Mechanical Properties and Tensile Fracture Mechanisms of Fe–Mn–(Al, Si) TRIP/TWIP Steels with Different Ferrite Volume Fractions

Abstract

The mechanical properties, damage, and fracture behaviors of Fe-Mn-(Al, Si) steels containing different Mn content and volume fraction of ferrite have been investigated through tensile testing. It is found that the volume fraction of ferrite has significant influences on the mechanical properties and damage accumulation. With increasing the Mn content, both the yield strength and ultimate tensile strength are decreased, while the uniform elongation is continuously increased, showing a typical trade-off relation between strength and elongation. The difference in the work-hardening behavior can be attributed to the increase in the stacking fault energy (SFE) caused by the addition of Mn. The failure mechanisms of the steels are found to be mainly influenced by deformation localization due to microstructural inhomogeneity. On the one hand, the Fe-Mn-(Al, Si) steel with a much more uniform distribution of austenite shows a slower rate of damage growth and a continuous void nucleation during the deformation process, resulting in a higher void density prior to the final fracture. On the other hand, the Fe-Mn-(Al, Si) steel with more ferrite exhibits accelerated void growth and catastrophic coalescence.

High temperature rise dominated cracking mechanisms in ultra-ductile and tough titanium alloy

“…In materials with almost inexistent work hardening like nanocrystalline materials or bulk metallic glasses, shear banding is often activated very soon after the onset of plasticity, resulting in a catastrophic failure 12,13 . On the other hand, damage accumulation usually dominates failure (or occurs soon after the onset of necking) in the most recent advanced metallic alloys (e.g., high strength Ti alloys like β-CEZ, TRIP and TWIP steels, Q&P steels, …), where numerous interfaces are integrated within the microstructure to increase strength, but often at the expense of ductility [14][15][16][17][18] . The introduction of a large density of interfaces is in principle detrimental as it provides more opportunities for damage nucleation before plastic localization, resulting from the strain incompatibility at these interfaces.…”