Effects of aging on toughness were studied in the simulated heat-affected zone (HAZ) as well as the HAZ of weld joint in duplex stainless steels. The results are summarized as follows. (1) Such welding thermal cycle conditions as rapid cooling rate, high heating temperature, long heating time, annealing following thermal cycle, and restraint of thermal strain raise susceptibility to the age-embrittlement in the simulated HAZ. (2) In contrast to the high susceptibility to the age embrittlement in the simulated HAZ specimen of a rapid cooling rate such as 150°C/s, TIG weld joint suffers age embrittlement by a far smaller amount. (3) Annealing after the age-embrittlement diminishes hardness and deterioration of toughness in aged specimens.

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Mechanisms of age-embrittlement in duplex stainless steels are discussed to explain the deterioration behavior of toughness by aging in the various specimens such as the simulated heat affected zone (HAZ) and TlG weld joint HAZ, which was reported in the preceding paper of this volume.

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