Trans-interface diffusion-controlled coarsening.
Accurate theoretical predictions of the volume-fraction dependence during diffusion-controlled coarsening of a polydisperse assembly of particles have proved difficult. Here, a new model of coarsening is presented, involving diffusive transport through the coherent interface between ordered and disordered phases, which atomistic calculations show has a ragged structure. The interface is a diffusion bottleneck when the ordered phase is dispersed. It is predicted that the square of the average radius grows linearly with time, that the depletion of solute decreases as the inverse square-root of time, and that there is no effect of volume fraction on kinetics and the scaled particle-size distributions. These differ dramatically from predictions of modern theories of diffusion-controlled coarsening. Data on coarsening in Ni-Al alloys is examined. We show that no other theory is consistent with the experimentally observed absence of an effect of volume fraction on coarsening of ordered gamma' (Ni3Al) precipitates in a disordered Ni-Al (gamma) matrix, and the strong volume-fraction dependence of coarsening of gamma precipitates in an ordered gamma' matrix.
Ardell
Alan J
AJ
Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095-1595, USA. aardell@ucla.edu
Ozolins
Vidvuds
V
D000497:Alloys; D000535:Aluminum / Q000737:chemistry; D004058:Diffusion; D007700:Kinetics; D009010:Monte Carlo Method; D009532:Nickel / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
D000497:Alloys; D009532:Nickel; D000535:Aluminum