On the Brittleness of Normalized Cast Steel Caused by the Grain Boundaries of Primary Austenite (1st Report)

AbstractTramp elements in steels such as tin have been thought harmful because of the hot brittleness at grain boundaries and will be enriched in new steels because of difficulty of removal. It has been an important and difficult matter for metallurgist to use these elements. In the present paper, the as-cast steel containing high concentration of tin is prepared in laboratory and tin precipitates at the manganese sulphide inclusions have been found. A theoretical model is established to calculate the size of manganese sulphide inclusions acted as the heterogeneous nucleation site of tin precipitation. The results show that the inclusions with the smaller contact angle between tin precipitate is more advantageous to be the nucleus of tin heterogeneous nucleation. In this experiment, the manganese sulphide inclusions whose size is 2~4 μm in diameter can act as the nuclei of the nucleation of tin precipitation.

Download Full-text

Analysis of Elemental Segregation in a Microalloyed Cast Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.2465 ◽

2013 ◽

Vol 652-654 ◽

pp. 2465-2468 ◽

Cited By ~ 2

Author(s):

Jing Wei Zhao ◽

Zheng Yi Jiang ◽

Dong Bin Wei

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Cast Steel ◽

Central Zone ◽

Energy Dispersive ◽

Surface Zone ◽

Quantitative Investigation ◽

X Ray ◽

Elemental Segregation

Quantitative investigation is made on the elemental segregation in different zones of a heavy microalloyed cast steel by energy dispersive X-ray spectroscopy. It is demonstrated that C shows serious segregation tendency than that of Mn and Si, and the degree of C segregation in the surface zone is higher than that in the central zone. C enrichment is generally observed at both dendrite arm and grain boundaries, and more C segregation at dendrite arm boundary in contrast to that at grain boundary is found in this steel. The distribution of C concentration shows a decreased trend from root to tip along the dendrite arm boundary. The C concentration at trigeminal boundary intersection shows higher level than that at other position of the grain boundaries.

Download Full-text

Microstructure and Tribological Properties of a Material with Cementite Eutectic Applied for Metallurgical Rolls

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.682.119 ◽

2016 ◽

Vol 682 ◽

pp. 119-124

Author(s):

Edyta Rożniata ◽

Janusz Krawczyk ◽

Robert Dąbrowski ◽

Marcin Madej ◽

Łukasz Frocisz ◽

...

Keyword(s):

Heat Treatment ◽

Wear Resistance ◽

Large Fraction ◽

Cast Steel ◽

Abrasive Wear Resistance ◽

Cast State ◽

Primary Austenite ◽

Austenite Grain ◽

Austenite Grains ◽

Steel Rolls

Three prototype metallurgical rolls were produced on the basis of G200CrNiMo4-3-3 material. The method applied for the microstructure forming was different for each roll: the roll marked WOT – as cast state (without a modification and heat treatment); the metallurgical roll marked WMT – during its casting the FeCaSi deoxidizing was applied and then modification by a complex inoculant and argoning; the metallurgical roll marked WNT – subjected to a heat treatment (incomplete normalizing).The mentioned above differences in the technology of making rolls caused changes in their microstructure.The cementite eutectic and pearlitic matrix occurred in each roll. The main differences in the microstructure of cast steel rolls concerned a morphology of precipitates of hypereutectoid cementite. In the WOT roll cementite was mainly in the Widmannstӓtten system. Precipitates of hypereutectoid cementite in the WMT roll occurred along grain boundaries of primary austenite. A large fraction of spheroidal hypereutectoid cementite, precipitated in the whole volume of the primary austenite grain, appeared in the WNT roll. The microstructure influenced the rolls hardness and was equal 260 ÷ 350 HBW.Tribological investigations indicated decreasing the abrasive wear resistance with increasing the hypereutectoid cementite fraction within the primary austenite grains.

Download Full-text

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071326 ◽

1973 ◽

Vol 31 ◽

pp. 176-177

Author(s):

D. E. Fornwalt ◽

A. R. Geary ◽

B. H. Kear

Keyword(s):

Electron Microscope ◽

Grain Boundaries ◽

Volume Fraction ◽

Rupture Life ◽

Stress Rupture ◽

High Volume ◽

Precipitate Morphology ◽

Stress Rupture Life ◽

Nickel Base ◽

Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

Download Full-text

Measurement of the Displacement Across a Coincidence Grain Boundary

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078213 ◽

1977 ◽

Vol 35 ◽

pp. 124-125

Author(s):

J. W. Matthews ◽

W. M. Stobbs

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Stacking Fault ◽

The Other ◽

Measuring Technique ◽

High Angle ◽

Twin Boundaries ◽

Rigid Displacement ◽

Cubic Crystals ◽

Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Download Full-text

Lattice Imaging of Grain Boundaries in Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078171 ◽

1977 ◽

Vol 35 ◽

pp. 114-115

Author(s):

D. R. Clarke ◽

G. Thomas

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Silicon Nitride ◽

Grain Boundaries ◽

High Temperature Strength ◽

Current Interest ◽

Lattice Imaging ◽

Special Significance ◽

Structural Applications ◽

Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Download Full-text

The Effect of Specimen Thickness and Probe Size on Aem Analysis of Cr-Depletion Profiles in Sensitized Stainless Steel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055436 ◽

1982 ◽

Vol 40 ◽

pp. 518-519

Author(s):

E. L. Hall

Keyword(s):

Grain Boundaries ◽

Boundary Region ◽

Chromium Concentration ◽

Foil Thickness ◽

Specimen Thickness ◽

Probe Size ◽

Analytical Electron ◽

Analytical Electron Microscope ◽

Sensitization Process ◽

Compositional Gradients

Sensitization in stainless steels is caused by the formation of chromium-rich M23C6 carbides at grain boundaries, which depletes the adjacent matrix and boundary region of chromium, and hence leads to rapid intergranular attack. To fully understand the sensitization process, and to test the accuracy of theories proposed to model this process, it is necessary to obtain very accurate measurements of the chromium concentration at grain boundaries in sensitized specimens. Quantitative X-ray spectroscopy in the analytical electron microscope (AEM) enables the chromium concentration profile across these boundaries to be studied directly; however, it has been shown that a strong effect of foil thickness and electron probe size may be present in the analysis of rapidly-changing compositional gradients. The goal of this work is to examine these effects.

Download Full-text

Electrolytic Isolation of Twin-Type Shock Deformation Structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061604 ◽

1967 ◽

Vol 25 ◽

pp. 318-319

Author(s):

F. I. Grace ◽

L. E. Murr

Keyword(s):

Grain Boundaries ◽

Thin Foil ◽

Electrolyte Composition ◽

Experimental Conditions ◽

Average Current Density ◽

Electron Transmission ◽

Deformation Structures ◽

The Matrix ◽

Average Current ◽

Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

Download Full-text