Microstructural evolution of compositionally complex solid-solution alloys under in-situ dual-beam irradiation

This work attempts to link the microstructural evolution of single-phase compositionally complex alloy (CCA) compositions under dual-beam irradiation to their Mn-content via the stacking-fault energy (SFE) and vacancy migration energies. Two alloys, Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35, along with less compositionally complex pure Ni and Fe56Ni44 binary were irradiated at 500 and 600 degrees C under dual-beam 1 MeV Kr2+ and 16 keV He+heavyions up to 7 displacements per atom (dpa) with a He/dpa ratio of 0.75 %/dpa using in situ transmission electron microscopy (TEM). Due to the bubble-stabilizing effect of implanted He, bubbles were observed in all irradiations, and populations of faulted interstitial loops were characterized in Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35. A reduction in swelling was observed in the two CCAs compared to pure Ni and Fe56Ni44. Although swelling increased from 500 to 600 degrees C in Fe56Ni44, Cr15Fe35Mn15Ni35 and Cr18Fe27Mn27Ni28 both swelled slightly more at 500 degrees C. This was attributed to the difference in vacancy mobility, stronger pinning effect of vacancies on He, and the sink strength of faulted dislocation loops. Faulted interstitial loops nucleated with a higher number density and dislocation line density in Cr15Fe35Mn15Ni35 at both temperatures, and at 600 degrees C in both materials. The differences in faulted loop population and temperature effect on swelling are correlated to the Mn-content and the measured SFE (20.2 +/- 6.7 mJ/m2 for Cr18Fe27Mn27Ni28 and 9.2 +/- 3.4 mJ/m2 for Cr15Fe35Mn15Ni35).