scholarly journals A modified mean-linear-intercept method for distinguishing lamellar and globular eutectic carbides in metallographic samples

2018 ◽  
Vol 52 (1) ◽  
pp. 83-87 ◽  
Author(s):  
K. Zelič ◽  
M. Godec
Keyword(s):  
Eutectic Carbides ◽  
Mean Linear Intercept

Early changes of lung function and structure in an elastase model of emphysema—a hyperpolarized 3He MRI study

2008 ◽  
Vol 104 (3) ◽  
pp. 773-786 ◽  
Author(s):  
Kiarash Emami ◽  
Robert V. Cadman ◽  
John M. Woodburn ◽  
Martin C. Fischer ◽  
Stephen J. Kadlecek ◽  
...  
Keyword(s):  
Lung Function ◽  
Lung Ventilation ◽  
Unit Group ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Entire Lung ◽  
Residual Capacity ◽  
Regional Basis ◽  
Mean Linear Intercept ◽  
Mri Study

Early changes of lung function and structure were studied in the presence of an elastase-induced model of emphysema in 35 Sprague-Dawley rats at mild (5 U/100 g) and moderate (10 U/100 g) severities. Lung ventilation was measured on a regional basis (at a planar resolution of 3.2 mm) by hyperpolarized 3He MRI at 5 and 10 wk after model induction. Subsequent to imaging, average alveolar diameter was measured from histological slices taken from the centers of each lobe. Changes of mean fractional ventilation, mean linear intercept, and intrasubject heterogeneity of ventilation were studied during disease progression. Mean fractional ventilation was significantly different between healthy controls (0.23 ± 0.04) and emphysematous animals at both time points in the 10-unit group (0.06 ± 0.02 and 0.12 ± 0.05, respectively). Changes in average alveolar diameter were not statistically observable until the 10th wk between healthy (37 ± 10 μm) and emphysematous rats (73 ± 25 and 95 ± 31 μm, for 5 and 10 units, respectively). Assessment of function-structure correlation suggested that the majority of the decline in fractional ventilation occurred in the first 5 wk, while enlargement of alveolar diameters appeared primarily between the 5th and 10th wk. A thresholding metric, based on the 20th percentile of fractional ventilation over the entire lung, was utilized to detect the onset of the disease with confidence, independent of whether the regional ventilation measurements were normalized with respect to the delivered tidal volume and estimated functional residual capacity of each individual rat.

scholarly journals The Joint Effects of Nitriding and Parameters Related to the Destabilisation of Austenite on Wear Resistance in White Cast Iron with 25% Cr

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 85
Author(s):  
Alejandro González-Pociño ◽  
Florentino Alvarez-Antolin ◽  
Juan Asensio-Lozano
Keyword(s):  
Wear Resistance ◽  
Cast Iron ◽  
White Cast Iron ◽  
Nitrided Layer ◽  
Erosive Wear ◽  
Air Cooling ◽  
Cast Irons ◽  
Eutectic Carbides ◽  
Noticeable Increase ◽  
Ionic Nitriding

In this article, the effects of an ionic nitriding treatment are analysed, together with deliberate variation of different thermal parameters associated with the destabilisation of austenite, on erosive wear resistance of white cast irons with 25% Cr. The methodology followed in this research was an experimental design, where six factors were analyzed by performing eight experiments. The thickness of the nitrided layer is much smaller than in white cast iron with lower percentages in Cr, never reaching 20 microns. The nitriding treatment entails considerable softening of the material underneath the nitriding layer. This softening behaviour becomes partially inhibited when the destabilisation temperature of austenite is 1100 °C and dwell times at such temperature are prolonged. This temperature seems to play a significant role in the solubilization of non-equilibrium eutectic carbides, formed during industrial solidification. The nitriding treatment leads to additional hardening, which, in these cases, favours a second destabilisation of austenite, with additional precipitation of secondary carbides and the transformation of retained austenite into martensite. Despite softening of the material, the nitriding treatment, together with air-cooling after destabilisation of the austenite, allows a noticeable increase in resistance to erosive wear.

scholarly journals Structure and Properties of Coatings Made with Self Shielded Cored Wire

