Grain Boundary Sliding in Isothermal and Thermal Fatigue of 304 Stainless Steel

Abstract

Grain boundary sliding (GB sliding) and grain boundary cracking in both isothermal fatigue under saw-tooth wave strain cycling and thermal fatigue were investigated on 304 stainless steel, in order to elucidate the physical meanings of the damage acceleration under these types of fatigue conditions found in the previous papers.In isothermal fatigue under saw-tooth wave and thermal fatigue, GB sliding was found to be accumulated in nearly proportion to the number of strain cycles, contrary to the case of isothermal fatigue under triangular wave where the accumulation of GB sliding was negligibly small. The direction of GB sliding accumulation both in isothermal fatigue under slow-fast saw-tooth wave and in-phase thermal fatigue was characterized as to induce the tensile residual strain of the specimen, while the direction both in isothermal fatigue under fast-slow saw-tooth wave and out-of-phase thermal fatigue was contrary.Grain boundary cracking was frequently observed in the vicinity of triple points or ledges on the grain boundary which accommodated the strain concentration due to GB sliding, and the higher amount of accumulation of GB sliding caused the earlier initiation of grain boundary cracking. Based on these metallurgical findings, it is concluded that the acceleration of fatigue damage is closely related to the accumulation of GB sliding.

Investigation of Mechanism for Intergranular Fatigue Crack Propagation of Low Carbon Steel JIS S10C in Hydrogen Gas Environment

“…In relation to the IG crack initiation, there were many reports except for the fracture surface of fatigued metals in hydrogen gas (5), (6) , for example, 'hydrogen embrittlement' such as delay fracture (20)~ (22) , SCC (23) , creep fracture at elevated temperature (24), (25) , temper embrittlement (26) , etc. In these reports, the IG fracture mechanism is explained by hydrogen diffusion and concentration in the grain boundary (22) , slip localization near the grain boundary (20) , impurity segregation (23), (26), (27) , and IG slip (24), (28) , respectively. It is considered that many factors affect the IG fracture.…”

Influence of Temperature and Dwelling Time on Low-Cycle Fatigue Characteristic of Isotropic Conductive Adhesive Joint

“…On the other hand, a grain boundary damage (gain boundary sliding) induced by creep deformation reduces fatigue life of polycrystalline materials at high temperatures (>0:5T m ). [16][17][18] The conductive adhesive, however, used in this study is not polycrystalline material that leads to a grain boundary sliding. Hence, the fatigue life was not degraded at the temperatures above the glass transition point, and then the fatigue life was kept at a higher level compared with the life at 298 K due to enhanced ductility.…”

Influence of Asymmetrical Waveform on Low-Cycle Fatigue Life of Micro Solder Joint

“…On the other hand, under low-speed and high-speed saw-tooth (slowfast) waves, residual grain boundary sliding remains, since significant grain-boundary sliding occurs during the low-strain-rate deformation, and grains deform internally with very little or no grain boundary sliding at the high strain rate. 17 The results suggest that the reduction in fatigue life under asymmetrical triangular waveforms is caused by irreversible sliding at grain boundaries. In this study, asymmetrical triangular waveforms did not have a significant effect on the fatigue life of Sn-AgCu micro solder joints (Figs.…”