メカニカルアロイングによる CaMg 系 bcc 合金の創製とその水素親和性

抄録

  We have demonstrated in our previous report that the excess energy created during mechanical alloying (MA) yielded alloying of elemental couples with even negative mixing enthalpy and that a formation of new ternary bcc phase. It was noticed that a structural correlation exists between the Laves and bcc structures. The aim of this study is to synthesize CaMg₂ based bcc alloys in relation to the Laves phase structure with additive bcc vanadium, and to clarify the above issue on the structure and hydrogenation properties. The parent materials used in this study were CaMg₂ and metallic element powder. The MA was performed under Ar gas atmosphere and the rotation speed is 710 rpm. The weight ratio of powder to ball is 1:40.
   With increasing MA time, the lattice parameter of bcc alloy increases. After 60 hours of MA, single bcc phase was formed. The TEM observations show that the alloy made after 60 hours of MA was composed of nano-structured bcc grains without deviation from the nominal composition. The TDS was used to measure the hydride properties of the synthesized bcc alloys. The result showed that 3 mass% of hydrogen was absorbed. A new phase appeared after the desorption of hydrogen. The reason can be explained by electronegativity argument of alloy elements relative to hydrogen. This result could encourage us to have a chance of formation of new alloy phases during hydrogenation.