Nanoindentation study on Al86Ni8Y6 glassy alloy synthesized via mechanical alloying and spark plasma sintering

The present work is focused on the investigation of hardness and scratch behavior of mechanically alloyed and various temperature (300 degrees C-500 degrees C) spark plasma sintered Al86Ni8Y6 glassy alloys. Glassy alloy sintered at higher temperature, exhibited significantly improved hardness attributed to the increase in metallurgical bonding, relative density and nano-crystalline phases. A large variation in hardness of sintered alloys was attributed to the diffusion controlled crystallization mechanism depending on the nucleation rate during spark plasma sintering, which led to the different degree of microstructural phase evolution in a different part of the sample as confirmed by the scanning probe microscopy revealing the varying depth of indentation. Nanoindentation conducted at lower load resulted in higher hardness attributed to the indentation size effect. The scratch test exhibited decrease in coefficient of friction from 0.40 to 0.30 with the increase in sintering temperature from 300 degrees C to 500 degrees C, attributed to decrease in surface roughness.