Aging behavior of Cu-rich precipitates in Fe-3% Si-Cu alloy

Abstract

Fe-3%Si-Cu alloys with different Cu content were aging treated at 500 ∼ 800 °C. In order to study the dynamic behavior of the aging precipitations, the microstructure and the aging precipitation behavior of copper-rich phase in these alloys under different aging heat treatment were tested by OM, TEM technology and Vickers hardness. The results show that the amount of the copper-rich precipitates in the two alloys are gradually increase with the aging time going after aging treated at 600 °C. Within the 103 s aging time, the size of the copper-rich precipitates of the two samples is below 20 nm. When it reaches 105.5 s, the copper-rich precipitates have obvious cluster phenomenon and the size are not more than 100 nm. After being treated with different aging temperature, the hardness of Fe-3% Si-Cu alloys with different copper component increases first and then decreases with time going, with obvious aging hardening peaks. When the aging temperature is 500 °C and the aging time is 104.5 s, the hardness of the two alloys reaches the maximum and they are 264 HV and 238 HV, respectively. The precipitation kinetics curve of the copper-bearing Fe-3% Si-Cu alloy is in the shape of 'C', and there is a certain precipitation incubation period. When the aging temperature is 600 ∼ 650 °C, the precipitation incubation period is the shortest. The increase of the copper content in the alloy will shorten the incubation period of the precipitation kinetic curve, increase the precipitation tendency of copper and cause the curve shifted to the left obviously.