Topic
Microalloyed steel
About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.
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TL;DR: In this article, a series of two-stage hot compression tests were performed on Gleeble 1500 Nb-V microalloyed steel and a modified Avrami model was proposed.
21 citations
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TL;DR: In this paper, a computer model based on three-dimensional Frontal Cellular Automata (FCA) for the simulation of grain refinement during multiaxial compression was developed, where strong grain refinement obtained in microalloyed steel through subdivision of the initial coarse-grained structure into dislocation substructure and subsequently into stabile UFG structure was simulated and analyzed.
21 citations
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22 Jul 2019-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The relationship between microstructure and crack arrest characteristics of a microalloyed steel with a yield strength of 460 MPa was elucidated in this article, with particular focus on the effect of the micro-structure on the propagation of brittle cracks.
Abstract: The relationship between microstructure and crack arrest characteristics of a microalloyed steel with a yield strength of 460 MPa was elucidated in this study with particular focus on the effect of the microstructure on the propagation of brittle cracks. The study emphasized that the acicular ferrite (AF) content could be increased to 41% by lowering the final rolling temperature and final cooling temperature, which reduces the average effective grain size (EGS) to as small as ~4.1 μm and increases the high-angle grain boundaries (HAGB) proportion to as high as ~48.8%. The presence of AF in large numbers could reduce the ductile-to-brittle transition temperature to approximately −87 °C through refinement of the microstructure. The presence of HAGB between adjacent grains could significantly arrest cracks by changing the propagation direction of brittle cracks and was a decisive factor in determining the characteristics of brittle fracture. Moreover, the fracture roughness varied directly with the proportion of the HAGB and inversely with the average EGS. Martensite/austenite islands with low content (0.92%) and small size (~1.5 μm) reduced the stress concentration significantly at the crack tip. The excellent crack arrestability was attributed to AF, which minimized the expansion of cleavage facets by the split nail effect ahead of the growth direction, so that the cleavage facets were divided into two or more branches, considerably reducing the stress concentration and retarding brittle crack growth during crack propagation at low ambient temperature.
21 citations
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TL;DR: In this article, the authors presented and analyzed material models for crash test simulations at frontal and lateral impact, using hot deep galvanized extra-deep drawing quality steel sheet, hot-deep galvanized microalloyed steel sheet.
21 citations
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TL;DR: In this paper, a coarse-grained Nb microalloyed austenite has been deformed in torsion at a temperature of 1100 °C and the microstructural changes occurring during static recrystallization were characterized by metallographic evaluation.
Abstract: Static recrystallization mechanisms have been studied in a coarse-grained Nb microalloyed austenite. An austenite with a coarse grain size of 800 µm, typical of thin slab casting processes, has been deformed in torsion at a temperature of 1100 °C. After deformation, the specimens have been held for different times at this high temperature and then water quenched. The microstructural changes occurring during static recrystallization were characterized by metallographic evaluation. It has been observed that new recrystallized grains nucleate preferentially on parent austenite grain boundaries and tend to form in clusters. Once all the boundaries have been consumed, intragranular nucleation is actived at late stages of recrystallization. Clustered nucleation allows impingement to take place early during the recrystallization process, favoring grain-coarsening phenomena to occur behind the recrystallization front, which is denoted by the significant reduction in the number of grains per unit volume observed during early stages of recrystallization. Static recrystallization proceeds heterogeneously, as a result of a nonuniform distribution of stored energy in the deformed material. A continuous decrease of the average migration rate of the recrystallization front is observed, which can be ascribed to the reduction of the driving force for migration as recrystallization advances.
21 citations