Ternary stage creep is associated with necking.

Explanation:
Creep is the time-dependent deformation that occurs in a material under a constant load or stress. It is a common phenomenon in materials exposed to high temperatures and constant loading conditions. Creep can be divided into three stages: primary (or transient), secondary (or steady-state), and tertiary (or accelerated) creep.

Ternary stage creep, also known as tertiary creep, is the final stage of creep where the deformation rate increases rapidly. During this stage, the material experiences significant necking.

Necking is the localized reduction in cross-sectional area of a material under tension. It typically occurs in ductile materials and is characterized by the formation of a narrow region of reduced diameter or thickness. Necking is a result of strain localization and can lead to fracture.

During the primary and secondary creep stages, the material undergoes uniform deformation without significant necking. The deformation is distributed evenly across the material. However, as the material enters the tertiary creep stage, the deformation becomes highly localized, and necking occurs. This is often accompanied by a rapid increase in the deformation rate.

Necking in the context of ternary stage creep is an important phenomenon to consider because it indicates that the material is approaching its ultimate failure. It signifies that the material has undergone significant plastic deformation and is getting closer to fracture. Therefore, the occurrence of necking during ternary stage creep is a critical factor in assessing the remaining life and structural integrity of the material.

In conclusion, ternary stage creep is associated with necking, which is the localized reduction in cross-sectional area of a material under tension. Necking occurs during the final stage of creep when the material undergoes rapid deformation and is an important indicator of impending failure.