Influence of Ball-Milling Time on Microstructure Evolution and Hydrogen Storage Characteristics of Ni-Added La-TiFe-Based Alloys

A cast alloy with the nominal composition Ti_1.06Zr_0.1La_0.04Fe_0.6Ni_0.3Mn_0.2 was fabricated by vacuum induction melting. Subsequently, this alloy was mechanically ball-milled with 7 wt.% Ni to prepare the La-TiFe-based composite. The composite alloy is mainly composed of the TiFe phase, with small amounts of ZrMn₂ and Ni phases. Furthermore, the effects of Ni addition via mechanical ball milling on the microstructure, phase composition, hydrogen absorption/desorption kinetics, and hydrogen storage thermodynamics were systematically investigated. The as-prepared Ti_1.06Zr_0.1La_0.04Fe_0.6Ni_0.3Mn_0.2 + 7 wt.% Ni composite was subjected to activation treatment under 3 MPa H₂ and 373 K. Experimental results indicate that the composite achieves optimal activation performance when ball-milled for 60 min. Microstructure characterization shows that proper mechanical ball milling significantly reduces the particle size, encapsulates Ni better on the surface of the alloy particles, and may provide accessible catalytic sites for H₂ dissociation. In contrast, particle refinement and milling-induced defects/interfaces are expected to facilitate hydrogen transport, which is consistent with the improved hydrogen absorption/desorption kinetics. Specifically, the composite milled for 60 min exhibited excellent hydrogen storage kinetics and capacity at ambient temperature. Thermodynamic tests further demonstrated that the 60-min milled alloy had the smallest hysteresis and the best overall thermodynamic performance.