A SEM (scanning electron microscopy)-based method to evaluate impurity segregation to prior austenite grain boundaries in high strength steels

It was previously reported that fatigue life of some alloys can be dramatically reduced if the grain boundaries contain a high level of impurity segregation before fatigue tests. In this paper the susceptibility of single phase brass samples (90Cu10Zn) to this form of damage is studied. After cold drawing of as cast brass bars, fatigue samples were heat treated at 800°C during 30min to promote recrystallization and impurity segregation at grain boundary. The samples were then tested under high frequency bending fatigue test at 200°C. After cracking, fracture surfaces were studied using both scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The SEM micrographs showed that the fractures were mostly intergranular. Chemical composition of intergranular cracks surface were analyzed using EPMA at low accelerating voltage. A high concentration of sulfur was found on most of grain boundary facets. The internal stress in alloys after fatigue was qualitatively estimated using electron backscattering diffraction in scanning electron microscopy. A high level of local misorientation was found near most grain boundaries. The mechanism of intergranular cracks formation during fatigue is discussed taking into account both the segregation of sulfur at grain boundaries and accumulation of plastic strain at grain boundaries

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Boron-Containing Precipitates Formed on the Prior Austenite Grain Boundaries in High Strength Low Alloy Steels

Tetsu-to-Hagane ◽

10.2355/tetsutohagane1955.66.5_506 ◽

1980 ◽

Vol 66 (5) ◽

pp. 506-513

Author(s):

Seiichi WATANABE ◽

Hiroo OHTANI

Keyword(s):

Grain Boundaries ◽

Prior Austenite ◽

High Strength ◽

Low Alloy Steels ◽

Austenite Grain ◽

Alloy Steels ◽

Prior Austenite Grain

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Influence of Annealing Conditions on the Austenite Size at the End of Soaking

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.562 ◽

2018 ◽

Vol 941 ◽

pp. 562-567 ◽

Cited By ~ 1

Author(s):

Matthieu Salib ◽

Irene de Diego Calderon ◽

Caio Ferreira de Melo ◽

Luiz Paulo Mendonca e Silva ◽

Artem Arlazarov

Keyword(s):

Grain Size ◽

Prior Austenite ◽

High Strength Steels ◽

High Strength ◽

Austenite Grain Size ◽

Austenite Grain ◽

Wide Range ◽

Prior Austenite Grain Size ◽

Prior Austenite Grain ◽

Soaking Temperature

Influence of chemical composition (C, Mn and Nb) and soaking temperature on the evolution of austenite grain size from a cold-rolled microstructure was studied on several Advanced High Strength Steels. A wide range of soaking temperatures was used to perform the heat treatments. Characterization of prior austenite grain size from the annealed samples using optical and confocal microscopes, Scanning Electron Microscope and Electron Back-Scattered Diffraction. Comparison of different methods was done to validate the methodology and the results were quite satisfactory. Concomitant effects of Manganese, Niobium, Carbon and of soaking temperature on the prior austenite grain size were analyzed and discussed. Important effect of Mn and Nb was underlined.

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Control of Cold Welding Cracks in 30CrMnSi Steel by Welding with Trailing Impacting and Rolling

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.295-297.1251 ◽

2011 ◽

Vol 295-297 ◽

pp. 1251-1258 ◽

Cited By ~ 1

Author(s):

Jian Guo Yang ◽

Lu Yong Huang ◽

Hai Bo Pan ◽

Xue Song Liu ◽

Hong Yuan Fang

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Welded Joints ◽

High Strength ◽

Cold Welding ◽

Low Alloy Steel ◽

Residual Welding Stress ◽

Welding Stress ◽

Scanning Electron ◽

Main Factor

As a kind of the high strength low alloy steel (HSLA), 30CrMoSi has been used widely in some industrial fields. However, just like some HSLA, this steel also faces some problems when it is welded, especially such problem as cold cracking in the welded joints. In this paper, the cold welding cracks and microstructure of the joints of 30CrMoSi steel were studied by scanning electron microscopy (SEM) and optical microscopy (OM), and a method called welding with trailing impacting and rolling (WTIR) was utilized to solve the problem mentioned above by decreasing the residual welding stress which is one main factor to lead to cold welding crack in the joint of HSLA. The crack-free joints of 30CrMoSi steel were obtained by using proper parameters.

