6Al 4V Alloy Research Articles

Effect of microstructure on high cycle fatigue behavior of Ti-20Zr-6.5Al-4V alloy

Room temperature fatigue behavior of Ti-20Zr-6.5Al-4V alloy containing equiaxed and lamellar microstructures is investigated. It is found that microstructures significantly affect high cycle fatigue strength. The fatigue strength for equiaxed microstructure at 107 cycles is around 575 MPa, which is lower than that for lamellar microstructure (775 MPa). Opposite scenario is observed at high stress level, especially above 825 MPa. A large scatter in fatigue life for lamellar microstructure is attributed to different crack initiation sites. For both types of microstructures, the pile-up of dislocations in α side of α/β interfaces provides preferable crack nucleation sites due to localized strain. Based on the results, effect of microstructure on high cycle fatigue properties is discussed.

Enhanced mechanical properties for mill-annealed Ti-20Zr-6.5Al-4V alloy with a fine equiaxed microstructure

To achieve a better balance of strength and ductility for Ti-20Zr-6.5Al-4V alloy, the fully equiaxed microstructure was obtained by post-deformation annealing process following water quench. The experimental results on microstructure evolution during the applied heat treatment routes are discussed with respect to the mechanical properties.

Optimization of Cutting Parameters in Drilling of Ti- 6Al-4V Alloy using Taguchi and ANOVA

Optimization of Cutting Parameters in Drilling of Ti- 6Al-4V Alloy using Taguchi and ANOVA

Corrosion and passivation of annealed Ti–20Zr–6.5Al–4V alloy

Corrosion and passivation behaviors of annealed Ti–20Zr–6.5Al–4V alloys were investigated in NaCl and HCl solutions. All the alloys exhibited spontaneous passivity and low corrosion current densities in 3.5% NaCl solution. An active–passive transition behavior was observed in 5% HCl solution. The corrosion resistance decreased with the increase in annealing temperature. Scanning electron microscopy analysis of the samples after the immersion tests revealed that the α/β interphase boundaries act as the preferential dissolution locations. The volume fraction of β phase as well as the grain size was identified as the main factor affecting the corrosion performance of the alloys.

Isothermal oxidation behavior of the TZAV-20 alloy

Abstract Oxidation behavior is important for secure and long-life service of metals and alloys. The isothermal oxidation behavior of the Ti–20Zr–6.5Al–4V alloy at 470 to 670 °C was investigated. The kinetics analysis shows that the oxidation of TZAV-20 alloy below 570 °C accords with the parabolic law. While the alloy oxidized at 670 °C, obeys the linear law. As oxidation temperature increases from 470 to 670 °C, the oxidation products change as: TiO2 → TiO2 + ZrO2 → TiO2 + ZrO2 + Al2O3. Relation between weight gain and thickness of oxidation film shows that the weight will increase 0.171 mg/cm2 for every 1 μm increasing in thickness. The surface hardness increases from approximately 380 HV for base material to 689 HV for 670 °C oxidized specimen. In short, the TZAV-20 alloy has favorable inoxidizability below 570 °C. The findings will not only promote practical applications of the new TiZrAlV series alloys but also supplement the oxidation theory.

Optimization of Machining Parameters for CNC Turning of Different Materials

Abstract. This paper proposes an experimental investigation of the most influencing machining parameters like spindle speed, feed rate and depth of cut on CNC turning of three metals viz. 316L Stainless steel, EN24 alloy steel and Ti 6 Al 4V alloy. Fractional factorial design with orthogonal array [L9 (33)] is employed for the optimization of these turning process parameters. All experiments were carried out using EMCO CNC 250 Turn machine with carbide cutting tool. The comparison revealed that feed rate and depth of cut are the most significant turning factors on surface roughness followed by spindle speed for these three metals.

Hot deformation behavior of Ti–20Zr–6.5Al–4V alloy in the α+β and single β phase field

The hot deformation behavior of Ti–20Zr–6.5Al–4V alloy in the α+β and single β phase field was investigated by compression tests in the temperature range of 800–1050°C and strain rate range of 10−3–100s−1. At low temperatures and high strain rates, the flow curves exhibited a pronounced stress drop at the very beginning of deformation, followed by a slow decrease in flow stress with increasing strain. The magnitude of the stress drop increased with decreasing deformation temperature and increasing strain rate. At high temperatures and low strain rates, the flow curves exhibited typical characteristics of dynamic recrystallization. A hyperbolic-sine Arrhenius-type equation was used to characterize the dependence of the flow stress on deformation temperature and strain rate. The activation energy of deformation in the α+β phase field decreased from 375.5 to 174.3kJ/mol with increasing strain, while it decreased from 220.6 to 172.5kJ/mol in the single β phase field. The processing maps for hot working at different strains were constructed. The optimum processing window was determined to be in the strain rate range of 7.4×10−3–1.2×10−1s−1 and temperature range of 895–1020°C.

