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Bainite
About: Bainite is a research topic. Over the lifetime, 9520 publications have been published within this topic receiving 145305 citations.
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TL;DR: In this article, the effects of the austenite grain size on the kinetics of martensite in Fe 31.9 Ni-0.02C were studied by methods of quantitative metallography.
70 citations
TL;DR: The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability and an analytical model for void evolution and coalescence was developed and applied.
Abstract: The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.
70 citations
TL;DR: In this paper, the development of martensite during sub-zero Celsius treatment of a 1 wt.% C, 1.6 Wt. Cr steel was investigated by in situ and ex- situ X-ray diffraction at the synchrotron facility HZB-BESSY II in order: (i) to quantitatively assess the fractions of retained austenite and Martensite; (ii) to measure the evolution of the lattice strain in retained Austenite; and (iii) to identify the different stages of tempering.
70 citations
31 Jan 2014-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructures and the mechanical properties of 30MnSiCrAlNiMo low-carbon steel were systematically optimized by a series of heat-treatment processes, and the heat treatment process of low-temperature bainite in low carbon steel was explored.
Abstract: The microstructures and the mechanical properties of 30MnSiCrAlNiMo low-carbon steel were systematically optimized by a series of heat-treatment processes, and the heat-treatment process of low-temperature bainite in low-carbon steel was explored. Results showed that the microstructure of low-temperature bainite in the low-carbon steel, containing a fine plate of carbide-free bainitic ferrite and a thin film of retained austenite, could be produced by continuous cooling transformation around the Ms temperature from Ms+10 °C to Ms−20 °C at a cooling rate of 0.5 °C min −1 . A new model was proposed to evaluate the comprehensive mechanical properties of steel, which found that the low-temperature bainite had the best comprehensive mechanical properties compared to any other microstructures for the low-carbon steel. The higher dislocation density and finer bainitic ferrite plate in the low-temperature bainite resulted in the higher yield strength and the higher toughness, but relatively lower ultimate tensile strength owing to the lower work-hardening rate caused by the higher initial dislocation density. There were some very fine particles in the bainitic ferrite of the steel after isothermal treatment at higher temperature. The ultimate tensile strength and the low-temperature impact toughness of the steel decreased with the volume fraction of the retained austenite increasing, while the elongation initially increased with an increase in the volume fraction of the retained austenite (
69 citations
TL;DR: In this paper, a new type of high strength, high toughness, martensitic steel, based on a newly proposed Quench and Partitioning (Q&P) process, is presented.
Abstract: A new type of high strength, high toughness, martensitic steel, based on a newly proposed Quench and Partitioning (Q&P) process, is presented. This high strength martensitic grade is produced by the controlled low temperature partitioning of carbon from as-quenched martensite laths to retained inter-lath austenite under conditions where both low temperature transition carbide formation and cementite precipitation are suppressed. The contribution focuses on both the current understanding of the fundamental processes involved and includes a discussion of the technical feasibility of large-scale industrial production of these steels as sheet products. The Q&P process, which is carried out on steels with a lean composition, should be implemented easily on some current industrial continuous annealing and galvanizing lines. In addition, martensitic Q&P sheet steel is characterized by very favourable combinations of strength, ductility and toughness, which are particularly relevant for high strength anti-intrusion automotive parts.
69 citations