Melting behavior and the correlation of Sn distribution on hardness in a nanostructured Al–Sn alloy

Nanostructured Al–20 wt.%Sn alloy was prepared by mechanical alloying (MA). The evolution of microstructure upon sintering, melting behavior of the alloy and the effect of microstructure variation on hardness was investigated using X-ray diffraction (XRD), differential scanning calorimetry, scanning electron microscopy (SEM), microhardness indentation and nanoindentation. The present work shows that the nanostructure of Al–Sn alloy can be formed and controlled by milling and subsequent sintering process. The melting point of Al and Sn phase and the eutectic point of Al–Sn in the as-milled Al–Sn powders decreased remarkably due to size reduction of the each phase. Different distributions of Sn phase in Al matrix result in different effects on hardness of Al–Sn alloys. Homogeneous distribution of Sn nanoparticles in Al matrix has dispersion hardening effect, while inhomogeneous distribution of coarse Sn phase along the grain boundaries has softening effect.