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1.
Fusheng Pan Peidao Ding Aitao Tang Mitsuji Hirohashi Yun Lu D. V. Edmonds 《Metallurgical and Materials Transactions A》2004,35(9):2757-2766
The effects of silicon additions up to 3.5 wt pct on the as-cast carbides, as-quenched carbides, and as-tempered carbides
of high-speed steels W3Mo2Cr4V, W6Mo5Cr4V2, and W9Mo3Cr4V were investigated. In order to further understand these effects,
a Fe-16Mo-0.9C alloy was also studied. The results show that a critical content of silicon exists for the effects of silicon
on the types and amount of eutectic carbides in the high-speed steels, which is about 3, 2, and 1 wt pct for W3Mo2Cr4V, W6Mo5Cr4V2,
and W9Mo3Cr4V, respectively. When the silicon content exceeds the critical value, the M2C eutectic carbide almost disappears in the tested high-speed steels. Silicon additions were found to raise the precipitate
temperature of primary MC carbide in the melt of high-speed steels that contained d-ferrite, and hence increased the size of primary MC carbide. The precipitate temperature of primary MC carbide in the high-speed
steels without d-ferrite, however, was almost not affected by the addition of silicon. It is found that silicon additions increase the amount
of undis-solved M6C carbide very obviously. The higher the tungsten content in the high-speed steels, the more apparent is the effect of silicon
additions on the undissolved M6C carbides. The amount of MC and M2C temper precipitates is decreased in the W6Mo5Cr4V and W9Mo3Cr4V steels by the addition of silicon, but in the W3Mo2Cr4V
steel, it rises to about 2.3 wt pct. 相似文献
2.
3.
The effect of Na2O on the equilibrium phosphorous distribution ratio between slag and iron or iron alloys, LP, has been measured for CaO-SiO2, CaO-FeOr-SiO2 (CaO or 2CaO·SiO2 saturated), and CaO-Al2-SiO2 slags. The addition of Na2O to CaO-SiO2 slags significantly increases LP and the phosphate capacity. A 25 pct CaO-25 pct Na2O-SiO2 slag has a distribution ratio nearly two orders of magnitude greater than a comparable binary 50 pct CaO-SiO2 slag. For the CaO-saturated slags containing 40 wt pct FeOT, the addition of 6 wt pct Na2O increases LP by a factor of 5. For the 2CaO·SiO2-saturated CaO-FeOT-SiO2 slag, there is an optimum FeOr content (20 wt pct) for dephosphorization, and 10 wt pct Na2O increases LP by a factor of 2. For reducing slags typically used in ladle metallurgy for Al-killed steels (50 pct CaO-40 pct Al2O3-10 pct SiO2), as little as 3 wt pct Na2O increases LP by a factor of 100. The present results indicate that small additions of Na2O to conventional steelmaking slags can greatly improve dephosphorization.
Formerly Graduate Student, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University. 相似文献
4.
The structures and mechanical properties of a series of thermomechanically processed, direct-quenched martensitic 0.1C-1.4Mn-0.5Mo-B
steels containing from 0 to 0.24 wt pct va have been investigated and compared to those obtained after a conventional austenitizing-and-quenching
treatment. For all processing conditions, vanadium additions to the base composition are found to increase hardenability (ideal
critical parameter,D,); the largest effects (up to a 90 pct increase inD
I) are noted when samples are hot-rolled prior to direct quenching. Vanadium additions are also observed to provide significant
strengthening in the quenched-and-tempered condition as the result of the precipitation of fine V-Mo carbides. The strengthening
increment due to these precipitates is approximately 100 MPa/0.1 wt pct V over the range of vanadium additions examined. At
the same time, however, these precipitates reduce notch toughness; on the average, the 20 J transition temperature increases
by about 4 °C for each 10 MPa increment in yield strength. For the conditions examined, the best balance of strength and toughness
is obtained in direct-quenched samples which are control-rolled(i.e., rolling is completed below the austenite recrystallization temperature) prior to quenching. 相似文献
5.
Activities of boron in the binary Ni-B and the ternary Co-Fe-B melts have been directly determined by the electromotive force
(emf) measurement. A boron crystal was mainly used as the reference electrode, and a ternary 29 wt pct B2O3-42 wt pct CaO-29 wt pct Al2O3 oxide melt was used as the electrolyte. Large negative deviations from Raoult’s law have been found in both the binary and
the ternary systems. The activity of nickel has been calculated from the measured boron activity by means of the Gibbs-Duhem
equation. Standard Gibbs energies of formation of Ni3B (s), Fe2B (s), and Co3B (s) were estimated and compared with available data.
