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1.
EfectofRareEarthsandNitrogenonGraphiteStructureofGrayCastIronZhaiQijie(翟启杰),ZengQi(曾奇)(FoundryInstitute,UniversityofSciencea... 相似文献
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The high chromium cast irons (HCCIs) with rare earth (RE) nanoparticles or inoculants were fabricated in the casting process. The phase compositions and microstructure were analyzed by X-ray diffraction (XRD) and optical microscopy (OM), respectively. The hardness and impact toughness were tested by Rockwel-hardmeter and impacting test enginery. And then, the morphology of fracture was researched by scanning electron microscopy (SEM). The results demonstrated that the phase compositions of HCCIs with addition of RE nanoparticles or inoculants which were M7C3 carbides + α-Fe did not change obviously. However, the prime M7C3 carbides morphology had great changes with the increase of RE nanoparticles, which changed from long lath to granular or island shape. When the content of RE nanoparticles was 0.4 wt.%, the microstructure of high chromium cast iron was refined greatly. The microstructure of carbides was coarser when the addition of RE nanoparticles was higher than 0.4 wt.%. The hardness and impact toughness of HCCIs were improved by addition of RE nanoparticles or inoculants. The impact toughness of HCCIs was increased 36.4% with RE nanoparticles of 0.4 wt.%, but the hardness changed slightly. In addition, the adding of RE nanoparticles or inoculants could reduce the degree of the brittle fracture. Fracture never seemed regular, instead, containing lots of laminates and dimples with the increase of the RE nanoparticles. The results also indicated that the optimal addition amount of the RE nanoparticles was 0.4%, under this composition, the microstructure and mechanical property achieved the best cooperation. In addition, through the study of erosion wear rate, when adding 0.4% RE nanoparticles into the HCCIs, the erosion wear rate got the minimum 0.32×10-3 g/mm2, which could increase 51.5% compared with that without any RE nanoparticles. 相似文献
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The plastic deformation behavior of cast irons, covering the majority of graphite morphologies, has not been comprehensively
studied previously. In this investigation, the effect of graphite morphology and graphite fraction on the plastic deformation
behavior of pearlitic cast irons has been evaluated. The investigation is based on tensile tests performed on various different
cast iron grades, where the graphite morphology and volume fraction have been varied. Pearlitic steel with alloying levels
corresponding to the cast irons were also studied to evaluate how the cast iron matrix behaves in tension without the effects
of the graphite phase. It is concluded that as the roundness of the graphite phase increases, the strain hardening exponent
decreases. This demonstrates that the amount of plastic deformation is higher in the matrix of lamellar cast iron grades compared
to compacted and nodular cast iron grades. Furthermore, this study shows that the strength coefficient in flake graphite cast
irons increases as the graphite fraction decreases due to the weakening effect of the graphite phase. This study presents
relationships between the strain hardening exponent and the strength coefficient and the roundness and fraction of the graphite
phase. Using these correlations to model the plastic part of the stress-strain curves of pearlitic cast irons, we were able
to calculate curves in good agreement with experimentally determined curves, especially for gray cast irons and ductile iron. 相似文献
5.
Solidification and Room Temperature Microstructure of a Fully Pearlitic Compacted Graphite Cast Iron
Alexandre Freulon Jon Sertucha Jacques Lacaze 《Transactions of the Indian Institute of Metals》2018,71(11):2651-2656
Compacted graphite cast irons are rapidly developing for they have better mechanical properties than lamellar graphite cast irons and present less porosity than spheroidal graphite cast irons. For many applications, an as-cast fully pearlitic matrix would be desired which can hardly be achieved when graphite is compacted. Addition of manganese, copper and tin are thus made as these elements are known to be pearlite promoters. However, their amount should be limited so as to avoid detrimental effects amongst which are heterogeneities in the matrix properties which impede easy machining. In the present work, a compacted graphite cast iron containing 0.3 wt% Mn, 0.8 wt% Cu and 0.1 wt% Sn was cast in sand mould and in standard thermal analysis cup. The cup sample showed a nearly fully pearlitic matrix and was selected for further study. The characterization consisted of measuring and correlating the distributions of pearlite interlamellar spacings and microhardness values. An attempt was made to look for the effect of solidification microsegregation on microhardness which did not reveal any trend. 相似文献
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The primary purpose of this research was to investigate the nondestructive ultrasonic wave response, in terms of acoustic
velocities and attenuation of sound energy, in cast irons with different nodularities and matrix structures and its correlation
with mechanical properties. The results indicated that the influences of matrix structures on the acoustic velocities were
not apparent in the cast irons investigated. As to the nodularity, when graphites were largely spheroidal in shape (i. e., nodularity over 80 pct), the velocity of longitudinal waves propagation was about 5300 to 5500 m/s. The velocities seemed
to decrease linearly down to nodularity of 25 pct, where velocity was approximately 4800 m/s. Below 25 pct nodularity, the
values of acoustic velocity dropped rapidly to about 4000 to 4200 m/s. This represented the velocity of longitudinal waves
propagation in gray cast iron, in which the graphites appeared in flake form. The analysis of the attenuation of ultrasonic
amplitude indicated that when the nodularity of cast irons is low, the echo sound amplitude will decay more rapidly with respect
to distance of echo sound travel. As to the matrix structures, ferritic, bainitic, ferritic-pearlitic (low pearlite content)
and tempered martensitic matrix structures were found to have similar ultrasonic attenuation characteristics at the testing
frequency of 2 MHz. A higher amount of pearlite (over 90 pct) or fresh martensite in the matrix of cast irons has resulted
in faster attenuation of ultrasonic energy, with the fresh martensitic matrix being the fastest. At a testing frequency of
4 MHz, the attenuation of the ultrasonic amplitude in pearlitic and fresh martensitic matrices was found to be even greater
than that of 2 MHz. However, other matrices exhibited similar attenuation behavior at both 2 and 4 MHz frequencies. The relationship
between the mechanical properties of various cast irons and ultrasonic characteristics was also examined.
