AMORPHOUS-CERAMIC Ni-BASED COMPOSITE REINFORCED WITH Al2O3 PROCESSED BY MECHANICAL ALLOYING AND POWDER CONSOLIDATION

An attempt was made to obtain bulk metallic glasses composite by mechanical alloying followed by powder compaction. Ni-based amorphous matrix was fabricated by milling of a mixture of pure crystalline elements. Two types of Al2O3 powders were added (20 vol. %) as the ceramic phase: micrometer in size (50 mu m) and nanopowder (80 nm). Mechanical alloying resulted in a full amorphization of the alloy. The addition of ceramic powder influenced the thermal stability of the amorphous phase. Especially in the case of nanopowders, the crystallization temperature of the first crystallization stage of amorphous phase was decreased by about 50 degrees C. The applied parameters of isostatic pressing (1.5 GPa, 0.5 h, 440 and 480 degrees C) resulted in partial crystallization of the alloy. It was verified by XRD and DSC studies. The quality of the compaction was checked by optical microscopy observations, revealing some micropores.