A model has been developed to account for the dependence of melting temperature on the size of nanosolids (nanoparticles, nanowires and nanofilms). In this model the effect of particle size and shape, lattice and surface packing factor, and the coordination number of the lattice and of the surface crystalline planes are considered. A general equation is proposed, having nonlinear form as a function of the reciprocal of nanosolid size. This model is consistent with reported experimental data for nanoparticles of In and Au, nanowires of Pb and In, and nanofilms of In.

The dependency of the surface-to-volume coordination number upon particle size has been obtained by an analytical function based upon our previous work, and a model for melting temperature as a function of size is presented. This expression for the melting temperature is a nonlinear relation in terms of the reciprocal of size. Also, the geometrical characteristics of nanoclusters have been applied to our general equation for the melting temperature of nanoparticles. It was found that the results of considering the geometrical characteristics of nanoclusters are in good agreement with the melting temperature achieved by the derived analytical function. Finally, this model has been compared with other theoretical models as well as the available experimental data. The predictions are consistent with the experimental data.

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Crack-free Hastelloy X fabricated through laser powder bed fusion (LPBF) from powder with a standard chemical composition is reported. Electron backscatter diffraction (EBSD) analysis evidenced columnar grains parallel to the building direction. The typical LPBF columnar dendrite microstructure was found to be finer than reported elsewhere. Mo-enriched carbides (~50 nm), presumed to play an important role in the cracking behavior of the alloy, were confirmed along interdendritic regions. Crack-free condition was maintained after heat treatment at 1177 °C for 1 h followed by water quenching, and the resulting microstructure was analyzed.

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