Fatigue life of implants made of titanium nickelide-based alloys

Basic principles of predicting the fatigue life of implants of various types made from titanium nick-elide-based alloys are determined. They include an analysis of the results of preliminary clinical tests for determining the change in the implant shape during the functional displacements of a patient, the calculation of the strain from the change in the implant shape, the determination of conditions for rapid fatigue tests of implants, and the prediction of the fatigue life of the implants using the results of rapid fatigue tests of the implant material.     

Structural transformations and mechanical behavior in the premartensitic state of titanium nickelide-based alloys

The premartensitic structural evolution in and the mechanical properties of alloys based on titanium nickelide and other titanium-based intermetallics with a B2-type lattice are studied. The unique mechanical properties of titanium nickelide (anomalously high plasticity, superelasticity) are found to be caused by the realization of specific structural states (SRDO, IDS, R phase) and the formation of a domain nanostructure in the premartensitic state. The dynamics and crystallographic geometry of premartensitic phenomena determine the fine structure of the B2 phase and, quite often, the radical differences in the properties of intermetallic-based alloys with different degrees and systems of alloying.     

Titanium carbide-based carbide steels made of chips of titanium alloys

Properties and microstructure of carbide steels produced on the basis of titanium carbide are studied. Powdered TiC was obtained from chip wastes of the titanium alloys VT1-0, VT20, VT3-1, VT25, VT5-1, and OT4-1 in three ways: nitridingcarbidizing, double carbidizing, and oxidizing-carbidizing. It has been determined that presence of nitrogen deteriorates the properties of carbide steels. The high values of strength and hardness obtained by oxidizing-carbidizing and double carbidizing of VT5-1 alloy chips testify to the advisability of using such chips for producing carbide steels.Translated from Poroshkovaya Metallurgiya, No. 10, pp. 78–82, October, 1992.     

Optimization of the process of manufacture of diamond-containing composite materials based on titanium carbide-steel alloys

Conclusions A study was made of the conditions of production of tungsten-free composite materials by sintering in a high-pressure chamber and in vacuum. Good-quality nonporous specimens of titanium carbide-steel materials cannot be produced by hot pressing in graphite dies. The hardness of materials sintered in a HPC is higher (81–86 HRA) than that of materials sintered in vacuum (75–82 HRA.). Heat treatment slightly lowers it (to 77–85 HRA). The highest wear resistance is exhibited by vacuum-sintered materials. In alloys sintered in a HPC a directional orientation of the steel binder with titanium carbide grain inclusions was observed. In service tests the properties of composition diamond-containing materials based on titanium carbide-steel alloys were found to match those of Tvesal alloys-diamond-containing composites based on a tungsten-group hard metal.Translated from Poroshkovaya Metallurgiya, No. 7 (259), pp. 21–25, July, 1984.     

大直径钨镧合金锻造棒材性能研究

采用纳米掺杂方法制备了大直径钨镧合金棒坯,通过与纯钨对比,研究了不同氧化镧质量分数的钨镧合金棒坯烧结性能以及含质量分数1.0%纳米氧化镧粉掺杂的钨镧合金锻造棒材的室温性能和高温再结晶性能。结果表明:采用质量分数1.0%、1.5%和2.0%三种含量的纳米氧化镧粉掺杂烧结后,合金掺杂分布和晶粒组织均匀,随着氧化镧含量的增高,棒坯密度逐渐降低、晶粒数逐渐越多;1.0%氧化镧粉掺杂钨镧合金棒坯经过78.7%锻造变形量后,较纯钨棒材硬度值更高,金相组织更细、更均匀,车加工后车削较长,表面光洁度较高,再结晶温度比纯钨高约150℃。     

Structural and hydraulic characteristics of porous materials made of VT6 titanium alloy fibers

The structural and hydraulic characteristics (maximum, average, and hydraulic pore diameters, permeability, and sinuosity of the pore channels) have been studied in materials made of discrete VT6 alloy fibers obtained by rapid solidification of a melt. The materials have structural parameters that are similar to those in materials made from smooth cylindrical fibers or powders and are superior in regard to permeability.Institute of Material Sciences, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5/6, pp. 85–89, May–June, 1995.     

Mechanisms of phase and structural transformations and texture formation in titanium alloy sheet semiproducts

Inverse pole figures are used to analyze texture formation in sheet semiproducts made from titanium alloys of various classes. The role of the mechanisms of phase and structural transformations in texture formation has been revealed. A VT6 alloy is used as an example to study the texture formation during hot, warm, and cold rolling of high-alloy α + β titanium alloys. Hot rolling followed by cooling is shown to form the β → α transformation texture. Warm or cold rolling of α + β titanium alloys leads to the (0001)〈hkio〉 deformation texture of the α phase, and subsequent annealing in the two-phase field results in the transformation texture with a strictly determined orientation distribution of α-phase crystallites due to the shear mechanism of α-phase nucleation. Specifically, the 〈10\(\overline 1 \)0〉 orientation is parallel to the rolling direction, the [0001] direction is parallel to the transverse direction, and the {11\(\overline 2 \)0} planes are parallel to the rolling plane. Thermohydrogen treatment in combination with rolling is shown to form nano-and submicrocrystalline structures with a virtually textureless α phase in VT6 sheet semiproducts. As a result, the anisotropy of the mechanical properties of the sheet semiproducts produced by this new combined hydrogen technology decreases sixfold.     

