Latent Heat Evolution from TiB₂ Particulate Reinforced Aluminium Alloys

Industrial use of TiB2-aluminium composites in the as-cast form is facilitated by solidification modelling. However, for accurate simulations the thermophysical properties of the composite material are required. One of the most important values when simulating casting is latent heat. The latent heat observed during both the melting and solidification of TiB2 particulate reinforced commercial purity (CP) aluminium was investigated using two Differential Scanning Calorimetry (DSC) techniques: i) a single pan DSC operating in constant heat extraction mode, and ii) a heat flux double pan DSC. Although the TiB2 does not react with the matrix, the amount of latent heat evolved or absorbed during solidification or melting of the composite material was found to be significantly reduced in comparison with the amount predicted using the rule of mixtures. Various hypotheses are presented in an attempt to find the possible forms of stored energy which might arise from the presence of particles in the matrix and could account for this discrepancy. These include: i) interfacial energy and ii) elastic strain energy. The interfacial energy was found to be relatively small compared with the elastic strain energy, suggesting that the latter is responsible for the discrepancy.