Interstitial atoms can also be present within the metal. In this case, the atom is much smaller than the matrix atoms and is located in the gaps. Most often, interstitial atoms can diffuse to the dislocation core due to more open structure and the local tensile stresses in this region of the crystal lattice. The presence of the interstitial can inhibit dislocation motion, leading to dislocation “locking”. This locking necessitates larger applied stresses to produce dislocation motion and further plastic deformation. In the classic example of carbon in iron, such a mechanism can result in discontinuous yielding. Deformation is not continuous, and a sharp upper yield point is typically observed followed by yielding at a constant stress. The serrations in the stress-versus-strain curve are most often attributed to the breakway of dislocations from the solute carbon atoms.

Interstitial atom 间隙原子

diffuse 扩散

dislocation core 位错中心

tensile stress 拉伸应力    

crystal lattice 晶格

plastic deformaiton 塑性变形  

mechanism 机制

discontinuous yielding 不连续屈服  

upper yield point 上屈服点

serration 锯齿  

stress-versus-strain 应力-应变

solute 溶质