What processing method often involves heating and stretching materials to improve their strength?

The processing method that often involves heating and stretching materials to enhance their strength is extrusion. In the extrusion process, a material (typically metal or plastic) is heated until it becomes malleable and then forced through a die to create a specific cross-sectional shape. As the material is drawn through the die, it experiences both heating and mechanical deformation, which aligns the material's microstructure and enhances its physical properties, particularly strength.

This method is particularly beneficial because it not only allows for complex shapes to be created with precision but also improves the overall material properties through the induced strain during the stretching. In cases where metals are used, the process can lead to grain refinement, which ultimately contributes to greater strength in the final product.

The other methods mentioned do not primarily focus on the combination of heating and stretching to enhance strength in the same way that extrusion does. For example, annealing is a heat treatment used to relieve stresses and improve ductility, while forging primarily involves compressive forces rather than stretching. Quenching is a rapid cooling process used to increase hardness but doesn't involve stretching.