Dany Centeno's scientific contributions

To achieve the desired microstructural properties, the ongoing development and innovation in new structural steels require novel thermal processing. This study aims to improve the mechanical properties of a commercial spring carbon–silicon steel by tailoring its microstructure through a process involving quenching and partitioning (Q&P) followed by bainitic transformation. A two‐stage Q&P process is proposed to generate a nanoscale dispersion of stable retained austenite and carbides within the tempered martensite and bainite microstructure. The resulting tensile properties demonstrate a yield strength of 1280 MPa, an ultimate tensile strength of 1875 MPa, and a total elongation of 8.03%. These values surpass those of conventional spring 9254 steel, highlighting the effectiveness of the thermal treatment design. Microstructure analysis reveals the presence of tempered martensite, bainite sheaves, nanoscale carbides, and aggregates of retained austenite. Moreover, the resulting body‐centered cubic matrix exhibits minimal lattice tetragonality of ≈1.0051, coupled with stable retained austenite featuring a carbon concentration of ≈3.42 ± 0.5 wt%, resulting in outstanding strength–ductility properties. These findings indicate that the proposed two‐stage Q&P process, followed by bainitic transformation, significantly enhances the mechanical properties of carbon–silicon steels, making it a promising candidate for high‐performance spring applications.

In the pursuit of lightweight, durable steel, we have successfully developed a multicomponent structure in AISI 9254 spring steel using a two-stage quenching and partitioning (Q&P) process. The primary objective of this process was to engineer an optimized microstructure consisting of nanobainite, martensite, and nano-carbides. Utilizing the insights gained from the results of advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT) performed on the as-received AISI 9254 spring steel, we refined the quenching and partitioning (Q&P) path, leading to the successful establishment of a bainitic transformation for superior mechanical properties. Our tensile tests revealed a high yield strength (≈ 1600 ± 25 MPa) and ultimate tensile strength (≈ 1850 ± 50 MPa), along with considerable elongation (≈ 11.15 ± 0.25%). We also identified that pre-formed martensite lath defects and high silicon content play crucial roles during the Q&P process, preventing carbide coalescence and increasing strain-hardening capacity. This study demonstrates the potential of a Q&P process to generate high-strength, ductile steel for automotive and aerospace applications.

This study delves into the formulation of an advanced microstructure in medium-carbon high-silicon spring steel through a series of engineered heat treatments. The microstructure, composed of lower bainite, proeutectoid ferrite, and pearlite, exhibits superior mechanical properties compared to traditional pearlitic steel. Specifically, the novel microstructure yields a strength of 870 MPa and an ultimate tensile strength of 1050 MPa, along with an enhanced total elongation of 9.75%, while the pearlitic steel achieved a yield strength of 745 MPa, an ultimate tensile strength of 845 MPa, and a total elongation of 9.0%. The steel’s heightened strength is attributed to dislocation and precipitation strengthening, with the proeutectoid ferrite at grain boundaries contributing to the excellent elongation. The study thus establishes a groundbreaking and readily implementable heat treatment process that significantly boosts the performance and longevity of heavy-haul rail system, owing to the synergistic contribution of lower bainite, proeutectoid ferrite, and pearlite in the microstructure.

o introduce desired microstructural properties, continued development and innovation in new structural steels require novel thermal processing. This study aims to enhance the mechanical properties of a commercial spring carbon-silicon steel by tailoring its microstructure through a quenching and partitioning process followed by bainitic transformation. A two-stage quenching and partitioning process is proposed to create a nanoscale dispersion of stable retained austenite and carbides within the tempered martensite and bainite microstructure. The resulting tensile properties confirmed a yield strength of 1280 MPa, an ultimate tensile strength of 1875 MPa, and a total elongation of 8.03%, which are superior to conventional spring 9254 steel, indicating an efficient thermal treatment design. The microstructure analysis showed the presence of tempered martensite, bainite sheaves, nanoscale carbides, and retained austenite aggregates. Additionally, the lattice tetragonality of the resulting BCC matrix was about 1.0076, coupled with stable retained austenite with a carbon concentration of ~3.42 ± 0.5 wt.%, resulting in excellent strength-ductility properties. These findings suggest that the proposed two-stage quenching and partitioning process followed by bainitic transformation can effectively enhance the mechanical properties of carbon-silicon steel, making it a promising candidate for high-performance spring applications.

Continued development and innovation in the new structural steels are required to introduce novel thermal processing to set desired microstructural properties. This study aimed to improve the mechanical properties of a commercial spring carbon-silicon steel by tailoring the microstructure using a quenching and partitioning process followed by bainitic transformation. A two-stage quenching and partitioning processing was suggested to set a nanoscale dispersion of stable retained austenite and carbide through the tempered martensite and bainite microstructure. Tensile properties confirmed a 2125 MPa yield strength, 2220 MPa ultimate tensile strength, and 11.35% total elongation, which are superior to conventional spring 9254 steel, indicating the efficient designed thermal treatment. Tempered martensite, bainite sheaves, nanoscale carbides, and retained austenite aggregates are characterized in the microstructure. Moreover, the lattice tetragonality of the resulting BCC matrix of about 1.0076 coupled with stable retained austenite with carbon concentration at ~3.42 ± 0.5 wt.%, resulting in an excellent strength-ductility behavior.