2016 ◽  
Vol 16 (3) ◽  
pp. 39-42 ◽  
Author(s):  
M. Gucwa ◽  
J. Winczek ◽  
R. Bęczkowski ◽  
M. Dośpiał
Keyword(s):  
Heat Input ◽  
Mining Industry ◽  
High Hardness ◽  
Properties Of Coatings ◽  
Cored Wire ◽  
Eutectic Carbides ◽  
Hard Particles ◽  
Wear And Corrosion ◽  
Flux Cored Arc Welding ◽  
Cored Wires

Abstract The welding technologies are widely used for design of protection layer against wear and corrosion. Hardfacing, which is destined for obtaining coatings with high hardness, takes special place in these technologies. One of the most effective way of hardfacing is using self shielded flux cored arc welding (FCAW-S). Chemical composition obtained in flux cored wire is much more rich in comparison to this obtained in solid wire. The filling in flux cored wires can be enriched for example with the mixture of hard particles or phases with specified ratio, which is not possible for solid wires. This is the reason why flux cored wires give various possibilities of application of this kind of filler material for improving surface in mining industry, processing of minerals, energetic etc. In the present paper the high chromium and niobium flux cored wire was used for hardfacing process with similar heat input. The work presents studies of microstructures of obtained coatings and hardness and geometric properties of them. The structural studies were made with using optical microscopy and X-ray diffraction that allowed for identification of carbides and other phases obtained in the structures of deposited materials. Investigated samples exhibit differences in coating structures made with the same heat input 4,08 kJ/mm. There are differences in size, shape and distribution of primary and eutectic carbides in structure. These differences cause significant changes in hardness of investigated coatings.

Mechanical Analysis of Low and High Chromium Steels Used in Hot Strip Work Rolls

2018 ◽  
Vol 279 ◽  
pp. 3-9
Author(s):  
Fethi Benkhenafou ◽  
Ines Fernández Pariente ◽  
F.Javier Belzunce ◽  
Abdelkader Ziadi ◽  
Ming Quan Shi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
High Speed ◽  
Volume Fraction ◽  
Research Work ◽  
High Speed Steel ◽  
Nodular Cast Iron ◽  
High Chromium ◽  
Eutectic Carbides ◽  
Hot Strip ◽  
Conventional Heat Treatment

Microstructure, hardness and fracture toughness of low and high chromium high speed steel used in hot strip mills and subjected to conventional heat treatment have been examined. The influence of tempering temperatures on the mechanical properties of these products, determined using tensile and fracture toughness tests, was studied in this research work. The developed microstructures have been characterized by XRD, optical microscopy and SEM examinations. Macrohardness and microhardness of the specimens have been evaluated by Vickers indentation technique. The fracture toughness of these products was investigated using the rupture weight on 3 points bending specimens. The plane strain fracture toughness KIc and the fracture strength were measured for each alloy. The shell is high harness high speed steels, and the core is nodular cast iron. It was found that most fracture occurred in the eutectic carbides formed by the high content alloy element, such as Mo,V,Cr, but that for the alloys with a reduced volume fraction of eutectic carbides, a small amount of crack propagation occurred in the austenitic dendrites.

scholarly journals A murine model of elastase- and cigarette smoke-induced emphysema

2017 ◽  
Vol 43 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Rubia Rodrigues ◽  
Clarice Rosa Olivo ◽  
Juliana Dias Lourenço ◽  
Alyne Riane ◽  
Daniela Aparecida de Brito Cervilha ◽  
...  
Keyword(s):  
Cigarette Smoke ◽  
Murine Model ◽  
Respiratory Mechanics ◽  
Lung Parenchyma ◽  
Time Frame ◽  
Significant Degree ◽  
Mean Linear Intercept ◽  
Distal Lung ◽  
Intranasal Instillation

