dding nanoparticles to soft matter and liquids is known to provide remarkable control in the processing of novel materials. Here

we demonstrate a similar potential in crystalline solids. Specifically

we show that the addition of a high density of W nanoparticles dramatically alters the coarsening behavior of precipitate-hardened Cu–Ag alloys. First

the nanoparticles suppress precipitate growth

but far more surprisingly

they induce non-equilibrium Ag wetting layers on grain boundaries. This observation is explained using kinetic Monte Carlo simulations

which show that caging of Ag precipitates by the W nanoparticles suppresses their growth and drives the formation of wetting layers.