THE SOLIDIFICATION MICROSTRUCTURE OF BIOMEDICAL TITANIUM ALLOYS UNDER THE CENTRIFUGAL FORCE

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4685-4690
Author(s):  
ZIYONG CHEN ◽  
LIJUAN XU ◽  
ZHIGUANG LIU ◽  
YUYONG CHEN
Keyword(s):  
Centrifugal Force ◽  
Graphite Crucible ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Crystal Boundary ◽  
X Ray ◽  
Solidification Defects ◽  
Solidification Microstructures ◽  
Centrifugal Equipment ◽  
Graphite Mould

Two biomedical alloys, Ti -39 Nb -5.1 Ta -7.1 Zr ( TNTZ1 ) and Ti -35.3 Nb -5.1 Ta -7.1 Zr ( TNTZ2 ) were melted using LZ5 type centrifugal equipment for casting titanium. The solidification microstructures of TNTZ1 and TNTZ2 alloys cast in graphite crucible without centrifugal force are mostly big arborescent crystal with dispersed porosity in it. After pouring into a graphite mould under centrifugal force, the lower part of ingot showed mostly arborescent crystals with few equiaxed crystals, while the upper part of ingot is basically spherical equiaxed crystals. The solidification defects, such as dispersed pores were very difficult to find. Nb is supposed to refine the arborescent crystals. X-ray diffraction (XRD) analysis showed Ti -phase and Nb -phase existing in the above two alloys. The content of Ti was found relatively low in crystal interior and relatively high in crystal boundary. The content of Nb/Zr was uniform in whole microstructure.

Metastable Solid Solutions of Impurities in Silicon

1981 ◽  
Vol 7 ◽  
Author(s):  
J. S. Williams ◽  
K. T. Short
Keyword(s):  
High Resolution ◽  
Solid Solutions ◽  
Impurity Concentration ◽  
Rutherford Backscattering ◽  
Equilibrium Solubility ◽  
Furnace Annealing ◽  
Strain Effects ◽  
Crystal Boundary ◽  
Silicon Lattice ◽  
Supersaturated Solid Solutions

ABSTRACTHigh resolution Rutherford backscattering and channeling techniques have been used to investigate the formation and stability of supersaturated solid solutions of As, Sb, In, Pb, Tℓ and Bi implants in (100) silicon. In all cases nearsubstitutional solid solubilities far exceeding maximum equilibrium solubility limits can be achieved by furnace annealing at temperatures ≤ 600°C. Details of the recrystallisation process indicate that the maximum impurity concentration which can be incorporated onto silicon lattice sites may be controlled by impurity size and associated strain effects at the amorphous-crystal boundary during epitaxial regrowth.

Thermo-Mechanical Fatigue of Mar-M247: Part 1—Experiments

1990 ◽  
Vol 112 (1) ◽  
pp. 68-79 ◽  
Author(s):  
D. A. Boismier ◽  
Huseyin Sehitoglu
Keyword(s):  
Grain Boundary ◽  
Prediction Model ◽  
Life Prediction ◽  
Crack Nucleation ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Boundary Crack ◽  
Mechanical Fatigue ◽  
Nickel Based Superalloy ◽  
Life Prediction Model

Isothermal fatigue tests, out-of-phase and in-phase thermo-mechanical fatigue tests were performed on Mar-M247 nickel-based superalloy. The experiments were conducted in the temperature range 500°C to 871°C. Results indicate that the lives differ with strain-temperature phasing and with strain rate. The results of out-of-phase thermo-mechanical tests correspond well with strain-life data of isothermal tests conducted at the peak temperature (871°C). However, the in-phase thermo-mechanical results differed depending on the strain amplitude. Significant surface and crack tip oxidation and gamma prime depletion has been observed based on metallographic and Auger Spectroscopic analyses. These changes were measured as a function of time. The environment induced changes significantly influenced the fatigue lives in isothermal and out-of-phase thermo-mechanical fatigue cases. In these cases transgranular cracking was observed. Grain boundary crack nucleation and grain boundary crack growth dominated the in-phase thermo-mechanical fatigue cases. Based on these observations the requirements for a life prediction model are outlined. The life prediction model and the predictions are given in Part 2 of this paper.