Formerly Graduate Student, Department of Metallurgy, The University of Tokyo. 相似文献
6.
G. R. Speich D. S. Dabkowski L. F. Porter 《Metallurgical and Materials Transactions B》1973,4(1):303-315
The effects of C (0.10 to 0.20 pct), Cr (0 to 3 pct), Mo (0 to 2 pct), and Co (0 to 8 pct) on the yield strength, toughness
(Charpy shelf energy), and tempering behavior of martensitic lONiCr-Mo-Co steels have been investigated. Variations in the
carbon content between 0.10 and 0.20 pct result in yield strengths between 160 and 210 ksi (1.1 and 1.45 GN/m2) when these steels are tempered at 900° to 1000°F (480° to 540°C) for times of 1 to 100 h. These steels exhibit a secondary-hardening
peak at 900° to 1000° F (480° to 540°C) where coarse Fe3C carbides are gradually replaced by a fine, dislocation-nucleated dispersion of (Mo, Cr)2C carbides. Maximum toughness at a given yield strength in these steels is only obtained when they are tempered for sufficiently
long times so that the coarse Fe3C carbides are completely dissolved. Molybdenum is primarily responsible for the secondary-hardening peak observed in these
steels. However, chromium additions do result in lower secondaryhardening temperatures and promote coarsening of the secondary-hardening
carbide. Best combinations of strength and toughness are obtained with steels containing 2 pct Cr and 1 pct Mo. Cobalt increases
the yield strength of these steels over the entire tempering range and results in a higher secondary-hardening peak. This
effect of cobalt is attributed to 1) a retardation in the rate of recovery of the dislocation substructure of the martensite,
2) the formation of a finer dispersion of secondary-hardening carbides, and 3) solid-solution strengthening. The finer dispersion
of secondary-hardening carbides in steels containing cobalt is favored by the finer dislocation substructure in these steels
since the (Mo, Cr)2C carbide is dislocation-nucleated. This fine dispersion of (Mo, Cr)2C carbide combined with the high nickel content accounts for the excellent combination of strength and toughness exhibited
by these steels. 相似文献
7.
Activities of boron in the binary Fe-B, Co-B, and Cu-B melts have been directly determined by the electromotive force (emf)
measurement. Boron-saturated liquid Cu-B alloy was used as the reference electrode and a ternary 28 wt pct Al2O3-29 wt pct B2O3-43 wt pct CaO oxide melt was used as the electrolyte. Deviations of the boron activities from Raoult's law have been found
largely negative for the Fe-B and Co-B systems but largely positive for the Cu-B system. Boron activities calculated from
the literature data have not been in good agreement with the measured data. Activities of iron, cobalt, and copper have been
calculated from the obtained boron activities by means of the Gibbs-Duhem equation. Some modifications to the liquidus curves
on the Fe-B and Co-B phase diagrams have been presented.
M. YUKINOBU, formerly Graduate Student, Department of Metallurgy, The University of Tokyo
S. GOTO, Professor, formerly with the Department of Metallurgy, The University of Tokyo 相似文献
8.
While superferritic stainless steels containing 29 pct chromium possess excellent resistance to corrosion, they may, under
certain conditions, be embrittled by the precipitation of intermetallic phases. The extent to which the precipitation reactions
can be retarded by alloying additions of aluminum and copper has been evaluated. It was found that additions of aluminum to
an Fe-29 pct Cr-4 pct Mo-1.5 pct Ni base alloy suppress the precipitation of the undesirable sigma and chi intermetallic phases,
but additions of up to 3 pct aluminum promote 475 ‡C embrittlement. Additions of copper slightly reduce the precipitation
of sigma and chi phases under most conditions but enhance 475 ‡C embrittlement. The resistance to corrosion in 10 pct H2SO4 and 10 pct FeCl3 was assessed. All the aluminum-containing alloys performed significantly better in H2SO4 than the base alloy; however, large additions of aluminum had a deleterious effect on the pitting resistance in FeCl3. Additions of copper improved the resistance to FeCl3 and lowered the rate of corrosion in the H2SO4 solution used. 相似文献
9.
W. M. Garrison 《Metallurgical and Materials Transactions A》1986,17(4):669-678
This paper discusses the effects of silicon and nickel additions on the mechanical properties of a 0.4 carbon low alloy steel.