ABSTRACT Objective: To describe a murine model of emphysema induced by a combination of exposure to cigarette smoke (CS) and instillation of porcine pancreatic elastase (PPE). Methods: A total of 38 C57BL/6 mice were randomly divided into four groups: control (one intranasal instillation of 0.9% saline solution); PPE (two intranasal instillations of PPE); CS (CS exposure for 60 days); and CS + PPE (two intranasal instillations of PPE + CS exposure for 60 days). At the end of the experimental protocol, all animals were anesthetized and tracheostomized for calculation of respiratory mechanics parameters. Subsequently, all animals were euthanized and their lungs were removed for measurement of the mean linear intercept (Lm) and determination of the numbers of cells that were immunoreactive to macrophage (MAC)-2 antigen, matrix metalloproteinase (MMP)-12, and glycosylated 91-kDa glycoprotein (gp91phox) in the distal lung parenchyma and peribronchial region. Results: Although there were no differences among the four groups regarding the respiratory mechanics parameters assessed, there was an increase in the Lm in the CS + PPE group. The numbers of MAC-2-positive cells in the peribronchial region and distal lung parenchyma were higher in the CS + PPE group than in the other groups, as were the numbers of cells that were positive for MMP-12 and gp91phox, although only in the distal lung parenchyma. Conclusions: Our model of emphysema induced by a combination of PPE instillation and CS exposure results in a significant degree of parenchymal destruction in a shorter time frame than that employed in other models of CS-induced emphysema, reinforcing the importance of protease-antiprotease imbalance and oxidant-antioxidant imbalance in the pathogenesis of emphysema.

Function–Structure Correlation Studies on Excised Hamster Lungs in Papain-induced Emphysema

1973 ◽  
Vol 51 (9) ◽  
pp. 635-641 ◽  
Author(s):  
P. A. Martorana ◽  
N. W. McKeel ◽  
J. W. Richard ◽  
N. N. Share
Keyword(s):  
Correlation Coefficients ◽  
Histological Evaluation ◽  
Functional Tests ◽  
Elastic Recoil ◽  
Mean Values ◽  
Functional Changes ◽  
High Prediction ◽  
Mean Linear Intercept ◽  
Structure Correlation ◽  
The Mean

Emphysematous lesions induced by a single exposure of hamsters to papain aerosol were evaluated both physiologically (lung elastic recoil) and histologically (mean linear intercept). The extent of the developed lesions was directly related to the concentration of papain employed, and progressed with time following exposure. Histological evaluation was most sensitive for quantitation of minimal lesions; an approximate 20% increase of the mean linear intercept being required for significant functional changes. Maximal mean increase of the mean linear intercept compatible with survival was approximately 75%. Using raw data values, all functional tests exhibited high correlation coefficients (r) with histological evaluation, but prediction efficiencies (r2) were below a practically acceptable value of 75%. However, using group mean values, thereby reducing individual biological variations, higher correlation coefficients as well as high prediction efficiencies were obtained for all functional tests with histological evaluation. In this regard, best prediction efficiencies were obtained for the functional specific static compliance and specific volume at full inflation versus the morphological mean linear intercept.

Cyclic annealing versus continuous annealing of 20 wt.% chromium white cast iron

2021 ◽  
Vol 118 (4) ◽  
pp. 404
Author(s):  
Siddhartha Sankar Mandal ◽  
Dipak Kumar Mondal ◽  
Karuna Sindhu Ghosh
Keyword(s):  
White Cast Iron ◽  
Annealing Treatment ◽  
Continuous Annealing ◽  
Air Cooling ◽  
Austenite Matrix ◽  
Subsequent Increase ◽  
Eutectic Carbides ◽  
Cyclic Annealing ◽  
Secondary Carbides ◽  
Forced Air

To destabilize as-cast microstructure of 20 wt.% chromium white iron, cyclic annealing involving repeated austenitization for short duration of 0.6 h at 900, 950, 1000, 1050 and 1100 °C followed by forced air cooling is conducted as an alternative to continuous annealing requiring austenitization for longer period of 4–6 h at the said temperatures followed by furnace cooling. Continuous austenitization destabilizes the austenite matrix through precipitation of secondary carbides and transforms the alloy depleted austenite to pearlite on furnace cooling, thereby reducing the as-cast hardness from HV 669 to HV466. In contrast, repeated austenitization not only destabilizes the austenite matrix through precipitation of secondary carbides followed by its transformation to martensite on forced air cooling, but also causes disintegration of longer eutectic carbides to shorter segments with subsequent increase in hardness to as high as HV 890. Notched impact toughness after both continuous and cyclic annealing remains uniformly at 12.0 J as compared to as-cast value of 6.0 J. Besides, an unexpected rise in abrasive wear resistance after cyclic annealing treatment makes the alloy superior than that obtained by continuous annealing treatment as practiced in industries.

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