Al-Sn Miscibility Gap Alloy produced by Power Bed Laser Melting for application as Phase Change Material

Abstract

Alloys based on the Al-Sn system are Miscibility Gap Alloys consisting of two phases: a low-melting Sn phase and a high-melting Al phase. The two phases are almost immiscible in solid state, with minimal miscibility of Al in liquid phase just above the Sn-phase melting temperature. This situation allows the alloy to be used as composite Phase Change Material, where the low-melting (active) phase (Sn) acts as the actual Phase Change Material, storing/releasing latent heat at each thermal cycle across its activation temperature, and the high-melting (passive) phase (Al) plays its main role in fast driving heat within the composite material, thanks to its high thermal conductivity. Thermal response of PCM composites is expected to be faster if the active phase is finely combined to the matrix. Moreover, if the active phase is embedded in the passive phase, leakage phenomena can be prevented and the continuity of the passive phase, acting as matrix, also allows residual structural properties to the composite above the temperature at which the low-melting phase is activated. In these conditions, the composite PCM can be considered as a form-stable composite material. In this paper, the effect of rapid solidification has been investigated as a tool to get suitable microstructure of an Al-Sn alloy in view of its application as a composite PCM. The rapid solidification has been obtained by a Power Bed Laser Melting (also known as Selective Laser Melting) process. In the case of positive results for microstructure, the process will allow to overcome critical points in the manufacturing of composite PCM parts by powder metallurgy, mainly consisting in limitations on size and geometrical features of the parts. Data availabilityThe raw data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. The processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.