Influence Of Titanium Research Articles

Influence of titanium and nitrogen on hot ductility of C–Mn–Nb–Al steels

The influence of small additions of titanium on the hot ductility of C–Mn–Nb–Al steels has been examined. Titanium and nitrogen levels varied in the ranges 0·014–0·045 and 0·004–0·011 wt-%, respectively, so that a wide range of Ti/N ratios could be studied. The tensile specimens were cast and cooled at average cooling rates of 25, 100, and 200 K min-1 to test temperatures in the range 1100–800°C and strained to failure at a strain rate of 2 × 10-3 s-1. It was found that ductility in the titanium containing niobium steels improved with a decrease in the cooling rate, an increase in the size of the titanium containing precipitates, and a decrease in the volume fraction of precipitates. Coarser particles could be obtained by increasing the Ti/N ratio above the stoichiometric ratio for TiN and by testing at higher temperatures. However, ductility was generally poor for these titanium containing steels and it was equally poor when niobium was either present or absent. For steels with ∼0·005 wt-%N ductility was very poor at the stoichiometric Ti/N ratio of 3·4 : 1. Ductility was better at the higher Ti/N ratios but only two of the titanium containing niobium steels gave better ductility than the titanium free niobium containing steels and then only at temperatures below about 950–900°C. One of these steels had the lowest titanium addition (0·014 wt-%), thus limiting the volume fraction of fine Ti containing particles and the other had the highest Ti/N ratio of 8 : 1. However, even for these two steels ductility was worse than for the titanium free steels in the higher temperature range. The commercial implications of these results are discussed.

Efficacy of micronized titanium dioxide-containing compounds in protection against UVB-induced immunosuppression in humans in vivo

Micronized pigment-containing sunscreens may provide a good alternative to chemical sunscreens in protection against ultraviolet (UV) B-induced immunosuppression. The metal particles in these products are likely to remain on the skin surface where they can offer broadband protection for both the UVA and UVB regions. We have tested the protective capacity of three titanium dioxide (TiO 2) -containing compounds in humans in vivo. The effect on sunburn cell formation has been investigated using transmission electron microscopy, while the mixed epidermal cell lymphocyte reaction (MECLR) has been used as a model for immunosuppression. Furthermore, the influence of titanium on the integrity of the stratum corneum barrier (intercellular lipids and desmosomes) has been examined using freeze fracture electron microscopy. We find that all three compounds protect against sunburn cell formation. The immunoprotection studies show that one of the three compounds does not prevent UVB-induced changes of the MECLR responses. Application of this compound without subsequent UVB irradiation also induces a significant decrease of the MECLR responses. Moreover, the same compound affects the intercellular lipid layers, and desmosomes cannot be detected. The deleterious effect of this compound is probably caused by an incomplete hydrolysis during the TiO 2 synthesis. Our findings indicate that micronized pigment-containing compounds can offer good protection against short-term UVB-induced immunomodulation in humans in vivo. However, accurate screening of the synthesis of these compounds is a prerequisite for their safe use as sunscreening agents in human subjects.

Effect of titanium on cast structure of high speed steel

High speed steel is a very difficult materialfor shape casting owing to the formation of eutectic carbide networks during its solidification. These networks cause the steel to be brittle which is detrimental to the mechanical properties of tools manufactured from the material. In the present research, the effect of replacement of vanadium and tungsten by titanium as a modifier of the cast structure of AISI type M7 high speed steel has been investigated. The influence of titanium on eutectic cell size, eutectic volume per cent, and eutectic carbide shape and type has been determined. The modification effect of titanium on the microstructure was studied by scanning electron microscopy. The carbide type was found with the aid of energy dispersive X-ray and wavelength dispersive X-ray analysers. Hardness values for modified steels following various heat treatments were studied to enable the optimum titanium content to be determined.

Study of the Electric Field-Induced Low Temperature Phase in Pb(Mg1/3Nb2/3)O3: Titanium Influence

La variation en temperature de la constante dielectrique de ceramiques de composition (1 - x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 (0 ≤ x ≤ 0,1) est etudiee alors qu'un champ dc est applique a l'echantillon. La taille des regions ordonnees, parametre-cle pour comprendre la reponse du materiau, est reduite par l'introduction de titane. Une transition de phase ferroelectrique peut etre induite sous champ a partir de la phase cubique en moyenne. Si PMN est un relaxeur, ne transitant qu'a condition d'avoir E ≥ 4 kV cm -1 , la transition cubique → rhomboedrique devient spontanee pour PMN: 10 % Ti (a 280 K au refroidissement). De plus, pour tous les echantillons, la temperature T f , deduite de la relation de Vogel-Fulcher est systematiquement trouvee voisine de celle d'apparition de la phase polaire sous champ.