JIA-MING SUEN, formerly Graduate Student, Department of Materials Engineering, Tatung Institute of Technology 相似文献
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In this work, an experimental verification for the transition theory from gray to white cast iron solidification is presented.
Experimental tests have been implemented using plate- and wedge-shaped castings of various sizes. The experiments included
inoculated and noninoculated cast irons of different chemical compositions and time-temperature histories of the inoculation
effects. In addition, thermal-analysis tests were employed to determine the degree of undercooling of graphite eutectic (ΔT
m
). This included microstructural evaluations in order to establish the eutectic-cell densities. This procedure enabled the
calculation of the theoretical chill width (w), as well as the chilling tendency (CT) of cast iron. It was found that the predictions of the theoretical analysis are in
good agreement with the experimental outcome for the chill exhibited in wedge- and plate-shaped castings. 相似文献
10.
G. Balachandran Aravind Vadiraj B. S. Sharath B. R. Krishnamurthy 《Transactions of the Indian Institute of Metals》2010,63(4):707-713
The effect of induction case hardening of a gray cast iron (FG 260) and SG iron (600/3) as a function of applied induction
power has been studied. The influence of various operating parameters on the penetration depth has been analysed. The case
depth as a function of applied power and the associated changes in microstructure has been investigated. The case depth of
SG iron was found to be twice than the gray iron due to higher resistivity of the material and increase in depth of penetration.
Both hardness and the depth of penetration increased with increase in applied power associated with martensitic case formation.
The surface hardness of both the irons varies between 600 to 800 VHN. The core microstructure in both the irons displayed
pearlitic matrix. In the case of SG iron, the nodule size, sphericity and nodularity have reduced in the induction hardened
case compared to the core. 相似文献
11.
Effects of RE and N on Properties of Corrosion Resistance and Oxidation Resistance of Gray Cast Iron 总被引:1,自引:0,他引:1
Zeng Qi 《中国稀土学报(英文版)》1998,16(3):189-192
ItiswelknownthatthemechanicalpropertiesofgraycastironcanbeimprovedbyaddingsuitableamountofREandN.Tohighcarbonequivalent(CE)gr... 相似文献
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Pig iron ingot molds manufactured with flake, compacted graphite cast iron, and spheroidal graphite cast iron were installed
on a pig iron casting machine and subjected to thermal cycling for studying thermal fracture endurance of the three cast irons.
The effects of graphite morphology on the fracture mechanism were analyzed by examining the fracture patterns, microstructures,
and microcracks in the failed molds. The determining factors of thermal fracture endurance were elucidated with thermal fracture
resistance indices. Compacted graphite cast iron exhibited better thermal fracture endurance than flake and spheroidal graphite
cast irons because of its higher strength-to-thermal stress ratio. 相似文献
13.
Addition of rare earth(RE)such as Y in the surface layer of gray cast iron or Ni-based superalloy by lasersutface melting was carried out using a 2 k W CO_2 laser.For delivering the element Y to the metal surface dur-ing laser irradiation,several methods were employed.It is found that Y-containing surface modified layer can hecontrollably obtained on substrates,a gray cast iron can be laser surface-modified with Cr+Al-Y powder re-sulting in a thin layer of Fe-Cr-Al-Y alloy such as 30Fe40Cr27Al3Y. 相似文献
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This research studied the ambient (25 ‡C) and intermediate (150 ‡C) temperatures plane strain fracture toughness(K
Ic
) and crack growth rateda/dN vs stress-intensity variation (δK) behaviors of compacted graphite (CG) cast irons in an atmospheric environment. As-cast ferritic
irons with different percentages of compacted graphite (vermicularity) were produced by using insufficient amounts of spheroidizer.