The four experimental steels used in the study were obtained by making additions of 1.5 wt pct nickel and 2 wt pct silicon,
both separately and in combination, to a 0.4C/1.5Ni/1.0Cr/0.5Mn base steel. The base + Ni + Si steel, resulting from combined
nickel and silicon additions, has a yield strength of 1682 MN/m2 and impact and fracture toughnesses of 65 J and 115 MN/m3/2, respectively. The other three steels have comparable strength levels but more typical impact and fracture toughnesses of
about 30 J and 75 MN/m3/2, respectively. The microstructures of the four steels are almost identical. The only significant observed difference among
the four steels is that the sulfides in the base + Ni + Si steel are almost three times as large as those in the other three
steels. As the four steels have similar sulfide volume fractions, there is a similar difference in sulfide spacings. The improved
toughness of the base + Ni + Si steel is attributed to the increased sulfide spacing due to the influence of combined nickel
and silicon additions on the average sulfide size. 相似文献
10.
Wei Yan Ping Hu Lifen Deng Wei Wang Wei Sha Yiyin Shan Ke Yang 《Metallurgical and Materials Transactions A》2012,43(6):1921-1933
Nitride-strengthened, reduced activation, martensitic steel is anticipated to have higher creep strength because of the remarkable
thermal stability of nitrides. Two nitride-strengthened, reduced activation martensitic steels with different carbon contents
were prepared to investigate the microstructure and mechanical property changes with decreasing carbon content. It has been
found that both steels had the microstructure of full martensite with fine nitrides dispersed homogeneously in the matrix
and displayed extremely high strength but poor toughness. Compared with the steel with low carbon content (0.005 pct in wt
pct), the steel with high carbon content (0.012 pct in wt pct) had not only the higher strength but also the higher impact
toughness and grain coarsening temperature, which was related to the carbon content. On the one hand, carbon reduction led
to Ta-rich inclusions; on the other hand, the grain grew larger when normalized at high temperature because of the absence
of Ta carbonitrides, which would decrease impact toughness. The complicated Al2O3 inclusions in the two steels have been revealed to be responsible for the initiated cleavage fracture by acting as the critical
cracks. 相似文献
11.
Fujio Abe 《Metallurgical and Materials Transactions A》1995,26(9):2237-2246
The effect of carbide precipitation on creep and creep rate curves was investigated for 10Cr-30Mn austenitic steel containing
0.003 to 0.55 wt pct carbon. After solution annealing, the specimens were subjected to creep testing at 873 K for up to 30
Ms (8300 hours). In the low-carbon steels containing below 0.1 wt pct carbon, where carbide precipitation scarcely occurred,
the decrease in creep rate with time in the transient creep region was described by log έ = A - (1/3) log t, where A is a
constant depending on stress and carbon concentration. On the other hand, in the high-carbon steels containing above 0.2 wt
pct carbon, where extensive precipitation of M23C6 occurred, the creep rate decreased significantly at long times above 3 to 5 ks (1 hour), deviating from the preceding equation
for the low-carbon steels. The Johnson-Mehl equation with the time exponent n = 2/3 provided a reasonable approximation for
the significant decrease in creep rate at long times. This resulted from a stress-induced precipitation of M23C6 on dislocation lines produced by creep deformation. The rate constant of the Johnson-Mehl equation depended on carbon concentration
but not on stress levels examined. 相似文献
12.
D. G. Kolman J. F. Bingert R. D. Field 《Metallurgical and Materials Transactions A》2004,35(11):3445-3454
The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order
to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3,
6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having
a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less
than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility.
Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis
indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue
crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation
and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement
is partially responsible for increased embrittlement. 相似文献
13.
Understanding the viscous behavior of silica-based molten fluxes is essential in maintaining the reliability of steel casting
operations and in preventing breakouts. In particular, high concentrations of aluminum in recently developed transformation
induced plasticity (TRIP) and twinning induced plasticity (TWIP) steels tend to promote reduction of silica in the mold fluxes
that result in the formation of alumina, which in turn increases the viscosity. To counteract this effect, significant amounts
of fluidizers such as CaF2 and Li2O are required to ensure that mold fluxes have acceptable lubrication and heat transfer characteristics. The viscous behavior
of the slag system based on CaO-SiO2-12 wt pct Na2O with various concentrations of CaF2 and Li2O has been studied using the rotating spindle method to understand the effects on the viscosity with these additives. CaF2 additions up to 8 wt pct were effective in decreasing the viscosity by breaking the network structure of molten fluxes, but
CaF2 concentrations above this level had a negligible effect on viscosity. Li2O additions up to 2 wt pct were also effective in decreasing the viscosity, but the effect was comparatively negligible above
2 wt pct. Using Fourier transform infrared (FTIR) analysis of as-quenched slag samples, it was concluded that the viscosity
was controlled more effectively by changing the larger complex silicate structures of rings and chains than by changing the
amounts of simpler dimers and monomers. 相似文献
14.
