Structural precipitation characteristics
Precipitation hardening of aluminum alloys

Consider an Al-M binary alloy (figure 2a ). For it to be suitable for precipitation hardening, the alloying element in the solid-state aluminum matrix must exhibit increasing solubility with temperature. For simplicity's sake, we assume that there is a eutectic reaction for this alloy at temperature T_E for concentration x_E. The ratio of the mean slopes of liquidus and solidus, called the partition coefficient, is then less than 1. This is the most general case for structurally hardening aluminum alloys produced by conventional solidification (equilibrium diagrams: binary alloys in this treatise). However, many alloys...