Tracing Microalloy Precipitation in Nb-Ti HSLA Steel During Austenite Conditioning

Microalloying of low carbon steel with niobium (Nb) and titanium (Ti) is standardly applied in high-strength low-alloy (HSLA) steels enabling austenite conditioning during thermo-mechanical controlled processing (TMCP), which results in pronounced grain refinement in the finished steel. The metallurgical effects of microalloying elements are related solute drag and precipitate particle pinning, both acting on the austenite grain boundary thereby delaying or suppressing recrystallization of the deformed grain. In that respect it is important to better understand the precipitation kinetics as well as the precipitation sequence in a typical Nb-Ti-microalloyed steel. Various characterization methods have been utilized in this study for tracing microalloy precipitation after simulating different austenite TMCP conditions in a Gleeble apparatus. Atom probe tomography (APT), scanning transmission electron microscopy in a focused ion beam equipped scanning electron microscope (STEM-on-FIB) and electrical resistivity measurements provide complementary information on the precipitation status and are correlated with each other. It will be demonstrated that accurate electrical resistivity measurements can monitor the general consumption of solute microalloys (Nb) during hot working which was complemented by APT measurements of the steel matrix. On the other hand, STEM revealed that a large part of Nb-containing particles during hot working are co-precipitated with titanium during cooling from the austenitizing temperature. Precipitates that form during cooling or isothermal holding can be distinguished from strain-induced precipitates by corroborating STEM measurements with APT results. APT specifically allows obtaining detailed information about the chemical composition of precipitates as well as the distribution of elements inside the particle. Electrical resistivity measurement, on the contrary, provides macroscopic information on the progress of precipitation and can be calibrated by APT. The current paper highlights the complementarity of these methods and shows first results within the framework of a larger study on strain-induced precipitation.

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Tracing Microalloy Precipitation in Nb-Ti HSLA Steel during Austenite Conditioning

Metals ◽

10.3390/met10020243 ◽

2020 ◽

Vol 10 (2) ◽

pp. 243 ◽

Cited By ~ 2

Author(s):

Johannes Webel ◽

Adrian Herges ◽

Dominik Britz ◽

Eric Detemple ◽

Volker Flaxa ◽

...

Keyword(s):

Electrical Resistivity ◽

Ion Beam ◽

Hsla Steel ◽

Isothermal Holding ◽

Elemental Distribution ◽

Steel Matrix ◽

Low Carbon ◽

Finished Steel ◽

Characterization Methods ◽

Resistivity Measurements

The microalloying with niobium (Nb) and titanium (Ti) is standardly applied in low carbon steel high-strength low-alloy (HSLA) steels and enables austenite conditioning during thermo-mechanical controlled processing (TMCP), which results in pronounced grain refinement in the finished steel. In that respect, it is important to better understand the precipitation kinetics as well as the precipitation sequence in a typical Nb-Ti-microalloyed steel. Various characterization methods were utilized in this study for tracing microalloy precipitation after simulating different austenite TMCP conditions in a Gleeble thermo-mechanical simulator. Atom probe tomography (APT), scanning transmission electron microscopy in a focused ion beam equipped scanning electron microscope (STEM-on-FIB), and electrical resistivity measurements provided complementary information on the precipitation status and were correlated with each other. It was demonstrated that accurate electrical resistivity measurements of the bulk steel could monitor the general consumption of solute microalloys (Nb) during hot working and were further complemented by APT measurements of the steel matrix. Precipitates that had formed during cooling or isothermal holding could be distinguished from strain-induced precipitates by corroborating STEM measurements with APT results, because APT specifically allowed obtaining detailed information about the chemical composition of precipitates as well as the elemental distribution. The current paper highlights the complementarity of these methods and shows first results within the framework of a larger study on strain-induced precipitation.

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Theoretical Study on Geometries of Electrodes in Laboratory Electrical Resistivity Measurement

Applied Sciences ◽

10.3390/app9194167 ◽

2019 ◽

Vol 9 (19) ◽

pp. 4167 ◽

Cited By ~ 3

Author(s):

Hong ◽

Chong ◽

Cho

Keyword(s):

Electrical Resistivity ◽

Multiple Scales ◽

Design Method ◽

Resistivity Measurement ◽

Experimental Tests ◽

Field Resistance ◽

Electrode Spacing ◽

Electrical Resistivity Measurement ◽

Resistivity Measurements ◽

Complementary Study

Electrical resistivity tests have been widely conducted in multiple scales, from a few centimeters to kilometers. While electrode spacing is used to define field resistance, laboratory measurements in a limited space need to consider electrode geometry. However, there are no studies that theoretically explore the effects of the geometries of electrodes and container size on laboratory electrical resistivity measurements. This study formulates a theoretical electrical resistance for the geometry of cylindrical electrodes and the size of a non-conductive container with the method of image charges. As a complementary study, experimental tests were conducted to verify the derived equations. The discussion includes the concepts of the spherical equivalent electrodes and a simple design method for container size.

