Quantitative phase analysis in Al86Ni8Y6 bulk glassy alloy synthesized by consolidating mechanically alloyed amorphous powder via spark plasma sintering

• Mechanically alloyed Al86Ni8Y6 powders were consolidated by spark plasma sintering.
• Effect of sintering temperature on phase evolution in sintered alloys was studied.
• Phenomenon of mechanical crystallization was observed during mechanical alloying.
• Alloys sintered up to 350 °C retained high amount amorphous phase with nano-phases.
• Stokes-Einstein equation based sintering mechanism dictated the phase evolution.

The aim of the present work was to understand the phase transformation sequence in Al86Ni8Y6 powder blend, subjected to prolonged mechanical alloying and in the bulk amorphous alloy consolidated via spark plasma sintering at various temperatures. The powder blend, mechanically alloyed up to 300 h, exhibited cyclic phase transformation by yielding (i) amorphous-crystalline matrix phase with distributed nanocrystalline phases at 80 h, (ii) fully amorphous phase at 140 h and again (iii) amorphous-crystalline matrix phase with distributed nano-crystals at 200 h of milling. The phase reversal due to the prolonged milling after achieving complete amorphization was attributed to mechanical crystallization. Amorphous powders were consolidated via spark plasma sintering in the temperature range of 250 °C to 500 °C. Quantitative phase analysis performed on the sintered alloys revealed at least 80% amorphous phase fraction in alloys sintered up to 350 °C. The higher temperature (450 °C and 500 °C) sintered alloys exhibited higher amount of nanocrystalline FCC-Al and various intermetallic nano-precipitates (Al3Ni, Al3Ni2 AlY, Al2Y and Al2NI6Y3) distributed in the retained amorphous matrix.

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