A microstructural study of rapidly solidified and heat-treated austenitic Fe–Mn−Al–Mo–W–Nb–C alloys

1995 ◽  
Vol 10 (6) ◽  
pp. 1371-1378 ◽  
Author(s):  
Kwan H. Han ◽  
Hyun E. Lee
Keyword(s):  
Solidification Process ◽  
Vacancy Defect ◽  
Treatment Schedule ◽  
Depletion Effect ◽  
Transmission Electron ◽  
Heat Treated ◽  
Melt Spun ◽  
The Matrix ◽  
Means Of Transmission ◽  
Rapidly Solidified

The microstructural characteristics of melt-spun and heat-treated austenitic Fe−28Mn−8.6Al−0.5Mo−0.7W−0.5Nb−1.1C (in wt. %) alloys have been investigated by means of transmission electron microscopy. The melt-spun alloy contained fine austenitic cells and some intercelluar Nb(C, N) precipitates. Detailed observations revealed fine {100} modulations in the matrix of the cells, as well as a concomitant L′I2 atomic ordering arising from it. These observations indicate that the onset of decomposition of the initial austenite phase occurred during the rapid solidification process. Aging of the melt-spun alloy at 823–1173 K produced various microstructures, including a general precipitation of Nb(C, N) in the matrix. On isochronal annealing for 1 h, this matrix Nb(C, N) precipitation commenced at 1073 K with the formation of metastable coherent K-carbide (K′) near cell boundaries. On annealing at temperatures above 1123 K, only the Nb(C, N) precipitates were formed, on a fine scale, being accompanied by the formation of precipitate-free regions in the vicinity of cell and grain boundaries. Both intercellular and matrix Nb(C, N) precipitates obeyed a cube-to-cube orientation relationship with austenite. The general matrix precipitation of Nb(C, N) and formation of precipitate-free regions are discussed in terms of a vacancy (defect)-depletion effect. Finally, it was demonstrated that, by employing a double heat-treatment schedule of annealing at 1173 K followed by aging at 823 K, a novel microstructure consisting of fine dispersoids of Nb(C, N) carbo-nitride, distributed over the matrix of {100} modulated structure, could be produced.

The effect of composition and cooling rate on the structure of rapidly solidified (Fe, Ni)3Al–C alloys

1989 ◽  
Vol 4 (1) ◽  
pp. 44-49 ◽  
Author(s):  
S. A. Myers ◽  
C. C. Koch
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Weight Percent ◽  
Quench Rate ◽  
Transmission Electron ◽  
Metastable Structures ◽  
Metastable Structure ◽  
The Matrix ◽  
Rapidly Solidified ◽  
Kinetics Of

There is controversy in the literature regarding the existence of the metastable γ′ phase with an ordered Ll2 structure in rapidly solidified Fe–Ni–Al–C alloys. In this study, the quench rate–metastable structure dependence was examined in the Fe–20Ni–8Al–2C (weight percent) alloy. The effect of silicon on the kinetics of phase formation was studied by adding two weight percent silicon to a base alloy of Fe–20Ni–8Al–2C. Samples were rapidly solidified in an arc hammer apparatus and examined by transmission electron microscopy. In the Fe–20Ni–8Al–2C alloy, the nonequilibrium γ′ and γ phases were found in foils 65 to 100 μm thick. At higher quench rates, i.e., thinner samples, the matrix was observed to be disordered fcc γ with K-carbide precipitates. Samples containing silicon were found to have a matrix composed of γ′ and γ structures when the foils were thicker than 40 μm. At higher quench rates, the matrix was disordered fcc γ with K-carbide precipitates. The nonequilibrium γ′ and γ structures are present in samples with or without silicon, but are observed at higher cooling rates with the addition of silicon. This sensitivity to cooling rate and composition in resulting metastable structures may explain the differences reported in the literature for these rapidly solidified materials.

