Precipitation strengthening at elevated temperature in Fe-Cu alloys

The mechanism of strengthening by copper (Cu) particles at 873K was discussed in terms of the interaction between dislocation and Cu particles in aged Fe-Cu alloys. The moving dislocation was pinned by the Cu particles and passed through them when the bowing angle reached some critical value (θ_c). The value of θ_c at 873K was around 33 degree regardless of the Cu particle size, although the θ_c at room temperature increased with an increase in the diameter of particle. This indicates that the interaction at 873K is significantly different from that at room temperature. TEM observation for the 3%Cu steel deformed by 1.9% at 873K revealed that the strain around dislocation is released at the particle/matrix interface and the attractive interaction is working between the dislocation and the Cu particles. The precipitation strengthening was evaluated by considering the effect of mean particle spacing (λ) and the θ_c, and it was found that the increment of yield stress was smaller than the Orowan stress.