Precipitation enhanced ultragrain refinement of Ti-Mo microalloyed ferritic steel during warm rolling

Control of Laves Precipitation in a FeCrAl-based Alloy Through Severe Thermomechanical Processing

“…The deformed grains with a <111>-γ fiber orientation are identified as preferential nucleation sites due to their higher stored energy [23,24]. It is reported that grains with large Taylor factors suffer high levels of slip activity during deformation and accumulate the largest dislocation densities and stored energy, although this is not homogeneous [25]. Due to higher Taylor factor, the stored energy in <111>-γ fiber is higher than that in other typical fibers [26].…”

“…The strain-induced precipitation has been widely researched and also applied for the microstructure control for many microalloyed steels or aluminum alloys [25,27]. Dutta et al describe the activation energy for heterogeneous nucleation as follows [28]:ΔG = ΔGchem + ΔGint + ΔGdisl = −43πR3ΔGv + 4πR2γ − 0.4μb2R where Δ G is the total free energy, Δ G chem is the chemical free energy, Δ G int is the interfacial energy, R is the particle radius, Δ G disl is the dislocation core energy over the precipitate radius, Δ G v is the change of volume free energy, γ is the surface energy of the precipitate, and μ and b are the shear modulus and Burgers vector, respectively.…”

An Initial Report on the Structure–Property Relationships of a High‐Strength Low‐Alloy Steel Subjected to Advanced Thermomechanical Processing in Ferrite

“…Mechanical properties of aTMP low alloyed steels vary, depending on the exact processing and steel chemistry, and have been reported to be in the range of 480-898 MPa for the ultimate tensile strength (UTS) with total elongation of 11.6 -27%, [4,8,9,20,21] . It has been shown that cold rolling and annealing of martensite [17,22,23] or tempforming of high-carbon steels via large strain caliber rolling [6] can lead to exceptional strengths of up to 1.5 GPa.…”

“…However, they applied twice as much strain as compared to our study. Cheng et al [20] achieved a yield to strength ratio of 0.95 and a elongation of 14.7% in a Fe-0.11C-0.21Si-1.48Mn-0.11Ti-0.31Mo-0.041Al-0.0028S-0.0054P steel after a strain of 55.6% at 850°C and a strain of 65% at 650°C followed by 30 min aging at 600°C.…”

“…However, they could obtain a UTS of 898 MPa, which is 250 MPa higher as compared to our study. Cheng et al [20] report that 'superdense' microbands are contributing to strengthening, besides precipitation enhanced grain refinement. They suggest that the formation of these microbands can be suppressed by stress fields around precipitates which promote the formation of HAGBs, especially in the γ-fiber [20] .…”