Recent Advances on Preparation Method of Ti-Based Hydrogen Storage Alloy

Ti-based hydrogen storage alloy is one of the most common solid-state hydrogen storage materials due to its high hydrogen absorption capacity, low dehydrogenation temperature and rich resources. This paper mainly presents the influence of several different preparation methods of Ti-based hydrogen storage alloys on the hydrogen storage performance including traditional preparation methods (smelting, rapid quenching and mechanical alloying) and novel methods by plastic deformation (cold rolling, equal channel angular pressing and high-pressure torsion). The microstructure analysis and hydrogen storage properties of Ti-based alloy are summarized thoroughly corresponding with the preparation processes mentioned above. It was found that slight introduction of lattice defects including dislocation, grain boundary, sub-grain boundary and cracks by severe plastic deformation (SPD) was beneficial to improve the hydriding/dehydriding kinetic characteristic. However, the nonuniform composition and residual stress of the alloy may be caused by SPD, which is not conducive to the improvement of hydrogen storage capacity. In the future, it would be expected that new methods and technologies combined with dopant and modification are applied to Ti-based hydrogen storage alloys to make breakthroughs in practical application.

Phase diagrams of permanent magnet alloys: Binary rare earth alloy systems

Thermodynamic optimization of the binary rare earth alloy(Cee La, Cee Pr, Cee Nd and Lae Nd) systems was performed in this work through the CALPHAD method based on the critical evaluation of all available phase diagram and thermodynamic data reported in the literature. During the thermodynamic modeling, the solution phases including liquid, bcc, fcc and dhcp, were treated as the substitutional solution model. Thermodynamic parameters of the stable phases in the Cee La, Cee Pr, Cee Nd and Lae Nd binary systems are obtained finally and would be used directly to develop the thermodynamic database of the multi-component Nde Fee B-based alloys, which is indispensable for designing alloy compositions and processes of Nde Fee B permanent magnets with highly abundant rare earth metals.

Effect of wheel speed on phase formation and magnetic properties of (Nd_(0.4)La_(0.6))-Fe-B melt-spun ribbons

The effect of wheel speed on phase formation and magnetic properties of （Ndo.4La0.6）lsFeTzsBzs and （Ndo.4La0.6）13.4Fe79.9B6.7 ribbons prepared by melt-spinning method was investigated experimentally. Based on X-ray diffraction results, all melt-spun ribbons consist of the main phase with the tetragonal 2：14：1 type structure and the minor α-Fe phase. Magnetic measurements show the maximum magnetic energy product （（BH）max） and the remanence （Mr） increases firstly and then decreases with the increase of wheel speed, while the coercivity （Hci） increases, resulting from the variation of the average volume fraction of the ^-Fe phase and the average grain size in the melt-spun ribbons. Using Henkel plots, the interaction between the 2：14：1 phase and the ^-Fe phase in the melt-spun ribbons was analyzed and the intergranular exchange coupling is manifested. Optimal magnetic properties of Hci - 7.27 kOe, Mr - 90.94 emu/g and （BH）max -- 12.10 MGOe are achieved in the （Ndo.4La0.6）lsFeTzsBT.s ribbon with the wheel speed of 26 m/s. It indicates that magnetic properties of Nd-Fe-B melt-spun ribbons with highly abundant rare earth element La can be improved by optimizing alloy composition and preparation process.