FE-SEM Study of Fine Nb Precipitates in Carbon Extraction Replicas

2005 ◽  
Vol 500-501 ◽  
pp. 663-668 ◽  
Author(s):  
Rocco Varano ◽  
A.M. Elwazri ◽  
Fulvio Siciliano ◽  
D.Q. Bai ◽  
Raynald Gauvin ◽  
...  
Keyword(s):  
High Strength ◽  
Volume Effect ◽  
Carbon Steels ◽  
Low Carbon ◽  
Thin Foils ◽  
Transmission Electron ◽  
Sem Study ◽  
Before And After ◽  
Linepipe Steel

Precipitation strengthening is an important parameter controlling the mechanical properties of low carbon steels. These precipitates are very fine and are normally analyzed using either thin foils or carbon extraction replicas under a transmission electron microscopy (TEM). In this work, field emission gun scanning electron microscope (FE-SEM) was applied successfully in the characterization of niobium (Nb) carbo-nitride (C,N) precipitates using carbon extraction replicas. FE-SEM observation of high strength linepipe steel replicas before and after aging at 400°C for 1 hr confirmed the presence of Nb(C,N) precipitates in ferrite. The FE-SEM could analyze small particles (below 50 nm) embedded in the steel but the analysis had to be carried out at low voltages to maximize spatial resolution resulting in a poor signal. However, carbon extraction replicas in the FE-SEM can be analyzed using high voltages, since the interaction volume effect is no longer a problem.

A New Approach Using EBSD to Quantitatively Distinguish Complex Transformation Products Along the HAZ in X80 Linepipe Steel

2014 ◽  
Author(s):  
Jennifer M. Reichert ◽  
Matthias Militzer ◽  
Warren J. Poole ◽  
Laurie Collins
Keyword(s):  
Orientation Relationship ◽  
Transformation Temperature ◽  
Retained Austenite ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Transformation Products ◽  
Carbon Steels ◽  
Low Carbon ◽  
Structure Property ◽  
Linepipe Steel

State-of-the-art linepipe steels are microalloyed low-carbon steels that combine high strength and fracture toughness with good weldability. During welding of pipe sections the heat affected zone (HAZ) experiences rapid thermal cycles resulting in a graded microstructure that can be significantly different from that of the base metal. In particular a variety of bainitic microstructures can form in the HAZ. Depending on the type of bainite mechanical properties may be improved or may lead to poor fracture resistance and be detrimental to the overall HAZ performance. Optical microscopy is not sufficient to differentiate bainitic morphologies which vary with the transformation temperature. The investigated X80 linepipe steel also contains retained austenite at room temperature. Based on the retained austenite it is possible to characterize the orientation relationship (OR) between austenite and the transformation products. It is found that bainite shows an orientation relationship near Kurdjumov-Sachs with the prior austenite. Variant selection is related to the driving force for the bainite reaction and hence depends on the transformation temperature. In the current study Electron BackScatter Diffraction (EBSD) mapping is used to characterize transformation products based on their orientation relationship. This approach offers a quantitative way to determine volume fractions of different types of bainite in complex HAZ microstructures which is necessary to establish structure-property relationships of the HAZ.

Low Temperature Precipitation in Nb-Added Si- and Si-Free Bainitic Steels

2012 ◽  
Vol 706-709 ◽  
pp. 2384-2389 ◽  
Author(s):  
Ian Zuazo ◽  
Sebastian Cobo
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Atom Probe ◽  
Carbon Steels ◽  
Peak Hardness ◽  
Low Carbon ◽  
Steel Strips ◽  
Bainitic Steels ◽  
Transmission Electron ◽  
Precipitation Phenomena

Precipitation strengthening by fine Nb-rich particles represents an important element on the design of low carbon high strength steels. This is typically obtained on steel strips by thermal holding at temperatures above 600°C following the austenite to ferrite transformation. These conditions are beneficial to obtain a large precipitation of small Nb-rich precipitates. On the other hand, precipitation at lower temperatures, in a phase already hard, such as bainite, has been scarcely studied. In this work, the precipitation phenomena occurring during isothermal treatments following the austenite to bainite transformation at 450°C are investigated. For this purpose, two Nb-alloyed low carbon steels with and without silicon are studied and the evolution of the microstructure is determined by the use of transmission electron microscopy and followed by hardness measurements. The presence of a hardness peak is not detected until long isothermal times (150h). Preliminary atom probe tomography (APT) characterization provides insight on the possible presence of fine NbC precipitates at the peak hardness treatment. A comparison with a Nb-free alloy indicates a significant hardening effect of niobium on the bainitic structure.

