Study of R-phase transformation in a Ti–50.7at%Ni alloy by in-situ transmission electron microscopy observations

1999 ◽  
Vol 273-275 ◽  
pp. 186-189 ◽  
Author(s):  
W Cai ◽  
Y Murakami ◽  
K Otsuka
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Transmission Electron ◽  
Ni Alloy

Microstructural Characterization, Mechanical Properties and Wear Resistance of TiCP Reinforced Ni-Alloy Coatings by Laser Synthesis

2000 ◽  
Author(s):  
D. L. Tu ◽  
A. Kar ◽  
X. L. Wu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Wear Resistance ◽  
Chemical Reaction ◽  
Phase Interface ◽  
High Fracture Toughness ◽  
Transmission Electron ◽  
Ni Alloy ◽  
The Matrix

Abstract Titanium carbide particle (TiCp)-reinforced Ni alloy composite coatings are synthesized by laser cladding using a cw 3 kW CO2 laser. Two kinds of coatings are possible in terms of the origin of TiCp: undissolved TiCp and in-situ generated TiCp. The former originates from the TiCp pre-coated on the sample whereas the latter from in-situ chemical reaction between titanium and graphite in the molten pool during laser irradiation. For the coating reinforced by TiCp formed in-situ, the sub-micron TiCp particles are formed and uniformly distributed because of the in-situ reaction and trapping effect during rapid solidification. Graded distribution of TiCp is obtained on a macro scale. The volume fraction increases from 1.86% at the coating-substrate interface to 38.4% at the coating surface. For the coating reinforced by undissolved TiCp, analytical transmission electron microscopy (ATEM) and high resolution transmission electron microscopy (HRTEM) observations show the existence of the epitaxial growth of TiC, the precipitation of CrB and M23C6, and the chemical reaction between Ti and B elements around phase interfaces of undissolved TiCp. In the matrix near the phase interface of undissolved TiCp, the loading curve obtained by nanoindenter exhibits pop-in phenomena due to the plastic deformation of cracks or debonding of TiCp from the matrix. For TiCp generated in-situ, no pop-in mark appears, indicating high fracture toughness. Coating with TiCp generated in-situ exhibits higher hardness and modulus than the coating with undissolved TiCp at regions near the phase interface. The coating reinforced by TiCp generated in-situ also displays higher impact wear resistance and abrasive wear resistance compared to the coatings with undissolved TiCp and without TiCp respectively.

In situ Transmission Electron Microscopy and Nanoindentation Studies of Phase Transformation and Pseudoelasticity of Shape-memory Titanium-nickel Films

2005 ◽  
Vol 20 (7) ◽  
pp. 1808-1813 ◽  
Author(s):  
X.-G. Ma ◽  
K. Komvopoulos
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Shape Memory ◽  
Heating And Cooling ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Titanium Nickel ◽  
In Situ Heating

Transmission electron microscopy (TEM) and nanoindentation, both with in situ heating capability, and electrical resistivity measurements were used to investigate phase transformation phenomena and thermomechanical behavior of shape-memory titanium-nickel (TiNi) films. The mechanisms responsible for phase transformation in the nearly equiatomic TiNi films were revealed by heating and cooling the samples inside the TEM vacuum chamber. Insight into the deformation behavior of the TiNi films was obtained from the nanoindentation response at different temperatures. A transition from elastic-plastic to pseudoelastic deformation of the martensitic TiNi films was encountered during indentation and heating. In contrast to the traditional belief, the martensitic TiNi films exhibited a pseudoelastic behavior during nanoindentation within a specific temperature range. This unexpected behavior is interpreted in terms of the evolution of martensitic variants and changes in the mobility of the twinned structures in the martensitic TiNi films, observed with the TEM during in situ heating.

In-Situ High Resolution Transmission Electron Microscopy of Dynamic Events During the Amorphous to Crystalline Phase Transformation in Silicon

1985 ◽  
Vol 62 ◽  
Author(s):  
M. A. Parker ◽  
T. W. Sigmon ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Solid State ◽  
High Resolution ◽  
Elevated Temperatures ◽  
Video Recording ◽  
Dynamic Events ◽  
Transmission Electron

ABSTRACTA technique has been developed which employs high resolution transmission electron microscopy (HRTEM) for the observation of the atomic mechanisms associated with solid state phase transformation as they occur at elevated temperatures. It consists of the annealing in-situ of cross-section transmission electron microscopy (TEM) specimens that have been favorably oriented for lattice fringe imaging and the video-recording of dynamic events as they occur in real-time. By means of this technique, we report the first video-recorded lattice images of crystallographic defect motion in silicon, viz. the motion of dislocations and stacking faults, as well as the first such images of the atomic mechanisms responsible for the amorphous to crystalline (a-c) phase transformation, viz. heterogeneous nucleation of crystal nuclei, coalescence of crystal nuclei by co-operative atomic processes, ledge motion at the growth interface, and normal growth in silicon. This technique holds great potential for the elucidation of the atomic mechanisms involved in reaction kinetics in the solid state.

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