PRECIPITATION HARDENING IN Al-CU, Al-Mg-SI,Cu-Be

1. PRECEPITATION HARDEING
IN AL-CU ALLOYS
GERUGANTI SUDHAKAR
ASSOC. PROFESSOR,ST.MARTIN’S ENGINEERING COLLEGE,J.N.TU,HYD.
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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.

9. Typical Aging Curve for
Aluminum Alloys