A code indicating the state of working and heat treatment of aluminum and other alloys in production. O means annealed, H strain-hardened and T thermally treated, with digits giving finer distinctions.
Japanese name: 質別
Temper designation appears in 2 practice questions across 2 topics, including Nonferrous metals and alloys, Metals and alloys.
Field: Nonferrous metals and alloys
The temper of an aluminum alloy is written after the alloy number, as in 5052-H34 or 6061-T6. F is as fabricated, with no special control; O is fully annealed to the softest state; H is strain-hardened by cold work; W is the unstable state after solution treatment while aging is proceeding at room temperature; and T is adjusted to stable properties by heat treatments such as solution treatment and aging. The same alloy can differ greatly in strength, elongation and corrosion resistance depending on its temper, so when ordering material or writing a drawing the alloy number and temper are always specified as a pair.
The first digit after H indicates the treatment after working: H1 is strain-hardened only, H2 strain-hardened and then partially annealed, H3 strain-hardened and then stabilized by low-temperature heating, and H4 strain-hardened and then heated by paint baking or a similar process. The second digit is the degree of hardness: 8 is the hardest state, 4 is half-hard, midway between O and 8, 2 is quarter-hard and 6 three-quarter-hard. Even comparing H14 and H24, H24 has been worked harder and then brought back by annealing, so its elongation is somewhat larger. 5000-series alloys with high Mg contents soften slowly at room temperature, so H3 tempers are often used.
The digit after T indicates the combination of heat treatments. T4 is solution treated and naturally aged at room temperature; T6 is solution treated and artificially aged to near-maximum strength; T5 is cooled from a high-temperature shaping process such as extrusion and then artificially aged; and T3 and T8 are solution treated, cold-worked and then aged. T7 is an overaged or stabilized condition, with aging carried past the peak to give up a little strength for better resistance to stress corrosion cracking and dimensional stability. Further digits, as in T651, indicate, for example, that residual stress has been relieved by stretching.
Answer: C. Strain-hardened and then heated at low temperature to stabilize the properties, with a hardness midway between O and the hardest state
H denotes strain-hardened material; the first digit indicates the treatment after working and the second the degree of hardness. H1x is strain-hardened only, H2x strain-hardened and then partially annealed, and H3x strain-hardened and then stabilized by low-temperature heating. A second digit of 8 is the hardest state, 4 is half-hard, midway between O (annealed) and 8, 2 is quarter-hard and 6 three-quarter-hard. 5000-series alloys with high Mg contents gradually soften and change their properties when kept at room temperature, so H3x tempers, given a low-temperature heating in advance to stop this, are used. Solution treatment and aging are treatments of the T tempers of heat-treatable alloys and are not applied to the non-heat-treatable 5052. Partial annealing is H2x, and a second digit of 4 means half-hard.
No. The 1000, 3000 and 5000 series do not precipitation-harden, so they are designated O for annealed or with H tempers for strain-hardened. T tempers are used for heat-treatable alloys such as the 2000, 6000 and 7000 series.
For the same alloy T6 is usually stronger; T4 has lower strength but greater elongation and suits forming such as bending. Parts are sometimes formed in T4 and then artificially aged to T6.
The temper designations in Japanese standards follow almost the same system as the Aluminum Association system used internationally. The basic O, H and T letters and the meanings of the main digits are common, so foreign documents can be read directly.
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.
In the aluminum alloy designation “A6061-T6” (JIS; 6061-T6 …Work hardening Al-Li alloy Alclad Beryllium copper GP zone Tough-pitch copper γ'' phase