Preparing Mg-Ni-Si amorphous powders by mechanical alloying and consolidation by pulsed current sintering

摘要

Mg-Ni-Si alloy powders were synthesized by mechanical alloying; then, bulk samples were consolidated by pulsed current sintering. Also, sample corrosion behaviour was investigated by measuring the corrosion rate. An amorphous phase was formed in powders with up to 80 at.% Mg by milling for 2520 ks. These powders contained Si particles and nano-crystals in addition to the amorphous phase. On the other hand, it was difficult to form an amorphous phase in powders with 85 at.% Mg or higher content. The amorphous phase was formed when the ratio of Ni-to-Mg content exceeded 15%. The crystallization temperature of the amorphous powder increased concomitant with Si content. When bulk alloys were sintered from the amorphous powder at 473 K, i.e. below the crystallization temperature, the amorphous phase was maintained, but Mg crystals grew in the alloy. Subsequently, reduced bulk amorphous alloy corrosion was observed due to exposure to 5 mass% NaCl solution for 96.4 ks (24 h) because that exposure formed a black layer like a passive film on the amorphous alloy surface.