Fracture toughness characteristics of thermo-mechanically rolled direct quenched and partitioned steels

Improvement of Mechanical Properties and Wear Resistance of Direct‐Quenched Wear‐Resistant Steel by Deformed Austenite

“…Gaurav Kumar used the TMCP + DQ process to achieve an excellent combination of tensile strength up to 1700 MPa and elongation of 20% for 0.2% C low‐alloy steel. [ 19 ] Muckelroy noted martensite block size as the main strengthening effect of the DQ process in a comparison of the DQ and reheating–quenching (RQ) processes. [ 20 ]…”

“…Gaurav Kumar used the TMCP þ DQ process to achieve an excellent combination of tensile strength up to 1700 MPa and elongation of 20% for 0.2% C low-alloy steel. [19] Herein, thermomechanically controlled processing (TMCP) and direct-quenching (DQ) process are investigated to improve the mechanical and wear properties of wear-resistant steel, compared to the reheating-quenching (RQ) process. Scanning electron microscope, electron backscatter diffraction, transmission electron microscope, and X-ray diffraction are employed to characterize the microstructures of the DQ and RQ specimens, and the mechanical and wear properties are investigated using the Vickers hardness, impact, tensile, and stirring wear tests for both processes.…”

Micromechanics-based understanding of the stability of film-like austenite in steels

“…In subsequent years, the principle of transformation toughening was effectively implemented to develop a series of steels known as transformation-induced plasticity (TRIP) steels [2,3]. These steels contain martensite and islands of metastable retained austenite, which undergoes strain-induced transformation to martensite near advancing cracks [4–23], improving the mechanical properties [9–22]. The austenite-to-martensite transformation involves volume expansion which, constrained by the surrounding martensitic matrix, induces compressive stresses and reduces the stress intensity factor at the crack tip, thereby increasing the ductility and fracture toughness [5–22].…”

“…These steels contain martensite and islands of metastable retained austenite, which undergoes strain-induced transformation to martensite near advancing cracks [4–23], improving the mechanical properties [9–22]. The austenite-to-martensite transformation involves volume expansion which, constrained by the surrounding martensitic matrix, induces compressive stresses and reduces the stress intensity factor at the crack tip, thereby increasing the ductility and fracture toughness [5–22]. Apart from the compressive stresses generated due to the volume expansion, the shear component of the martensitic transformation plays an important role in transformation toughening by delaying the shear instability and enhancing fracture toughness [23].…”

“…In a recent study, Kumar et al [9] demonstrated that a large part of the inter-martensite lath film-like retained austenite present in a 0.21% C thermo-mechanically rolled (TMR), direct quenched and partitioned (DQP) steel transformed to martensite in the region close to the crack during fracture toughness testing and showed higher fracture toughness than in the absence of the retained austenite. X-ray diffraction (XRD) measurements aided with Rietveld refinement were used to calculate the phase fractions of the retained austenite.…”