The effect of ageing duration on the mechanical properties of Al alloy 6061-garnet composites

2001 ◽  
Vol 215 (2) ◽  
pp. 113-119
Author(s):  
S C Sharma
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Al Alloy ◽  
Destructive Testing ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Reinforcing Particle ◽  
Alloy 6061

A well-consolidated composite of Al alloy 6061 reinforced with 4, 8 and 12 wt% garnet was prepared by a liquid metallurgy technique, the composite was heat treated for different ageing durations (T6 treatment), and its mechanical properties were determined by destructive testing. The results of the study indicated that, as the garnet particle content in the composites increased, there were marked increases in the ultimate tensile strength, compressive strength and hardness but there was a decrease in the ductility. There was an improvement in the tensile strength, compressive strength, and hardness with ageing due to precipitation. Precipitation in Al alloy 6061, with and without garnet particulate reinforcement, was studied using transmission electron microscopy. The fracture behaviour of the composites was altered significantly by the presence of garnet particles and the crack propagation through the matrix, and the reinforcing particle clusters resulted in final fracture.

Rapidly solidified and thermally treated microstructures of beryllium-1wt.% Yttrium alloy

1988 ◽  
Vol 46 ◽  
pp. 782-783
Author(s):  
L. A. Jacobson ◽  
P.L. Martin ◽  
T. E. Mitchell
Keyword(s):  
Melting Point ◽  
Elevated Temperatures ◽  
Alloying Element ◽  
High Melting Point ◽  
Superplastic Behavior ◽  
Dilute Alloys ◽  
Arc Melting ◽  
Transmission Electron ◽  
Heat Treated ◽  
Rapidly Solidified

Renewed interest in the possible use of beryllium at elevated temperatures has led to the examination of several dilute beryllium alloys with elements that form high melting point beryllide intermetallic compounds. One such alloying element is yttrium, which forms a beryllide, YBe13, with a melting point of over 1900° C. This system has been reported to have a eutectic between Be and YBe13 at a composition under 1 wt% Y. 13 Dilute alloys in this system have been investigated as to their superplastic behavior.Samples were prepared by arc melting l0g buttons of Be-1wt% Y alloy, melting at least three times to promote homogeneity. Very small pieces of a button were then arc melted on a water cooled copper hearth and splat-quenched by means of a spring loaded hammer. Pieces of splat material were heat treated for 2h at 1000°C, and 3mm disks were punched out for subsequent twin jet electrolytic thinning and examination by transmission electron microscopy.

The structure of rapidly solidified Fe-Ni-Mo-Co-B ribbons

1989 ◽  
Vol 47 ◽  
pp. 290-291
Author(s):  
D. M. Vanderwalker
Keyword(s):  
Electron Microscopy ◽  
Cell Walls ◽  
Lattice Parameter ◽  
Rapid Solidification Processing ◽  
Solidification Processing ◽  
Casting Technique ◽  
Transmission Electron ◽  
Structural Applications ◽  
Melt Spun ◽  
Rapidly Solidified

Fundamental aspects of solidification can be examined by experimentation in rapid solidification processing. The structure produced depends on parameters such as cooling rate, degree of undercooling, heat flow, and growth rate. Rapidly solidified iron base alloys are being developed for structural applications.RSR I Fe-19.7Mo-14.4Ni-7.3Co-1.9Bwt % and RSR II Fe-15.0Ni-11.1Mo-7.4Co-0.84B wt% ribbons were melt spun by a jet casting technique. RSR I ribbons were annealed for one hour at 816°C.Specimens were prepared for transmission electron microscopy by punching 3 mm discs from ribbons and electropolishing in a methanol 5% perchloric acid solution.The TEM was performed on the JEM 200CX electron microscope.As solidified RSR I was found to be canposed of fine (7nm) polycrystalline α-Fe. There is evidence for the presence of Ni Mo and FeB (Fig.1). On annealing, the α-Fe transforms to γ-Fe and FeB2Mo2, with significant grain growth (Fig.2). The as-solidified RSR II contains cellular γ-Fe with fcc-Fe2 3B6 of lattice parameter a=l.067nm at the cell walls (Fig. 3).

Luminescence Properties of SnO2 Nanoparticles Dispersed in Eu3+ Doped SiO2 Matrix

2008 ◽  
Vol 8 (3) ◽  
pp. 1489-1493 ◽  
Author(s):  
R. S. Ningthoujam ◽  
V. Sudarsan ◽  
A. Vinu ◽  
P. Srinivasu ◽  
K. Ariga ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Sno2 Nanoparticles ◽  
Phase Segregation ◽  
The Other ◽  
Significant Extent ◽  
Sio2 Matrix ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Different Temperatures

