Journal of Alloys and Compounds | 2019
Enhancement of the thermal stability of the amorphous structure by addition of Y in Al-Ca-Ni alloy
Abstract
Abstract The enhancement of the thermal stability of the amorphous structure in Al-Ca-Ni alloy has been investigated in two steps: 1) selection of ternary Al-Ca-Ni composition; and 2) effect of addition of Y. The thermal stability of the amorphous structure is significantly improved by the addition of Y in Al87.5Ca7.5Ni5 alloy. Among the alloys investigated in the present study, i.e. (Al87.5Ca7.5Ni5)100-xYx (x\u202f=\u202f0, 1, 2, 3 and 4\u202fat%), alloys with ≥2\u202fat% Y exhibit glass transition behavior during heating and viscosity drop at the supercooled liquid region. The activation energy for the first-step crystallization increases with increasing Y amount, i.e. from 167\u202fkJ/mol for Y\u202f=\u202f0\u202fat% alloy to 347\u202fkJ/mol for Y\u202f=\u202f4\u202fat% alloy, indicating that the thermal stability of the amorphous structure is improved with Y addition. The increase of activation energy for crystallization may be due to the change of crystallization mode depending on Y amount; eutectic crystallization (Y\u202f=\u202f0\u202fat%) → polymorphic crystallization (Y\u202f=\u202f2\u202fat%) → primary crystallization (Y\u202f=\u202f4\u202fat%).