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A quantitative atom probe study of the Nb excess at prior austenite grain boundaries in a Nb microalloyed strip-cast steel

Acta Materialia ◽

10.1016/j.actamat.2012.06.013 ◽

2012 ◽

Vol 60 (13-14) ◽

pp. 5049-5055 ◽

Cited By ~ 35

Author(s):

Peter J. Felfer ◽

Chris R. Killmore ◽

Jim G. Williams ◽

Kristin R. Carpenter ◽

Simon P. Ringer ◽

...

Keyword(s):

Grain Boundaries ◽

Prior Austenite ◽

Cast Steel ◽

Atom Probe ◽

Austenite Grain ◽

Strip Cast ◽

Prior Austenite Grain

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Cavitation control in steels of high residual element content

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1980.0121 ◽

1980 ◽

Vol 295 (1413) ◽

pp. 305-305 ◽

Cited By ~ 4

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Prior Austenite ◽

Low Alloy Steels ◽

Boundary Zone ◽

Austenite Grain ◽

Alloy Steels ◽

Austenite Grain Boundary ◽

Prior Austenite Grain ◽

Transverse Boundary

The cavitational mode of failure of prior austenite grain boundaries in bainitic creep-resisting low alloy steels is now well established as a principal factor in the high incidence of cracking problems which has developed on modern power plant in recent years. The microstructural features dominating the cavitation process at the reheat temperature in a ½CMV bainitic steel of high classical residual level have been determined. The prior austenite grain boundaries become zones of comparative weakness ca . 1 pm thick at 700 °C and are incapable of sustaining significant shear loads. Deformation is therefore initiated by a relaxation of load, through a process of prior austenite grain boundary zone shear, from inclined to transverse boundaries such that a concentration of normal stress develops across the latter. The overall deformation is thereafter determined by cavitation of the transverse boundary zones, the necessary inclined boundary displacements being accommodated by further grain boundary zone shear. Transverse boundary cavitation is shown to be an essentially time-independent process of localized ductile microvoid coalescence resulting from the plastic deformation of the boundary zone.

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Substructure and Crystallography of Degenerate Pearlite in an Fe-C Binary Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.4832 ◽

2007 ◽

Vol 539-543 ◽

pp. 4832-4837 ◽

Cited By ~ 9

Author(s):

Tadashi Furuhara ◽

Tomokazu Moritani ◽

K. Sakamoto ◽

Tadashi Maki

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Growth Front ◽

Isothermal Transformation ◽

High Angle ◽

Austenite Grain ◽

Transmission Electron ◽

Proeutectoid Ferrite ◽

Lamellar Pearlite ◽

Scanning Electron

Microstructures formed by degenerate pearlite transformation in an Fe-0.38mass%C alloy were studied by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Degenerate pearlite which contains fine cementite particles even at the growth front was observed with other structures such as proeutectoid ferrite, lamellar pearlite and bainite in a temperature range between 773K and 923K. As the isothermal transformation temperature is lowered, a fraction of the degenerate pearlite increases. The degenerate pearlite consists of ‘block’ (a region in which ferrite orientations are nearly the same) and ‘colony’ (a region containing cementite particles of nearly the same orientation), both of which are similar to those in lamellar pearlite. Block boundaries within an austenite grain are generally of high-angle type and their misorientations deviate largely from intervariant relationships for the K-S orientation relationship. In contrast, colony boundaries are of low-angle type. Cementite films are formed along those ferrite boundaries in the degenerate pearlite, presumably formed by encounter of the blocks or colonies.

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