Typical age hardening alys at % Cu 20 25 30 35 40 45 0 5 10 15 BROC Liquid, L 800 ()+L 33% 500 85 a Q9. (20 p.) Precipitation hardening, or age hardening, provides one of the most widely used mechanisms for the strengthening of metal alloys. In precipitation hardening of Al-4%Cu alloys precipitates which are rich in copper are produced. (a)Briefly explain the precipitation hardening heat treatment steps used for Al-4%Cu alloys using the phase diagram provided and draw the microstructure after each step. (b) Discuss the precipitation squence of precipitates formed during heat treatment. (c) Draw hardness versus aging time curves by showing different precipitates formed at different time. And also, discuss what kind of precipitate should be obtained after age hardening. ? Temperature, T (C) 800 700 400 300 200 + Compound B.CuAl 100 0 10 20 30 40 50 60 70 Al wt % Cu