The use of self-propagating high-temperature synthesis and argon-arc overlaying when strengthening the surface of products made of titanium alloys

A new method for the deposition of protective coatings (wear-resistant overlaying) that are 2 to 10 mm thick and more on the surface of titanium articles is suggested, developed, approved, and patented. The method, called “SHS-arc overlaying,” combines the exothermic synthesis of adding material (AM) and argon-arc overlaying, which proceed simultaneously with the deposition of the coating. AMs made of exothermic mixtures are developed. Using this new method, protective composite coatings for titanium articles are obtained. The physicochemical, microstructural, and exploitation properties of the overlaying are investigated. Its operational characteristics exceed the characteristics of standard samples by a factor of 1.5–2.0. This new technology can be recommended for the deposition of protective coatings on products of wide indentation made of titanium alloys.     

A new class of electric-spark coatings for articles made of titanium alloys for use in extreme conditions

The formation, structure, composition, and properties of electric-spark coatings on titanium alloys (VT 6, VT 20) obtained with the use of hard-alloy electrode materials (EM) on the basis of titanium carbide and boride, as well as nanodispersed tungsten carbide are considered. The peculiarities of the mass transfer of EM on VT 20 grade titanium alloy when the parameters (current strength, frequency, and duration) of the pulsed current discharge vary are investigated. The optimum power mode of the electric-spark treatment of the Ti alloy by new EMs (I = 175 A, f = 800 Hz, and = τ μs) are determined. Investigations of the structure, phase composition, and properties (such as continuity; thickness; microhardness; friction coefficient; and wear-, heat-, and fretting resistance) of formed electric-spark coatings are carried out. Their phase composition and topography are investigated after high-temperature treatment (at 600°C for 100 h). It is shown that electric-spark treatment by new hard-alloy EMs improves the properties of electric-spark coatings on VT 20 titanium alloy compared to similar coatings obtained with the use of widely spread electrodes VK8, T15K6, and relit.     

Determination of the thermophysical properties of titanium alloys from liquid bath profiles

An experimental–theoretical technique is proposed to determine the thermophysical properties of titanium alloys in the liquid phase. This technique is based on analyzing the liquid bath profiles in fully solidified ingots after vacuum arc remelting (VAR). The experimental part of the technique makes it possible to easily estimate liquid bath contours without any markers, such as radioactive isotopes. The theoretical part is based on solving the inverse heat conduction problem for a solidifying ingot. The developed technique is used to determine some thermophysical parameters of the liquid bath and boundary conditions for VAR of titanium alloys Ti–6Al–4V, Ti–5Cr, and Ti–3Fe, since it is extremely difficult to measure them directly.     

X-ray-line-profile analysis of titanium alloys

X-ray-line-profile analysis has been used to investigate the dislocation structures resulting from severe plastic deformation in a series of titanium alloys. The effect of oxygen level (up to 0.33 wt pct) on the dislocation arrangements in titanium as well as in a series of titanium-aluminum alloys (4, 6, and 9 wt pct Al) was the principal thrust of the investigation. Although correlations were found between the stacking fault probability and alloying elements, the dislocation arrangements can not be interpreted solely in terms of stacking fault energies. Short-range order definitely plays an important role, and solute-dislocation interactions may be active.     

钛合金的环保电化学抛光工艺

针对航空用钛合金开发了一种不采用氢氟酸、甲醇、铬酐类等有毒物质的低毒、无刺激、环保型电化学抛光工艺,并采用光学显微镜、原子力显微镜等方法对电化学抛光后的钛合金表面形貌进行研究.该工艺所用溶液由无水乙醇、乳酸、高氯酸和高氯酸钠组成,将Ti-10V-2Fe-3Al钛合金在直流电源恒电流模式下电化学抛光,可以通过改变抛光时间、电流密度和高氯酸浓度等参数控制腐蚀深度.分别在体积分数为5%,10%和15%的三种高氯酸溶液中和在20,25和30 A·dm^-2三个电流密度下进行电化学抛光.抛光后的钛合金表面形貌观察结果表明:在高氯酸含量较低(5%)的溶液中以20 A·dm^-2电流密度抛光可以取得较理想的效果.     

Methodological aspects of the quantitative texture analysis of HCP Alloy (Ti,Zr) sheet semiproducts

The specific features of the existing methods of quantitative texture analysis of semiproducts and products made of titanium and zirconium alloys are analyzed. A technique is proposed to determine the Kearns coefficients (f parameters) for sheets made of hcp-metal-based alloys with allowance for the weighting factor of each reflection in the standard stereographic triangle. The f parameters calculated for sheets made of a zirconium alloy and various titanium alloys using different techniques are compared. The accuracy of measuring the Kearns coefficients by the inverse pole figure method is estimated.