What is the effect of cold forging on a metal's grain structure?

Cold forging is a metalworking process that involves deforming the metal at room temperature, which has a significant impact on the grain structure of the material. During this process, the mechanical work applied to the metal leads to dislocation movement and subsequent grain refinement. When a metal is cold forged, the grains are subjected to strain, causing them to elongate and become smaller in size. This refinement contributes to improved mechanical properties, such as increased strength and hardness, due to the finer grain structure that develops.

Additionally, the increased dislocation density resulting from the deformation helps to enhance the material's resistance to further deformation, a phenomenon commonly known as strain hardening. Therefore, the effect of cold forging on a metal's grain structure is characterized by refinement and reorganization, making the chosen answer accurate.