An Electron Microscope Study of Interdiffusion and Compound Formation in Ta-Au Thin Films

1973 ◽  
Vol 31 ◽  
pp. 32-33 ◽  
Author(s):  
T. C. Tisone ◽  
S. Lau
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Thermally Grown Oxide ◽  
Ion Milling ◽  
Compound Formation ◽  
Technology Application ◽  
Transmission Electron ◽  
Before And After ◽  
Au Thin Films

In a study of the properties of a Ta-Au metallization system for thin film technology application, the interdiffusion between Ta(bcc)-Au, βTa-Au and Ta2M-Au films was studied. Considered here is a discussion of the use of the transmission electron microscope(TEM) in the identification of phases formed and characterization of the film microstructures before and after annealing.The films were deposited by sputtering onto silicon wafers with 5000 Å of thermally grown oxide. The film thicknesses were 2000 Å of Ta and 2000 Å of Au. Samples for TEM observation were prepared by ultrasonically cutting 3mm disks from the wafers. The disks were first chemically etched from the silicon side using a HNO3 :HF(19:5) solution followed by ion milling to perforation of the Au side.

MITTAL DI-FORM T700, HF80Y100T

Alloy Digest ◽  
2007 ◽  
Vol 56 (2) ◽  
Keyword(s):  
Automotive Industry ◽  
High Strength ◽  
Martensite Phase ◽  
Carbon Steels ◽  
Ferrite Phase ◽  
Dual Phase ◽  
Low Carbon ◽  
Advanced High Strength Steel ◽  
Dp Steels ◽  
Soft Ferrite

Abstract MITTAL DI-FORM T700 and HF80Y100T are low-carbon steels with a manganese and silicon composition. Dual-phase (DP) steels are one of the important advanced high-strength steel (AHSS) products developed for the automotive industry. Their microstructure typically consists of a soft ferrite phase with dispersed islands of a hard martensite phase. The martensite phase is substantially stronger than the ferrite phase. The DI-FORM grades exhibit low yield-to-tensile strengths, and the numeric designation in the name corresponds to the tensile strength. This datasheet provides information on microstructure and tensile properties as well as deformation and fatigue. It also includes information on forming. Filing Code: SA-561. Producer or source: Mittal Steel USA Flat Products.

scholarly journals Austenite Reverse Transformation in a Q&P Route of Mn and Ni Added Steels

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 862 ◽  
Author(s):  
Maribel Arribas ◽  
Teresa Gutiérrez ◽  
Eider Del Molino ◽  
Artem Arlazarov ◽  
Irene De Diego-Calderón ◽  
...  
Keyword(s):  
Microstructure Evolution ◽  
Microstructural Characterization ◽  
Carbon Steels ◽  
Reverse Transformation ◽  
Low Carbon ◽  
Effective Mechanism ◽  
Low Carbon Steels ◽  
Heat Treated ◽  
Final Microstructure

In this work, four low carbon steels with different contents of Mn and Ni were heat treated by quenching and partitioning (Q&P) cycles where high partitioning temperatures, in the range of 550 °C–650 °C, were applied. In order to elucidate the effect of applying these high partitioning temperatures with respect to more common Q&P cycles, the materials were also heat treated considering a partitioning temperature of 400 °C. The microstructure evolution during the Q&P cycles was studied by means of dilatometry tests. The microstructural characterization of the treated materials revealed that austenite retention strongly depended on the alloy content and partitioning conditions. It was shown that the occurrence of austenite reverse transformation (ART) in the partitioning stage in some of the alloys and conditions was a very effective mechanism to increase the austenite content in the final microstructure. However, the enhancement of tensile properties achieved by the application of high partitioning temperature cycles was not significant.

