共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Saccone S. Delfino D. Macciò R. Ferro 《Metallurgical and Materials Transactions A》1992,23(3):1005-1012
The Er-Mg system was examined using differential thermal analysis (DTA), X-ray examination, metallography, and microprobe
analysis. Four intermediate phases are found to exist, and their crystal structures have been confirmed or determined as the
following:β phase (≈Er2Mg) (cubic, cI2-W type, peritectic formation 1255 °C); ErMg (cubic, cP2-CsCl type, peritectic formation 830 °C); ErMg2 (hexagonal, hP12-MgZn2 type, peritectic formation 670 °C); and Er5Mg24 (cubic, cI58-α-Mn type, peritectic formation 600 °C). Theβ phase undergoes a eutectoidal decomposition at 680 °C and 30.5 at. pct Mg. A eutectic reaction was observed to occur at 570
°C and 89.5 at. pct Mg. Comparisons of the general properties between the ErMg phases and with those of the other R-Mg compounds
(R = rare earth) are briefly discussed. Properties and structures of the R-Mg, R-rich alloys are specially considered and
compared with those of a few groups of rare-earth alloys. The alloying behavior of R-rich R-Me alloys (R = Ho, Er, Tm, Lu;
Me = Mg, Cd, In, Tl) is systematically presented and/or predicted. 相似文献
2.
R. M. Waterstrat 《Metallurgical and Materials Transactions B》1973,4(2):455-466
The system V-Pt was investigated over the entire composition range by metallography, X-ray diffraction and electron microprobe
studies. There are at least four equilibrium intermediate phases in this system and they are stable to progressively higher
temperatures with increasing vanadium concentration. The phases which have been observed are: γ′, cubic, Cu3Au type; θ, tetragonal, TiAl3 type; δ, orthorhombic, MoPt2 type; ζ, orthorhombic, AuCd type; and β, cubic, Cr3Si type (A15). The gg′ phase is possibly metastable. A very stable ribbon-like growth of ζ phase in the fcc platinum terminal solid solution has
been observed in alloys containing about 43 at. pct V. The platinum terminal solid solution forms a congruent melting maximum
at about 1805°C. A eutectic reaction occurs at 1720° ± 10°C and a peritectic reaction is indicated at 1800° ± 10°C. Vanadium
is soluble in the fcc platinum terminal solid solution up to about 57 at. pct at 1720°C. Platinum dissolves only to the extent
of about 12 at. pct at 1800°C in bcc α-V. 相似文献
3.
A. Saccone D. Macciò S. Delfino R. Ferro 《Metallurgical and Materials Transactions A》1999,30(5):1169-1176
The Nd-Au phase diagram was studied in the 0 to 100 at. pct Au composition range by differential thermal analysis (DTA), X-ray
diffraction (XRD), optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA).
Six intermetallic phases were identified, the crystallographic structures were determined or confirmed, and the melting behavior
was determined, as follows: Nd2Au, orthorhombic oP12-Co2Si type, peritectic decomposition at 810 °C; NdAu, R.T. form, orthorhombic oP8-FeB type, H.T. forms, orthorhombic oC8-CrB type and, at a higher temperature, cubic cP2-CsCl type, melting point 1470 °C; Nd3Au4, trigonal hR42-Pu3Pd4 type, peritectic decomposition at 1250 °C; Nd17Au36, tetragonal tP106-Nd17Au36 type, melting point 1170 °C; Nd14Au51, hexagonal hP65-Gd14Ag51 type, melting point 1210 °C; and NdAu6, monoclinic mC28-PrAu6 type, peritectic decomposition at 875 °C. Four eutectic reactions were found, respectively, at 19.0 at. pct Au and 655 °C,
at 63.0 at. pct Au and 1080 °C, at 72.0 at. pct Au and 1050 °C, and, finally, at 91.0 at. pct Au and 795 °C. A catatectic
decomposition of the (βNd) phase, at 825 °C and ≈1 at. pct Au, was also found. The results are briefly discussed and compared to those for the other
rare earth-gold (R-Au) systems. A short discussion of the general alloying behavior of the “coinage metals” (Cu, Ag, and Au) with the rare-earth
metals is finally presented. 相似文献
4.
