What is 'creep' primarily associated with in material science?

Creep is primarily associated with gradual deformation over time when a material is subjected to a constant load or stress, typically at elevated temperatures. This phenomenon occurs in materials, especially metals and polymers, where the internal structure slowly adjusts under the sustained force, leading to permanent deformation.

In the context of engineering and material science, this understanding is crucial for the design and selection of materials, particularly in applications where components are expected to carry loads continuously over long periods. The implications of creep can significantly affect the longevity and safety of structures, making it essential for engineers to consider this behavior when analyzing potential failures or the performance of materials under load.

The other options describe different material behaviors not associated with creep. For example, rapid deformation under stress is related to elastic and plastic deformation, immediate breakage refers to brittle failure, and resistance to temperature changes pertains to thermal stability rather than mechanical deformation. These concepts, while important in their own right, do not capture the essence of creep as a time-dependent deformation under sustained loading.