PRECEPITATION HARDEING IN AL-CU ALLOYS

1. PRECEPITATION HARDEING
IN AL-CU ALLOYS
GERUGANTI SUDHAKAR
ASSOC. PROFESSOR,ST.MARTIN’S ENGINEERING COLLEGE,J.N.TU,HYD.
PHD(MATERIALS ENGINEERING),HYDERABAD CENTRAL UNIVERSTIY.

2. The process of strengthening by precipitation hardening plays a
critical role in high strength aluminum alloys
Precipitation hardening consists of three steps:
(1) solution heat treating:
In solution heat treating, the alloy is heated to a temperature
that is highenough to put the soluble alloying elements in
solution.
(2) rapidly quenching to a lower temperature:
After holding at thesolution treating temperature for some
period of time, it is quenched to a lowertemperature (e.g.,
room temperature) to keep the alloying elements trapped
insolution.
(3)aging:
During aging, the alloying elements trapped in solution
precipitateto form a uniform distribution of very fine particles.
This fine distribution of precipitates strengthens and hardens
the alloy by creating obstacles to disloca-tion movement. Some
aluminum alloys will harden after a few days at
roomtemperature – a process called natural aging, while others
are artificially agedby heating to an intermediate temperature.

3. Precipitation Hardening of an Aluminum–Copper Alloy
The alloy is then artificially aged at 340F for 10h. During the
aging process,very fine particles of aluminum–copper are
precipitated and the strength andhardness increases
dramatically.

7. Typical Aging Curve for
Aluminum Alloys