Microstructural changes observed in a rapidly solidified Ni3Al alloy during isothermal treatments

2000 ◽  
Vol 8 (2) ◽  
pp. 115-120 ◽  
Author(s):  
A.M Barros ◽  
J.A.S Tenório
Keyword(s):  
Microstructural Changes ◽  
Ni3al Alloy ◽  
Rapidly Solidified

Lüders bands formation in a rapidly solidified Ni3al alloy ribbon

1995 ◽  
Vol 43 (12) ◽  
pp. 4281-4287 ◽  
Author(s):  
G. González-Doncel ◽  
P. Adeva ◽  
M.C. Cristina ◽  
J. Ibáñez
Keyword(s):  
Alloy Ribbon ◽  
Ni3al Alloy ◽  
Rapidly Solidified ◽  
Lüders Bands

scholarly journals Complex Study of H-Induced Structural Rearrangements in FeZr Glasses

2012 ◽  
Vol 729 ◽  
pp. 509-514 ◽  
Author(s):  
Balázs Vehovszky ◽  
Pável Kamasa ◽  
Jozef Kováč ◽  
Zsolt Fogarassy
Keyword(s):  
Heat Treatment ◽  
Crystallization Temperature ◽  
Room Temperature ◽  
Relaxation Processes ◽  
Structural Rearrangements ◽  
Microstructural Changes ◽  
Complex Study ◽  
Rapidly Solidified

Microstructural changes and relaxation processes were examined in Fe-Zr based rapidly solidified samples. These phenomena occur far below crystallization temperature in the course of heat treatment, or even at room temperature, induced by absorbed hydrogen.

scholarly journals Microstructural Changes and Magnetic Properties of Nanostructured Fe-Si-B-Cu Ribbon Cores Containing a Small Amount of Ca and Zr

2021 ◽  
Vol 59 (3) ◽  
pp. 168-176
Author(s):  
Su-Bong An ◽  
Su-Hwan Jang ◽  
Won-Wook Park ◽  
Keun-Yong Sohn
Keyword(s):  
Magnetic Properties ◽  
Grain Boundaries ◽  
Flux Density ◽  
Grain Growth ◽  
Core Loss ◽  
Magnetic Flux Density ◽  
Magnetic Characteristics ◽  
Microstructural Changes ◽  
Minor Elements ◽  
Rapidly Solidified

Nanocrystalline Fe-Si-B-Nb-Cu Finemet alloys show low saturation magnetic flux density compared to amorphous Fe-Si-B alloys. In the Fe-Si-B-Cu base amorphous alloys, Cu atoms form clusters which act as heterogeneous nucleation sites for α-Fe crystals. The addition of Ca element atoms, distributed along grain boundaries, helps inhibit grain growth and increase resistivity. These alloys can be crystallized into fine nanograins through proper heat treatment, with increased saturated flux density and decreased core loss. According to previous studies, the addition of Zr element can also reduce nanograin size and suppress grain growth by its distribution mainly along the grain boundaries. In this experiment, the effects of added Ca and Zr on the microstructural changes and magnetic properties of Fe-Si-B-Cu were evaluated in detail. Fe-Si-B-Cu alloys containing Ca, and Zr elements were melt-spun to make rapidly solidified ribbons ~20 μm in thickness. The ribbons were then wound into toroidal shaped ribbon cores and heat treated to obtain the nanocrystalline soft magnetic ribbon cores. The microstructure was observed using TEM, and the magnetic characteristics were evaluated using an B-H meter and impedance analyzer. Based on the results, the FeSi-B-Cu ribbon core containing 0.037 wt.% Ca and 1.68 wt.% Zr was determined to have the lowest core loss among the alloys, when annealed at 440 <sup>o</sup>C for 30 min. It was also confirmed that the added Ca and Zr elements were distributed along the grain boundary, and suppress the growth of crystals. In conclusion, the addition of minor elements Ca and Zr to the nanocrystalline ribbon core was very effective at reducing core loss, and the saturated flux density of the core also increased pronouncedly compared to the Fe-Si-B-Nb-Cu Finemet alloys.

Phenomena Associated with Oxygen in Titanium

1967 ◽  
Vol 25 ◽  
pp. 310-311
Author(s):  
E. U. Lee ◽  
P. A. Garner ◽  
J. S. Owens
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Microstructural Changes ◽  
Electrolytic Polishing ◽  
Interstitial Impurities ◽  
Thin Foils ◽  
Transmission Electron ◽  
Iodide Titanium ◽  
Alpha Titanium

Evidence for ordering (1-6) of interstitial impurities (O and C) has been obtained in b.c.c. metals, such as niobium and tantalum. In this paper we report the atomic and microstructural changes in an oxygenated c.p.h. metal (alpha titanium) as observed by transmission electron microscopy and diffraction.Oxygen was introduced into zone-refined iodide titanium sheets of 0.005 in. thickness in an atmosphere of oxygen and argon at 650°C, homogenized at 800°C and furnace-cooled in argon. Subsequently, thin foils were prepared by electrolytic polishing and examined in a JEM-7 electron microscope, operated at 100 KV.

