Depression of the peritectic melting point of FeSn_2 in FeSn_2-FeSn nanocomposites produced by mechanical milling

摘要

The particle size effect on the peritectic melting of FeSn_2 particles in FeSn-FeSn_2 nanocomposites was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FeSn - 10 wt.% FeSn_2 compounds mechanically milled for 30 min exhibit in DSC curves a considerable decrease in the incongruent melting point from an equilibrium value of 786 K to approximately 680 K. Although FeSn_2 grains grow from 10 to 40 nm upon heating in DSC before peritectic melting sets in, the melting temperature is reduced substantially. Small latent heat during peritectic melting and large interfacial energy of FeSn-FeSn_2 nanocomposites are held responsible for the large particle size effect on incongruent melting. For rapid local heating under ball collisions during MM grain growth is hardly possible and therefore, a reduction in the peritectic melting temperature should be even substantially larger. Therefore, it can be concluded that local incongruent melting under ball collisions is the mechanism which underlies the mechanically driven decomposition of intermetallics.