Combined Effects of Gamma-Ray Radiation and Repeated Hot-then-Cold Stresses on the Springback Degradation in Invar Alloy

Abstract

In this paper, we report the characterization of springback degradation of an Invar sheet with a combination of gamma-ray irradiation and repeated hot-then-cold stresses. The springback factor value of fresh Invar without radiation shows a linear increase with the number of hot-then-cold stress cycles. Continuous springback degradations are observed as the number of hot-then-cold stress cycles reaches 100. When the Invar sheet is subjected to gamma-ray irradiation, the springback factor is greater than that of the repeated hot-then-cold stressed samples. After applying the repeated hot-then-cold stresses to the post-irradiated Invar sheets, the springback factors are first restored to the value of fresh Invar, and then revert to an increasing trend. Our previous X-ray diffraction (XRD) analysis excluded the crystalline structural changes in the post-irradiated Invar. It is believed that the radiation-induced defects, which are closely related to the springback degradation, are possibly annealed during the first 20 hot-then-cold stress cycles. These cycles ultimately dominate the springback behavior of the stressed Invar sheets.