Quantitative phase analysis in Al_(86)Ni_8Y_6 bulk glassy alloy synthesized by consolidating mechanically alloyed amorphous powder via spark plasma sintering

摘要

The aim of the present work was to understand the phase transformation sequence in Al_(86)Ni_8Y_6 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 ℃ to 500 ℃ Quantitative phase analysis performed on the sintered alloys revealed at least 80% amorphous phase fraction in alloys sintered up to 350 ℃ The higher temperature (450 ℃ and 500 ℃) sintered alloys exhibited higher amount of nanocrystalline FCC-Al and various interme-tallic nano-precipitates (Al_3Ni, Al_3Ni_2 AlY, Al_2Y and Al_2NI_6Y_3) distributed in the retained amorphous matrix.