Aluminium alloy identification — duralumin composition: Select the composition range that corresponds to classic duralumin (a precipitation-hardenable Al–Cu–Mg wrought alloy).

Introduction / Context:
Duralumin is a foundational wrought aluminum alloy system that achieves strength through precipitation hardening. Correctly identifying its composition helps distinguish it from casting alloys like Y-alloy and from other series such as 7xxx Al–Zn–Mg.

Given Data / Assumptions:

• Duralumin emphasizes copper and magnesium with a small amount of manganese.
• It is a wrought, not a casting, alloy in its classic form.
• Balance is aluminum with trace impurities.

Concept / Approach:
The classic duralumin composition is approximately 4% copper, about 0.5% magnesium, and about 0.5% manganese. This balance enables solution treatment and aging for strength. The listed range in option (a) matches this profile, while the Ni-bearing composition in option (b) is characteristic of Y-alloy used for cast parts at higher temperatures.

Step-by-Step Solution:
Look for Cu ~4%, Mg ~0.5%, Mn ~0.5% in a wrought alloy.Match to option (a) exactly.Eliminate options featuring nickel (Y-alloy) or zinc (7xxx series).Select option (a) as duralumin.

Verification / Alternative check:
Historical standards and textbooks list duralumin within these composition ranges and describe its age-hardening behavior.

Why Other Options Are Wrong:
Option (b) is Y-alloy; option (c) is magnesium-rich and not classic duralumin; option (d) represents bearing alloys; option (e) corresponds to Al–Zn–Mg–Cu 7xxx family, not duralumin.

Common Pitfalls:
Mixing cast and wrought alloy families; assuming the presence of nickel in duralumin, which is incorrect.

Final Answer:
3.5 to 4.5% copper, 0.4 to 0.7% magnesium, 0.4 to 0.7% manganese and balance aluminium