Final answer:
The weld-pool segment of a fusion weld is similar to a small metal casting because both involve liquid metal solidifying to take a new shape.
Step-by-step explanation:
The weld-pool segment of a fusion weld is analogous to a small metal casting due to its transformation process from a liquid to a solid state. In welding, metals are joined together by melting the base material and adding a filler material to the joint, forming a pool of molten metal called the weld pool. Once it solidifies, the fusion weld joint resembles a small, local cast. This solidification process is similar to the metal casting technique known as the lost-wax casting process. During lost-wax casting, molten metal is poured into a mold that was created by making a wax model and then encasing it in a refractory material. As the molten metal cools down and solidifies, it takes the shape of the original wax model, much like the solidified weld metal takes the form of the joint cavity.