Aluminum alloy (6061) (Al with 0.6 wt.% Si and 1.0 wt.% Mg) is subjected to age hardening treatment.
(a) Plot the temperature versus time of the heat treatment process with reference to the pseudo-binary phase diagram below. Indicate the different heat treatment steps on your graph.
600
+ Liquid 1.85%
595°C
Temperature (°C) 400 200
-
X + MgSi
0 Al
1.62 wt.% MgSi
(b) Please make a sketch of the hardness as a function of annealing time (precipitation treatment) and explain why does the hardness increase and/or decrease over time?