Off-eutectic composite solidification and properties in Al-Ni and Al-Co alloys

Abstract

To investigate the range of “coupled” eutectic growth in Al-Co alloys from 1 to 4 wt% Co and Al-Ni alloys from 5 to 10 wt% Ni directional solidification, using rates from 0.8×10⁻² cm/sec to 10.6×10⁻² cm/sec, was employed. Both alloy systems exhibited coupled zones skewed towards the hypereutectic compositions. Fully eutectic structures were obtained in the ranges Al-1 wt% Co to Al-3 wt% Co and Al-5.7 wt% Ni to Al-9.2 wt% Ni.

The off-eutectic alloys which exhibit a fully eutectic structure behave as reinforcing composite materials, with the tensile strength and microhardness increasing as the volume fraction of the strengthening phase increases.