Pinning of grain boundaries by second phase particles in equal-channel angularly pressed Cu-Fe-P alloy

Isothermal annealing was applied to an equal-channel angularly pressed (ECAP) Cu-Fe-P alloy to investigate the stability of the fine-grained microstructure. The starting as-cast microstructure of the alloy contained two sets of second phase particles, fine γ-Fe particles, and coarse Fe₃P intermetallic particles. Following ECAP, while the fine Fe particles were well dispersed in the interior of the grains, many Fe₃P particles were found outside the grains, along or at the junctions of grain boundaries. The presence of Fe₃P particles at the grain boundaries enhanced the stability of the fine grain structure by delaying grain growth until 873 K when a coarse-grained structure developed. The different roles of the two sets of particles are discussed in terms of the difference in their deformation behavior.