Abstract
The electric resistivity of Al-Si alloys annealed at various temperatures for a sufficient time to complete precipitation of Si phase and air cooled was measured at 77K. The solid solubility of Si in aluminum varies from 0.86 at% at 773K to 0.14 at% at 623K. The excess entropy of mixing and the heat of mixing on the basis of temperature dependence of the solid solution are 7.24 R and 47.7kJ/mol respectively. The residual resistivity for Si in aluminum is(6.7±0.1)×10-9Ωm/at%. The electric resistivity of Al-Si alloys containing 0.60, 0.90 and 1.19wt% aged at 523 to 673K was measured at 77K to determine the variation of Si concentration in the matrix due to coarsening of the Si precipitates. The Si concentration in the matrix linearly decreases with t-1/3. The Ce value and the Si concentration in equilibrium with a Si particle of infinite size are given. These data were applied to obtain reliable values of the particle-matrix interfacial free energy and the "effective diffusivity" of the solute in the matrix.
