phase transformation occurs there?
0.76% carbon @ 727 deg C (1340F);
Austenite to pearlite
What is the eutectic point of cast iron (temp and composition)? What phase forms there?
composition of 4.26 wt% C and a temperature of 1148°C (2100 F)
Cementite
