A special metastable phase of metallic glass Pd77.5Ni6Si16.5

1988 ◽  
Vol 109 (1) ◽  
pp. K1-K2 ◽  
Author(s):  
Zongquan Li ◽  
Hui Shen ◽  
Lanping Yue ◽  
Yizhen He
Keyword(s):  
Metallic Glass ◽  
Metastable Phase

scholarly journals Devitrification of Zr55Cu30Al15Ni5Bulk Metallic Glass under Heating and HPT Deformation

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1329 ◽  
Author(s):  
Galina Abrosimova ◽  
Boris Gnesin ◽  
Dmitry Gunderov ◽  
Alexandra Drozdenko ◽  
Danila Matveev ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Metallic Glass ◽  
Metastable Phase ◽  
Hexagonal Structure ◽  
Crystalline Phases ◽  
Space Group ◽  
Activation Energy Of Crystallization ◽  
Nanocrystal Formation ◽  
Crystallization Stage

The nanocrystal formation in Zr55Cu30Al15Ni5 bulk metallic glass was studied under heat treatment and deformation. The activation energy of crystallization under heating is 278 kJ/mol. Different crystalline phases were found to be formed during crystallization under heating and deformation. At the first crystallization stage, the metastable phase with a hexagonal structure (lattice of space group P63/mmc with the parameters a = 8.66 Å, c = 14.99 Å) is formed under heat treatment. When the temperature rises, the metastable phase decays with the formation of stable crystalline phases. The crystalline Zr2Cu phase with the lattice of space group Fd3m is formed during crystallization under the action of deformation. It was determined that during deformation nanocrystals are formed primarily in the subsurface regions of the samples.

scholarly journals Tracking Metastable Phase Selection during Devitrification in a Metallic Glass

2019 ◽  
Vol 25 (S2) ◽  
pp. 1874-1875
Author(s):  
Lin Zhou ◽  
Fanqiang Meng ◽  
Shihuai Zhou ◽  
Kewei Sun ◽  
Tae-Hoon Kim ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Metastable Phase ◽  
Phase Selection

scholarly journals In situ correlation between metastable phase-transformation mechanism and kinetics in a metallic glass

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jiri Orava ◽  
Shanoob Balachandran ◽  
Xiaoliang Han ◽  
Olga Shuleshova ◽  
Ebrahim Nurouzi ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Metallic Glass ◽  
Metastable Phase ◽  
Equilibrium Composition ◽  
Phase Evolution ◽  
High Energy ◽  
High Temporal Resolution ◽  
Transformation Mechanism ◽  
Flash Annealing

AbstractA combination of complementary high-energy X-ray diffraction, containerless solidification during electromagnetic levitation and transmission electron microscopy is used to map in situ the phase evolution in a prototype Cu-Zr-Al glass during flash-annealing imposed at a rate ranging from 102 to 103 K s−1 and during cooling from the liquid state. Such a combination of experimental techniques provides hitherto inaccessible insight into the phase-transformation mechanism and its kinetics with high temporal resolution over the entire temperature range of the existence of the supercooled liquid. On flash-annealing, most of the formed phases represent transient (metastable) states – they crystallographically conform to their equilibrium phases but the compositions, revealed by atom probe tomography, are different. It is only the B2 CuZr phase which is represented by its equilibrium composition, and its growth is facilitated by a kinetic mechanism of Al partitioning; Al-rich precipitates of less than 10 nm in a diameter are revealed. In this work, the kinetic and chemical conditions of the high propensity of the glass for the B2 phase formation are formulated, and the multi-technique approach can be applied to map phase transformations in other metallic-glass-forming systems.

TEM study of order, structure and defects of β and martensite in Cu-Al-Mn shape memory alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 188-189
Author(s):  
J.M. Guilemany ◽  
F. Peregrin
Keyword(s):  
Shape Memory ◽  
Orthophosphoric Acid ◽  
Isopropyl Alcohol ◽  
Metastable Phase ◽  
Characteristic Temperature ◽  
Ethanol Solution ◽  
Order Structure ◽  
Thin Foils ◽  
Polycrystalline Alloys ◽  
Diamond Saw

The shape memory effect (SME) shown by Cu-Al-Mn alloys stems from the thermoelastic martensitic transformation occuring between a β (L2,) metastable phase and a martensitic phase. The TEM study of both phases in single and polycrystalline Cu-Al-Mn alloys give us greater knowledge of the structure, order and defects.The alloys were obtained by vacuum melting of Cu, Al and Mn and single crystals were obtained from polycrystalline alloys using a modified Bridgman method. Four different alloys were used with (e/a) ranging from 1.41 to 1.46 . Two different heat treatments were used and the alloys also underwent thermal cycling throughout their characteristic temperature range -Ms, Mf, As, Af-. The specimens were cut using a low speed diamond saw and discs were mechanically thinned to 100 μm and then ion milled to perforation at 4 kV. Some thin foils were also prepared by twin-jet electropolishing, using a (1:10:50:50) urea: isopropyl alcohol: orthophosphoric acid: ethanol solution at 20°C. The foils were examinated on a TEM operated at 200 kV.

