Precipitation of B2 Phase and Aging Hardening in Fe-Cu Binary Alloy

The relationship between the grain size and hardness for binary Fe-Cu alloys with different chemical compositions was investigated under the condition of supersaturation. The solid solution hardening of Cu element in the binary Fe-Cu alloys has been investigated in this study. The aging hardening phenomenon and precipitation behavior have been investigated for Fe-Cu binary alloys. Results show that the hardness of Fe-Cu alloys is almost doubled by aging treatment. TEM observation reveals that with prolonging the aging time, the size of the precipitates increases, and the morphology of the precipitates changes from spherical shape to bar-like shape. The electron diffraction analyses show that the precipitate of Cu is of B2 crystal structure corresponding to the peak aging condition. The B2 precipitates keep parallel lattice orientation relationship with the Fe matrix. The observation of interaction between dislocation and precipitates by TEM shows that there exists a typical attractive interaction between the moving dislocation and precipitates. The pinning-up of moving dislocation by soft precipitates prevents the movement of dislocation during deformation and provides strengthening in Fe-Cu binary alloys.