Daniel P. Abraham Sean M. McDeavitt Jangyul Park 《Metallurgical and Materials Transactions A》1996,27(8):2151-2159
Stainless steel-zirconium alloys have been developed at Argonne National Laboratory to contain radioactive metal isotopes
isolated from spent nuclear fuel. This article discusses the various phases that are formed in as-cast alloys of type 304
stainless steel and zirconium that contain up to 92 wt pct Zr. Microstructural characterization was performed by scanning
electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), and crystal structure information was obtained by
X-ray diffraction. Type 304SS-Zr alloys with 5 and 10 wt pct Zr have a three-phase microstructure—austenite, ferrite, and
the Laves intermetallic, Zr(Fe,Cr,Ni)2+x. whereas alloys with 15, 20, and 30 wt pct Zr contain only two phases—ferrite and Zr(Fe,Cr,Ni)2+x. Alloys with 45 to 67 wt pct Zr contain a mixture of Zr(Fe,Cr,Ni)2+x and Zr2(Ni,Fe), whereas alloys with 83 and 92 wt pct Zr contain three phases—α-Zr, Zr2(Ni,Fe), and Zr(Fe,Cr,Ni)2+x. Fe3Zr-type and Zr3Fe-type phases were not observed in the type 304SS-Zr alloys. The changes in alloy microstructure with zirconium content have
been correlated to the Fe-Zr binary phase diagram. 相似文献
15.
T. J. Garosshen T. D. Tillman G. P. McCarthy 《Metallurgical and Materials Transactions A》1987,18(1):69-77
The boron and carbon levels of a P/M nickel base superalloy were systematically varied in order to determine the mechanisms
by which these elements strengthen the alloy, and their optimum concentration. Carbon levels were reduced to 20 ppm while
the boron level was varied from 0.02 to 0.10 wt pct. Carbon levels of 0.002 and 0.05 wt pct were also studied, while maintaining
a boron concentration of 0.02 wt pct. Zirconium levels were maintained at 0.06 wt pct. The resulting alloys were subjected
to identical heat treatments and examinedvia SEM, TEM, and STEM microscopy. The alloys were also subjected to tensile, creep, stress-rupture, and fatigue crack growth
tests. Results show that both carbon and boron have a strong influence on the formation of grain boundary precipitates, as
expected. Carbon was present as the MC and M23C6 type carbides, while boron combined to form an intergranular M3B2 boride. Boron and zirconium were observed to be critical to the alloys' mechanical properties, although boron levels above
the solubility limit resulted in no further improvement or debit in strength. Carbon additions resulted in no improvement
in properties, indicating the feasibility of a carbon-free P/M superalloy. The role of the minor element additions is discussed
in terms of both microstructural features and related strengthening mechanisms. 相似文献
16.
A. Inoue Y. Kojima T. Minemura T. Masumoto 《Metallurgical and Materials Transactions A》1981,12(7):1245-1253
By the rapid quenching technique, nonequilibrium Ni3Al-type compounds with high strength and hardness as well as large elongation have been found in Fe-Ni-Al-C and Fe-Mn-Al-C
systems. This formation region is limited to about 7 to 55 wt pct Ni, 3 to 9 wt pct Al and 0.8 to 2.4 wt pct C for Fe-Ni-Al-C
and to about 7 to 65 wt pct Mn, 3 to 9 wt pct Al and 0.8 to 2.4 wt pct C for Fe-Mn-Al-C. The Ni3Al-type compound has fine grains of about 1 to 10 μm in diam. Their Vickers hardness and yield strength increase with increase
in the amounts of carbon, aluminum or nickel and the highest values attain about 665 DPN and 1690 MPa for Fe-Ni-Al-C and 600
DPN and 1740 MPa for Fe-Mn-Al-C. Elongation increases with decrease in carbon or aluminum and attains about 11 pct for Fe-20
wt pct Ni-6 wt pct Al-1.2 wt pct C and 28 pct for Fe-20 wt pct Mn-8 wt pct Al-1.6 wt pct C. The good strength and ductility
of the Ni3Al-type compounds remain unchanged on tempering for 1 h until heated to about 750 K. Further, it has been found that the addition
of chromium, molybdenum or cobalt is effective for the improvement of mechanical properties and thermal stability of the compounds.