M. Giovannini A. Saccone R. Marazza R. Ferro 《Metallurgical and Materials Transactions A》1995,26(1):5-10
Ternary Y-La-Mg alloys have been studied by X-ray diffraction, optical microscopy, scanning electron microscopy, and electron
probe microanalysis. Phase equilibria have been established in the isothermal section at 500 °C in the 50 to 100 at. Pct Mg
composition range. The sections (YxLa1-x) Mg (continuous solid solution), (YxLa1-xMg2 (cF24-Cu2Mg type for 0 ≤x ≤ 0.72 and hP12-MgZn2 type for 0.82 ≤x ≤ 1 solid solutions), and YxLa1-xMg3 (0 ≤x ≤ 0.47) have been especially studied. The ≈YxLa1-xMg5 (0.35 ≤x ≤ 0.77) ternary compound (cF440-GdMg5 type) has been found. A reinvestigation of selected regions of the binary La-Mg and Y-Mg systems proved necessary. The La5Mg41 phase, not previously reported, has been found by the annealing of samples at 600 °C. The YMg2 phase shows a wide homogeneity range up to 73 at. Pct Mg. The ternary section has been compared with a simulated one that
was created by placing sections of binary systems of Mg with different rare earth elements side by side. The results are related
to the pseudolanthanide concept. 相似文献
5.
R. M. Waterstrat B. C. Giessen RosemariE Koch R. C. Manuszewski 《Metallurgical and Materials Transactions A》1978,9(5):643-648
The Ta-Pd system was investigated over the entire composition range by metallography, X-ray diffraction and electron microprobe
analysis. The solubility limits of terminal and intermediate phases and solidus temperatures were determined. α-Ta dissolved
∼20 at. pct Pd at 2550°C and ∼10 at. pct Pd at 1000°C; α-Pd dissolves ∼22 at. pct Ta at 1730°C and ∼18 at. pct Ta at 1000°C.
The presence of four intermediate phases a, (β-U type), α-TaPd (TiCu type), TaPd2 (MoPt2 type), and TaPd3 (TiAl3 type) was confirmed; they melt or decompose (α-TaPd) at about 2550, 1410; 1800, and 1770°C, respectively. In addition, an
equiatomic high temperature phase, β-TaPd was found which melts at ∼1720°C and may be an extension of and isomorphous with
the α-Pd solution. Seven three-phase reactions are described.
Formerly with Massachusetts Institute of Technology 相似文献
6.
W. Duffy B. L. Cheng M. Gabbay G. Fantozzi 《Metallurgical and Materials Transactions A》1995,26(7):1735-1739
The internal friction (Qsu−1) and Young’s modulus (E) of BaTiO3-based ceramics were measured vs temperature from −100 °C to 150 °C. Rectangular bars of high-density (96 to 99 pct) ma-terials
were driven electrostatically in flexural vibration at a resonance frequency of about 3 kHz, at maximum strain levels of about
10−6. The curves ofQ
−1(T) andE(T) allow the study of the following three phase transformations: tetragonal to cubic (about 130 °C in pure material), orthorhombic
to tetragonal (about 0 °C in pure material), and rhombohedral to orthorhombic (about −80 °C in pure material). Internal friction
and modulus data were obtained on pure material and on materials doped with niobium and cobalt to give semiconducting and
insulating X7R behavior. Permittivity, dielectric loss, and microstructure data are given and used to aid interpretation of
the mechanical measurement data.
This article is based on a presentation given in the Mechanics and Mechanisms of Material Damping Symposium, October 1993,
in Pittsburgh, Pennsylvania, under the auspices of the SMD Physical Metallurgy Committee 相似文献
7.
M. Raghavan 《Metallurgical and Materials Transactions A》1977,8(7):1071-1078
Decomposition of a Cu-30 pct Ni-1 pct Nb alloy on aging in the range of 866 K (600°C) to 1073 K (800°C) was investigated.
The initial decomposition, concomitant with age hardening, occurred through the precipitation of body centered tetragonal
metastable Ni3Nb-γ” precipitates on the 100 matrix planes. Equilibrium orthorhombicβ phase formed either through a grain boundary cellular reaction at low temperature (≤973 K (700°C)) or as Widmanstaettenplatelets
on the 1ll planes at higher temperatures (≥1073 K (800°C)) with the following crystallographic relationship: (0l0)β//111γ [100]β//[1•11]γ. Based on the observations, a schematic transformation sequence is presented. 相似文献
8.
