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Nonferrous metals and alloys

Which is the correct pairing of the thousands digit of the four-digit designation of wrought aluminum alloys with the main alloying element?

  1. A2000 series Zn, 5000 series Si, 6000 series Cu, 7000 series Mg
  2. B2000 series Cu, 5000 series Mg, 6000 series Mg and Si, 7000 series Zn
  3. C2000 series Mg, 5000 series Mn, 6000 series Cu and Mg, 7000 series Si
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Answer: B. 2000 series Cu, 5000 series Mg, 6000 series Mg and Si, 7000 series Zn

The thousands digit indicates the main alloying element: the 1000 series is pure aluminum (at least 99.00%), the 2000 series Cu, the 3000 series Mn, the 4000 series Si, the 5000 series Mg, the 6000 series Mg and Si, and the 7000 series Zn (most also contain Mg and Cu). 2000-series alloys such as 2024 are used in aircraft as duralumin; 5000-series alloys such as 5052 and 5083 are used in ships and containers for their corrosion resistance and weldability; 6000-series alloys such as 6061 and 6063 are used for extruded sections; and 7000-series alloys such as 7075, the strongest, are used in aircraft and sports equipment. The 2000, 6000 and 7000 series are heat-treatable alloys strengthened by precipitation hardening, while the 1000, 3000 and 5000 series are non-heat-treatable alloys strengthened by work hardening and solid-solution strengthening. The other pairings are mistakes that swap the elements between series.

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More Nonferrous metals and alloys questions

  1. In the ASTM designation system for magnesium alloys, what does “AZ91,” widely used for die casting, stand for?
  2. Among the temper designations of aluminum alloys, what does “H34,” used for alloys such as 5052, stand for?
  3. Consider why aluminum is used for overhead power lines by comparing the masses of conductors of the same length and the same electrical resistance. Taking the conductivities as 61% IACS for aluminum and 100% IACS for copper, and the densities as 2.70 g/cm³ for aluminum and 8.96 g/cm³ for copper, about how many times the mass of the copper conductor is the mass of the aluminum conductor?
  4. Sheet of alloys such as 2024 used for aircraft skins is often supplied as clad sheet (Alclad), with thin layers of pure aluminum or an Al-Zn alloy roll-bonded to both faces. Which is the main role of these layers?
  5. When an Al-Cu alloy is solution treated, quenched and aged, the precipitates change roughly in the sequence GP zones → θ'' → θ' → θ (Al₂Cu). Which statement about GP zones is correct?