Why non-ferrous alloy does not have endurance limit?

Answer 1

Many non- ferrous alloys do not exhibit well-defined endurance limits.
An effective endurance limit for these materials is sometimes defined as the stress that causes failure at 1 x 10^8 or 5x10^8 loading cycles.
The concept of an endurance limit is used in infinite-life or safe stress designs.
It is due to interstitial elements ( such as Carbon or Nitrogen in Iron ) that pin dislocations , thus preventing the slip mechanism that leads to the formation of micro cracks.

Answer 2

As bill said, none of those are alloys because they're pure elements (they are non-ferrous though because they don't contain iron). A ferrous alloy would be something iron-based like steel, cast iron, or invar Non ferrous alloys include brass, sterling silver, and nichrome.

Answer 3

They enter the plastic stage quickly.