Kinetics and Mechanism of the C49 to C54 Titanium Disilicide Polymorphic Transformation

1993 ◽  
Vol 320 ◽  
Author(s):  
Z. Ma ◽  
G. Ramanath ◽  
L.H. Allen
Keyword(s):  
Polymorphic Transformation ◽  
Structural Transition ◽  
Structural Characteristics ◽  
Kinetics And Mechanism ◽  
Orientation Relationships ◽  
Titanium Disilicide ◽  
Transmission Electron ◽  
Interphase Boundaries ◽  
Two Phases

ABSTRACTThe kinetics and mechanism of the C49 to C54 TiSi2 polymorphic transformation have been investigated in a temperature range from 660 to 720°C using in situ sheet resistance measurement and transmission electron microscopy. The kinetics results were correlated with the microstructural changes during the phase transformation. The main structural characteristics demonstrating the mechanism of the transformation were established by examining the nucleation and growth of the C54-TiSi2 in the polycrystalline C49-TiSi2 thin films. It was found that the C54 nuclei predominantly formed at grain edges (three-grain junctions) of the C49 phase and grew very fast by moving its incoherent interphase boundaries. Preliminary results have not revealed rigorous orientation relationships between the two phases. It is suggested that the C49 to C54 structural transition is massive in nature.

In situ TEM observations of melting in nanosized eutectic Pb-Cd inclusions embedded in Al

1996 ◽  
Vol 54 ◽  
pp. 986-987
Author(s):  
S. Hagège ◽  
U. Dahmen ◽  
E. Johnson ◽  
A. Johansen ◽  
V.S. Tuboltsev
Keyword(s):  
Electron Microscope ◽  
Melt Spinning ◽  
Ternary Alloys ◽  
Solid Matrix ◽  
Eutectic System ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Orientation Relationships ◽  
Transmission Electron

Small particles of a low-melting phase embedded in a solid matrix with a higher melting point offer the possibility of studying the mechanisms of melting and solidification directly by in-situ observation in a transmission electron microscope. Previous studies of Pb, Cd and other low-melting inclusions embedded in an Al matrix have shown well-defined orientation relationships, strongly faceted shapes, and an unusual size-dependent superheating before melting.[e.g. 1,2].In the present study we have examined the shapes and thermal behavior of eutectic Pb-Cd inclusions in Al. Pb and Cd form a simple eutectic system with each other, but both elements are insoluble in solid Al. Ternary alloys of Al (Pb,Cd) were prepared from high purity elements by melt spinning or by sequential ion implantation of the two alloying additions to achieve a total alloying addition of up to lat%. TEM observations were made using a heating stage in a 200kV electron microscope equipped with a video system for recording dynamic behavior.

scholarly journals Imaging the Polymorphic Transformation in a Single Cu6Sn5 Grain in a Solder Joint

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2229 ◽  
Author(s):  
Flora Somidin ◽  
Hiroshi Maeno ◽  
Xuan Tran ◽  
Stuart D. McDonald ◽  
Mohd Mohd Salleh ◽  
...  
Keyword(s):  
Solder Joint ◽  
Polymorphic Transformation ◽  
Structural Evolution ◽  
Real Space ◽  
Transformation Behavior ◽  
New Approach ◽  
Transmission Electron ◽  
Contrast Pattern ◽  
In Situ Observations

In-situ observations of the polymorphic transformation in a single targeted Cu6Sn5 grain constrained between Sn-0.7 wt % Cu solder and Cu-Cu3Sn phases and the associated structural evolution during a solid-state thermal cycle were achieved via a high-voltage transmission electron microscope (HV-TEM) technique. Here, we show that the monoclinic η′-Cu6Sn5 superlattice reflections appear in the hexagonal η-Cu6Sn5 diffraction pattern upon cooling to isothermal 140 °C from 210 °C. The in-situ real space imaging shows that the η′-Cu6Sn5 contrast pattern is initiated at the grain boundary. This method demonstrates a new approach for further understanding the polymorphic transformation behavior on a real solder joint.

