Modification of Copper & Copper Alloys

[scott_for_the_game]

G'day Forum,

Struggling with the old materials science. Can someone please help me with the processes involved in modifying the properties of copper.

I read that generally it doesn't respond to heat treatment.. is that true?

Something bout cold working and hot working? what's the effect of hot working it?

Bit confused so many different processes mentioned and not sure which is appropriate.

Cheers for the feedback folks.

 

[FredGarvin]

Take a look here:
http://www.key-to-metals.com/Article27.htm

look for the sections on hot and cold working. Some copper alloys can also be hardened through precipitation hardening.

 

[Astronuc]

G'day Forum,

Struggling with the old materials science. Can someone please help me with the processes involved in modifying the properties of copper.

I read that generally it doesn't respond to heat treatment.. is that true?

Something bout cold working and hot working? what's the effect of hot working it?

Adding to what FredGarvin mentioned, hot working involves (as the name implies) working a metal which has been heated. Heating the material softens it, which allows for reduced mechanical energy in working (deforming) the material. Hot working increases the range for plastic deformation and reduces the likelihood of cracking (but hot tearing can be a factor). Hot working a material will also result in a different dislocation structure in the grains, and that is also dependent upon temperature, particularly with respect to the annealing temperature or about 1/3 of melting temperature.

The ideal temperature depends on the alloy composition, but from a practical standpoint (cost of energy) hot working would be performed at the lowest temperature possible while achieving the desired mechanical properties.

Often materials which are cold worked will be annealed to soften the material for subsequent cold working. In addition, some alloys which have been through several cycle of cold working and annealing may be heated about a particular solution temperature in order to dissolve particular phases (intermetallic compounds). Then the alloy is rapidly quenched to force precipitation of fine second phase particles. Some alloys go through precipitation anneals as well.

 

[vaib30]

please let me know the cold working procedure of copper

 

[Astronuc]

Cold Working processes include

Cold Rolling - a billet or strip is passed between two rollers with a smaller gap (obviously) than the thickness of the billet or strip. The rolling compress the metals and elongation occurs in the rolling direction.

Drawing - barstock is passed through a die, which is how wire is made.

Pressing - a metal (e.g. copper or copper alloy) sheet is pressed onto a shaped die or mould to form an intricate shape.

Stamping - a punch is passed through a sheet of metal (e.g. copper or copper alloy)

Cold working, the permanent (plastic) deformation of a metal below its recrystallization temperature (and usually below its annealing temperature), produces additional dislocations within the metal's crystal lattice. Cold working induces http://learningzone.coruseducation.com/schoolscience/KS5specialiststeels/steelch2pg2.html

When two or more dislocations meet, the movement of one tends to interfere with the movement of the other. The more dislocations there are, the more they will hinder each other's movement.

Initially the dislocations produced by cold working can move through the metal structure and the shape of the material will change. As the working continues, however, the movement of the dislocations becomes more difficult. This increases the strength of the metal and also makes it stiffer. Therefore it becomes less malleable and ductile. That is, it is more difficult to change its shape. We say that the metal has become work hardened.

To make it more malleable and ductile again, the metal can be annealed.

See also - Annealing, Hot Working, Quenching - http://learningzone.coruseducation.com/schoolscience/KS5specialiststeels/steelch2pg3.html