Structural and electrochemical characterization of a melt spun AB 5-type alloy

Abstract

Melt spun Mm(NiCoMnAl) 5.15 has been characterized both structurally and electrochemically for cooling rates during rapid solidification in the range from 8.2 × 1 0 3 to 9.5 × 1 0 5 K s − 1 . The unit cell volume decreases when the cooling rate increases from 8.2 × 1 0 3 to 3.3 × 1 0 4 K s − 1 , before the unit cell volume increases up to a cooling rate of 6.1 × 1 0 4 K s − 1 . When the cooling rate increases further to 9.5 × 1 0 5 K s − 1 , a decrease has been observed in the unit cell volume. The density shows a variation in the same way as the unit cell volume, when the cooling rate changes. This might be due to different amount of vacancies in the materials. Another contribution to the change in the unit cell volume might be the difference in the amount of amorphous phase observed at the different cooling rates. Both the equilibrium discharging potential and the discharge capacity at low current seem to decrease when the unit cell volume decreases and increase when the unit cell volume increases. When the discharge current is increased, the correlation between the unit cell volume and the discharge capacity diminishes. The equilibrium discharging potential and the discharge capacity at low discharge current seem to be almost linearly correlated to the unit cell volume.