Suppression of γ’ Precipitation in a Laser-Melted Nickel-Base Alloy

1977 ◽  
Vol 35 ◽  
pp. 270-271
Author(s):  
J. M. Walsh ◽  
J. C. Whittles ◽  
B. H. Kear ◽  
E. M. Breinan
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Material Surface ◽  
Intimate Contact ◽  
Absorbed Power ◽  
Perfect Contact ◽  
Nickel Base ◽  
Rapidly Solidified ◽  
Limiting Case ◽  
The Heat Transfer Coefficient

Conventionally cast γ’ precipitation hardened nickel-base superalloys possess well-defined dendritic structures and normally exhibit pronounced segregation. Splat quenched, or rapidly solidified alloys, on the other hand, show little or no evidence for phase decomposition and markedly reduced segregation. In what follows, it is shown that comparable results have been obtained in superalloys processed by the LASERGLAZE™ method.In laser glazing, a sharply focused laser beam is traversed across the material surface at a rate that induces surface localized melting, while avoiding significant surface vaporization. Under these conditions, computations of the average cooling rate can be made with confidence, since intimate contact between the melt and the self-substrate ensures that the heat transfer coefficient is reproducibly constant (h=∞ for perfect contact) in contrast to the variable h characteristic of splat quenching. Results of such computations for pure nickel are presented in Fig. 1, which shows that there is a maximum cooling rate for a given absorbed power density, corresponding to the limiting case in which melt depth approaches zero.

On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder

1977 ◽  
Vol 35 ◽  
pp. 260-261
Author(s):  
J. M. Walsh ◽  
K. P. Gumz ◽  
J. C. Whittles ◽  
B. H. Kear
Keyword(s):  
The Other ◽  
Coarse Grained ◽  
Microcrystalline Structure ◽  
Routine Examination ◽  
Atomization Process ◽  
Centrifugal Atomization ◽  
Splat Quenching ◽  
Powder Particles ◽  
Dendritic Microstructures ◽  
Rapidly Solidified

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.

Lorentz electron microscopy of magnetic domains in rapidly solidified and annealed Pt-Co-B alloys

1991 ◽  
Vol 49 ◽  
pp. 784-785
Author(s):  
N. Qiu ◽  
J. E. Wittig
Keyword(s):  
Rapid Solidification ◽  
Ion Beam ◽  
Magnetic Behavior ◽  
High Coercivity ◽  
Magnetic Domains ◽  
Beam Angle ◽  
Tem Analysis ◽  
Intrinsic Coercivity ◽  
Hard Magnets ◽  
Rapidly Solidified

PtCo hard magnets have specialized applications owing to their relatively high coercivity combined with corrosion resistance and ductility. Increased intrinsic coercivity has been recently obtained by rapid solidification processing of PtCo alloys containing boron. After rapid solidification by double anvil splat quenching and subsequent annealing for 30 minutes at 650°C, an alloy with composition Pt42Co45B13 (at.%) exhibited intrinsic coercivity up to 14kOe. This represents a significant improvement compared to the average coercivities in conventional binary PtCo alloys of 5 to 8 kOe.Rapidly solidified specimens of Pt42Co45B13 (at.%) were annealed at 650°C and 800°C for 30 minutes. The magnetic behavior was characterized by measuring the coercive force (Hc). Samples for TEM analysis were mechanically thinned to 100 μm, dimpled to about 30 nm, and ion milled to electron transparency in a Gatan Duomill at 5 kV and 1 mA gun current. The incident ion beam angle was set at 15° and the samples were liquid nitrogen cooled during milling. These samples were analyzed with a Philips CM20T TEM/STEM operated at 200 kV.

Tensile Creep of Y-Si3N4: II. Cavitation

1991 ◽  
Vol 49 ◽  
pp. 972-973 ◽  
Author(s):  
B. J. Hockey ◽  
S. M. Wiederhorn
Keyword(s):  
Silicon Nitride ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Sintering Aids ◽  
Microstructural Changes

ATEM has been used to characterize three different silicon nitride materials after tensile creep in air at 1200 to 1400° C. In Part I, the microstructures and microstructural changes that occur during testing were described, and consistent with that description the designations and sintering aids for these materials were: W/YAS, a SiC whisker reinforced Si3N4 processed with yttria (6w/o) and alumina (1.5w/o); YAS, Si3N4 processed with yttria (6 w/o) and alumina (1.5w/o); and YS, Si3N4 processed with yttria (4.0 w/o). This paper, Part II, addresses the interfacial cavitation processes that occur in these materials and which are ultimately responsible for creep rupture.

Microstructural Variations in Melt-Spun Rapidly Solidified Ribbons

1985 ◽  
Vol 43 ◽  
pp. 54-55
Author(s):  
L. A. Bendersky ◽  
W. J. Boettinger
Keyword(s):  
Solid State ◽  
Processing Parameters ◽  
Heat Extraction ◽  
Solid State Reactions ◽  
Careful Examination ◽  
Ion Milling ◽  
Melt Spun ◽  
Wheel Side ◽  
Rapidly Solidified ◽  
Heat Extraction Rate

Rapid solidification produces a wide variety of sub-micron scale microstructure. Generally, the microstructure depends on the imposed melt undercooling and heat extraction rate. The microstructure can vary strongly not only due to processing parameters changes but also during the process itself, as a result of recalescence. Hence, careful examination of different locations in rapidly solidified products should be performed. Additionally, post-solidification solid-state reactions can alter the microstructure.The objective of the present work is to demonstrate the strong microstructural changes in different regions of melt-spun ribbon for three different alloys. The locations of the analyzed structures were near the wheel side (W) and near the center (C) of the ribbons. The TEM specimens were prepared by selective electropolishing or ion milling.

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