The application of the infrared thermography on titanium alloy for studying fatigue behavior

The infrared thermography is an attractive tool for studying the fatigue behavior of materials. Based on two theoretical models of fatigue damage indicators, this work studied the fatigue properties of the virgin Ti- 6Al-4V alloy. According to the two damage indicators and the energy theory, the relationship between the macro-phenomenon and the micro-structural evolution during fatigue process was discussed. The fatigue limit of the titanium alloy was rapidly determined based on the measured temperature increment signals. The capability of the infrared thermographic method on the evaluation of fatigue properties was validated.

Brazing of Ceramic ZrO2 /Titanium Alloy Using Amorphous Solder

Because difference of the linear thermal expansion coefficient of ceramic and metal, when ceramic and metal is joined there is a mass of the residual stress in the joint, which leads to decrease the strength. The joining of ceramic and metal is attention subject. In this composition, ceramic ZrO2 and metallic Ti-6Al-4V alloy are jointed by using a amorphous Ti33Zr17Cu50(at.%) solder. The microstructure and the properties of the joint are investigated. The results show that the microstructure and mechanical properties are significantly influenced by the brazing temperature, the heat time and the cooling rate. The brazing seam is composed of ZrO2/Cu2Ti4O+(Ti,Zr)2Cu/TiO+Ti2O/CuTi2+(Ti,Zr)2Cu/CuTi2/Ti-6Al-4V alloy. The shear strength of the joint decreases as the brazing temperature, the heat time the cooling rate increase. The maximum shear strength of the brazing joints reaches 165 MPa with the optimal technical parameters:The brazing temperature of 1 173 K, the heat time of 10 min and the cooling rate of 5 K/min.

Interface microstructure of the brazed zirconia and Ti-6Al-4V using Ti-based amorphous filler

The polycrystalline ZrO2?3mol.%Y2O3 was brazed to Ti-6Al-4V using a Ti47Zr28Cu14Ni11 (at.%) amorphous ribbon at 1123 K in a high vacuum. The microstructure of the interface and evolution mechanism of the joint was investigated. The experimental result showed that the typical interfacial microstructures of the joints consisted of ZrO2/TiO+TiO2+Cu2Ti4O+Ni2Ti4O/?-Ti+(Ti,Zr)2(Cu,Ni) eutectic/(Ti,Zr)2(Cu,Ni)/acicular Widmanst?ten structure/Ti-6Al-4V alloy. The microstructure of the brazed joint was related to the solution and chemical reaction among atoms during brazing. According to the mechanical property tests the joint brazed at 1123 K for 30 min obtained the maximum shear strength 63 MPa. Both the white block intermetallic compound (Ti,Zr)2(Cu,Ni) and the coarse ?-Ti+(Ti,Zr)2(Cu,Ni) eutectic structure should be avoided forming in the brazed joint.

Microstructural evolution and formation mechanism of FCC titanium during heat treatment processing

The phase transformation of Ti–20Zr–6.5Al–4V alloy was studied during different heat treatment processes. Due to the addition of zirconium possessing the high-stacking-fault energy, a small amount of Ti underwent allotropic transformation from hcp-Ti to face-centered cubic (fcc) Ti during heat treatment. The alloy, which was subjected to solid solution treatment at 950°C for 60min and subsequent water quenched, underwent the following phase transformations: β→α+β (residual)+α″+fcc phase. The fcc phase was also found in the subsequent aging process, and when aging temperature reached 700°C, the fcc-Ti completely decomposed into hexagonal close-packed α phase. The transus temperature of fcc-Ti was between 650°C and 700°C. It was found that the mechanical properties of the alloy are remarkably dependent on fcc phase content.

