Al-Y-Ni-B非晶質合金玻璃形成能力及結晶行為研究

Abstract

In this study, 15 at.% of boron is added to increase amorphous forming ability of Al87Y8Ni5 alloy ribbons by single roller melt-spinning process. Thermal properties including crystallization activation energy and the Avrami exponent of crystallization are obtained by non-isothermal and isothermal analyses. The (Al87Y8Ni5)85B15 amorphous alloy ribbon demonstrates a glass transition temperature (Tg) at 529 K, and its ΔTx (=Tx-Tg) value is 24.6 K. Crystallization kinetic study show that the 15 at.% of boron increases the activation energy for crystallization from 159 to 228 kJ/mol. The Avrami exponent n value of Al87Y8Ni5 amorphous alloy is 1.5~2.1 indicating a decreasing nucleation rate with crystallization time, whereas the n value of (Al87Y8Ni5)85B15 amorphous alloy ribbon is 2.3~3.1 or the nucleation rate increases with time. The maximum hardness is obtained for both non-boron and boron added alloys after crystallization at 593-598 K due to formation of nano-crystallites. The highest hardness achieved is 566 and 575Hv for Al87Y8Ni5 and (Al87Y8Ni5)85B15 alloys, respectively. It is further found that the Al3Y and AlNi phases delay their precipitations till higher temperatures due to boron addition. The boron addition apparently improves the stability of Al87Y8Ni5 amorphous alloy.