Orientation Relationships in the System Nb-NbCr2

1997 ◽  
Vol 3 (S2) ◽  
pp. 707-708
Author(s):  
P. G. Kotula ◽  
K. C. Chen ◽  
D. J. Thoma ◽  
F. Chu ◽  
T. E. Mitchell
Keyword(s):  
Microstructural Characterization ◽  
Laves Phase ◽  
Orientation Relationships ◽  
Ion Milling ◽  
Two Phase ◽  
Laves Phases ◽  
Arc Melting ◽  
Transmission Electron ◽  
Structural Applications ◽  
Two Phases

Laves-phase intermetallics are of potential use as high-temperature structural materials. NbCr2-based C15-structured alloys are of particular interest for such applications. by themselves, Laves phases generally have poor ductility and fracture toughness at low temperatures. Two phase alloys (i.e., Laves phase and the ductile bcc phase) are considered more promising for structural applications. The orientation relationships between the two phases can contribute to the mechanical behavior of the material. In this study, observations of two different orientation relationships in a Nb-NbCr2 eutectic are discussed and compared with previous studies of the NbCr2 system, as well as the TiCr2 system.A Nb-NbCr2 eutectic alloy was prepared by arc-melting high-purity alloys followed by annealing at 1400°C for 100 h and then cooling at l°C/min. The complete details of the materials preparation have been given elsewhere. Specimens were prepared for observation in the transmission electron microscope (TEM) by cutting 3 mm discs with a coring saw, followed by dimpling and ion milling. Microstructural characterization was performed with a Philips CM30 TEM operating at 300 kV.

In situtransmission electron microscopy study of the thermally induced formation of δ′-ZrO in pure Zr and Zr-based alloy

2017 ◽  
Vol 50 (4) ◽  
pp. 1028-1035 ◽  
Author(s):  
Hongbing Yu ◽  
Zhongwen Yao ◽  
Fei Long ◽  
Peyman Saidi ◽  
Mark R. Daymond
Keyword(s):  
Electron Microscopy ◽  
Thin Foil ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Orientation Relationships ◽  
Thermally Induced ◽  
Thin Foils ◽  
Orientation Relations ◽  
Transmission Electron

This study reportsin situobservations of the formation of the δ′-ZrO phase, occurring during the annealing of transmission electron microscopy (TEM) thin foils of both pure Zr and a Zr–Sn–Nb–Mo alloy at 973 K in a transmission electron microsope. The lattice parameters of δ′-ZrO were measured and determined to be similar to those of the ω-Zr phase. The orientation relationship between the δ′-ZrO and α-Zr phases has been identified as either {(11 \overline{2}0)}_{\rm ZrO}//{(0002)}_{\alpha} and {[0002]}_{\rm ZrO}//{[11 \overline{2}0]}_{\alpha} or {(\overline{1}011)}_{\rm ZrO}//{(0002)}_{\alpha} and {[01{\overline 1}1]_{{\rm{ZrO}}}}//{[11{\overline 2}0]_\alpha} depending on the orientation of the α grain relative to the TEM thin-foil normal. The nucleation and growth of δ′-ZrO were dynamically observed. This study suggests a new and convenient way to study oxidation mechanisms in Zr alloys and provides a deeper understanding of the properties of the newly reported δ′-ZrO. Since δ′-ZrO has a Zr sublattice which is identical to that of ω-Zr, the orientation relationships between the α and δ′-ZrO phases may also shed light on the orientation relations existing between α- and ω-Zr, and hence α- and ω-Ti.

