Simulation of bcc-Cu precipitation in ternary Fe-Cu-M alloys

Abstract

The precipitation of bcc-Cu in the ferrite matrix of Fe-Cu-M alloys, where M is Al, Mn and Ni, is simulated using the Kampmann-Wagner-Numerical (KWN) model with the classical nucleation theory (CNT) and the theory of diffusion-controlled growth by Zener and Kirkaldy. The instantaneous local equilibrium interfacial concentrations of Cu and M were calculated at every time interval, which revealed that the influence of M diffusion is insignificantly small no matter it is faster or slower than the diffusion of Cu. Whilst the capillarity-corrected Cu concentration at the interface in the matrix essentially dictated the growth and coarsening, the concentration of M in the particle affected by capillarity also had an appreciable influence on the number of Cu particles. Al decreased the Cu solubility in the bcc-Fe matrix, increased the number of Cu particles, and decreased the matrix supersaturation fastest. Mn decreased the number and increased the mean radius of bcc-Cu particles due to the increase in Cu solubility to a large extent. The effects of Ni on particle number were less pronounced than one would expect from experimental observations in multicomponent steel. The small changes in particle/matrix interfacial energy and strain energy of nucleus can alter significantly the evolution of particle number and size during aging.