Study on Erosion Resistance of Structural Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 1323-1326
Author(s):  
Chong Gao Bao ◽  
Wei Pan ◽  
He Zhuo Miao ◽  
Long Hao Qi
Keyword(s):  
Erosion Resistance ◽  
Failure Mechanisms ◽  
Ceramic Materials ◽  
Solid Particles ◽  
Failure Pattern ◽  
Structural Ceramics ◽  
Crystal Boundary ◽  
Binding Phase ◽  
Rotary Disk ◽  
Main Factors

The erosion resistance performances of high-Cr cast iron Cr15Mo3 and three kinds of structural ceramics, a-Al2O3, ZTA, Si3N4, were investigated in flowing suspensions of solid particles with a rotary disk erosion wear tester. The microcosmic failure mechanisms of their wear surfaces were analyzed. The results showed that the erosion resistance of Si3N4, ZTA, a-Al2O3 is 21.8, 8.2, 5.6 times than that of Cr15Mo3 respectively. For ceramic materials, toughness and strength are two main factors that affect erosion resistance rather than hardness. The wear rate of ceramic materials is in proportion to the strength and the biquadratic toughness. Due to erosion, Cr15Mo3 is worn out most in the whole, the erosion holes are very clear and its failure pattern is in “W” shape. The wear of ZTA and Al2O3 mainly occurs in the binding phase of the crystal boundary. Thus, the crystal grains are exposed, but without breaks and cracks. The failure pattern is in the shape of “U”. Si3N4 only loses some binding phase of the crystal boundary and the erosion surface is smooth.

Control of friction coefficient by applying electric fields across liquid crystal boundary films

Wear ◽  
1994 ◽  
Vol 175 (1-2) ◽  
pp. 143-149 ◽  
Author(s):  
Yoshitsugu Kimura ◽  
Ken Nakano ◽  
Takashi Kato ◽  
Shin Morishita
Keyword(s):  
Liquid Crystal ◽  
Friction Coefficient ◽  
Electric Fields ◽  
Crystal Boundary ◽  
Boundary Films

scholarly journals The change in lattice spacing at a crystal boundary

1928 ◽  
Vol 121 (787) ◽  
pp. 247-259 ◽  
Keyword(s):  
Surface Layer ◽  
Crystal Lattice ◽  
Lattice Spacing ◽  
Crystal Surface ◽  
Bragg Reflection ◽  
The Other ◽  
X Rays ◽  
Crystal Boundary ◽  
De Broglie Waves ◽  
Is Theory

Some recent experiments of Davisson and Germer on the scattering of electrons by a crystal have drawn attention to the conditions at a crystal boundary. In interpreting their results in terms of de Broglie waves, the authors have to postulate a contraction of the crystal lattice at the surface— in some cases of as much as 30 per cent.f It is, therefore, important that other independent methods should be devised to indicate what change (if any) takes place at a crystal surface. Unfortunately X-rays are unable to help in this respect as several hundred atomic layers are necessary to produce a Bragg reflection pattern ; nor is theory able to provide an answer in the case of metallic crystals such as are used by Davisson and Germer because little is known of the forces which hold a metal together. Certain other cases can, however, be considered theoretically, and these may indicate the order of the effect to be expected in metallic crystals. In this paper we consider the change in spacing at a (100) boundary of a crystal of the NaCl type, this boundary being considered because it is a natural plane of crystal. Two effects are to be anticipated: (1) a change of spacing between planes at the boundary; (ii) a change of spacing between atoms in the surface layer itself. These effects are considered separately and independently. Actually, of course, each affects the other, but this is assumed to be a correction of the second order.

The specific energy of crystal boundaries in tin

1950 ◽  
Vol 201 (1065) ◽  
pp. 210-215 ◽  
Keyword(s):  
Free Energy ◽  
Surface Energy ◽  
Specific Surface ◽  
Surface Free Energy ◽  
Specific Energy ◽  
Lattice Theory ◽  
Strong Support ◽  
Crystal Boundary ◽  
The Difference ◽  
Crystal Boundaries

Specimens of tin, consisting of three crystals of predetermined orientations, were prepared with various differences of orientation between two of the crystals. The equilibrium angles between the three boundaries were measured. Relative values of specific surface free energy were deduced from the angles, and it was found that the surface energy decreases progressively as the difference of orientation decreases below about 6°. The curve relating surface energy with differences of orientation extrapolates to zero surface energy at zero angle. The result is considered to provide strong support for the ‘transitional lattice’ theory of the crystal boundary.

Bridge Action of Double-Deck Films Interface Electrons

2012 ◽  
Vol 217-219 ◽  
pp. 1038-1042
Author(s):  
Zhi Guo Zhang
Keyword(s):  
Short Circuit ◽  
Sno2 Film ◽  
Boundary Scattering ◽  
Film Resistance ◽  
Crystal Boundary ◽  
Ito Film

When both SnO2 film and a-Si film with infinite square resistance are deposited on an ITO film, the square resistance of the ITO film notably decreases. This phenomenon is more remarkable, when an ITO film has large square resistance. We believe that the films are composed of spaced crystalline grains. The film resistance is due to crystal boundary scattering carriers. Smaller crystalline grain and greater distance to the crystal boundary lead to fiercer scattering. The crystalline grains of the SnO2 film and a-Si film short-circuit the spaced ITO grains to form bridges so interface electrons can flow trough.

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