SnO2 nanoparticles dispersed in Eu3+ doped silica (SnO2-SiO2:Eu3+) were prepared at a low temperature (185 °C) in ethylene glycol medium. Transmission electron microscopy studies on as-prepared samples have established that SnO2 nanoparticles having size of 4.6 nm are uniformly covered by the SiO2 matrix. Significant extent of exciton mediated energy transfer between SnO2 and Eu3+ ions in heat treated SnO2-SiO2:Eu3+ samples has been attributed to the diffusion of Eu3+ ions from the SiO2 matrix to the near vicinity of SnO2 nanoparticles and its incorporation in the SnO2 matrix. On the other hand, very weak energy transfer exists for SnO2:Eu3+ nanoparticles heated at different temperatures due to the phase segregation of Eu3+ ions from the matrix.

Evolution of Microstructure in Martensitic GX12CrMoVNbN9 – 1 Cast Steel after Low Cycle Fatigue

2013 ◽  
Vol 199 ◽  
pp. 418-423
Author(s):  
Grzegorz Golański ◽  
Joanna Kępa
Keyword(s):  
Low Cycle Fatigue ◽  
Cast Steel ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Tempered Martensite ◽  
Transmission Electron ◽  
The Matrix ◽  
The Mean ◽  
Means Of Transmission ◽  
Evolution Of Microstructure

The paper presents the results of microstructural research on GX12CrMoVNbN91 cast steel in the as-received condition (after heat treatment) and after the process of low cycle fatigue at room temperature. The microstructural tests were carried out by means of transmission electron microscope and completed with quantitative study determining: the mean diameter of subgrains, density of dislocations and shape factor. Performed research has proved that in both states: the as-received one, as well as after fatigue, the investigated cast steel is characterized by lath microstructure of tempered martensite with numerous precipitations of the M23C6 and MX type. Fatigue in the low cycle scope leads to the processes of recovery and polygonization of the matrix, as a result of a decrease in the dislocation density and an increase in the subgrain width. Intensity of these processes depends not only on the temperature of testing, but also on the level of total strain amplitude εac. Stability of the substructure of the examined cast steel depends on the morphology of precipitates of M23C6, precipitated on the boundaries of grains/subgrains.

scholarly journals Microstructure and Microhardness Evolutions of High Fe Containing Near-Eutectic Al-Si Rapidly Solidified Alloy

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Emad M. Ahmed ◽  
M. R. Ebrahim
Keyword(s):  
Length Distribution ◽  
Spherical Shape ◽  
Solidification Process ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fe Content ◽  
Melt Spun ◽  
Solid Solubility Extension ◽  
Rapidly Solidified

Al-11 wt.% Si-11 wt.% Fe (11.29 at.% Si-5.6 at.% Fe) melt was rapidly solidified into ribbons and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and microhardness technique. The Rietveld X-ray diffraction analysis was applied successfully to analyze microstructure and phase precipitations. On the basis of the aluminum peak shifts measured in the XRD scans, a solid solubility extension value of 1 at.% Si in α-Al was determined. SEM investigations confirmed presence of a spherical shape α-phase particles in addition to needle and spherical shape β-phase particles with contents of 1.1 wt.% and 10.1 wt.% as deduced by XRD analysis. During prolonged annealing process at 350°C/25 h, α-phase disappeared, β-phase content increased to 30 wt.%, and Si presence becomes more evident as deduced by XRD analysis. EDS analysis confirmed that these β particles observed in the as-melt spun alloy are of lower Fe content comparing to those usually observed in the as-cast counter-part alloy. Besides, the length distribution of needle shape β-particles has been shortened to be diverse from 1 to 5 μm. The as-melt spun ribbons exhibited enhancement of hardness to 277 HV and further increased during heat treatment (150°C/12 h) to 450 HV. This improvement of microstructure and hardness are the influence of microstructural refinement and modification obtained during the rapid solidification process.

scholarly journals Microstructure and Magnetic Properties of Grain Refined Pr2Co14B Melt-Spun Ribbons

2019 ◽  
Vol 5 (1) ◽  
pp. 6
Author(s):  
I. Nlebedim ◽  
M. Huang ◽  
K. Sun ◽  
L. Zhou ◽  
R. McCallum ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Anisotropy Field ◽  
Triple Junctions ◽  
Heat Treated ◽  
Melt Spun ◽  
The Matrix ◽  
Melt Spun Ribbons ◽  
Low Solubility ◽  
Microstructure And Magnetic Properties

