In the context of welding metallurgy, what is the term used for the zone of altered properties adjacent to the weld?

The term used for the zone of altered properties adjacent to the weld is referred to as the heat-affected zone (HAZ). This area is critical in welding metallurgy because it experiences changes in microstructure and mechanical properties due to the heat generated during the welding process. As the base metal is heated and subsequently cooled, the characteristics can be altered, which may lead to issues like decreased toughness, increased brittleness, or the formation of undesirable microstructures.

In contrast, weld metal refers specifically to the material that has been added during the welding process, which becomes part of the joint itself. The fusion zone is the area where the base metal and the weld metal have melted and subsequently solidified, forming a continuous mass. The base metal is the original material before welding occurs, and while it is important, it does not describe the altered properties due to welding. Understanding the distinction between these zones is essential for assessing the integrity and performance of welded structures.