In the context of creep, threshold stress is defined as the limiting stress value below which no practically measurable creep rate can be achieved. Threshold creep behaviour for precipitation/dispersion-hardened alloys, metal-matrix composites, etc. is widely reported.

Question - Whether threshold stress in creep exists for two-phase alloys for ex. Zr-2.5Nb material?

The micro-structure Zr-2.5Nb is comprised of elongated α-grain lamellae along with inter-granular distribution of very thin layer of β-phase.