Dynamical mechanism of formation of Fe nanoparticles in Tin bronze alloys

The dynamical mechanism of formation of nanoparticles during the solidification of molten Tin bronze melt is investigated. Since the melting depth phenomenon occurs immediately after nucleation during the initial stage of solidification under the influence of anisotropic surface tension, some parts on the surface of the Fe nucleus move first inward up to a melting depth distance, then start to move outward with other parts. The melting depth induced by the anisotropic surface tension leads to that the inner diameter of the Fe nucleus is less than two times its critical radius for nucleation and some parts present weaker strength than other parts. When a forced flow by stirring and centrifugal means etc. is exerted on the molten Tin bronze melt, the Fe nucleus is dragged or distorted when it grows, and then the Fe nucleus is broken into more fine Fe nanoparticles. Due to the interaction between the convection and the anisotropy of surface tension, a great number of Fe nanoparticles form during the solidification of molten Tin bronze melt and dispersedly strengthen the Tin bronze alloys.