Although sometimes dynamic strain aging is used interchangeably with the Portevin–Le Chatelier effect

Portevin–Le Chatelier effect

The Portevin–Le Chatelier effect describes a serrated stress-strain curve or jerky flow, which some materials exhibit as they undergo plastic deformation, specifically inhomogeneous deformation...

 (or serrated yielding), dynamic strain aging refers specifically to the microscopic mechanism that induces the Portevin–Le Chatelier effect. This strengthening mechanism

Strengthening mechanisms of materials

Methods have been devised to modify the yield strength, ductility, and toughness of both crystalline and amorphous materials. These strengthening mechanisms give engineers the ability to tailor the mechanical properties of materials to suit a variety of different applications. For example, the...

 is related to solid-solution strengthening

Solid solution strengthening

Solid solution strengthening is a type of alloying that can be used to improve the strength of a pure metal. The technique works by adding atoms of one element to the crystalline lattice of another element . The alloying element diffuses into the matrix, forming a solid solution...

 and has been observed in a variety of fcc and bcc

Cubic crystal system

In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....

 substitutional and interstitial alloys, metalloids like silicon, and ordered intermetallics within specific ranges of temperature and strain rate.

Description of Mechanism

In materials, the motion of dislocation

Dislocation

In materials science, a dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials...

s is a discontinuous process. When dislocation meets obstacles (like forest dislocations) they are temporary arrested for a certain time. During this time solutes (such as interstitial particles) diffuse around the dislocations further strengthening the obstacles held on the dislocations. Eventually these dislocations will overcome these obstacles with sufficient stress and will quickly move to the next obstacle where they are stopped and the process can repeat again. This process most well-known manifestations are Lüders bands and the Portevin–Le Chatelier effect. Though the mechanism is known to effect materials without these physical observations.Atkinson, JD and Yu, J.(1997) “The Role of Dynamic Strain-Aging in the Environment Assisted Cracking observed in Pressure Vessel Steels”. Fatigue Fracture Eng. Mater. Struct. Vol.20 No. 1:1-12

Material Property Effects

Although serrations in the stress-strain curve

Stress-strain curve

During tensile testing of a material sample, the stress–strain curve is a graphical representation of the relationship between stress, derived from measuring the load applied on the sample, and strain, derived from measuring the deformation of the sample, i.e. elongation, compression, or distortion...

 caused by the Portevin–Le Chatelier effect are the most visible effect of dynamic strain aging other effects may be present when this effect is not seen. Often when serrated flow is not seen, dynamic strain aging is marked by a lower strain rate sensitivity. That becomes negative in the Portevin–Le Chatelier regime. Dynamic strain aging also causes a plateau in the strength, a peak in flow stress a peak in work hardening

Work hardening

Work hardening, also known as strain hardening or cold working, is the strengthening of a metal by plastic deformation. This strengthening occurs because of dislocation movements within the crystal structure of the material. Any material with a reasonably high melting point such as metals and...

, a peak in the Hall–Petch constant

Grain boundary strengthening

Grain-boundary strengthening is a method of strengthening materials by changing their average crystallite size...

, and minimum variation of ductility

Ductility

In materials science, ductility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized...

 with temperature. Since dynamic strain aging is a hardening phenomenon it increases the strength of the material. Oddly, it will often effect the ultimate tensile strength of the material more than the yield strength of the material.

Material specific example of Dynamic Strain Aging

Dynamic strain aging has been shown to be linked to these specific material problems:

• Decrease the fracture resistance of AL-Li alloys
• Decrease low cycle fatigue
  Fatigue (material)
  'In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.Fatigue occurs...
  
  life of Austenitic stainless steels and super alloys under test condition which are the service conditions in liquid metal cooled fast breeder reactors which the material is used for.
• Reduce fracture toughness by 30-40% and shorten the air fatigue live of RPC steels and may worsen the cracking resistance of steels in aggressive environments. The susceptibility of RPC steels to environment assisted creating in high temperature water coincides with DSA behavior
• PLC specific problems like blue brittleness in steel, loss of ductility and bad surface finishes for formed Aluminum Magnesium alloys.