Influence of Annealing Temperature on Microstructure and Three-Stage Strain Hardening Behavior in Cold-Rolled Fe-Mn-Al-C Steel

Microstructural evolution and tensile deformation behavior of cold-rolled Fe-27Mn-12Al-0.9C steel were investigated as a function of annealing temperature in a range from 900 degrees C to 1050 degrees C. The austenitic duplex steels exhibited an excellent combination of ultimate tensile strength of about 1000 MPa and elongation of about 40%. The influence of annealing temperature on deformation behavior was analyzed using a Hollomon equation, and the cold-rolled steel presented a three-stage strain hardening behavior during plastic deformation at room temperature. The superior mechanical properties substantially came from stage II and stage III. The annealing temperature mainly affected the deformation behavior by controlling the steady plastic deformation capacity and strain hardening capacity in stage II. The dislocation substructure of austenite showed planar dislocation glide characteristics. The deformation characteristics formed at a relatively lower strain than those in hot-rolled steel due to the grain refinement and internal stress caused by the cold rolling process.