Enhancing the helium retaining ability of metal tritide by multi-principle element alloying with severe lattice distortion

Helium (He) bubble induced tritium retention is a critical factor affecting the cyclic tritium storage capacity of tritium storage materials, with helium retaining ability serving as a key indicator for evaluating comprehensive tritium storage properties. This study systematically investigated He bubble growth behavior and helium release characteristics in Ti_20.2Zr_16.6Hf_18.1Nb_45.1 multi-principal element alloy (MPEA) tritide and titanium tritide using transmission electron microscopy (TEM) and He instantaneous release fraction (IRF) techniques. Results reveal that He bubbles maintain spherical growth in Ti_20.2Zr_16.6Hf_18.1Nb_45.1T₁₁₁ tritide, whereas TiT_1.68 tritide undergoes a morphological transition from spherical to platelet-like bubbles. The He release fraction of Ti_20.2Zr_16.6Hf_18.1Nb_45.1T₁₁₁ tritide is one order of magnitude lower than that of titanium tritide. The severe lattice distortion of MPEA effectively retards He migration and diffusion increases He bubble nucleation density, and significantly decelerates bubble growth. This study confirms that MPEAs exhibit excellent helium retaining ability, suggesting their potential as high-performance tritium storage materials.