Columnar grains are typically observed in which region of a welded joint?

Columnar grains are typically observed in which region of a welded joint?

• A. In the weld metal
• B. In the base metal
• C. In the heat affected zone
• D. In the filler material

Answer: (A)

Columnar grains form during the directional solidification of the molten weld pool as it cools, growing from the fusion boundary into the weld metal. The region where this happens is the weld metal—the melted area that includes any filler metal that has melted and fused with the base metal. The heat-affected zone is heated but not molten, so its grains may coarsen or recrystallize but don’t develop the columnar solidification pattern seen in a solidifying weld pool. The base metal outside the weld retains its original grain structure. So, columnar grains are a feature of the weld metal.