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.