Influence of titanium and carbon contents on the hydrogen trapping of microalloyed steels

The presence of traps for hydrogen atoms influences the diffusivity and solubility of hydrogen itself in steels. In the present work, permeation measurements were carried out on hot-rolled microalloyed steels with different C and Ti contents in order to evaluate the number of irreversible and reversible traps. The number per unit volume of irreversible traps was correlated to calculated volume fraction of Ti(C,N) precipitates. These results, combined with microstructural investigations by transmission electron microscopy (TEM), showed that the largest number of irreversible traps was associated with steels having the largest volume fraction of fine and coherent Ti(C,N) precipitates. The reversible traps were associated with free Ti atoms, dislocations, and ferritic grain boundaries. Theoretical calculations confirmed the hydrogen binding energy of Ti free atoms (−27.1 kJ/mol).

Effect of substitution on nanostructure and dielectric properties in the perovskite Pb(Mg1/3Nb2/3)O3

Abstract The influence of titanium on the field-induced phase transition in PMN based ceramics is studied.

Columnar to equiaxed transition in high Cr white iron castings

The microstructure and properties of 17 wt.% Cr–2.9 wt.% C cast irons with up to 3.17 wt.% Nb additions, in both as-cast and heat treated state, have been studied. Also the influence of titanium and cerium on the structure and properties of 17 wt.% Cr–2.9 wt.% C-2 wt.% Nb alloys are examined. NbC carbides present in the structure of tested alloys, due to their characteristic morphology, show higher wear resistance and toughness than M7C3 carbides. Increasing amount of this type of carbides, caused by the increase of niobium in Fe–Cr–C–Nb alloys, contributes to the improvement of wear resistance and dynamic fracture toughness. The alloy containing approximately 3% Nb gives the best compromise between wear resistance and fracture toughness. This alloy shows about 30% greater dynamic fracture toughness and about 30% greater abrasion wear resistance than the basic Fe–Cr–C alloy. Titanium and cerium affect the crystallisation process of Fe–Cr–C–Nb alloys and the transformation of austenite during the cooling after solidification. The addition of 0.26% Ti results in a substantial change in the morphology and distribution of NbC carbides. The secondary carbides which precipitate in the matrix regions of the tested 17 wt.% Cr–2.9 wt.% C-2 wt.% Nb white iron containing titanium has an impact on the abrasion behaviour and fracture toughness. The alloy containing 0.28% Ti and 0.19% Ce has pearlite–austenitic matrix microstructure in as-cast condition. The pearlite, due to its high microhardness, improves the wear resistance under low-stress abrasion conditions, but drastically reduces the toughness of tested alloy.

Experimental evidence for a spontaneous relaxor to ferroelectric phase transition in [formula omitted] - 10% Ti

From X-ray diffraction, polarization and dielectric measurements, it is shown that a 0.9 Pb(Mg 1 3 Nb 2 3 )O 3 - 0.1 PbTiO 3 ceramic undergoes a zero-field rhombohedral phase transition. This material transforms spontaneously from a relaxor into a normal ferroelectric upon cooling. On such an observation, the influence of titanium on Pb(Mg 1 3 Nb 2 3 )O 3 based ceramics is discussed.

Influence of titanium on the structural stability of sputter-deposited W-Co-C films

A film of W 45Ti 9Co 12C 34 has been synthesized by non-reactive r.f. sputtering onto a steel substrate and heat treated in a high vacuum furnace at increasing temperatures up to 800°C. Investigation of its structure, hardness and adhesion is performed before and after each heat treatment. The results show that the presence of titanium in W-Co-C films promotes spontaneous crystallization and improves their thermal stability during annealing at increasing temperatures.

Influence of titanium on the static recrystallization of a medium carbon microalloyed steel

Static recrystallization kinetics of three medium carbon steels, microalloyed with vanadium and titanium (titanium varied from 0.003 to 0.039% in weight), were studied by hot torsion test simulation. A higher recrystallization time was observed in the steel with 0.019 wt% Ti. This difference in recrystallization time was checked by metallographic observations and mechanical softening. This time shift implies different activation energies, which were calculated by the time needed to obtain a 50% recrystallized structure and also by solving the Zener-Hollomon equation. Evolution of the kinetics of recrystallization as a function of temperature was also studied. In addition, the critical allowable temperature for a fully recrystallized structure was investigated.

