Question

(2) Is it possible to produce a precipitation hardened 2014 aluminium alloy having a minimum yield strength of 350MPa and a ductility of at least 15%EL? If so, specify the precipitation heat treatment. Explain why. (Figure QB2 shows that the precipitation hardening characteristics of a 2014 aluminium alloy at different aging temperatures: (a) yield strength, and (b) ductility (%EL)) [7marks] 1 min 1 h 1 day 1 month 1 year 1210 300 1490 Yield strength (MP) 200 2040 100 2600 0 10 104 (a) 10-1 10 10 101 Duration of precipitation heat treatment (h) 1 min 1h 1 day 1 month 1 year 30 2040 1496 1210 Ductility (El inom 20 101 10 (b) 10 10 10 Duration of precipitation heat treatment (h) Figure 4.1.

Answer 1

- 4 Yes . it is possible. to make a * solute and vacancies. slightly higher solution treatment at 500 c Single phase solid solution. Quench to rom temprature from 500 c Alloy will be super saturated with Aging: Allow to diffuse at temprature Excess amorint will be ejected as Precipitates quenching Aging * a *) on o G.P zones a Olsss time depends on aging and alloy composition. at Aging 149° c will give our for 10 hours wired properties req, 380 Mpa > 350 MPa yield Strength 15% ~ 15% EL % Elongation after quenching C at I hoor. at co hours Precipitate number is important to resist the dislocation motion. la sen aging and over overaging Precipitates number will be less. So strength will be less. At