Phase separation in Fe9S10 crystal

1986 ◽  
Vol 44 ◽  
pp. 462-463
Author(s):  
Thao A. Nguyen ◽  
Linn W. Hobbs
Keyword(s):  
Low Temperature ◽  
Iron Sulfide ◽  
Temperature Phase ◽  
The Past ◽  
Transmission Electron ◽  
In Situ Heating ◽  
Two Phases ◽  
The Stability ◽  
Low Temperature Phase

The low temperature phase relation of iron sulfide compounds Fe1-xS, with composition ranging from FeS to Fe7S8, has been investigated extensively over the past several decades. Despite these efforts conflicting reports on the stability of low temperature phases still exist and major disagreements between proposed phase diagrams remain unresolved. In this paper we report preliminary findings of our effort to determine whether the low temperature iron sulfide compounds form a homologous series Fen-l,Sn n≥ 8 [1] or a solid solution [2]. We have examined the stability of iron sulfide crystal of composition Fe9S10 using in situ heating experiment and image contrast transmission electron microscopy. We have found that Fe9S10 decomposes to two distinct phases. These two phases are labelled as H and K phases.

Behavior of Heavy Plastic Deformation of Cu-15Cr-0.1Zr In Situ Composite

2009 ◽  
Vol 79-82 ◽  
pp. 2191-2194
Author(s):  
Yan Li ◽  
Xiao Hong Chen ◽  
Ping Liu ◽  
Lin Hua Gao ◽  
Bao Hong Tian
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
Cold Drawing ◽  
Degree Of Deformation ◽  
Transmission Electron ◽  
Fibrous Morphology ◽  
Two Phases ◽  
Relationship Of ◽  
The Relationship

The behavior of plastic deformation of Cu-15Cr-0.1Zr in-situ composite under different degree of cold drawing deformation was analyzed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that both Cu and Cr phases are elongated along cold drawn direction and appear a fibrous morphology; However, Cu phase shows a thread-like fibrous morphology and Cr phase shows a band-like fibrous morphology. The two phases have a coherent relationship of (111)Cu //(011)Cr; When the degree of deformation(ε)is equal to 6.43, the relationship shows// [111]Cu // [110]Cr //cold drawn direction. Furthermore, forming two different morphologies of Cu and Cr phases during cold drawing is also analyzed.

Nucleation and Growth of Triangular Prismatic Iron Carbides in Amorphous Films by In Situ Transmission Electron Microscopy

2011 ◽  
Vol 172-174 ◽  
pp. 959-964 ◽  
Author(s):  
Elizabeth Bauer-Grosse
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Carbon Content ◽  
Carbon Film ◽  
Nucleation And Growth ◽  
Orientation Relationships ◽  
Iron Carbides ◽  
Transmission Electron ◽  
Nucleation Sites

The crystallization mechanisms of sputtered Fe1-xCx amorphous thin films for three values of atomic carbon content x = 0.28, 0.30 and 0.32 are directly observed using hot stage transmission electron microscopy. Images recorded sequentially are used to track the change caused by heating. Observations concern the nucleation and the growth of iron carbides and their structural identification. Information is also given about their crystallochemistry. They belong to the family of interstitial carbides with carbon atoms located inside iron Triangular Prisms (TP). They are built either from TP Sheets (TPS) stacks deriving from the cementite θ-Fe3C or from TP Chains (TPC) arrangements deriving from the Eckström-Adcock Fe7C3 carbide. The sharp transition between dominant TPS and dominant TPC carbides formations is illustrated. Nucleation and growth processes of both types of carbides are discussed and focus is put on the TPC crystals. They are the first to be formed whatever carbon content of the specimen and really correspond to the dominant phase for the richest-carbon film. When they are less numerous, they can act as nucleation sites for TPS carbides and it is in situ illustrated during the crystallization of the poorest-carbon film where orientation relationships can be found between the TPC-Fe7C3 carbideand a TPS carbide close to the Hägg carbide χ-Fe5C2 The crystallization ofFe0.70C0.30 film corresponds to a particular case where TPC carbides and TPS carbides can coexist with the same composition.

