Tailoring LPSO phases in Mg-Y-Zn alloys to govern hydrogenation kinetics

A series of Mg-Y-Zn alloys with varying long-period stacking ordered (LPSO) phase fractions were prepared through control of alloy content, heat-treatment, and single-pass extrusion. The effect of LPSO phase volume fraction and microstructure refinement on the hydrogen absorption/desorption properties of ball-milled powders prepared from the extruded alloys was experimentally assessed. The hydrogen absorption and desorption kinetics scaled with the LPSO phase volume fraction, though the results of this study suggest that the scaling is not linear. Variations in the LPSO phase fraction and alloy content did not alter the (de)hydrogenation equilibrium pressure, indicating there is no significant change in thermodynamics of hydrogenation. Hydrogen absorption experiments on thin foils made from the extruded Mg-Y-Zn alloy with a high LPSO phase fraction demonstrated that the LPSO structures decompose into Mg phase, lamellar Mg/Mg-Zn structures and YH2 particles at hydrogen partial pressures sufficient to form YH2. This study shows that the hydrogen absorption/desorption kinetics in the Mg-Y-Zn alloys can be controlled by tailoring the LPSO phases using conventional metallurgical techniques. [GRAPHICS] .