Precipitation sequences in a Cu-14 pct Al-4 pct Ni (wt pct) shape memory alloy were studied by means of transmission electron
diffraction and microscopy as well as X-ray microanalysis techniques. On aging thin foil specimens up to 550 °C in the electron
microscope, an as-quenched sample having a mixture of 2H-type and D03-type metastable structures transformed to the stable simple cubic γ2 phase at or above 450 °C. The remaining matrix either showed precipitates of the fcc α-phase on prolonged annealing at 500
to 550 °C for a longer period, or transformed to martensite on cooling below theM
s temperature (~150 °C). 相似文献
9.
The Nb-Pt system was investigated over the entire composition range by metallography and X-ray diffraction analysis. The solubility
limits of terminal and intermediate phases and solidus temperatures were determined. α-Nb dissolves ≈12 at. pct Pt at 2040
°C and ≈5 at. pct Pt at 1150 °C; α-Pt dissolves ≈20 at. pct Nb at 2000 °C and ≈ 18 at. pct Nb at temperatures below 1700 °C.
The presence of six intermediate phases, Nb3Pt (Cr3O, A15 or β-W type), σ(≈Nb2Pt, β-U type), Nb1−xPt1+x (AuCd type), α′-Pt (undetermined structure), NbPt2 (MoPt2 type), α-NbPt3 (TiCu3 type), and β-NbPt3 (β-NbPt3 type) was confirmed. The phase NbPt3 melts congruently at ≈2040 °C, and σ forms peritectically at ≈1800 °C. By analogy with related systems, the high-temperature
phase α′-Pt is probably an extension of and isomorphous with α-Pt solid solution. Eight three-phase reactions are described,
the mean atomic volumes are given, and crystal chemical relationships among the six homologous T5-T10 systems (T5 = V, Nb, Ta; T6 = Pd, Pt) are discussed. 相似文献
10.
J. Zhang D. B. Williams J. I. Goldstein 《Metallurgical and Materials Transactions A》1994,25(8):1627-1637
The low-temperature (<500 °C) decomposition of Fe-Ni martensite was studied by aging martensitic Fe-Ni alloys at temperatures
between 300 °C and 450 °C and by measuring the composition of the matrix and precipitate phases using the analytical electron
microscope (AEM). For aging treatments between 300 °C and 450 °C, lath martensite in 15 and 25 wt pct Ni alloys decomposed
with γ [face-centered cubic (fcc)] precipitates forming intergranularly, and plate martensite in 30 wt pct Ni alloys decomposed
with γ (fcc) precipitates forming intragranularly. The habit plane for the intragranular precipitates is {111}fcc parallel to one of the {110}bcc planes in the martensite. The compositions of the γ intergranular and intragranular precipitates lie between 48 and 58 wt
pct Ni and generally increase in Ni content with decreasing aging temperature. Diffusion gradients are observed in the matrix
α [body-centered cubic (bcc)] with decreasing Ni contents close to the martensite grain boundaries and matrix/precipitate
boundaries. The Ni composition of the matrix α phase in decomposed martensite is significantly higher than the equilibrium
value of 4 to 5 wt pct Ni, suggesting that precipitate growth in Fe-Ni martensite is partially interface reaction controlled
at low temperatures (<500 °C). The results of the experimental studies modify the γ/α + γ phase boundary in the present low-temperature
Fe-Ni phase diagram and establish the eutectoid reaction in the temperature range between 400 °C and 450 °C.
Formerly Research Assistant, Department of Materials Science and Engineering, Lehigh University 相似文献
11.
