Engineering Hierarchical Microstructures via Advanced Thermo-Mechanical Processing of a Modern HSLA Steel

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

“…This article is protected by copyright. All rights reserved contrast to our first study [34] . Overall, the recrystallization mechanism present in this study is CDRX which has not yet reached its steady state.…”

“…Additional discontinuous dynamic recrystallization (DDRX) can be seen due to the formation of newly grains confined my HAGBs along original HAGBs (necklace structures), around in-grain shear bands/microbands and in areas of local C segregation [35][36][37][38] . The newly Similar to previous studies of some of the current authors [19,34] , 2 types of precipitates were found: Larger FeMNC-rich precipitates along grains boundaries and some smaller (<50 nm) TiNbC-rich precipitates. Furthermore, the average precipitate size (including small and large precipitates) after 60 min direct aging is similar for the present study with an average of 84 nm (minimum 6 nm and maximum 474 nm) as compared to the precipitates in the macroscopic shearband of 93 nm (minimum 3 nm and maximum 430 nm) [34] and an optimized aTMP of 113 nm (minimum 9 nm and maximum 630 nm) [19] .…”

“…The microstructure obtained after rolling (see Figure 1) is different to the microstructure obtained after thermo-mechanical processing in a Gleeble in terms of grain sizes and strain localization [19] . The grain size achieved after warm-rolling without direct aging is slightly larger with 0.77 µm as compared to grain sizes of 0.37 µm within a macroscopic shearband during plane strain compression testing [34] and to 0.5 µm by following an optimized aTMP route [19] . This suggests that the applied strain during rolling is not sufficient to provide grain refinement across the entire cross section as achieved after plane strain compression in the Gleeble.…”

“…The aim of the current paper is to up-scale processing our previous aTMP processing route using the same HSLA steels as in our previous studies [19,34] in a Hille 100 rolling mill. This enables more thorough mechanical testing in order to verify the success of the process design regarding strength, ductility and target microstructures.…”

“…This was carried out in a muffle furnace at 950°C for 40 min followed by water quenching. The resulting microstructure was a mixture of martensite and bainite [34] . Tapering was necessary to guarantee a smooth feeding of the samples into the rolls.…”