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Metals and alloys

In the aluminum alloy designation “A6061-T6” (JIS; 6061-T6 in Aluminum Association notation), what treatment does “T6” indicate?

  1. ASolution heat-treated and then naturally aged at room temperature
  2. BSolution heat-treated and then artificially aged
  3. CWork-hardened by cold working
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Answer: B. Solution heat-treated and then artificially aged

In aluminum alloy designations, the four-digit number gives the alloy series (the 6000 series is Al-Mg-Si) and the temper designation after the hyphen gives the processing condition. T6 means solution heat-treated and quenched, then artificially aged by heating to about 150–200 °C, strengthened by fine Mg₂Si-type precipitates. Solution heat-treated and naturally aged at room temperature is T4, somewhat weaker than T6. Work hardening by cold working is designated H and is used for non-heat-treatable alloys such as the 5000 series. In addition, O means annealed (the softest condition) and F means as-fabricated. Because strength varies widely with temper even for the same alloy, drawings specify both.

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