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Schematic diagrams of interrupted uniaxial tensile plus quasi-situ EBSD samples. Dimensions in mm, TD: transverse direction, RD: rolling direction, the same below.
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As a representative of the third generation of advanced high strength steel, the quenching and partitioning steel has excellent potential in automobile manufacturing. The characterization and analysis of the mechanical properties and microstructure of the quenching and partitioning steel during deformation is an effective way to explore the microst...
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... V Tensile samples with a gauge length of 10 mm and a gauge width of 4 mm, as shown in Figure 2, were used for interrupted uniaxial tensile plus quasi-situ EBSD experiment [17] and quasi-tensile test. The samples were wire-cut from the heat-treated sheets, and the long axis was kept paralleling to the RD (rolling direction) of the sheet. ...
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The volume increase and shape change during austenite to martensite transformation in dual-phase (DP) steels are largely accommodated in the microstructure by the deformation of the surrounding ferrite matrix. Accurate estimation of transformation-induced deformation of ferrite via experiments and modeling is essential for predicting the subsequent...
Citations
... The subsequent isothermal treatment, known as "partitioning", occurs either at the quenching temperature (one-step Q&P) or at a higher temperature (two-step Q&P), which allows for carbon redistribution from the quenched martensite to untransformed austenite. The addition of elements, such as Al, Si, or P, prevents the formation of cementite Materials 2023, 16, 6102 2 of 12 during partitioning [10]. Consequently, the carbon-enriched austenite is stabilized at room temperature after the final cooling. ...
... Cold rolling with a reduction rate (ratio of the reduction in plate thickness to the initial thickness of the plate) of 60-70% is necessary [15], as the typical required thickness for Q&P steel in service is considerably thinner (0.7~1.2 mm) than that of conventional hot-rolled plates (2~3 mm). Meanwhile, in order to reduce the cold rolling force, the hot rolling-coiling temperature must be controlled to adjust the microstructure of the hot-rolled plate to a softer ferrite-pearlite structure [16]. To address the global focus on carbon reduction, especially in steel industry, the thin slab casting and rolling (TSCR) technology is being widely promoted due to its environmentally friendly and energy-saving characteristics [17]. ...
... Materials 2023, 16, 6102 ...
Quenching and partitioning (Q&P) steel has garnered attention as a promising third-generation automotive steel. While the conventional production (CP) method for Q&P steel involves a significant cumulative cold rolling reduction rate (CRRR) of 60–70%, the thin slab casting and rolling (TSCR) process has emerged as a potential alternative to reduce or eliminate the need for cold rolling, characterized with a streamline production chain, high-energy efficiency, mitigated CO2 emission and economical cost. However, the effect of the CRRR on the microstructure and properties of Q&P steel with an initial ferrite-pearlite microstructure has been overlooked, preventing the extensive application of TSCR in producing Q&P steel. In this work, investigations involving different degrees of CRRRs reveal a direct relationship between increased reduction and decreased yield strength and plasticity. Notably, changes in the microstructure were observed, including reduced size and proportion of martensite blocks, increased ferrite proportion and decreased retained austenite content. The decrease in yield strength was primarily attributed to the increased proportion of the softer ferrite phase, while the reduction in plasticity was primarily linked to the decrease in retained austenite content. This study provides valuable insights for optimizing the TSCR process of Q&P steel, facilitating its wider adoption in the automotive sector.
... It is should be noted that Ni 3 Mo is rod-shaped, where the length direction of the rod and matrix is in the <111> direction [2]. The close-packed surface and direction of δ-Ni 3 Mo and η-Ni 3 Nb phases are parallel to the matrix, with the existence of the coherent or semicoherent relation between δ-Ni 3 Mo/η-Ni 3 Nb and matrix, thus the strength is remarkably improved [1,2,[51][52][53][54]. packed surface and direction of δ-Ni3Mo and η-Ni3Nb phases are parallel to the matrix, with the existence of the coherent or semicoherent relation between δ-Ni3Mo/η-Ni3Nb and matrix, thus the strength is remarkably improved [1,2,[51][52][53][54]. ...
... The close-packed surface and direction of δ-Ni 3 Mo and η-Ni 3 Nb phases are parallel to the matrix, with the existence of the coherent or semicoherent relation between δ-Ni 3 Mo/η-Ni 3 Nb and matrix, thus the strength is remarkably improved [1,2,[51][52][53][54]. packed surface and direction of δ-Ni3Mo and η-Ni3Nb phases are parallel to the matrix, with the existence of the coherent or semicoherent relation between δ-Ni3Mo/η-Ni3Nb and matrix, thus the strength is remarkably improved [1,2,[51][52][53][54]. The phases of X6CrNiMoVNb11-2 steels after various heat treatments are shown in Table 4. Table 4. Phases of X6CrNiMoVNb11-2 martensitic steel after various heat treatments. ...
... Meanwhile, when the quenching temperature is too high, the austenite grains will be coarsened, resulting in coarser martensite [51]. Therefore, a quenching temperature should be selected within an appropriate range, neither too low nor too high, or the expected requirements will not be met [41,52]. Then, the effect of quenching cooling rate on the mechanical properties during quenching at 1040 • C and tempering at 650 • C is investigated through the analysis of the measured data. ...
X6CrNiMoVNb11-2 supermartensitic stainless steel, a special type of stainless steel, is commonly used in the production of gas turbine discs in liquid rocket engines and compressor disks in aero engines. By optimizing the parameters of the heat-treatment process, its mechanical properties are specially adjusted to meet the performance requirement in that particular practical application during the advanced composite casting-rolling forming process. The relationship between the microstructure and mechanical properties after quenching from 1040 °C and tempering at 300–670 °C was studied, where the yield strength, tensile strength, elongation and impact toughness under different cooling conditions are obtained by means of mechanical property tests. A certain amount of high-density nanophase precipitation is found in the martensite phase transformation through the heat treatment involved in the quenching and tempering processes, where M23C6 carbides are dispersed in lamellar martensite, with the close-packed Ni3Mo and Ni3Nb phases of high-density co-lattice nanocrystalline precipitation created during the tempering process. The ideal process parameters are to quench at 1040 °C in an oil-cooling medium and to temper at 650 °C by air-cooling; final hardness is averaged about 313 HV, with an elongation of 17.9%, the cross-area reduction ratio is 52%, and the impact toughness is about 65 J, respectively. Moreover, the tempered hardness equation, considering various tempering temperatures, is precisely fitted. This investigation helps us to better understand the strengthening mechanism and performance controlling scheme of martensite stainless steel during the cast-rolling forming process in future applications.
