scholarly journals Bainite Transformation-Kinetics-Microstructure Characterization of Austempered 4140 Steel

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 236
Author(s):  
Jian G. Zhu ◽  
Xichen Sun ◽  
Gary C. Barber ◽  
Xue Han ◽  
Hao Qin
Keyword(s):  
Linear Trend ◽  
Bainitic Ferrite ◽  
Lower Bainite ◽  
Structure Evolution ◽  
Bainite Transformation ◽  
Solid Diffusion ◽  
Wide Range ◽  
Upper Bainite ◽  
Kinetics Of

Bainite transformation is a kinetic process that involves complex solid diffusion and phase structure evolution. This research systematically studies the bainite transformation of austempered 4140 steel in a wide range of isothermal temperatures, in which four bainite phases structures were generated: upper bainite; mixed upper bainite and lower bainite; lower bainite and mixed lower bainite and martensite. The kinetics of bainite transformation has been described with a linear trend using an Avrami n-value. It was found that the bainitic ferrite sheaves grow with widthwise preference. The sheaves are stable when half-grown and are variable in length, due to austenite size limit or soft/hard impingement, or autocatalytic nucleation, or these conditions combined. The full-grown upper/lower bainite sheaves were found to be 1.9 μm/1.2 μm in width under the conditions of this study. Each individual bainite sheave is lath-like instead of wedge-like. The upper bainite sheaves mostly appear as broad-short-coarse lath, while the lower bainite sheaves appear as narrow-long-fine lath. The overall bainite transformation activation energy ranges from 50–167 kJ/mol.

Slow Bainite: an Opportunity to Determine the Carbon Content of the Bainitic Ferrite during Growth

2011 ◽  
Vol 172-174 ◽  
pp. 111-116 ◽  
Author(s):  
Francisca García Caballero ◽  
Michael K. Miller ◽  
Carlos García-Mateo
Keyword(s):  
Solid Solution ◽  
Carbon Content ◽  
Atom Probe Tomography ◽  
Early Stage ◽  
Bainitic Ferrite ◽  
Atom Probe ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Parent Austenite ◽  
Kinetics Of

The amount of carbon in solid solution in bainitic ferrite at the early stage of transformation has been directly determined by atom probe tomography at 200 °C, taking advantage of the extremely slow transformation kinetics of a novel nanocrystalline steel. Results demonstrated that the original bainitic ferrite retains much of the carbon content of the parent austenite providing strong evidence that bainite transformation is essentially displacive in nature.

Accelerated Nano Super Bainite in Ductile Iron

MRS Advances ◽  
2018 ◽  
Vol 3 (45-46) ◽  
pp. 2789-2794
Author(s):  
Eric Jiahan Zhao ◽  
Cheng Liu ◽  
Derek O. Northwood
Keyword(s):  
Ductile Iron ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Isothermal Treatment ◽  
Strengthening Effect ◽  
Matrix Microstructure ◽  
Upper Bainite ◽  
Multi Phase ◽  
Step Heat Treatment ◽  
Kinetics Of

ABSTRACTA commercial unalloyed ductile iron has been developed to produce a multiphase matrix microstructure consisting of lenticular prior martensite, feathery upper bainite and a nano-scaled super bainite of lath bainitic ferrite and carbon-enriched film retained austenite. Multi-step heat treatment composed of austenizing, rapidly quenching and isothermally holding at low temperature have been developed. A tensile strength of more than 1.6 GPa, a hardness higher than HRC 54, and an elongation in excess of 5%, are achieved. This is attributed to a synergistic multi-phase strengthening effect. The developed nano super bainite exhibits a good balance between strength and toughness. The presence of martensite formed during the quenching prior to the isothermal treatment, accelerates the kinetics of subsequent nano super bainitic transformation by bainitic laths nucleating quickly at the martensite-austenite interfaces.

scholarly journals Assay of phospholipases A2and their inhibitors by kinetic analysis in the scooting mode

1992 ◽  
Vol 1 (2) ◽  
pp. 85-100 ◽  
Author(s):  
Mahendra Kumar Jain ◽  
Bao-Zhu Yu ◽  
Michael H. Gelb ◽  
Otto G. Berg
Keyword(s):  
Platelet Activating Factor ◽  
Interface Quality ◽  
Cellular Processes ◽  
Catalytic Function ◽  
Membrane Surfaces ◽  
Wide Range ◽  
Interfacial Catalysis ◽  
Inflammatory Processes ◽  
Kinetics Of

