Metallic composites as form-stable phase-change alloys

Metallic materials can be used as Phase Change Materials for thermal storage, since they absorb/release relatively high latent heat for solid/liquid transformation during the heating/cooling parts of thermal cycles including their melting/solidifying range. The active PCM phase can also be mixed to another phase, melting at higher temperature, forming metallic composites, also referred in literature as Phase Change Alloys. To be considered as ‘form stable’ material, leakage of the molten active phase must be prevented. The present contribution focuses on the processing/microstructure/ properties correlations of PCAs based on the simple Al-Sn system, with activation temperature of about 230°C. They were produced by mixing Al powders to two different Sn powders adopting different compaction techniques and heat treatments, and cycled to simulate service. Their microstructure, thermal and mechanical response in as-manufactured and after service revealed that, amongst those experimentally available, PCA produced by compaction at room temperature inhomogeneous a blend of the powders is the optimal procedure, with good absorbed/released enthalpy and thermal stability after service.