Aging effects on the microstructures and mechanical properties of the Ti–20Zr–6.5Al–4V alloy

This study aims to evaluate the effects of heat treatment on the structural evolution and mechanical properties of the Ti–20Zr–6.5Al–4V (wt%) alloy. The alloy was melted via electromagnetic induction, homogenized, transus-processed, solid-solubilized, and then aged at different temperatures (from 450°C to 700°C) for 120min. X-ray diffraction was used to characterize the phase compositions in the alloy under different conditions. During the solution treatment process, the alloy underwent the following phase transformation: β→α+β (retained)+α″+fcc phase. Martensite α″ and β phases transformed into the α phase after the aging treatment. The fcc phase became completely dissolved when the aging temperature increased to 700°C. At this temperature, the mechanical properties of the alloy reached their optimum combination at σb=1437MPa, σ0.2=1294MPa, and ε=6.69%.

Evolution of solidification microstructure of centrifugal cast Ti–6Al–4V alloy

Ti–6Al–4V alloy castings were obtained with different centrifugal holding time in induction skull melting. The effects of centrifugal radius, riser and centrifugal holding time on the solidification microstructure of centrifugal cast Ti–6Al–4V alloy were investigated in detail. Results show that, under a certain centrifugal holding time, the average grain size of Ti–6Al–4V alloy castings decreases with the increasing in centrifugal radius. The microstructure of the Ti–6–Al–4V alloy casting with riser is finer. Meanwhile, the grain size increases greatly as the centrifugal holding time decreasing from 15 to 1·5 min.

The Fabrication of Hydroxyapatite Teargets and the Characteristics of Hydroxyapatite/Ti-6Al-4V alloy Thin Films by RF Sputtering(I)

RF sputtering process was applied to produce thin hydroxyapatite［HA, Ca10(<TEX>$PO_4$</TEX>)<TEX>$_{6}$</TEX> <TEX>$ (OH)_2$</TEX>films on Ti-6Al-4V alloy substrates. To make a 101.6 mm dia.<TEX>${\times}$</TEX>5 mm HA target, the commercial HA powder was first calcinated for 3h at <TEX>$200^{\circ}C$</TEX>. A certain amount of the calcinated HA powder was pressed under a pressure of 20,000 psi by the cold isostatic press(CIP) and the pressed HA target was sintered for 6 h at <TEX>$1,200^{\circ}C$</TEX>. The effects of different heat treating conditions on the bonding strength between HA thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the alloy substrates were annealed for 1 h at <TEX>$850^{\circ}C$</TEX> under <TEX>$3.0<TEX>${\times}$</TEX>10^{-3}$</TEX> Xtorr, and after deposition, the hydroxyapatite/Ti-6Al-4V alloy thin films were annealed for 1 h at 400, 600 and <TEX>$800^{\circ}C$</TEX> under the atmosphere, respectively. Experimental results represented that the HA thin films on the annealed substrates had higher hardness than non-heat treated substrates before the deposition.

Measurement of flow stress by the ring compression test.

To measure the flow stress of metals under forming conditions, i. e., at large strain rates and elevated temperatures, a method based on the ring compression test is proposed. In this method, ring-shaped specimens are compressed between two flat tools with or without lubrication. The coefficient of friction between the specimen and the tool is determined from the change in inner diameter, and then the load and reduction in height measured in the test are converted into average flow stress are derived from the rigid-plastic finite element calculation. This method is simple to carry out and does not require control of the friction during compression. Ring compression tests for some kinds of lubricants, billet materials an strain rates are carried out. The method is confirmed to provide flow stress-strain curves within an error of 5%, and is effective especially for measuring the flow stress of heat-resistant materials such as Ti alloys and Ni base superalloys which are formed at elevated temperatures. As an example, flow stress-strain curves of Ti-6 Al-4V alloy measured by the present method are demonstrated.

Grinding Titanium With Coated Abrasives Under an Aqueous Solution of Inorganic Phosphate Salts

Aqueous solutions of inorganic salts are known to be effective grinding lubricants for titanium. Early work by Professor Shaw at MIT drew particular attention to the use of phosphate salts, and although not commercially available as grinding fluids, some metal fabricators have compounded phosphate-containing fluids for their own use from the raw chemicals. In this paper, the dynamics of grinding Ti(6Al-4V) alloy are described using phosphate salt solutions. The results show that both aluminum oxide and silicon carbide coated abrasive belts have unique advantages in this application, with aluminum oxide exhibiting easy penetration and fast cutting behavior early on, while silicon carbide appears to have longer range durability.

高強度Ti-6 Al-4V合金の腐食疲労特性 (微視割れ機構とAE発生挙動の比較検討)

高強度Ti-6 Al-4V合金の腐食疲労特性 (微視割れ機構とAE発生挙動の比較検討)