Several cellular processes are regulated by interfacial catalysis on biomembrane surfaces. Phospholipases A2(PLA2) are interesting not only as prototypes for interfacial catalysis, but also because they mobilize precursors for the biosynthesis of eicosanoids and platelet activating factor, and these agents ultimately control a wide range of secretory and inflammatory processes. Since PLA2carry out their catalytic function at membrane surfaces, the kinetics of these enzymes depends on what the enzyme ‘sees’ at the interface, and thus the observed rate is profoundly influenced by the organization and dynamics of the lipidwater interface (‘quality of the interface’). In this review we elaborate the advantages of monitoring interfacial catalysis in the scooting mode, that is, under the conditions where the enzyme remains bound to vesicles for several thousand catalytic turnover cycles. Such a highly processive catalytic turnover in the scooting mode is useful for a rigorous and quantitative characterization of the kinetics of interfacial catalysis. This analysis is now extended to provide insights into designing strategy for PLA2assays and screens for their inhibitors.

scholarly journals Study on Kinetics of Transformation in Medium Carbon Steel Bainite at Different Isothermal Temperatures

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2721
Author(s):  
Wei Pei ◽  
Wei Liu ◽  
Yue Zhang ◽  
Rongjian Qie ◽  
Aimin Zhao
Keyword(s):  
Bainitic Ferrite ◽  
Isothermal Transformation ◽  
Medium Carbon Steel ◽  
Transformation Kinetic ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Medium Carbon ◽  
Microstructure And Properties ◽  
Treatment Processes ◽  
Kinetics Of

Ultra-fine carbide-free bainitic (UCFB) steel, also known as nano-bainite (NB) steel, is composed of bainitic ferrite laths with nanoscale thickness and carbon-rich film-like retained austenite located between laths. The bainite transformation kinetic model can accurately describe the bainite transformation kinetics in conventional austempering (CA) processes based on the shear mechanism combined with the dilatometer test. UCFB steels with medium and high carbon composition are designed in this work to systematically study the transformation kinetics of bainite, and the evolution of its microstructure and properties, and reveal the influence of heat treatment processes on the microstructure and properties the UCFB steels. The results show that the activation energy for BF nucleation decreases during the CA process and isothermal transformation temperature decreases. The bainite transformation is first nucleated at the grain boundaries, and then nucleated at the newly formed bainitic ferrite/austenite interface.

scholarly journals Network Hamiltonian models reveal pathways to amyloid fibril formation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yue Yu ◽  
Gianmarc Grazioli ◽  
Megha H. Unhelkar ◽  
Rachel W. Martin ◽  
Carter T. Butts
Keyword(s):  
Amyloid Fibril ◽  
Prion Diseases ◽  
Data Bank ◽  
Fibril Formation ◽  
Toxic Species ◽  
Hamiltonian Models ◽  
Amyloid Fibril Formation ◽  
Wide Range ◽  
Kinetics Of

Abstract Amyloid fibril formation is central to the etiology of a wide range of serious human diseases, such as Alzheimer’s disease and prion diseases. Despite an ever growing collection of amyloid fibril structures found in the Protein Data Bank (PDB) and numerous clinical trials, therapeutic strategies remain elusive. One contributing factor to the lack of progress on this challenging problem is incomplete understanding of the mechanisms by which these locally ordered protein aggregates self-assemble in solution. Many current models of amyloid deposition diseases posit that the most toxic species are oligomers that form either along the pathway to forming fibrils or in competition with their formation, making it even more critical to understand the kinetics of fibrillization. A recently introduced topological model for aggregation based on network Hamiltonians is capable of recapitulating the entire process of amyloid fibril formation, beginning with thousands of free monomers and ending with kinetically accessible and thermodynamically stable amyloid fibril structures. The model can be parameterized to match the five topological classes encompassing all amyloid fibril structures so far discovered in the PDB. This paper introduces a set of network statistical and topological metrics for quantitative analysis and characterization of the fibrillization mechanisms predicted by the network Hamiltonian model. The results not only provide insight into different mechanisms leading to similar fibril structures, but also offer targets for future experimental exploration into the mechanisms by which fibrils form.

scholarly journals Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

2017 ◽  
Vol 13 ◽  
pp. 1145-1167 ◽  
Author(s):  
Serge Pérez ◽  
Daniele de Sanctis
Keyword(s):  
Synchrotron Radiation ◽  
Structural Characterization ◽  
Crystalline State ◽  
Structural Diversity ◽  
Interacting Proteins ◽  
X Ray ◽  
Wide Range ◽  
Kinetics Of

