Al-Si

Abstract

AI-Si is a simple eutectic system with two solid solution phases, fcc (AI) and diamond cubic (St). The assessed phase diagram is compared in Fig. 1, 2, 3, and 4 to the experimental data on which it is based, and its topological features are summarized in Table 1. The present diagram is calculated from Gibbs energies optimized with respect to thermochemical and phase boundary data. The reconciliation of phase diagram and thermochemical data is discussed in detail in the section entitled "Thermodynamics". AI-Si alloys are among the most important commercial alloys when small additions (0.01 wt.%) of Na are made. These alloys are denoted "modified" and are greatly improved in microstructure and mechanical properties over the binary alloys. Cu or Mg is added for age-hardening. Much work has been done on solidification structures in AI-Si alloys as a function of composition, cooling rate, growth velocity, and ternary additions. [71Hell provided an extensive review of this subject. Although this topic is beyond the scope of the phase diagram assessment, a list of solidification references was provided because of the importance of solidification processes.