Effect of ferrite-martensite interface morphology on bake hardening response of DP590 steel

Interstitial-Free Bake Hardening Realized by Epsilon Martensite Reverse Transformation

“…In a mechanically metastable HEA, the strain-induced FCC-austenite to HCP-martensite transformation is stimulated upon pre-straining (Figs. ductility synergy between a conventional bake-hardenable Fe-based alloy [16] and the present HEA undergoes bake-reversion hardening. necessary dislocation (GND) density versus local strain level within the FCC-austenite (an FCC lattice constant of 3.61 Å measured from synchrotron X-ray diffraction was adopted for the GND density computation).…”

“…Such a low transformation temperature range raises the possibility of feasible thermal processing opportunities similar to bake hardening (BH) treatment, which has not yet been explored; and (2) classical BH treatment in interstitial strengthened Fe-or Al-based alloys involves thermally-assisted segregation of interstitials to dislocation sites, creating a strengthening effect due to the enhanced solute pinning. [16,17] . However, it often inevitably results in cumulative ductility compensation because of the deficiency in dislocation multiplication, leading to the deterioration in strain hardening capability.…”

“…Fig. 1 | Bake-reversion hardening in a metastable Fe 45 Mn 35 Co 10 Cr 10 HEA: (a) EBSD phase map of undeformed microstructure corresponded with EDS elemental mapping; (b) engineering stress-strain curves of as-homogenized and bake-reversion treated HEA with strain hardening rate plot inserted; (c) comparison of strength-cumulative ductility synergy between a conventional bake-hardenable Fe-based alloy [16] and the present HEA undergoes bake-reversion hardening.…”

“…Considering the low annealing temperature and similar to the bake hardening treatment, Fig. 1 (c) presents a comparison of the variation in tensile properties with a bake hardenable Fe-based alloy [16] (pre-strained and annealed at 170 o C for 20 min) that shows a similar UTS value to the present HEA at its reference state. It is recognized that the interstitial-assisted BH mechanism within the Fe-based alloy enables increasing UTS at various pre-strained levels, whereas the cumulative fracture elongation witnesses a monotonic decreasing trend down to 24 % (inset of Fig.…”

Processing, microstructure adjustments, and mechanical properties of dual phase steels: A review

“…In general, three stages of strengthening effect during the bake hardening process in AHSS include: (I) Cottrell atmosphere formation in the vicinity of mobile dislocations in ferrite, (II) precipitation of low temperature carbides in ferrite, and (III) formation of precipitate clusters and particles in martensite/bainite interface [213,222]. It has been reported that bake hardening could increase the yield strength of DP and TRIP steels up to 100 MPa after 2-10% pre-straining [213,217,218,[222][223][224]. Thus, mechanical properties of DP steels can be further enhanced via the bake hardening process.…”