The constitution of the Pb-Sn-Sr system from the Pb-Sn binary up to 36 at. pct Sr was determined by differential thermal analysis,
metallography, microprobe analysis, and X-ray diffraction. Pb3Sr forms a continuous series of solid solutions with Sn3Sr, and is referred to here as the8 phase. Sn4Sr was the only other intermetallic phase found and is designated here as γ. A eutectic-like trough is formed between (Pb)
and δ. It originates at 1.0 at. pct Sr and 324.5 °C (the (Pb)/Pb3Sr eutectic) and falls monotonically to ~75 at. pct Pb, 24.5 at. pct Sn, and 0.45 at. pct Sr at 283 °C. At 283 °C, a Class
II, four-phase reaction occurs: L + δ→ (Pb) + γ. A eutectic-like trough between (Pb) and γ falls from the four-phase plane at 283 °C to the ternary eutectic at
~26 at. pct Pb, ~74 at. pct Sn and <0.3 at. pct Sr at 182 °C. The ternary eutectic reaction is L → (Pb) + (Sn) + γ. 相似文献
12.
This study is directed toward improvement of the ductility of long-range ordered alloys through control of their ordered crystal
structure. A series of ordered alloys was prepared with a base composition of Co3V, where Co was partially replaced with Fe and Ni. The stability and structure of the ordered phases in these (Fe,Co,Ni)3V alloys were characterized by various metallurgical methods. The results indicate that the ordered structure in this alloy
system can be controlled by adjusting the electron density, and that the L12 type cubic ordered structure (α′) is stable in the alloys with electron density less than 7.888. The phase relation in the
cubic ordered alloys depends on the Fe concentration. For the alloys containing <20 pct Fe, the disordered α solid solution
transforms to the cubic α′ ordered on the fcc lattice at temperatures below 1000°C. For the alloys containing >20 pct Fe,
the α′ is formed through a peritectoid reaction, namely, α+σ→α′. Tensile tests indicate that the alloys with multilayered
hexagonal ordered structure are very brittle, while the alloys with the cubic ordered structure are ductile at room temperature.
The ductility of the cubic ordered alloys increases with decreasing Co content. The alloys with <55 pct Co showed dimple type
ductile rupture with elongation over 40 pct at room temperature. The correlation of ductility with ordered structure is discussed. 相似文献
13.
B. C. Giessen N. J. Grant D. P. Parker R. C. Manuszewski R. M.Waterstrat 《Metallurgical and Materials Transactions A》1980,11(5):709-715
The Nb-Pd system was investigated over the entire composition range by metallography and X-ray diffraction analysis. The solubility
limits of terminal and intermediate phases and solidus temperatures were determined. α-Nb dissolves ∼36 at. pct Pd at. 1520°C
and ∼20 at. pct Pd at 800°C; α-Pd dissolves ∼31 at. pct Nb at 1610°C and ∼18 at. pct Nb at temperatures below 1500°C. The
presence of three intermediate phases NbPd2 (MoPt2-type), α-NbPd3 (TiAl3-type), and β-NbPd3 (β-NbPd3-type) was confirmed; NbPd2 melts at 1610°C and one of the NbPd3 phases transforms at the same temperature into α-Pd solid solution which melts at 1625°C. In addition, an approximately equiatomic
high-temperature phase α-NbPd with a homogeneity range of ∼11 at. pct was found which melts at 1520 to 1565°C and probably
is an extension of and isomorphous with the α-Pd solid solution. Five three-phase reactions are described, and crystal chemical
relationships are discussed.
D. P. PARKER formerly with MIT .
R. C. MANUSZEWSKI formerly with the ADAHF Research Unit at NBS. 相似文献
14.
W. F. Smith 《Metallurgical and Materials Transactions B》1973,4(10):2435-2440
The effect of reversion treatments on an Al-1.35 at. pct Mg2Si alloy fully age hardened for 24 h at 160°C was studied by electron microscopy and tension tests. This alloy aged to full
strength at 160°C did not show true reversion when heated 15 min at 200 to 300°C. The G.P. zones did not dissolve rapidly
at a particular temperature but instead were replaced by the more stable phase, β′ (the intermediate partially coherent form
of Mg2Si). After reheating the fully age hardened alloy 15 min at 250°C, a slight increase in strength was obtained, but the ductility
was slightly lowered. Reversion treatments at higher temperatures (275 to 300°C) gradually decreased the strength of the alloy.
Two simultaneous reactions are believed to occur during the reversion treatments: 1) the growth of some of the G.P. zones
and the dissolution of others and 2) the formation of needles of β′. 相似文献
15.