The correlation between the grain refining effect of TiC on the microstructure of Pr2Co14B melt-spun ribbons and the magnetic properties is presented in this study. TiC enabled greater control of microstructure both in the as-spun and heat treated Pr2Co14B, compared with the material without TiC. As a result, coercivity of the sample with TiC was nearly twice that of the sample without TiC. In addition to Pr2Co14B, two other phases were found in the sample with TiC: one rich in Co and the other having a composition near PrCo2. TiC was found near the grain boundaries and at triple junctions. Also no Ti or C was found in the matrix phase indicating extreme low solubility of the elements when both are present with Pr2Co14B. As expected, both the samples with and without TiC have similar anisotropy field but the presence of room temperature non-ferromagnetic phases (TiC and PrCo2), caused a small decrease in magnetization of the sample with TiC although the romance of the isotropic materials were comparable.

Phase and lattice parameter relationships in rapidly solidified and heat-treated (Mn0.53Al0.47)100−xCx pseudo-binary alloys

1992 ◽  
Vol 7 (7) ◽  
pp. 1690-1695 ◽  
Author(s):  
C.T. Lee ◽  
K.H. Han ◽  
I.H. Kook ◽  
W.K. Choo
Keyword(s):  
Carbon Content ◽  
Cell Volume ◽  
Unit Cell Volume ◽  
Binary Alloys ◽  
Lattice Parameter ◽  
Unit Cell ◽  
Type I ◽  
Heat Treated ◽  
Melt Spun ◽  
Rapidly Solidified

The phase constitution and the lattice parameter relationships in the rapidly solidified and heat-treated (Mn0.53Al0.47)100−xCx pseudo-binary alloys (x = 0–6) have been investigated by means of x-ray diffraction and transmission electron microscopy. The melt-spun alloys contained a single ∊ phase (cph) with 0.63–4.0 at. % C, and below and beyond this carbon composition range small traces of γ2-MnAl and Al4C3 compounds were formed, respectively. The heat treatment of the melt-spun alloys at 823 K produced a single τ phase (ordered bct, CuAu type I, L10) with 0.63–3.6 at.% C. The c lattice parameter of the ∊ unit cell was observed to increase pronouncedly with the carbon content whereas that of the a-axis revealed no apparent change; the corresponding increase of the unit cell volume was taken to indicate an interstitial dissolution of the carbon atoms in the ∊ lattice. On the other hand, for the τ phase, the c lattice parameter increased markedly with the carbon content while the a parameter decreased slightly, so that a large increase of c/a ratio was produced. The lattice parameter data for the τ phase thus indicated an increase of the unit cell volume with the carbon content, providing new evidence that the carbon atoms dissolve interstitially in the bct lattice. In addition, it was deduced that the higher c/a ratio with increasing carbon content may arise from a preferential site occupation of the carbon atoms at a specific type of octahedral interstitial site lying in the manganese atom layers.

Deformation Mechanisms in TiAl-Based Alloys Containing Low Oxygen

1990 ◽  
Vol 213 ◽  
Author(s):  
S. Sriram ◽  
Vijay K. Vasudevan ◽  
Dennis M. Dimiduk
Keyword(s):  
Analytical Electron Microscopy ◽  
Deformation Mechanisms ◽  
Low Oxygen ◽  
Weak Beam ◽  
Transmission Electron ◽  
Heat Treated ◽  
Analytical Electron ◽  
The Matrix ◽  
Recent Developments ◽  
High Purity Alloy

ABSTRACTThe effects of oxygen on the deformation behavior of Ti-(48-52)Al alloys is reported. Two types of studies were conducted. In the first, high purity alloy buttons containing low oxygen (~250 ppm) were prepared, whereas in the second, alloys with additions of 1 at.% Er to scavenge the oxygen from the matrix were prepared. The alloys were heat treated to produce large grains and the microstructures characterized by analytical electron microscopy. Samples prepared from the heat treated alloys were electropolished and deformed in compression to a plastic strain of 1.0-1.5% at temperatures between 25 and 800°C and the yield stress measured. The morphology of deformation, that is, slip lines and the presence of twinning, was studied by optical microscopy and the dislocation structures were characterized by weak-beam imaging in the transmission electron microscope. The results of these various studies are presented and discussed in terms of recent developments regarding the factors that appear to control the dislocation structure and the mobility of dislocations.

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