Abnormal crystallization in Al_(86)Ni_6Y_(4.5)Co_2La_(1.5) metallic glass induced by spark plasma sintering

摘要

Abnormal crystallization was observed in Al_(86)Ni_6Y_(4.5)Co_2La_(1.5) metallic glass powder at about 20 °C below its glass transition temperature (T_g, 271.5 °C) during spark plasma sintering (SPS). The crystallization product, identified to be a hexagonal-structured Al_5Co_2 phase, was not detected in the same powder when annealed in a differential scanning calorimeter (DSC). Nor was it detected in other Al-based metallic glasses of similar compositions which were annealed around their T_g temperatures by con ventional heating. SPS is effective to introduce a unique nanometric intermetallic phase in the amor phous matrix. The abnormal crystallization is attributed to the high applied pressure and non-thermal effects of SPS.