The influence of titanium on the static recrystallization of hot deformed austenite and on induced precipitation kinetics

The influence of titanium on the static recrystallization of hot deformed austenite and on induced precipitation kinetics

Effect of the chemical composition of Fe‐Mn‐C‐P alloys on the brittle‐ductile transition temperature in the solidification range

The brittle‐ductile transition temperature in the solidification range depends on the composition of the phase which solidifies as the last one. The paper presents a thermochemical study of Fe‐Mn‐C‐P system, determining the conditions of crystallisation of carbides, phosphides and the pseudo‐ternary eutectic ML‐M3C‐M3P. Manganese raises the phosphorus concentration in eutectic. The eutectic temperature attains its maximum at about 6% of Mn. Then the brittle‐ductile transition temperature is about 30 K higher than in ternary Fe‐C‐P alloy. A further raise is possible when the alloy is modified by an element forming stable, solide carbide, for ex. titanium.The results of theoretical analysis were verified by experimental work. The influence of titanium on the inclusions appearing in the vicinity of hot cracks of Hadfield cast steel has been studied.

Ageing characteristics of rapidly solidified Al-Li-Ti alloys at 473 K

The influence of titanium on the δ′ precipitate free zones (PFZs) and on the stable δ phase is investigated in four melt-spun Al-Li-Ti alloys with ∼ 2 mass% lithium and 0.10–0.35 mass% titanium. Rapid solidification gives rise to a homogeneous distribution of titanium on the wheel side of the ribbons, and to a cellular distribution of solute atoms in intermediate regions and on the gas side. Heat treatments of up to 1000 h at 473 K do not modify titanium distribution, which remains in solid solution. During ageing, preferential coarsening of δ′particles occurs on cell walls. The growth rate of the δ′ PFZs is lower than in other Al-Li alloys and is mainly controlled by the titanium concentration of the alloys. The nucleation and growth of the stable δ phase is also delayed by the presence of titanium. These results indicate that the effect of titanium in solid solution is to retain vacancies thus reducing lithium diffusion rate.

Influence of titanium on hot ductility of as cast steels

The influence on hot ductility of a small addition (0·02%) of titanium to C–Mn–Al–Nb steel and 0·05/0·15%C–Mn–Al steels has been examined over the temperature range 700–1100°C and at a strain rate of 5×10−3 s−1. The tensile samples used were tested after melting, solidifying, and cooling directly to test temperature. The γ grain sizes at test temperature were coarse and were independent of titanium or carbon content. In niobium containing steel, little influence of titanium was observed when the cooling rate to test temperature was 100 K min−1, but a marked improvement of hot ductility was noted at a slower cooling rate of 25 K min−1. Examination of precipitate distributions suggests that at 25 K min−1, the niobium can precipitate out at high temperatures on the coarse TiN particles leaving less niobium available for precipitating during deformation in the temperature range 800–1000°C. In C–Mn–Al steels cooled at 60 K min−1 a very slight improvement of hot ductility due to the presence of titanium occurred, independent of carbon content. The improvement is considered to be due to titanium removing nitrogen from solution and preventing precipitation of the more detrimental AIN. Increasing the carbon content shifted the hot ductility trough to lower temperatures and increased its width. Both these observations are explained in terms of the change of transformation temperature which occurs with carbon content. The limitations of the hot ductility test in simulating the conditions present during the straightening operation in vertical continuous casting operations are discussed.MST/1368

Influence of titanium on hot ductility of as cast steels

The influence on hot ductility of a small addition (0·02%) of titanium to C–Mn–Al–Nb steel and 0·05/0·15%C–Mn–Al steels has been examined over the temperature range 700–1100°C and at a strain rate of 5×10−3 s−1. The tensile samples used were tested after melting, solidifying, and cooling directly to test temperature. The γ grain sizes at test temperature were coarse and were independent of titanium or carbon content. In niobium containing steel, little influence of titanium was observed when the cooling rate to test temperature was 100 K min−1, but a marked improvement of hot ductility was noted at a slower cooling rate of 25 K min−1. Examination of precipitate distributions suggests that at 25 K min−1, the niobium can precipitate out at high temperatures on the coarse TiN particles leaving less niobium available for precipitating during deformation in the temperature range 800–1000°C. In C–Mn–Al steels cooled at 60 K min−1 a very slight improvement of hot ductility due to the presence of titanium occurred, independent of carbon content. The improvement is considered to be due to titanium removing nitrogen from solution and preventing precipitation of the more detrimental AIN. Increasing the carbon content shifted the hot ductility trough to lower temperatures and increased its width. Both these observations are explained in terms of the change of transformation temperature which occurs with carbon content. The limitations of the hot ductility test in simulating the conditions present during the straightening operation in vertical continuous casting operations are discussed.MST/1368

