1. Annealing Processes
All the structural changes obtained by hardening and tempering may be eliminated by annealing.
to relieve stresses
to increase softness, ductility, and toughness
to produce a specific microstructure
Process consists of
heating to the desired temperature
holding
cooling to room temperature
annealing time must be long enough to allow for any necessary transformation reactions

2. Normalizing - used to refine the grains
cooling in air, less expensive, some sections of a part may cool too fast
Full anneal: Utilized in low and medium carbon steels that will be machined or plastically deformed
cooling in furnace to room temperature
final product is coarse perlite (soft and ductile)
Spheroidizing
for medium and high carbon steels
Fe3C will turn into the spheroids

4. Some parts should be hard on the surface but soft and ductile inside
shafts, gears, guideways of machine tools
carious surface hardening processes
heating on the surface only and
quenching it
flame hardening (by torch)
induction hardening
carburizing

10. Precipitation Hardening
Hardening of non-allotropic alloys
The properties of nonferrous substances that do not readily form allotropes cannot be changed by controlled cooling.
Such substances are known as non-allotropic alloys, and include aluminum, copper, and magnesium alloys as well as stainless steels containing Ni.
The method of hardening is called precipitation hardening and age hardening.
Precipitation involves the formation of a new crystalline structure through the application of controlled quenching and tempering. Precipitation disperses hard particles throughout the existing more ductile material.

11. These particles disrupt long dislocation planes of the material, restricting the movement of dislocations and increasing the strength and stiffness of the alloy.
The final step is to hold the material at a specific temperature for a given amount of time.
When aluminum is quenched in water to room temperature, the solubility of copper is drastically decreases and a compound of copper aluminide forms that slowly disperses along grain boundaries and slip planes to harden the alloy.

16. Summary primarily interest to increase YS
it means increase the load-carrying capacity of elements
the methods to increase YS are based on the various mechanisms of interfering with dislocation movements.
Methods:
Obtaining fine grain material
combination of hot working and recrystallization
annealing after cold work
Cold work (strain hardening)
the total amount of strain is limited by a total loss of ductility
Solid solution treatment
for alloys in which a solute-rich solid-solution phase exists at room temperature

17. Precipitation hardening
for alloys in which substantial solid solubility exists at an elevated temperature
followed by quenching it yields a supersaturated solution that releases fine, coherent precipitate
Allotropic hardening
only for steels
heating up to austenite and quenching leads to a martensitic structure (very hard and brittle)
tempering is followed in order to get some ductility

18. Engineering Metals
This section describes the most common metallic alloys, their properties, and their usage. The alloys considered are steels, cast irons, alloys of aluminum, copper, titanium, and Ni- and Co-based superalloys.
The production volumes in tons per year in the United States of the individual classes of metals are given below:
Steels and cast irons: 100 million
Aluminum alloys: 36 million
Copper alloys: 1 million
Ni-based alloys: <100,000
The significance of the individual classes of metals is not entirely expresses by these tonnages. For example, the Ni-based alloys are extremely important for gas turbines and jet engines; without them modern aircraft would not exist, and there would not be such a great need for aluminum alloys.

19. Steels: Carbon Steels no alloying elements other than C
impurities: Si, S, and P
adverse effect on ductility and toughness
Mn improves hardenability
low carbon steels (nonhardenable) with less than 0.2% C
thin sheet steel for car bodies, appliances, and for sidings of houses, heavy steel plates for ships and tanks, for the structures and frames of heavy machinery
hardenable steels
medium carbon steels, with more than 0.3% C
high carbon steels
hot rolled carbon steels
cold rolled carbon steels

21. Low alloy steels
almost always used in a heat treated (quenched and tempered) state

23. High alloy steels
contain over 5% of alloying elements
austenite could be present at room temperature, Ni widens the field, Cr narrows
Two classes
stainless steels
tool steel

27. Tools steels:
Each grade of tool steel is designed for a specific purpose, and as such, there are few generalizations that can be made about tool steel. Each tool steel exhibits its own blend of the three main performance criteria: toughness, wear resistance, and hot hardness.
Some of the few generalizations possible are listed here:
An increase in carbon content increases wear resistance and reduces toughness.
An increase in wear resistance reduces toughness.
Hot hardness is independent of toughness.
Hot hardness is independent of carbon content.

29. Aluminum alloys
pure Al is light, about three times lighter than iron
excellent electric conductor
excellent ductility
good resistance to corrosion
Tm = 660 degree C
could be strengthened by cold work
used from electric wire to extruded structural shapes for housing construction
it is usually used as an alloy
alloying elements: Si, Cu, Mn, and Mg
above 3% of Si improves fluidity
above 12% Si improves hardness and wear resistance
Cu improves the age hardenability, it is a primary element in achieving high mechanical strength in aluminum alloys at elevated temperatures.

31. Magnesium
its density is 2/3 that of Al
Tm = 650 degree C
is alloyed with Al, Zn, Mn, Ce, and Ag
main use in the aerospace industry
UTS below 350 MPa
it is difficult to cold form
extrusion, forging, and deep drawing possible on higher temperature