PT3V Titanium Alloy Research Articles

Possibility to Strengthen the Joint between a Titanium Alloy and Stainless Steel Formed by Diffusion Welding through an Interlayer

The mechanical properties and the fracture of the joints between a PT3V titanium alloy and 12Cr18Ni10Ti stainless steel formed by diffusion welding through ultrafine-grained layers of nickel and a Cr2Ni98 alloy are studied. The highest strength of the joint (about 390 MPa) is achieved upon welding at T = 700°C, 20 min irrespective of the interlayer material. However, in the case of the nickel interlayer, fracture occurs in the regions adjacent to the TiNi layer; in the case of the Cr2Ni98 alloy, along the alloy/steel interface.

Manufacture of parts from a titanium alloy under superplasticity conditions

A pseudo-α PT3V titanium alloy with a grain size of about 10 μm is shown to demonstrate all evidence of superplasticity in the temperature range 880–920°C during tensile deformation at a strain rate of 10–3–10–2 s–1: the relative elongation is higher than 300% and the strain-hardening exponent is higher than 0.4. It is concluded that the use of isothermal stamping of bottom-type parts from the titanium alloy in the superplastic state is profitable.

Corrosion and Corrosion Crack Resistance of the PT3V Titanium Alloy in Aqueous Solutions of Ammonia

We describe some results of experimental investigations into the influence of the structure of the PT3V titanium pseudo-α-alloy, formed by plastic deformation and heat treatment, on its mechanical properties, corrosion, and cyclic crack resistance in aqueous ammonia media of various concentrations and temperatures. The kinetics of electrode processes on a smooth surface and at the tip of a fatigue crack is studied. By using the methods of the dropping mercury electrode and a disk rotating electrode, we identified the main partial electrochemical reactions and determined the limiting stage of the cathodic process (diffusion of molecular oxygen), the hydrodynamic conditions of the course of these reactions, and the diffusivity of oxygen in aqueous ammonia media at 298 K (D = 4.8·10−8m2/sec). The kinetics of fatigue and corrosion-fatigue fracture of the alloy under study (crack initiation and growth) was investigated as well. We have established that, at the stage till crack initiation in air, alloys with a globular structure have the maximum lifetime, which is 1.5–2 times as much as that of lamellar structures. In corrosive media, the time to crack initiation increases with the ammonia concentration and solution temperature. A corrosive medium strongly affects fatigue crack growth in the alloy for ΔK below 5–7 MPa m1/2, i.e., if V > (2·10−8–8·10−9) m/cycle, especially for the initial (thin-lamellar) and β-transformed structures. With the help of investigations of electrochemical processes in a corrosion-fatigue crack, we established the linear dependence of the stabilized value of the electrolytic potential Est on ΔK. Specific features of the fatigue fracture of alloys having different structures in air and aqueous ammonia media were discovered on the basis of metallographic analysis. Finally, we analyzed the kinetics and the mechanisms of corrosion and corrosion-fatigue crack growth.

Influence of Preliminary Plastic Deformation on the Low-Cycle Fatigue of a Titanium Alloy under Conditions of Deep Cooling

We consider the results of testing of PT3V titanium alloy (4.5% Al, 2.1% V, balance Ti) for low-cycle fatigue at temperatures of 293, 77, and 4.2 K, taking into account the influence of the degree (0.05, 1.0, and 3.0%) of plastic prestraining of the material (performed at the same temperatures) on durability. To simplify the procedure of testing and data processing and decrease the costs of testing, we apply the methods of mathematical design of experiments and factor analysis. It is shown that the maximum decrease in the durability of the tested alloy is attained for a degree of prestraining of 3% at a testing temperature of 4.2 K realized in liquid helium.

Variation of the creep limit and structure of a welded joint in pT-3V titanium alloy under cyclic loading. Report 3

The metallographic methods and microanalysis were used for investigation of the welded butt-joint specimens from PT-3V titanium alloys. The specimens were in initial state and after cyclic loading. Duration of loading was 5·104 and 1·107 cycles on a frequency of 35 Hz. The stress amplitude was 150 MPa; this value is below the endurance limit of weld material. The polished sections for investigations were cut out from a working part of specimens, which contains all zones of weld including the base metal. The plane of the polished section was disposed parallel to the surface of the weld and the axis of the polished section was located perpendicularly to the axis of the weld. The results show that migration of interstitial impurities takes place to boundaries of weld zones and regions of primary segregation of substitution elements. This process occurs under the action of cyclic loading that is followed by reduction of relative density of movable dislocations and length of dislocation segments, which are described in Communication 2. The mentioned causes lead to stabilization of weld material structure and enable an increase in the cyclic and static creep limits as is described in Communication 1. The physical processes, responsible for stabilization of dislocation structure and growth of creep stresses, are mainly completed after 5·104 cycles of loading.

Variation of the creep limit and structure of a welded joint in PT-3V titanium alloy under the effect of cyclic loading. Report 2

Comparative analysis of the characteristics of amplitude-dependent internal friction (IF) was carried out to explain reasons leading to an increase of the creep limit of the butt welded joint in PT-3V titanium alloy (PT-2V filler material) after cyclic loading. IF was measured by the method of the direct torsional pendulum on cylindrical specimens representing the gage part of the specimens subjected to preliminary cyclic loading. The data were processed using the Granato-Lucke theory. The results show that the reduction of IF after cyclic loading took place as a result of an increase of the number and redistribution of pinning points of the dislocations. Consequently, the density of mobile dislocations decreases by 8% and the length of dislocation segments by 18%. These processes of stabilization of the structure were completed within 5·104cycles of preliminary loading. Stabilization of the dislocation structure of the material of the welded joint increases its creep limit.

