Twin-Induced Plasticity of an ECAP-Processed TWIP Steel

Abstract

The TWIP steels show high strain hardening rates with high ductility which results in high ultimate tensile strength. This makes their processing by equal channel angular pressing very difficult. Up to now, this has only been achieved at warm temperatures (above 200°C). In this paper, a FeMnCAl TWIP steel has been processed at room temperature and the resulted microstructure and mechanical properties were investigated. For comparison, the material has also been processed at 300°C. The TWIP steel processed at room temperature shows a large increase in yield strength (from 590 in the annealed condition to 1295 MPa) and the ultimate tensile strength (1440 MPa) as a consequence of a sharp decrease in grain size and the presence within the grains of a high density of mechanical twins and subgrains. This dense microstructure results also in a loss of strain hardening and a reduction in ductility. The material processed at 300°C is more able to accommodate deformation and has lower reduction in grain size although there is a significant presence of mechanical twins and subgrains produced by dislocation activity. This material reaches an ultimate tensile strength of 1400 MPa with better ductility than the room temperature material.

Modeling the Effect of Primary and Secondary Twinning on Texture Evolution during Severe Plastic Deformation of a Twinning-Induced Plasticity Steel

“…This induces the formation of new twins, i.e., secondary twins are formed inside primary twins. This behavior has been observed frequently in TWIP steels subjected to large strains and/or complex deformation conditions, e.g., during tension [ 53 ], cold rolling [ 13 , 54 ], asymmetric rolling [ 55 ], and ECAP [ 25 , 56 ]. The present modeling approach also includes secondary twining, treating it in the same manner as primary twining.…”

Severe Plastic Deformation Steel Aisi 316

“…Amplitude of plastic deformation was the key factor for control of fatigue process. The following equation was used for the dependence ap -Nf [1] :…”

Low-Cycle Fatigue of Steel Aisi 316 After Ecap

“…Cyclic stress-strain curves were also determined for complex assessment of response of steel after the ECAP to alternating plastic deformation in tractionpressure [11]:…”