Microstructure development of steel during severe plastic deformation

Abstract

The microstructure development during plastic deformation was reviewed for iron and steel which were subjected to cold rolling or mechanical milling (MM) treatment, and the change in strengthening mechanism caused by the severe plastic deformation (SPD) was also discussed in terms of ultra grain refinement behavior. The microstructure of cold-rolled iron is characterized by a typical dislocation cell structure, where the strength can be explained by dislocation strengthening. It was confirmed that the increase in dislocation density by cold working is limited at 10 , which means the maximum hardness obtained by dislocation strengthening is HV3.7 GPa. However, the iron is abnormally work-hardened over the maximum dislocation strengthening by SPD of MM because of the ultra grain refinement caused by the SPD. In addition, impurity of carbon plays an important role in such grain refinement: the carbon addition leads to the formation of nano-crystallized structure in iron.

Gigacycle fatigue behaviour of austenitic stainless steels used for mercury target vessels

“…On the other hand, it is known that the dislocation density is increased by cold work level, and the hardness is proportional to the square root of the dislocation density [37]. Although the dislocation density of the specimen is not measured directly in this study, the cyclic hardening of SA seems to be caused by the accumulation of dislocation by cyclic loading.…”

Ultrafine Grain Formation in Ferritic Stainless Steel during Severe Plastic Deformation

“…[5,6] Several special techniques were developed to achieve very large strains. Among those are mechanical milling, [7,8] torsion under high pressure, [9] equal channel angular extrusion, [10,11] accumulative roll bonding, [12] etc., which are applicable to a wide variety of structural metals and alloys. These processing methods, however, require costly equipment and have to use some additional consolidation working to make a bulky product.…”

Regularities of Deformation Microstructures in Ferritic Stainless Steels during Large Strain Cold Working

“…3,5,[15][16][17][18][19] The novel methods of severe deformation allow treating almost all metallic materials. The grain size in structural materials can be reduced down to tens nanometers after processing by severe deformation.…”