The high magnitude of quench-induced residual stress in thick aluminum plates is attributed not only to high thermal stress but also to high yield strength due to quench-induced precipitation hardening. To date, lowering the thermal stress is the only path to reduce the residual stress in the design of quenching technology. In this paper, a new path is proposed that reduces the residual stress through decreasing the yield strength at ambient temperatures by eliminating the precipitation hardening effect during quenching. As certified in several experiments, the high yield strength of thick as-quenched plates decreases rapidly from a short period of extra heat preservation at relatively higher temperatures. Therefore, an interrupted quenching method is proposed, wherein quenching is interrupted after an initial cooling period and the sample is placed in air to make the temperature field uniform; afterward, the sample is cooled to room temperature. Interrupted quenching tests were conducted on 115 mm thick 7050 aluminum plates and significant residual stress reductions were observed in the specimens compared with the residual stresses in the specimens subjected to regular quenching.
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