Abnormal crystallization in Al86Ni6Y4.5Co2La1.5 metallic glass induced by spark plasma sintering

Abnormal crystallization was observed in Al86Ni6Y4.5Co2La1.5 metallic glass powder at about 20 degrees C below its glass transition temperature (T-g, 271.5 degrees C) during spark plasma sintering (SPS). The crystallization product, identified to be a hexagonal-structured Al5Co2 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 conventional heating. SPS is effective to introduce a unique nanometric intermetallic phase in the amorphous matrix. The abnormal crystallization is attributed to the high applied pressure and non-thermal effects of SPS. (C) 2013 Elsevier Ltd. All rights reserved.