A Review of Electrically-Assisted Manufacturing With Emphasis on Modeling and Understanding of the Electroplastic Effect

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Brandt J. Ruszkiewicz ◽  
Tyler Grimm ◽  
Ihab Ragai ◽  
Laine Mears ◽  
John T. Roth
Keyword(s):  
Fuel Economy ◽  
Elastic Recovery ◽  
Fuel Efficiency ◽  
High Strength ◽  
Carbon Steels ◽  
Metallic Materials ◽  
Low Carbon ◽  
Electroplastic Effect ◽  
Electrically Assisted ◽  
Electrically Assisted Manufacturing

Increasingly strict fuel efficiency standards have driven the aerospace and automotive industries to improve the fuel economy of their fleets. A key method for feasibly improving the fuel economy is by decreasing the weight, which requires the introduction of materials with high strength to weight ratios into airplane and vehicle designs. Many of these materials are not as formable or machinable as conventional low carbon steels, making production difficult when using traditional forming and machining strategies and capital. Electrical augmentation offers a potential solution to this dilemma through enhancing process capabilities and allowing for continued use of existing equipment. The use of electricity to aid in deformation of metallic materials is termed as electrically assisted manufacturing (EAM). The direct effect of electricity on the deformation of metallic materials is termed as electroplastic effect. This paper presents a summary of the current state-of-the-art in using electric current to augment existing manufacturing processes for processing of higher-strength materials. Advantages of this process include flow stress and forming force reduction, increased formability, decreased elastic recovery, fracture mode transformation from brittle to ductile, decreased overall process energy, and decreased cutting forces in machining. There is currently a lack of agreement as to the underlying mechanisms of the electroplastic effect. Therefore, this paper presents the four main existing theories and the experimental understanding of these theories, along with modeling approaches for understanding and predicting the electroplastic effect.

Development of Low Carbon Microalloyed Bainitic Steels for Structural Plate Applications

2005 ◽  
Vol 500-501 ◽  
pp. 573-580 ◽  
Author(s):  
D. Ormston ◽  
Volker Schwinn ◽  
Klaus Hulka
Keyword(s):  
High Strength ◽  
Carbon Steels ◽  
Chemical Compositions ◽  
Low Carbon ◽  
Controlled Processes ◽  
Bainitic Steels ◽  
Steel Grades ◽  
Carbon Microalloyed ◽  
Hot Rolled ◽  
Plate Steels

Steels with bainitic microstructures show the capacity to fulfil the requirements of high strength and low temperature toughness necessary for plate steels in specialised industrial constructions. The introduction of steels with higher strength allows for weight reductions of steel constructions. This paper investigates the development of hot rolled structural plate steels through laboratory hot rolling simulations of thermo-mechanically controlled processes (TMCP). Specific alloying and microalloying along with an optimised TMCP process has allowed high tensile properties to be achieved in combination with high levels of toughness. Tensile strengths of up to 900 MPa have been achieved with Charpy V-notch toughness greater than 200J at –40°C. Elements such as molybdenum, niobium and boron have been added to low carbon steels to promote the formation of fully bainitic microstructures with much lightened chemical compositions. The presented concepts allow the production of steel grades above S500 up to S690.

Elaboration and characterization of novel polyamide-12-layered titanoniobates nanocomposites

2009 ◽  
Vol 24 (11) ◽  
pp. 3358-3371 ◽  
Author(s):  
Sophie Chausson ◽  
Richard Retoux ◽  
Jean-Michel Rueff ◽  
Loïc LE Pluart ◽  
Pierre-Jean Madec ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Thermomechanical Properties ◽  
Polyamide 12 ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Before And After ◽  
Basic Reaction

This article describes the synthesis and the characterization of a polyamide-12 filled with a nanostructured organic/inorganic titanoniobate hybrid material. The pristine oxide KTiNbO5 has been successfully organomodified by N-alkyl amines via an acido-basic reaction after a cationic exchange step as shown by x-ray diffraction. Transmission electron microscope study and scanning transmission electron microscope observations have been used to describe the change of morphology of the nanofillers before and after processing; the micronic aggregates were changed into single sheets and dispersed in the polymer. Thermomechanical properties of the composites have been determined, and their analyses with structure-properties models are consistent with the exfoliation of the organomodified titanoniobates.

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