F. C. Levey M. B. Cortie L. A. Cornish 《Metallurgical and Materials Transactions A》2000,31(8):1917-1923
A gold alloy with 18 wt pct Cu and 6 wt pct Al undergoes a reversible displacive phase transformation between an incompletely
ordered L21 parent phase and a tetragonal product. The characteristics of these transformations were studied using acoustic emission,
dilatometry, X-ray diffraction, and metallography. The morphology of the transformation products, the structure of the parent
phase, and the generation of significant acoustic emission during the transformations indicate that they are at least quasi-martensitic,
if not martensitic, and that this system is an example of a β-phase shape-memory alloy (SMA). The onset temperatures of the transformations depend on the prior thermal history of the
sample. The martensite start (M
s
) temperature is between 30 °C and 20 °C. The system exhibits hysteresis and will revert to the parent phase when reheated,
with an austenite start (A
s
) temperature between 55 °C and 80 °C. However, freshly cast or solution-annealed and quenched samples of the alloy do not
transform to the tetragonal phase. Aging of such material at temperatures between 30 °C and 200 °C is required before they
will manifest the displacive transformation. The “martensite” phase is considerably more resistant to aging-induced stabilization
than that of most other SMAs. 相似文献
16.
A peritectic reaction between Mg bismuthide and Mg plumbide changes from an even to an odd reaction at 310 °C (0.14 wt pct
Bi and 4 wt pct Mg) owing to the incorporation of 1.6 wt pct Bi into Mg plumbide; this value was calculated from material
balances of equilibrium studies of this reaction and confirmed by direct analysis of crystals using a “Cameca Microbeam” electroprobe
microanalyzer. A model is presented in which an atom of Pb in the unit cell, 46 Mg2Pb Mg2Pb5, is replaced by an atom of Bi which gives a concentration of 1.63 to 1.71 wt pct Bi depending on the actual species of Mg
plumbide present. The phase boundary for double saturation with Pb and Mg plumbide, established from the data of equilibrium
tests, shows a minimum temperature of 251.8 °C at 0.008 wt pct Bi and 2.2 wt pct Mg. Alloys in the primary Pb phase field
adjacent to this boundary show undercooling to less than 248.5 °C followed by one or two sharp temperature increases to 250.5
°C, with the initiation of the removal of Bi when double saturation occurs giving a final liquid phase containing less than
0.001 wt pct Bi. Crystallization paths for alloys in the Mg plumbide phase field show a catatectic reaction and polymorphic
transformations in the intermetallic compound. The removal of Bi is dependent on the concentration of Bi and Mg in the initial
alloy. In systems containing sufficient Mg, a final alloy containing less than 0.001 wt pct Bi can be produced, and these
conditions have been used as the starting point for the development of a process for the removal of Bi from Pb. Finally, the
crystallization paths show there is a change in the thermal properties of the liquid alloy at 0.008 wt pct Bi which is independent
of the temperature and concentration of Mg, and further work is required to resolve this finding. 相似文献
17.
T. Hamajima G. Luetjering S. Weissmann 《Metallurgical and Materials Transactions B》1972,3(11):2805-2810
The influence of aluminum additions to a Ti-7 at. pet Mo alloy on the phase equilibria was investigated. The microstructures
of the alloys, Ti-7 pct Mo-7 pct Al and Ti-7 pct Mo-16 pct Al, were determined by light and electron microscopy. It was found
that with increasing aluminum concentration the formation of the metastable w phase was suppressed. In the Ti-7 pct Mo-16
pct Al alloy the β phase decomposed upon quenching by precipitating coherent, ordered particles having a B2 type of crystal
structure (β2). At low temperatures the equilibrium phases for this alloy were β + α+ β
2, whereas at high temperature (850° to 950°C) the Ti3Al phase was in two-phase equilibrium with the β phase. The four-phase equilibrium which exists at a temperature of about
550°C involves the reaction β + Ti3Al ⇌ α + β2.
G. LUETJERING, formerly Staff Member Materials Research Center, Allied Chemical Corp., Morristown, N. J., 相似文献
18.
