Papers by Keyword: TC4

Abstract: Titanium alloys have been taken as Oil Country Tubular Goods (OCTG) owing to their higher strength, and better corrosion resistance, but there are some problems in their application process. The corrosion types of titanium alloys were emphatically discussed, and corrosion mechanism was analyzed in this paper. The results showed that the main corrosion type of titanium alloys in hydrochloric acid was pitting, and the surface roughness of titanium alloys could affect it. The critical current density of titanium alloys in phosphoric acid was closely related to temperature and phosphoric acid concentration. The passivation of titanium alloys could be carried out by the growing oxide film at low current density, to achieve the higher stability of passivating film in the concentrated sulfuric acid. Titanium alloys suffered from more serious corrosion in the CO₂-containing completion fluid environment than that in the CO₂-containing formation water environment. H₂S would cause electrochemical corrosion and stress corrosion of titanium alloy pipe, leading to hydrogen embrittlement and even cracking of OCTG. Passivating film was the key to corrosion resistance of titanium alloys, and its composition would change with the depth of the film, presenting N-type. The dynamic corrosion of titanium alloys was mainly controlled by charge transfer.

Abstract: This paper, using the finite element software ABAQUS, establishes the model of laser shock peening (LSP) of TC4 titanium alloy, and analyzes the influence of different parameters on the residual stress of TC4 titanium alloy and plastic deformation. The results show that LSP can make the surface of TC4 titanium alloy have large compressive stress and plastic deformation, hardness and prolong the fatigue life of materials. Laser energy and the impact frequency are the main factor of surface residual stress effects. The multi-point LSP can perform processing enhanced in surface area, and form residual compressive stress on the surface of the material and in a certain depth.

Abstract: Galvanic corrosion behavior of TC4 titanium alloy coupled LY12 aluminum alloy was investigated in 3.5% NaCl solution. Particular attention was given to the effect of three different oxidation films. Galvanic corrosion test was conducted on TC4 titanium alloy which coupled LY12-sulfuric acid anodic film (LY12/A(S)), LY12-chromic acid anodic film (LY12/A(Cr)), LY12-hard anodic film (LY12/A(S) hd) and bare LY12, respectively. Galvanic corrosion current (Ig) and average galvanic current density (Ig’) were monitored. Corrosion morphology was observed by camera and corrosion mechanism was discussed. The results show that the three anodic films improve the corrosion resistance of the anode in different magnitudes. LY12/A(S) hd is found to be least susceptible to galvanic corrosion when coupled TC4 titanium alloy. LY12/A(S) and LY12/A(Cr) are found to be moderately susceptible to galvanic corrosion. But the bare LY12 is highly susceptible to galvanic corrosion in corrosive environment.

Abstract: Blisks are important components of aircraft engines. Its machining plays an important role in a aerospace industry. Blisk processing efficiency has become a hot topic in the field of machining. Disk milling is a new processing method to achieve efficiency. In order to optimize disk milling process parameters of blisk, the use of full-factor experimental for researching TC4 titanium disc milling process. Analyze the impact of different cutting parameters on cutting force, the results show: during milling titanium by Discal Cutter, with the increasing of feed per tooth, the cutting force increases. But cutting forces in three directions has the different influence. Feed per tooth corresponding with radial cutting depth. In order to guarantee the material removal rate, it can be selected smaller feed per tooth and larger radial cutting depth. Through the stress simulation analysis on the blade, it can be carried out that the maximum strain of blade is concentrated at the tip arc. The equivalent stress is mainly concentrated at the main cutting edge and the tip arc. It can provide the basis for future tool design.

Abstract: LY12/TC4 joints have wide applications in many industrial areas such as aerospace, nuclear and chemical industries. In the present study, TC4 alloy and LY12 alloy with and without aluminum thin film was produced under low temperature of 380 ^oC. The microstructure and mechanical properties of the joints were investigated. The addition of the Al thin interlayer had largely improved the interfacial microstructure and shear strength of the joints. The average shear strength of LY12/Al/TC4 joints was 64.3 MPa which was 2.5 times larger than the LY12/TC4 joints’ strength. The shear fracture mainly occurred on the interface of LY12 and TC4 from the XRD result of fracture surfaces.

Abstract: The influence of laser remelting on the mechanical property and fracture behavior of the superplastic diffusion bonding between TiAl intermetallics and TC4 alloy was investigated. The joint bonded by the pre-remelted samples displayed well diffusion, but the mechanical properties of the joint should be further enhanced. The mechanical properties of the joint pre-remelted under the diffusion bonding conditions of 915/80MPa/1h are lower than that of the joint without remelting. After the heat treatment on pre-remelted joint sample at 860, the mechanical properties have been enhanced greatly.

Abstract: This paper presents investigations on turning TC4 alloy with PVD TiAlN coated cemented carbide inserts. The turning test was conducted with variable cutting speeds ranging from 80 to 120 m/min. Wear surfaces of the cutting tools are analyzed to study the wear mechanism of PVD TiAlN coated cemented carbide tools in turning of titanium alloy TC4. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer( EDS) analyses by wear maps indicated that the wear of coated cemented carbide tools was caused by adhesion, coating delamination and mechanical fatigue. The analysis of EDS indicated no oxidation wear generated during the machining. The excellent chemical stability and oxidation resistance performance of TiAlN coating made contribution to prevent oxidation wear.

Abstract: Straight TC4 wire rod is demanded by many industries, however the technology of straightening for it has not been solved. In the present paper, a horizontal-vertical roller thermal straightening system is designed and the theory of rolling reduction is concluded. Based on the new system and the rolling reductions calculated for each roller, the method of finite element analysis is used to show the process of straightening at 600°C. The result of straightening is ideal, which proves the straightening system is adequate for Φ4.5 TC4 wire rod.

Abstract: This paper provides the method of calculating the film pore area and comparing the density of the looser and compact layer by AC impedance, then to compare the corrosion resistance of the film by comparing the pore area and the dielectric constant. The resistance of the film decreases fellow the soaking time extending, the capacitance of the loose and compact layer increases with the soaking time extending. The capacitance of the compact layer is smaller than that of the loose layer.

Abstract: In this paper, TC4 (Ti6Al4V) alloy has been cut at high speed minutely .Chip roots is extracted by rapid knife device. The optical microscopic image of the root chip is analyzed. The reasons why it is difficult to cut for TC4 alloy are firstly due to the low ability for heat transfer, while the second one maybe the cutting path is mainly the trans-granular failure which will consume more energy due to the coarse grains of TC4 alloy.