Variation of the creep limit and structure of a welded joint in PT-3V titanium alloy under cyclic loading. Report 1

The creep of PT-3V titanium alloy and of a butt welded joint in this alloy (PT-2V filler material) was investigated on cylindrical specimens 7 mm in diameter with a gage length of 50 mm. The plane of the weld 10-mm wide, produced by manual submerged-arc welding, was situated in the center of the specimen in the direction normal to its longitudinal axis. The results show that in the examined cyclic stress amplitude range the preliminary cyclic loading lasting 5·104cycles with a frequency of 35 Hz increases the cyclic creep limit of PT-3V alloy by 11% and the static creep limit of the welded joint by 19%. This variation of the mechanical properties can be regarded as one of the reasons for the positive effect of the vibrotreatment technology, used in industry, leading to stabilization of the dimensions and form of components.

Effect of size, manufacturing and prestrain on high-rate failure (spall) of PT-3V titanium alloy and 12Kh18N10T steel

Experimental results are presented on the spall strength of PT-3V titanium alloy and 12Kh18N10T steel as the system size is changed by a factor of five. The effects of a 0.5–5% dynamic prestrain and of the direction of the load relative to the manufacturing rolling direction on spall failure were also studied for the titanium alloy. It was established that failure of these metals under high-rate one-dimensional strain shows significant energy-related size effects. Effects of the rolling direction and prestrain were less pronounced for the titanium alloy than for steel.

Effect of the protogenic nature of the medium on the rate of corrosion transformations in PT3V titanium alloy

The dependence of the rate of partial electrode reactions on the protengenic nature of medium on a titanium electrode can be evaluated by comparing parameters of the electrochemical processes on the electrode in a proton dimethyl formamide (DMFA) and protogenic aqueous medium. This problem can be solved most efficiently by the rotating disk electrode method (RDE). The RDE method was used previously for examining the main cathodic and anodic partial reactions on the electrode of PT3V titanium pseudo-{alpha}-alloy in water-ammonia media of different concentration. We investigated PT3V alloys in different structural states after holding the specimens in liquid and gaseous ammonia, freon-12 and DMFA solutions with background salts.4 refs., 3 figs., 2 tabs.

Effects of tensile stresses on corrosion parameters for model crack grooves

Measurements have been made on the electrochemical parameters in a model corrosion gap as affected by tensile stresses σ varying from zero up to the yield point of the material. It is shown on various constructional materials (D16T aluminum alloy, steel 45, Kh18N12T steel, and PT-3V titanium alloy) that the passivation time for a freshly renewed surface is reduced by a factor 1.5–3.5 as σ increases, while the galvanic current increases by a factor 1.2–3.0 and the electrode potentials shift by 30–100 mV in accordance with the pH. Numerical values are given for the parameters as functions of σ and pH.

Corrosion resistance of PT-3V titanium alloy and its welded joints in sulfide solutions

Corrosion resistance of PT-3V titanium alloy and its welded joints in sulfide solutions

Effect of the conditions of electron beam welding on the static cracking resistance of welded joints in PT3V titanium alloy

Effect of the conditions of electron beam welding on the static cracking resistance of welded joints in PT3V titanium alloy

Welding PT-3V titanium alloy on unmachined edges after plasma-arc cutting

(1989). Welding PT-3V titanium alloy on unmachined edges after plasma-arc cutting. Welding International: Vol. 3, No. 6, pp. 509-510.

Using the similarity theory of fatigue fracture for PT3V titanium alloy with different structures

As shown by the tests on the specimens (smooth and with stress raisers) in pure bending with rotation (series I), the globular structures ensure the highest fatigue resistance (Table 2, structural states 4, 5). The endurance of the alloy with the plate-shaped structure is more sensitive to the variation of the structural parameters than the globular structure. The increase of the size of the a-particles in the globular structure by a factor of 2-3 has almost no effect on the endurance limit while the increase of the parameters of the plateshaped structure reduces the fatigue resistance of the alloy (Table 2, structural states i, 2, 3). The endurance decreases especially markedly in the presence of E-grains (D O = 800-1200 #m, ~-transformed structure) with a plate-shaped a-phase (d o 50-100 ~m, b S 4 Bm). The alloy with this type of structure has the lowest endurance limit equal to Oo4a B (state 3). The increase of the thickness of the a-plates and of the size of the G-colonies of the alloy as a result of the annealing (state 2) also reduces the endurance limit in comparison with its level in the initial state.

Effect of deep cooling on the low-cycle fatigue of PT3V titanium alloy

Effect of deep cooling on the low-cycle fatigue of PT3V titanium alloy

Fatigue resistance of PT3V titanium alloy at increased temperatures

The authors investigate the life of a titanium alloy in the 292-623/sup 0/K temperature range and of features of the fracture surface. Metallographic investigations showed that the structure of the alloy is coarse grained with a fine lamellar intragranular structure and is beta-grains inherited from the beta-area, colonies of lamellar alpha-phase, and also a second phase. Fractographic analysis showed that of the fracture surfaces of unnotched specimens, the test temperature influences the crack growth rate and the morphology of the relief.