N. Srisukhumbowornchai S. Guruswamy 《Metallurgical and Materials Transactions A》2004,35(9):2963-2970
The feasibility of obtaining [001] preferred texture in polycrystalline Fe85Ga15 and Fe85Al15 magnetostrictive alloys containing 1 mol pct NbC using a low-cost conventional thermomechanical processing approach is shown
in this work. Thermomechanical processing conditions examined consisted of a sequence of hot rolling, two-stage warm rolling
at 400 °C with intermediate anneal at 900 °C and texture anneal in the temperature range of 900 °C to 1300 °C for time periods
up to 24 hours. Textures present prior to and after texture annealing were characterized using orientation imaging microscopy
in a scanning electron microscope. In the case of Fe85Ga15 alloy with 1 mol pct NbC, the deformation-induced texture after a two-stage warm rolling consists of mixed {100} 〈110〉 and
{111} 〈110〉 type partial textures. Texture annealing of the Fe85Ga15 alloy with 1 mol pct NbC at 1150 °C for 2 hours changes the texture to a predominant texture that is close to {001}〈100〉.
On increasing the annealing time to 24 hours, the texture shifts toward {110}〈100〉. While texture anneal at both 1150 °C and
1300 °C produces a [001] or near-[001] preferred orientation along the rolling direction in the Fe85Ga15 alloy with 1 mol pct NbC, 1150 °C-24 hour treatment was found to provide the strongest [001] orientation among the conditions
examined. Similar trends are observed for the case of Fe85Al15 alloy with 1 mol pct NbC. 相似文献
19.
Metallographie, thermal, and X-ray techniques were used to determine the phase relations in the Nd-Zn system. Eight compounds,
three eutectics and a eutectoid were found. The compounds NdZn, NdZn2, and Nd2Znn melt congruently at 923°, 925°, and 981°C respectively. The compounds Nd3Zn11, NdZn4.46, and Nd3Zn22 undergo peritectic decomposition at 870°, 902°, and 950°C respectively, while NdZn3 undergoes peritectoid decomposition at 849°C. The eutectics occur at 12 wt pct Zn and 630°C, 38 wt pct Zn and 868°C, and
56 wt pct Zn and 854°C. The eutectoid occurs at 4 wt pct Zn and 622°C. The existence of a NdZn12 phase of the SmZn12 type structure has been confirmed. An allotropie transformation between the tetragonal NdZn11 structure and the hexagonal NdZn12 defect structure is proposed. 相似文献
20.
Moo-Chin Wang Nan-Chung Wu Sheng Yang Shaw-Bing Wen 《Metallurgical and Materials Transactions A》2002,33(1):171-181
Beta-spodumene (Li2O·Al2O3·4SiO2, LAS) powders were prepared by a sol-gel process using Si(OC2H5)4, Al(OC4H9)3, and LiNO3 as precursors and LiF as a sintering aid agent. Dilatometry, X-ray diffraction (XRD), scanning electron microscopy (SEM),
scanning transmission electron microscopy (STEM), and electron diffraction (ED) were utilized to study the sintering, phase
transformation, microstructure, and properties of the β-spodumene glass-ceramics prepared from the gel-derived precursor powders with and without LiF additives. For the LAS precursor
powders containing no LiF, the only crystalline phase obtained was β-spodumene. For the pellets containing less than 4 wt pct LiF and sintered at 1050 °C for 5 hours the crystalline phases were
β-spodumene and β-eucryptite (Li2O·Al2O3·2SiO2). When the LiF content was 5 wt pct and the sintering process was carried out at 1050 °C for 5 hours, the crystalline phases
were β-spodumene, β-eucryptite (triclinic), and eucryptite (rhombohedral (hex.)) phases. With the LiF additive increased from 0.5 to 4 wt pct
and sintering at 1050 °C for 5 hours, the open porosity of the sintered bodies decrease from 30 to 2.1 pct. The grains size
is about to 4 to 5 μm when pellect LAS compact contains LiF 3 wt pct as sintered at 1050 °C for 5 hours. The grains size grew to 8 to 25 μm with a remarkable discontinuous grain growth for pellet LAS compact contain LiF 5 wt pct sintered at 1050 °C for 5 hours.
Relative densities greater than 90 pct could be obtained for the LAS precursor powders with LiF > 2 wt pct when sintered at
1050 °C for 5 hours. The coefficient of thermal expansion of the sintered bodies decreased from 8.3 × 10−7 to 5.2 × 10−7/°C (25 °C to 900 °C) as the LiF addition increased from 0 to 5 wt pct. 相似文献