What is nil ductility temperature (NDT) ?

Question

This question is from Material Science and Engineering.

Answer 1

*Many  metals  that  are  ductile  under  some  conditions become brittle if the conditions  are altered.   The effect of   temperature   on   the   nature   of   the   fracture   is   of considerable  importance.    Many  steels  exhibit  ductile fracture  at  elevated  temperatures  and brittle  fracture  at low   temperatures. The   temperature   above   which   a material is ductile and below which it is brittle is known as the Nil-Ductility Transition (NDT) temperature.  This temperature is not precise, but varies according to prior mechanical  and  heat  treatment  and  the  nature  and  amounts  of  impurity   elements.     It  is determined by some form of drop-weight test (for example, the Izod or Charpy tests).

*In physics/materials science the ductile-brittle transition temperature (DBTT), nil ductility temperature (NDT), or nil ductility transition temperature of a material represents the point at which the fracture energy passes below a pre-determined point (for steels typically 40 J for a standard Charpy impact test). DBTT is important since once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming. For example, ZAMAK 3, a zinc die casting alloy exhibits good ductility at room temperature but shatters at sub zero temperatures when impacted. DBTT is a very important consideration in materials selection when the material in question is subject to mechanical stresses.