Small Angle Neutron Scattering Study of Nano Sized Precipitates in Ferrous Alloys.

Nano-sized precipitates in a Fe-1 wt% Cu alloy were studied by SANS (Small Angle Neutron Scattering). The SANS experiments were performed with the 40 m SANS instrument at HANARO. Due to the ferromagnetic nature of the ferrous alloys, a horizontal magnetic field of 1 Tesla was applied during the SANS experiment. The nano-sized Cu precipitates were quantitatively analyzed by SANS in the Fe-1 wt% Cu alloy. The size of the precipitates increased from 2 nm to 4 nm with increasing aging time from 20 min. to 1800 min. at 753 K. The measured A-ratio obtained from SANS data increased from 2.2 to 6.6 with increasing aging time. It is surmised that Cu clusters containing a large amount of Fe are initiated at the early stage of aging and the Fe content in the Cu precipitate decreases with increasing aging time and eventually an almost pure BCC Cu precipitate is formed.