Enhanced thermal stability of the devitrified nanoscale icosahedral phase in novel multicomponent amorphous alloys

Abstract

In this paper, details are given for the structural evolution of (Ti amorphous alloys, part of wider program of alloy development by equiatomic substitution. All three alloys initially crystallize by forming a nanoscale icosahedral phase. However, at higher temperatures, their decomposition sequences differ significantly. The nanoscale icosahedral phase in the (Ti 33 Zr 33 Hf 33 ) 70 (Ni 50 Cu 50 ) 20 Al 10 alloy decomposes into a mixture of Zr 2 Cu-type and icosahedral phases. This icosahedral phase still exists after heating up to 970 K, indicating a high thermal stability of this phase. The nanoscale icosahedral phase in the (Ti 33 Zr 33 Hf 33 ) 70 (Ni 33 Cu 33 Ag 33 ) 20 Al 10 alloy also transforms into a mixture of Zr 2 Cu-type and icosahedral phase during the second exothermic reaction but then transforms into a mixture of Zr 2 Cu-type and Ti 2 Ni-type phases. The nanoscale icosahedral phase in the (Ti 25 Zr 25 Hf 25 Nb 25 ) 70 (Ni 50 Cu 50 ) 20 Al 10 alloy decomposes into a mixture of Ti 2 Ni-type and MgZn 2 -type phases during the second exothermic reaction. It is concluded that the formation of the Zr 2 Cu-type phase retards the decomposition of the nanoscale icosahedral phase, which increases the thermal stability. In contrast, formation of Ti 2 Ni-type and MgZn 2 -type phases accelerates the decomposition of the nanoscale icosahedral phase, which decreases its thermal stability.

Multicomponent and High Entropy Alloys

“…Using equiatomic substitution, Kim, Zhang, Warren, Eckert and Cantor [3,[24][25][26][27][28][29][30][31][32][33][34] investigated the structure of a wide range of melt spun and chill cast alloys in the TiZrHfNbFeCoNiCuAgAl system. The alloys were based on the generic formula ETM100−x−yLTMxAly where ETM and LTM are early and late transition metals respectively.…”

Structural relaxation and glass transition behavior of novel (Ti33Zr33Hf33)50(Ni50Cu50)40Al10 alloy developed by equiatomic substitution

“…From our previous studies of good glass forming multicomponent (Ti 33 Zr 33 -Hf 33 ) 100ÀxÀy (Ni 50 Cu 50 ) x Al y alloys over the composition range x = 20-70 at.% and y = 10-30 at.%, the amorphous alloy (Ti 33 Zr 33 Hf 33 ) 50 and enlarged supercooled liquid region prior to crystallization [15][16][17]. However, so far there is no detailed investigation on structural relaxation and glass transition of such complex amorphous alloys.…”