Effects of ball milling time on the microstructure and hydrogen storage performances of Ti21.7Y0.3Fe16Mn3Cr alloy

Abstract

TiFe alloy can store hydrogen at room temperature and low hydrogen pressure, and its theoretical hydrogen storage capacity is up to 1.8 wt%. However, TiFe alloy needs to be activated at high pressure (5 MPa hydrogen) and high temperature (673–723 K), which limits the practical application of TiFe alloy. The as-cast Ti 21.7 Y 0.3 Fe 16 Mn 3 Cr alloy was milled for 0, 0.5, 0.75, 1, and 3 h to study the effects of ball milling on phase structures and hydrogen storage performances. Emphasis was focused on the activation process of as-milled alloys at different temperatures, including the activation process at 483, 443, and 403 K. The results show that the alloys were consisted of TiFe phase, and [Fe, Cr] solid solution. The nanocrystalline boundary produced by milling and the phase boundary provided by the second phase provide a large number of channels for hydrogen diffusion and promote the improvement of hydrogen storage performances. The time required for activation process of as-milled alloys was significantly reduced, and the activation time of as-milled (0.75 h) was only 4 min, and its enthalpy variation for hydrogen absorption and desorption was 22.943 and 26.215 kJ mol −1 H 2 , respectively. • The phase composition and micro-structure of the milled Ti 21.7 Y 0.3 Fe 16 Mn 3 Cr alloy were studied. • Nanocrystalline boundary produced by milling provides many channels for hydrogen diffusion. • Ball milling improves the activation process of the alloy and shortens the activation time. • The optimum milling time of the alloy is 45 min, and its activation time is shortened to 4 min.