Development of Mg based hydrogen absorbing alloys prepared by mechanical alloying

• The Mg17Al12 alloy was successfully synthesized by using combined ball-milling and spark plasma sintering (SPS) at 673 K.
• Using the SPS system, homogenous Mg17Al12 bulk has formed at 673 K for 30 min.
• Synthesized Mg17Al12 alloy could react with hydrogen rapidly and then MgH2 formed.
• And after the hydrogen desorption, the single Mg17Al12 phase have revived.

We carried out the spark plasma sintering (SPS) heat treatment method for Mg17Al12 phase in order to synthesize of mixture powder prepared with shorter MA time. The average particle size can be estimated around 20 μm after 8 h of MA in argon atmosphere observed by SEM images. And the mixture prepared by 8 h of MA shows amorphous phase by X-ray diffraction (XRD) measurements. However, the obtained bulk form mixture shows Mg17Al12 structure after 30 min of SPS heat treatment at 673 K. And the powder characteristic of synthesized alloy shows nano-crystalline and remarkably low level of contamination measured by XRD analysis and EDX analysis. Moreover, the heat treated mixtures could absorb hydrogen rapidly without heat activation treatment measured by high pressure hydrogen differential scanning calorimeter (DSC) apparatus. This result suggests that the SPS heat treatment after short term MA is proved to be an efficient and simple expedient to synthesize hydrogen absorbing Mg-based alloys.