Subject Mould casting

If the two metals that form the alloy are insoluble in one another, then they will exist as two separate phases, often in alternate layers such as observed in tin-lead alloys or cast irons, where the carbon is often found as minute tadpole like shape (flakes) adjacent to the pure iron. These types of two-phase alloys are extremely difficult if not impossible to shape by hot or cold working. Fortunately, these alloys have a melting point well below that of the parent metals and are very suitable to shape by casting into moulds. This is the reason why iron 4.5% carbon alloys were called cast irons. These alloys have two important limitations in that first, they are very brittle when subjected to impact loads, and second, their corrosion resistance is inferior to pure metals or single-phase alloys. 

---