Thus, the use of materials containing Ni3Al-type compounds may be attractive for fine gage high-strength wire or plate applications.
Formerly Graduate Student of Tohoku University. 相似文献
17.
K. Han D. V. Edmonds G. D. W. Smith 《Metallurgical and Materials Transactions A》2001,32(6):1313-1324
Systematic research has been undertaken on the effects of single and combined additions of vanadium and silicon on the mechanical
properties of pearlitic steels being developed for wire rod production. Mechanical test results demonstrate that the alloy
additions are beneficial to the mechanical properties of the steels, especially the tensile strength. Silicon strengthens
pearlite mainly by solid-solution strengthening of the ferrite phase. Vanadium increases the strength of pearlite mainly by
precipitation strengthening of the pearlitic ferrite. When added separately, these elements produce relatively greater strengthening
at higher transformation temperatures. When added in combination the behavior is different, and substantial strength increments
are produced at all transformation temperatures studied (550 °C to 650 °C). The addition of silicon and vanadium to very-high-carbon
steels (>0.8 wt pct C) also suppresses the formation of a network of continuous grain-boundary cementite, so that these hypereutectoid
materials have high strength coupled with adequate ductility for cold drawing. A wire-drawing trial showed that total drawing
reductions in area of 90 pct could be obtained, leading to final tensile strengths of up to 2540 MPa in 3.3-mm-diameter wires. 相似文献
18.
Richard A. Parr Mary Helen Johnston 《Metallurgical and Materials Transactions A》1978,9(12):1825-1828
Microstructures are shown for directionally solidified Al-3.4 wt pct Bi alloys with 0.2 wt pct Fe and 0.6 wt pct Fe additions.
The third element causes the LI/SI
+ LII growth interface to become cellular. The bismuth forms at the cell nodes, appearing either as uniformly spaced arrays
of spheres in the case of 0.2 wt pct Fe, or as an irregular net-work in the case of 0.6 wt pct Fe. Changes in the growth conditions
which are known to control cellular structure are seen to have a similar effect on the bismuth spacing, with the cross sectional
spacing varying as the inverse ofG (Temperature gradient) .R (Growth rate). 相似文献
19.
S. K. Mishra P. K. P. Rupa S. K. Das V. Shcherbakov 《Metallurgical and Materials Transactions B》2006,37(4):641-647
A detailed investigation of the effect of alumina diluent on the Al2O3-TiB2/ZrB2 composite by self propagating high temperature synthesis (SHS) dynamic compaction was carried out. A dense composite could
be obtained and microstructure could be tailored and controlled by adding alumina as diluent during the SHS reaction. The
microhardness values decreased for 5 and 10 wt pct additions of alumna but increased for 15 and 20 wt pct additions. Hardness
is influenced by the different phases present and the grain size. 相似文献
20.
Vasudeo Barburao Tare Dieter Janke W. A. Fischer 《Metallurgical and Materials Transactions B》1978,9(4):399-402
The activity of oxygen in technically important nickel melts containing 15 wt pct cobalt and 5 wt pct molybdenum has been
determined at 1600‡C for various concentrations of chromium ranging from 0 to 30 wt pct and aluminum varying from 0 to 15
wt pct. The activity of oxygen was measured by an electrochemical technique using yttria-doped thoria electrolyte cells. The
results obtained are analyzed in terms of activity coefficients of oxygen as a function of aluminum and chromium contents
in the melts. Clear positive deviations of the experimentally determined from the calculated activity coefficients of oxygen
were found when aluminum was added to Ni-Co-Mo melts with or without chromium. From the results obtained in the range between
1 and 10 wt pct aluminum, the following equilibrium constants for the reaction 2 [Al] + 3 [O] ⇋ Al2O3 in the nickel based melts at 1600‡C were calculated: loga
0 =-2/3 log [pct Al] - 3.94 for 0 pct Cr loga
0 = -2/3 log [pct Al] - 4.21 for 10 pct Cr loga
0 = -2/3 log [pct Al] - 4.81 for 20 pct Cr loga
0 = -2/3 log [pct Al] - 5.06 for 30 pct Cr. 相似文献