Can Heat Treatment Really Make Materials Softer?

[CuriousCookie]

Hello, there's something that's been bugging me for quite some time now, and i hope anyone can enlighten me on this. So i'll get straight to the point.

Can heat treatment be used to make a material softer?

In normalising, you can say that the longer the time given for the subject to cooled, the softer the material gets. Is it true?

I've heat treated an aluminium subject using normalising and quenching method. I've found out that hardness of the subject using normalising is higher than the subject for quenching. The test is done in a furnace for 90minutes at 300 degrees. For quenching the quenchant used was water for 15 minutes. For normalising, the subject is cooled to room temperature for a period of 5 hours.

I hope someone can help me on this. Books and google has made me even more confuse XD

 

[Astronuc]

Hello, there's something that's been bugging me for quite some time now, and i hope anyone can enlighten me on this. So i'll get straight to the point.

Can heat treatment be used to make a material softer?

In normalising, you can say that the longer the time given for the subject to cooled, the softer the material gets. Is it true?

I've heat treated an aluminium subject using normalising and quenching method. I've found out that hardness of the subject using normalising is higher than the subject for quenching. The test is done in a furnace for 90minutes at 300 degrees. For quenching the quenchant used was water for 15 minutes. For normalising, the subject is cooled to room temperature for a period of 5 hours.

I hope someone can help me on this. Books and google has made me even more confuse XD

It depends on the alloy and temperature. There is annealing of cold-worked materials which softens the material and increases ductility. There is solution annealing, and precipitation or age hardening which increases yield strength. Precipitation hardening is used for aluminum and other maleable alloys.

http://en.wikipedia.org/wiki/Precipitation_hardening

See - users.mrl.uiuc.edu/cahill/308/precipitation.pdf - for an example
users.mrl.uiuc.edu/cahill/308/precipitation.pdf

 

[pukb]

You can certainly make a material softer(ductile) by heat treating it.You allow it to be heated to enough time and temperature such that the recrystallisation process is complete and grain growth occurs. Larger the grains more will be its ductility and less hardness.