Irons with pearlitic matrix were obtained by heat treating the as-cast structure. The results of fracture toughness testing
indicated that (1) for the same matrix, CG irons with higher vermicularity yielded lowerK
Ic
values, but their values were still much higher than those of gray (flake graphite) cast iron; (2) for the same vermicularity,
CG irons with pearlitic matrix exhibited higher fracture toughness values than those of ferritic matrix; (3) at intermediate
temperature (150 ‡C), the influence of vermicularity and matrix on fracture toughness is the same as at ambient temperature,
except that theK
Ic
values were all a bit lower (1 to 8 pet). From crack growth ratevs stress-intensity variation experiments, the Paris equationda/dN = C(δK)
n
was derived, where a smaller value of indicates better crack growth resistance of materials. Compacted graphite cast irons
with pearlitic matrix and/or greater vermicularity rendered highern values and, thus, inferior crack growth resistance. At elevated temperature, then values were all lower, indicating that the crack growth resistance was improved.
Formely a Graduate Student, Department of Materials Engineering, Tatung Institute of Technology. 相似文献
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EffectofREComplexInoculationontheFatigueWearBehavioursofHighChromiumCastIronWangJiubin(InstituteofIron&SteelResearch,AnshanIr... 相似文献
17.
Havva Kazdal Zeytin Ceylan Kubilay Hseyin Aydin Ali Aslan Ebrinc Bilal Aydemir 《钢铁研究学报(英文版)》2009,16(3):32-36
Ductile cast irons are used as high temperature materials in internal combustion engines,because they are microstructurally stable at high operating temperatures.SiMo granular graphite cast irons contain Fe2 MoC and M6C carbide precipitates due to their higher concentration of both silicon and molybdenum.The microstructure of these cast irons consists of carbides dispersed within the ferrite matrix.The microstructural change and the crack formation mechanism in manifolds produced from SiMo ductile iron are studied.Chemical analysis,optical and scanning electron microscope studies have been completed and evaluated. 相似文献
18.
Gray Cast Iron With Directional Graphite Flakes Produced by Cylinder Covered Compression Process 总被引:1,自引:0,他引:1
A new plastic deformation process for gray cast iron named cylinder covered compression (CCC) was developed. By CCC process, gray cast iron (GCI) specimens, which are embedded in steel cylinders, were hot compressed up to 80% reduction in height without the cracking problem. It was clearly observed that the uniform distribution of directional graphite flakes appeared after more than 45% reduction hot compression. The strength, ductility, and microhardness of GCI after 80% reduction deformation were significantly enhanced: the tensile strength varied from 117 MPa to 249 MPa, while the total elongation varied from 0 to 52%, and the microhardness varied from 153 HV to 217 HV. It was shown that the tensile fracture surface presented ductility characters after more than 45% reduction hot deformation. 相似文献
19.
Oscar A. Ruano Lawrence E. Eiselstein Oleg D. Sherby 《Metallurgical and Materials Transactions A》1982,13(10):1785-1792
Superplastic properties of three different composition white cast irons were investigated in the temperature range of 630
to 725 °C. Fine structures consisting of 1 to 2 μm ferrite grains were developed in these materials by consolidation of rapidly
solidified powders at intermediate temperatures below the A1 critical temperature. Tensile elongations of 1410 pct were found for a 3.0 pct C + 1.5 pct Cr white cast iron, 940 pct for
a 3.0 pct C white cast iron, and 480 pct for a 2.4 pct C white cast iron when tested at 700 °C and at a strain rate of 1 pct
per minute. The superplastic white cast irons exhibited a high strain rate sensitivity exponent,m, of 0.5 and activation energies for plastic flow were found to be nearly equal to the activation energy for grain boundary
self-diffusion in iron. These observations are in agreement with the creep behavior of superplastic materials controlled by
grain boundary diffusion.
OSCAR A. RUANO, formerly with the Department of Materials Science and Engineering, Stanford University.
LAWRENCE E. EISELSTEIN, formerly with the Department of Materials Science and Engineering, Stanford University. 相似文献
20.
D. W. Kum G. Frommeyer N. J. Grant O. D. Sherby 《Metallurgical and Materials Transactions A》1987,18(10):1703-1711
Superplastic behavior of two commercial grade white cast irons, eutectic Fe-C and Ni-Cr white cast irons, was investigated
at intermediate temperatures (650 to 750 °C). For this purpose, rapidly solidified powders of the cast irons were fully consolidated
by compaction and rolling at about 650 °C. The volume fractions of cementite in the eutectic cast iron and in the Ni-Cr cast
iron were 64 pct and 51 pct, respectively, and both cast irons consisted of fine equiaxed grains of cementite (1 to 2 μm)
and ferrite (0.5 to 2 μm). The cast iron compacts exhibited high strain-rate sensitivity (strain-rate-sensitivity exponent
of 0.35 to 0.46) and high tensile ductility (total elongation of 150 pct to 210 pct) at strain rates of 10-4 to 10-3 s-1 and at 650 °C to 750 °C. Microstructure evaluations were made by TEM, SEM, and optical microscopy methods. The equiaxed grains
in the as-compacted samples remained unchanged even after large tensile deformation. It is concluded that grain boundary sliding
(e.g., along cementite grain boundaries in the case of the eutectic cast iron) is the principal mode of plastic deformation in
both cast irons during superplastic testing conditions.
Formerly with the Department of Materials Science and Engineering, Stanford University
Formerly Visiting Scholar, Department of Materials Science and Engineering, Stanford University 相似文献