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The Reconstructive Crystal Structure and the Exchange Energy

MRS Proceedings ◽

10.1557/proc-0966-t10-20 ◽

2006 ◽

Vol 966 ◽

Author(s):

Ahmad Yazdani ◽

Reza Osati Araghi ◽

Farid Arya

Keyword(s):

Electrical Resistivity ◽

Magnetic Transition ◽

Resistivity Measurement ◽

Stable State ◽

Electrical Resistivity Measurement ◽

X Ray ◽

Resistivity Measurements ◽

Pattern Change ◽

Field Independent

ABSTRACTIn order to describe the role of temperature variation on suppress of broad range of magnetic transition, the effect of annealing on different samples of a Gd-based intermetallic compound (i.e., Gd2Au) is investigated. The X-ray, AC and D.C susceptibility and electrical resistivity measurements for different annealed samples revealed that: (i) A great exchange dispersion is observed in A.C susceptibility (ii) This unstable exchange can be stabilized at certain annealing temperature, where the short rang unstable Ferromagnetic (F.M) breaks down or even changes to an Antiferromagnetic (AF.M) stable state. (iii) The DC susceptibility shows a spin-glass like transition temperature at TN= 61 K, above which the compound exhibits a completely paramagnetic (P.M) behavior and is field independent. (iv) the iso-termal magnetization does not follow the field induced transition (F.I.T) and behaves completely as a paramagnet which is independent of the field up to the highest available fields. The electrical resistivity measurement shows: a) A pronounced sharp bend at TN=61 K is manifested in ρ(T). b)some strong peak of X-ray pattern change into double adjacent lines in some intervals of low temperatures

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An upgrade of the materials irradiation facility with in-situ electrical resistivity measurement at the Demokritos TANDEM accelerator

HNPS Proceedings ◽

10.12681/hnps.1833 ◽

2019 ◽

Vol 26 ◽

pp. 251

Author(s):

A. Theodorou ◽

Z. Kotsina ◽

M. Axiotis ◽

G. Apostolopoulos

Keyword(s):

Electrical Resistivity ◽

Radiation Damage ◽

Research Evaluation ◽

Ion Beam ◽

Resistivity Measurement ◽

Electrical Resistivity Measurement ◽

Tandem Accelerator ◽

Fusion Materials ◽

Beam Currents

As an important part of fusion materials research, evaluation of radiation damage in fusion materials has been emphasized more than a half century. In order to improve our understanding of radiation damage in fusion materials, an upgrade has been performed of the materials irradiation facility IR2, which is located at the NCSR “Demokritos” 5.5 MV TANDEM accelerator. The upgraded facility allows irradiation at higher ion beam currents while ensuring that the target temperature remains below 10 K. It provides in-situ electrical resistivity measurements on several samples for real-time monitoring of radiation damage as well as in-situ post-irradiation annealing up to 300 K. The upgraded IR2 facility has been successfully employed in radiation damage and recovery studies of metallic materials with applications in fusion research.

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Selection of electrodes for the ˝in situ˝ electrical resistivity measurements of molten aluminium

Journal of Mining and Metallurgy Section B Metallurgy ◽

10.2298/jmmb130118029p ◽

2013 ◽

Vol 49 (3) ◽

pp. 279-283 ◽

Cited By ~ 2

Author(s):

M. Petric ◽

S. Kastelic ◽

P. Mrvar

Keyword(s):

Electrical Resistivity ◽

Contact Resistance ◽

Electrode Material ◽

Aluminium Alloys ◽

Resistivity Measurement ◽

Electrical Resistivity Measurement ◽

Measuring Cell ◽

Resistivity Measurements ◽

Selection Of

The aim of this paper is the selections of proper electrode material for four-probe technique electrical resistivity measurement of aluminium and aluminium alloys. The biggest problem of electrodes is oxidation during measurement causing high contact resistance and giving wrong results. Various materials have been tested and aluminium electrodes have been chosen. Advantage of aluminium electrodes is that they are melted in specimen right after the pouring and causing no interface which is resulting with any contact resistance. The device together with measuring cell for ?in situ? measurement of electrical resistivity was developed using four-probe DC technique.

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Formation of Dislocations in NiAl Single Crystals Studied by In Situ Electrical Resistivity Measurement

MRS Proceedings ◽

10.1557/proc-500-49 ◽

1997 ◽

Vol 500 ◽

Cited By ~ 1

Author(s):

Y. Q. Sun ◽

P. M. Hazzledine ◽

D. M. Dimiduk

Keyword(s):

Electrical Resistivity ◽

Single Crystals ◽

Yield Point ◽

Resistivity Measurement ◽

Electrical Resistivity Measurement ◽

Plastic Yielding ◽

Resistivity Measurements ◽

Density Of Dislocations ◽

Abrupt Jump

ABSTRACTThis paper reports experiments in which in situ electrical resistivity measurements were used to monitor the formation of dislocations in initially dislocation-free NiAl single crystals. The electrical resistivity is found to exhibit an abrupt jump at the onset of plastic yielding. This is interpreted to result from an abrupt nucleation of a massive density of dislocations at the yield point.

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