Improved Tensile Strength and SCC Resistance via Nonisothermal Creep Aging under a High Stress Level

Abstract

Compared with conventional isothermal creep aging, non‐isothermal creep aging does not involve a prolonged holding stage, but only has heating and cooling stages. During the non‐isothermal creep aging process, the precipitates nucleate and grow up in the early part of heating stage, resulting in fluctuations in creep rate and an increase in strength. The coarsening of precipitates in the later part of the heating stage, can lead to significantly increase of creep rate. Upon approaching the peak temperature, the dissolution of the precipitates occurs in conjunction with a partial coarsening of the remaining precipitates, causing a reduction in strength. However, the secondary precipitation during the cooling stage facilities a significant strength enhancement in a relatively shorter period. In contrast to the isothermal creep aging, the targeted non‐isothermal creep aging treatment gives an increase in ultimate strength while improves the stress corrosion cracking resistance. Moreover, the time required for non‐isothermal creep aging to obtain ultimate strength is only 13.9 % of that of the ICA treatment. A large amount of creep strain can be generated during the NICA process, which is equivalent to 630 % of that of creep age forming treatment.This article is protected by copyright. All rights reserved.