Chapter 11 Flashcards
What are the two classifications of metal alloys?
Ferrous and nonferrous
What are the two categories of ferrous/iron-based metal alloys?
Steels and cast irons
What wt% C are steels and cast irons?
Steel: <1.4 wt% C
Cast Irons: 3-4.5 wt% C
What are the three microstructures of cast irons?
ferrite, graphite, cementite
What are the two categories of steels?
Low alloy and high alloy
What are the three different types of low alloy steels? How do they behave? How much does the high steel alloy have?
low carbon: <0.25 wt% C
med carbon: 0.25-0.6 wt% C
high carbon: 0.6-1.4 wt% C
As it moves from low to high carbon content, the steel increases strength and decreases ductility
High alloy: stainless steel > 11% Cr
What are the properties of cast irons?
Low melting point, easy to cast, brittle
What does cementite decompose into?
ferrite and graphite
What is graphite formation usually promoted by?
1) Si> 1st%
2) slow cooling
What are the five types of cast iron?
1) gray iron
2) ductile iron
3) white iron
4) malleable iron
5) compacted graphite iron
What are the characteristics of gray iron?
5 characteristics
1) graphite flakes
2) weak & brittle in tension
3) stronger in compression
4) excellent vibrational dampening
5) wear resistant
What are the characteristics of ductile iron?
3 characteristics
1) add Mg and/or Ce
2) graphite as nodules not flakes
3) matrix often pearlite- stronger but less ductile
What are the characteristics of white iron?
3 characteristics
1) <1 wt% Si
2) pearlite + cementite
3) very heard and brittle
What are the characteristics of compacted graphite iron?
1) relatively high thermal conductivity
2) good resistance to thermal shock
3) lower oxidation at elevated temperatures
What are the characteristics of malleable iron?
3 characteristics
1) heat treat white iron at 800-900 C
2) graphite in rosettes
3) reasonably strong and ductile
What are three limitations of Ferrous alloys?
1) Relatively high densities
2) Relatively low electrical conductivities
3) Generally poor corrosion resistance
What are six examples of nonferrous alloys?
1) Cu Alloys
2) Al Aloys
3) Ti Alloys
4) Mg Alloys
5) Noble metals
6) Refractory
What are the four types of hardening?
Cold Work, grain boundaries, solid solution strengthening, precipitation hardening
What is precipitation hardening?
Hardening, strengthening due to formation of precipitate particles
What are some different alloys that precipitation harden?
1) Al-Cu
2) Al- Mg
3) Cu-Be
4) Cu-Sn
What happens in the different parts of precipitation hardening?
1) Pt A: heat treatment
2) Pt B: quench to room temperature
3) Pt C: reheat to nucleate small theta particles within the alpha phase
What is the effect of precipitation heat?
TS increases and % EL decreases
What does precipitation hardening occur at room temperature for?
Natural aging alloys
What distinguishes stainless steel from other steel types?
It’s more corrosion resistant
