[1E01-03] Irradiation Effects in Nuclear and Fusion Materials

10:05 AM - 10:20 AM JST(1:05 AM - 1:20 AM UTC)

[1E01] Atomic-Scale Observation of Helium-Irradiation-Induced Phase Transition in C14 Laves Phase

*ZONGDA YANG¹, Sho Kano², Hiroaki Abe¹ (1. UTokyo, 2. QST)

Keywords:

Plasma,RIA,Phase transition,Atomic-resolution STEM

Under fusion environments, the synergistic effects of displacement damage and helium (He) irradiation challenge the phase stability of C14 Laves phase in RAFM steels. Here, (Fe,Cr)2W C14 Laves specimens were subjected to 160 keV He+ irradiation at 250C and 350C. Using atomic-resolution STEM-HAADF along perpendicular [1-210] and [0001] zone axes, we resolved the radiation-induced defects. At 350C, a novel crystalline-to-decagonal crystal approximant (CA) transition was observed in the peak He region. At the atomic level, He-bubble-associated interstitial dislocation loops form on {10-10}planes, showing "half-atom planes" with localized atomic shuffling (Fe-W replacement). The elastic interactions of "jogged" and "piled-up" stacking faults drive the self-organization of Laves icosahedra into five-fold symmetric decagonal clusters. DFT calculations confirmed the energetic favorability of this transition, deepening the understanding of intermetallic phase stability under irradiation.