Synchrotron radiation is the most versatile way to explore biological materials in different states: monocrystalline, polycrystalline, solution, colloids and multiscale architectures. Steady improvements in instrumentation have made synchrotrons the most flexible intense X-ray source. The wide range of applications of synchrotron radiation is commensurate with the structural diversity and complexity of the molecules and macromolecules that form the collection of substrates investigated by glycoscience. The present review illustrates how synchrotron-based experiments have contributed to our understanding in the field of structural glycobiology. Structural characterization of protein–carbohydrate interactions of the families of most glycan-interacting proteins (including glycosyl transferases and hydrolases, lectins, antibodies and GAG-binding proteins) are presented. Examples concerned with glycolipids and colloids are also covered as well as some dealing with the structures and multiscale architectures of polysaccharides. Insights into the kinetics of catalytic events observed in the crystalline state are also presented as well as some aspects of structure determination of protein in solution.

scholarly journals Continuous Cooling Transformation (CCT) Diagrams Of Carbidic Nodular Cast Iron

2015 ◽  
Vol 60 (2) ◽  
pp. 705-710 ◽  
Author(s):  
G. Gumienny ◽  
T. Giętka
Keyword(s):  
Cast Iron ◽  
Chemical Composition ◽  
Nodular Cast Iron ◽  
Lower Bainite ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Upper Bainite ◽  
Transformation Diagrams ◽  
Cct Diagrams ◽  
Kinetics Of

Abstract This work presents continuous cooling transformation diagrams for different kinds of carbidic nodular cast iron. We investigated the cast iron, chemical composition of which in nodular cast iron allows the obtainment of a metal matrix which consists of: pearlite, upper bainite and its mixture with lower bainite, ausferrite and martensite when the casts were cooled in the mold. The influence of the rate of cooling on the obtained microstructure and hardness of the casts was shown. The work describes the influence of the alloy additives on the curves of austenite decomposition in the carbidic nodular cast iron. Diagrams were plotted which enable an understanding of the kinetics of the transformations of austenite in carbidic nodular cast iron. The diagrams also indicate the possibility of obtaining pearlite, bainite, martensite and ausferrite with the established chemical composition and the wall thickness of the cast.

Influence of Silicon on Bainite Transformation in Ductile Iron; Relation to Mechanical Properties

1984 ◽  
Vol 34 ◽  
Author(s):  
H. Nieswaag ◽  
J. W. Nijhof
Keyword(s):  
Mechanical Properties ◽  
Silicon Content ◽  
Retained Austenite ◽  
Room Temperature ◽  
Lower Bainite ◽  
Isothermal Transformation ◽  
Ductile Cast Iron ◽  
Bainite Transformation ◽  
The Matrix ◽  
Upper Bainite

ABSTRACTUsing a dilatometer the isothermal transformation of austenite to bainite has been studied in ductile cast iron with 0.05 % Mn and a silicon content varying from 2.4 to 3.8 %. The alloys were austenitized to a carbon content in the matrix of 0.65 %. It appears that silicon retards the formation of carbides in the upper bainite region (400 °C), resulting in an amount of retained austenite up to 40 % present in the final structure at room temperature. Silicon improves the strength; in the lower bainite region the yield strength in particular. An elongation up to 10 % or more is obtained after austempering at 400 0C independent of the silicon content.

scholarly journals Austenite-Bainite Transformation Kinetics in Austempered AISI 5160 Steel

2018 ◽  
Vol 14 (12) ◽  
pp. 1
Author(s):  
Xue Han ◽  
Gary Barber ◽  
Zhenpu Zhang ◽  
Bingxu Wang ◽  
Jian Zhu ◽  
...  
Keyword(s):  
Optical Microscopy ◽  
Lower Bainite ◽  
Experimental Results ◽  
Micro Hardness ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Steel Bar ◽  
Upper Bainite ◽  
Multi Phase

This research investigates the process of the formation of bainite in austempered 5160 steel. Steel bar samples were austenitized at 1128 K for 20 minutes followed by holding at various times from 10 seconds to 2 hours and isothermal temperatures from 561K to 728K to obtain a multi-phase matrix. Micro-hardness analysis and metallurgical optical microscopy were used to analyze the experimental results. Hardness results indicated that at the 561K, 589K, and 566K isothermal temperatures for 5160 steel, lower bainite transformation occurred. However, from 644K to 728K, upper bainite transformation was found from the steel. The formation of the bainitic phase in SAE 5160 steel was characterized using thermodynamic and kinetic theories.

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