Phase Diagrams

· A material with a hypo-eutectic composition: C₄ = Pb - 40 wt % Sn shows a more complex solidification behavior.

· Above 300 C (j) the alloy is a homogeneous liquid. On cooling to (k) the α-phase has started to solidify, and α-crystals continue to grow until the eutectic invariant temperature (183 C) is reached (l).
· At 183 C the remaining liquid has the eutectic composition (Pb - 61.9 wt % Sn) and solidifies as a lamella solid (m) with Primary α-inclusions.

After: Callister, "Materials Science and Engineering," Wiley (1994)