A Metastable Crystalline Phase Coexisted with the Decagonal Quasicrystals in Rapidly Solidified Al-Ir Al-Pd and Al-Pt Alloys

1990 ◽  
Vol 48 (1) ◽  
pp. 572-573
Author(s):  
Wang Rong ◽  
Ma Lina ◽  
K.H. Kuo
Keyword(s):  
Metastable Phase ◽  
Hexagonal Phase ◽  
Icosahedral Quasicrystal ◽  
Decagonal Quasicrystal ◽  
Decagonal Phase ◽  
Decagonal Quasicrystals ◽  
Pt Alloy ◽  
Pt Alloys ◽  
Diffraction Patterns ◽  
Rapidly Solidified

Up to now, decagonal quasicrystals have been found in the alloys of whole Al-Pt group metals [1,2]. The present paper is concerned with the TEM study of a hitherto unreported hexagonal phase in rapidly solidified Al-Ir, Al-Pd and Al-Pt alloys.The ribbons of Al5Ir, Al5Pd and Al5Pt were obtained by spun-quenching. Specimens cut from the ribbons were ion thinned and examined in a JEM 100CX electron microscope. In both rapidly solidified Al5Ir and Al5Pd alloys, the decagonal quasicrystal, with rosette or dendritic morphologies can be easily identified by its electron diffraction patterns(EDPs). The EDPs of the decagonal phase for the two alloys are quite similar. However, the existance of decagonal quasicrystal in the Al-Pt alloy has not been verified by our TEM study. It is probably for the reason that the cooling rate is not great enough for the Al5Pt alloy to form the decagonal phase. During the TEM study, a metastable hexagonal phase has been observed in the Al5Ir, Al5Pd and Al5Pt alloys. The lattic parameters calculated from the X-ray powder data of this phase are a=1.229 and c=2.647nm(Al-Pd) and a=1.231 and c=2.623nm(Al-Ir). The composition of this phase was determined by EDS analysis as Al4(Ir, Pd or Pt). It coexists with the decagonal phase in the alloys and transformed to other stable crystalline phases on heating to high temperature. A comparison between the EDPs of the hexagonal and the decagonal phase are shown in Fig.l. Fig. 1(a) is the EDPs of the decagonal phase in various orientions and the EDPs of the hexagonal phase are shown in Fig.1(b), in a similar arrangement as Fig.1(a). It can be clearly seen that the EDPs of the hexagonal phase, especially the distribution of strong spots, are quite similar to their partners of the decagonal quasicrystal in Fig.1(a). All the angles, shown in Fig.l, between two corresponding EDPs are very close to each other. All of these seem strongly to point out that a close structural relationshipexists between these two phases:[110]//d10 [001]//d2(D) //d2 (P)The structure of α-AlFeSi is well known [3] and the 54-atom Mackay icosahedron with double icosahedral shells in the α-AlFeSi structure [4] have been used to model the icosahedral quasicrystal structure. Fig.2(a) and (b) show, respectively, the [110] and [001] projections of the crystal structure of α- AlFeSi, and decagon-pentagons can easily be identified in the former and hexagons in the latter. In addition, the optical transforms of these projections show clearly decagons and hexagons of strong spots, quite similar to those in [110] and [001] EDPs in Fig.1(b). This not only proves the Al(Ir, Pt, Pd) metastable phase being icostructural with the α-AlFeSi phase but also explains the orientation relationship mentioned above.

Structural analysis of a binary metallic glass model. I. — The Pd80Si20 alloy

1985 ◽  
Vol 46 (2) ◽  
pp. 235-241 ◽  
Author(s):  
F. Lançon ◽  
L. Billard ◽  
J. Laugier ◽  
A. Chamberod
Keyword(s):  
Structural Analysis ◽  
Metallic Glass ◽  
Glass Model
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