Study on In Situ Synthesized Titanium Matrix Composites

2007 ◽  
Vol 561-565 ◽  
pp. 751-756
Author(s):  
Di Zhang ◽  
Jun Qiang Lu ◽  
Wei Jie Lu ◽  
Ji Ning Qin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Rare Earth ◽  
Hot Forging ◽  
Matrix Composites ◽  
Orientation Relationships ◽  
Titanium Matrix ◽  
Titanium Matrix Composites ◽  
Transmission Electron

In the present work, titanium matrix composites reinforced with TiB, TiC, and Re2O3 (Nd2O3 or Y2O3) were fabricated via common casting and hot-forging technology utilizing the chemical reaction between Ti, B4C (or C), rare earth (Re) and B2O3 through homogeneously melting in a non-consumable vacuum arc remelting furnace. In this work, Nd and Y were chosen as rare earth (Re) added in the in situ reaction. The thermodynamics of in situ synthesis reactions was studied. The results of X-ray diffraction (XRD) proved that no other phases appeared except for TiB, TiC and Re2O3. The microstructures of the composites were examined by optical microscopy (OM). The results showed that there were mainly three kinds of reinforcements: TiB whiskers, TiC particles and Re2O3 particles. The reinforcements were fine and were homogeneously distributed in the matrix. The interfaces of TiB-Ti and Y2O3-Ti have been examined by high-resolution transmission electron microscopy (HREM).Transmission electron microscopy (TEM) and selected area diffraction (SAD) were used to analyze the orientation relationships of TiB-Ti, Nd2O3-Ti, and Y2O3-Ti. The mechanical properties at room temperature improved with the addition of TiB whiskers and TiC particles although some reduction in ductility was observed. The (TiB+TiC)/Ti6242 composite with TiB:TiC=1:1 shows higher tensile strength and ductility.

Nanoscale Sn Inclusions in Al – Structure and Melting-Solidification Properties

1999 ◽  
Vol 580 ◽  
Author(s):  
E. Johnson ◽  
C.R.H. Bahl ◽  
V.S. Touboltsev ◽  
A. Johansen
Keyword(s):  
Size Dependence ◽  
Rutherford Backscattering Spectrometry ◽  
Lattice Parameters ◽  
Orientation Relationships ◽  
Size Dependent ◽  
Transmission Electron ◽  
The Matrix ◽  
Al Matrix ◽  
Melting And Solidification

AbstractAl-Sn surface alloys with 2-3 at.% Sn have been made by ion implantation of Sn in Al. The microstructure of the alloys consists of dense distributions of nanoscale Sn inclusions embedded in the Al matrix. For implantations carried out at 425 K the inclusions have sizes in the range from about 2 to 15 nm. The structure of the inclusions is tetragonal - the white Sn structure – with lattice parameters of a = 0.583 nm and c = 0.318 nm respectively, i.e. identical to the lattice parameters of bulk Sn. The inclusions grow in preferred alignment with the matrix and the most commonly observed orientation relationships is given by (100)Sn ||(111)Al and [010]Sn || [211]Al. The shape of the inclusions is partly faceted and partly rounded with larger flat facets on the {100}Sn/{111}Al interfaces. Melting and solidification of the inclusions, which have been studied by in-situ transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) in combination with channeling, shows a distinct hysteresis. Melting of the inclusions which is associated with a distinct premelting, takes place in the range from about 430 K to 485 K, i.e. significantly below the bulk melting point of 505 K. The premelting is size dependent and the smallest inclusions melt at the lowest temperatures. Solidification requires a substantial undercooling and takes place from around 400 K with a much weaker size dependence.

Edge-to-Edge Matching at Ti-TiH Interfaces: Kinetics of Hydride Growth and Clustering of Precipitates with Different Orientation Relationships

2011 ◽  
Vol 172-174 ◽  
pp. 242-247 ◽  
Author(s):  
Egle Conforto ◽  
Daniel Caillard
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Volume Expansion ◽  
Three Dimensional ◽  
Orientation Relationships ◽  
Edge Matching ◽  
Transmission Electron ◽  
Isotropic Distribution ◽  
Kinetics Of

The motion of steps during the growth of hydride precipitates has been observed by in situ transmission electron microscopy. Precipitates in different orientation relationships (OR) are shown to obey to the rules of three-dimensional edge-to-edge matching. They form clusters in order to realize a more isotropic distribution of the volume expansion, and to decrease their total elastic energy.

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