Fractal Analysis of the Effect of Grain Boundary Character on Te-Induced Brittle Cracking in GH3535 Alloy

GH3535 alloy has been used as the main structural material of molten salt reactor, which exhibits good high-temperature strength and excellent corrosion resistance to the molten salts. The intergranular cracking of GH3535 was detected after four years of operation of the molten salt reactor experiment, which was attributed to the inward diffusion of fission products Te. Grain boundary engineering (GBE) has been successfully applied to enhance the grain-boundary-related properties of the materials by increasing the frequency of low S coincidence site lattice grain boundaries and tailoring the grain boundary network. The in situ three-point bending test was used to assess the cracking properties of NonGBE and GBE samples following Te infiltration at 700 degrees C for 500 h. Fractal analysis statistics of various types of grain boundaries and cracks following in situ three-point bending tests were used. The result shows that the fractal dimension of cracks is in accord with that of the random grain boundaries (RGBs).The stronger the fracture resistance of materials, the lower the value of the RGB fractal dimension. The GH3535 alloy GBE samples with a bigger average size and more uniformly distributed twin grain clusters will have greater cracking resistance.

Automated summary

GH3535 alloy has been utilized in molten salt reactor as the main structural material due to its impressive high-temperature strength and excellent resistance to corrosion from the molten salts. However, after four years of operation in the reactor experiment, intergranular cracking of the GH3535 alloy was detected, which was caused by the inward diffusion of fission product Te. Grain boundary engineering (GBE) technique has been employed to enhance the grain-boundary-related properties of the alloy, resulting in better cracking resistance.