The influence of titanium and oxygen vacancies on the chemical bonding in titanium oxide

The three TiO phases, alpha -, beta - and gamma -TiO, with stoichiometric composition, contain about 15% vacancies on both the Ti and the O sublattices. The low-temperature modification alpha -TiO, which is stable below 940 degrees C, crystallises in a monoclinic structure corresponding to the formal composition Ti0.833O0.833. In order to study the influence of the Ti and O vacancies on the chemical bonding in TiO, the related NbO structure, of formal composition Ti0.75O0.75 (Ti3O3), has been chosen as a model for the much more complicated real structure of TiO. This choice is based on the assumption that the model shows the essential effects with less computational effort. A self-consistent LAPW band structure calculation has been performed for the hypothetical TiO having the NbO structure. The calculated density of states and the local partial densities of states are compared with the corresponding data for stoichiometric TiO containing no vacancies, and for a model structure of TiO0.75 containing ordered O vacancies. A characteristic feature in Ti3O3 is the occurrence of an additional band caused by the O vacancies and of three further bands with predominant d character, in the energy region between the 'p band' and the 'd band' of TiO. This effect leads to the disappearance of the band gap between the 'p band' and the 'd band' existing in stoichiometric TiO.

Copolymerization of dienes with various unsaturated compounds on cis-regulating catalysts of the Ziegler-Natta type. Review

Some aspects of the copolymerization of the dienes with various unsaturated compounds on cis-regulating catalytic systems of the Ziegler type are considered Attention is focussed on the results of study of copolymerization under the influence of titanium, cobalt and lanthanide compounds. The effect of the nature of the transition metal and its ligand surroundings on the copolymerization constants and microstructure of the chain is examined.

Titanium distribution in multilayer oxide scales on oxidized INCOLOY 800H

Different samples of INCOLOY 800H were exposed up to 950 °C and 10 000 h to a gas atmosphere simulating exposure to steam reforming methane process gas. The results indicated the predominant role of titanium in the formation of the main reaction products. The influence of titanium could be described by the following modifications of the primary oxide phases: (1) changing the lattice parameters of Cr2O3 by small amounts of Ti, (2) formation of solid solution of the spinels MnCr2O4 and Mn2TiO4, and (3) existence of an additional Ti containing phase of ilmenite type. Furthermore, it was observed that (1) manganese was practically insoluble in the Cr2O3 and (2) after long annealing time manganese was lost.

On the Effect of Impurities on the Photovoltaic Behavior of Solar Grade Silicon: II . Influence of Titanium, Vanadium, Chromium, Iron, and Zirconium on Photovoltaic Behavior of Polycrystalline Solar Cells

Structural, electrical, and photovoltaic properties of single impurity doped polycrystalline silicon were investigated in order to forecast the behavior of more complicated impurity matrixes, like those deriving from upgrading MG silicon. To this purpose, silicon was doped with increasing amounts of titanium, vanadium, chromium, iron, and zirconium, and the diffusion length of minority carriers was measured as a function of the impurity concentration and microstructural features like grain boundaries (GB), dislocations, twins, and stacking faults. Results are displayed in three‐dimensional diagrams which permit observations on the dependence of simultaneously with the impurity concentration and with the total density of electrically active structural defects.

The effect of titanium and gallium on photosynthetic rate of algae

Abstract The influence of titanium (Ti) and gallium (Ga) on photosynthesis in synchronized algae (Anacystis nidulans) has been investigated. At moderately low concentrations, Ti and Ga enhanced photosynthetic oxygen evolution and a three‐fold increase in fructose‐1, 6‐bisphosphatase activity. In the presence of Ti, growth as determined by dry weight of Anacystis nidulans was increased, but not so influenced by Ga if the cultures were exposed to continuous illumination.