Fracture toughness of VT6ch titanium alloy

The change in fracture toughness of VT6ch titanium alloy bars under the influence of the structure factor and strengthening heat treatment is investigated. The advantages and disadvantages of various combinations of microstructure and mechaniical properties are analyzed.Translated from Problemy Prochnosti, No. 3, pp. 25–30, March, 1992.     

The influence of texture on superplasticity of the titanium alloy VT 6

This paper describes a specific influence of crystailographic texture on tensile properties of the titanium alloy VT6 under superplastic flow conditions. The texture effect has been examined on alloy states with identical microstructures but with different preferred grain orientations. Tests over wide temperature and strain-rate intervals have shown that the formation of a strong texture as a result of pretreatment of a titanium alloy leads to a decrease in flow stress, an increase in plasticity and a shift of the optimum strain-rate region to higher rates. Data on the effect of texture on the anisotropy of properties of the VT6 alloy are also presented. The present results suggest that the influence of preferred orientation on the characteristics of superplastic flow is a general phenomenon for finegrained superplastic materials.     

Influence of oxynitriding on the wear resistance of VT14 titanium alloy

We investigate the wear resistance of VT14 titanium alloy after oxynitriding realized by modifying nonstoichiometric titanium nitride by oxygen. It is shown that the oxide component in an oxynitride coating improves the wear resistance of the alloy in a friction pair with BrAZh9-4l brass. It is established that the wear rate of a “VT14 titanium alloy with oxynitride coating–U8 steel” tribopair is an order smaller than that of a “VT14 titanium alloy with oxynitride coating–BrAZh9-4l brass” tribopair. It is also established that the tribologic behavior of the former tribopair improves after replacing AMH-10 lubricant by I-40A lubricant.     

Physicochemical properties of electric-spark coatings based on VT6 titanium alloy

We establish regularities of the process of formation and physicomechanical and physicochemical properties of the surface of VT6 titanium alloy subjected to electric-spark alloying with electrode materials based on refractory compounds of titanium and zirconium. It is shown that, in the process of electricspark alloying, the maximum hardness and electrochemical resistance of the alloyed layer in natural corrosive environments are attained for materials based on carbide and titanium carbonitride and the highest resistance to high-temperature oxidation is attained for materials based on zirconium nitride and titanium carbonitride. Frantsevich Institute of Problems in Materials Science, Ukrainian Academy of Sciences, Kiev. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 5, pp. 55–59, September–October, 1996.     

Ion beam nitriding of titanium and titanium alloy

Titanium and Ti8A/1Mo1V alloy have been nitrided with an ion beam source of nitrogen or agon and nitrogen, at a total pressure of 2?10×10^?4 torr. The treated surface has been characterized by surface profilometry, X-ray diffractometry, Auger Electron Spectroscopy (AES), and microhardness measurements. It was found that tetragonal Ti₂N phase forms in pure titanium and Ti8A/2Mo1V alloy with traces of AIN in the alloy. Two opposite processes were found to compete during the ion beam nitriding: (a) formation of nitrides in the surface layers; (b) sputtering of the nitrided layers by the ion beam. The highest surface hardness, of about 500 kg mm^?2 in titanium and 800 kg mm^?2 in Ti8A/1Mo1V, was obtained by nitriding with an ion beam of pure nitrogen at 4.2×10^?4 torr, at beam voltage of 1000 V.     

Strain hardening and fracture of VT6 alloy synthesized by the method of powder metallurgy

We study the deformation behavior of VT6 alloy produced by the method of powder metallurgy and according to the traditional technology (casting and high-temperature deformation). It is shown that, in both types of materials, the evolution of the dislocation structure and strain hardening in tension obey the same physical laws. The deformation and hardening of both the powder material and VT6 alloy with lamellar structure obtained by using the traditional technology are controlled by the β-phase with bcc lattice according to the mechanism of composition hardening. Independently of the temperature of sintering, powder alloys fail according to the mechanism of ductile shear and tension. The residual pores in the powder material do not play the role of sites of crack initiation. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 107–111, May–June, 2008.     

Effects of nitriding on titanium alloy strength and plasticity

Summary Studies have been made on the effects of temperature and time on nitriding and from the pressure of the nitrogen on the strength and plasticity of pseudo- and + titanium alloys. Factors are observed that provide for retaining a high level of mechanical characteristics.Karpenko Physicomechanics Institute, Ukrainian Academy of Sciences, L'vov. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 1, pp. 81–84, January–February, 1993.     

Analysis of the creep and long-term strength of VT6 titanium alloy with preliminarily injected hydrogen

We describe the results of experimental and theoretical investigation of the influence of the concentration of preliminarily injected hydrogen on the creep and long-term strength of VT6 titanium alloy under the action of tensile stresses equal to 47–217 MPa. The tests carried out at a temperature of 600°C show that hydrogen (up to 0.3 wt.%) strongly decreases the steady-state creep rate of this alloy, increases the time to fracture, and lowers (severalfold) its ultimate fracture strain. The obtained results are interpreted on the basis of the analysis of changes in the structural state of the alloy. The proposed version of the kinetic theory of creep gives good agreement between the experimental and theoretical values of the principal characteristics of creep and long-term strength. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 5, pp. 98–104, September–October, 2008.