Solution to Technological Problems of Raising the Reliability and Quality of Castings Based on Titanium Alloys

2019 ◽  
Vol 946 ◽  
pp. 258-264
Author(s):  
Galina I. Shcherbakova ◽  
Maxim S. Varfolomeev ◽  
Pavel A. Storozhenko
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Contact Interaction ◽  
Physicochemical Interaction ◽  
Alpha Case ◽  
Aluminum Yttrium ◽  
Temperature Melting ◽  
Cast Products

We consider the problems of the complex application of the aluminium-yttrium binder in the fabrication of high-temperature resistant melting crucibles and investment molds thermoschemically resistant to titanium melts. The results of the contact interaction investigations of a molten titanium alloy with a material of aluminum-yttrium ceramics are presented. The usage of ceramic products of α-Al2O3–Y3Al5O12∙α-Al2O3 composition under conditions of high-temperature melting and pouring under vacuum minimizes the physicochemical interaction and significantly reduces the alpha case layer on cast products, thereby improving their operational properties.

Martensite decomposition during post-heat treatments and the aging response of near-α Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) titanium alloy processed by selective laser melting (SLM)

2021 ◽  
pp. 2050018
Author(s):  
Haiyang Fan ◽  
Yahui Liu ◽  
Shoufeng Yang
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Selective Laser Melting ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Aging Treatment ◽  
Water Quenching ◽  
Laser Melting ◽  
Aging Response

Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near-[Formula: see text] titanium alloy explicitly designed for high-temperature applications, consists of a martensitic structure after selective laser melting (SLM). However, martensite is thermally unstable and thus adverse to the long-term service at high temperatures. Hence, understanding martensite decomposition is a high priority for seeking post-heat treatment for SLMed Ti-6242. Besides, compared to the room-temperature titanium alloys like Ti–6Al–4V, aging treatment is indispensable to high-temperature near-[Formula: see text] titanium alloys so that their microstructures and mechanical properties are pre-stabilized before working at elevated temperatures. Therefore, the aging response of the material is another concern of this study. To elaborate the two concerns, SLMed Ti-6242 was first isothermally annealed at 650[Formula: see text]C and then water-quenched to room temperature, followed by standard aging at 595[Formula: see text]C. The microstructure analysis revealed a temperature-dependent martensite decomposition, which proceeded sluggishly at [Formula: see text]C despite a long duration but rapidly transformed into lamellar [Formula: see text] above the martensite transition zone (770[Formula: see text]C). As heating to [Formula: see text]C), it produced a coarse microstructure containing new martensites formed in water quenching. The subsequent mechanical testing indicated that SLM-built Ti-6242 is excellent in terms of both room- and high-temperature tensile properties, with around 1400 MPa (UTS)[Formula: see text]5% elongation and 1150 MPa (UTS)[Formula: see text]10% elongation, respectively. However, the combination of water quenching and aging embrittled the as-built material severely.

scholarly journals An experimental research on the machinability of a high temperature titanium alloy BTi-6431S in turning process

2018 ◽  
Vol 5 ◽  
pp. 12
Author(s):  
Yanfeng Gao ◽  
Yongbo Wu ◽  
Jianhua Xiao ◽  
Dong Lu
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Tool Wear ◽  
Titanium Alloys ◽  
Cutting Forces ◽  
Shear Bands ◽  
Cutting Parameters ◽  
Aircraft Manufacturing ◽  
Mechanical And Physical Properties ◽  
Alpha Titanium

Titanium alloys are extensively applied in the aircraft manufacturing due to their excellent mechanical and physical properties. At present, the α + β alloy Ti6Al4V is the most commonly used titanium alloy in the industry. However, the highest temperature that it can be used only up to 300 °C. BTi-6431S is one of the latest developed high temperature titanium alloys, which belongs to the near-α alloy group and has considerably high tensile strength at 650 °C. This paper investigates the machinability of BTi-6431S in the terms of cutting forces, chip formation and tool wear. The experiments are carried out in a range of cutting parameters and the results had been investigated and analyzed. The investigation shows that: (1) the specific cutting forces in the machining of BTi-6431S alloy are higher than in the machining of Ti6Al4V alloy; (2) the regular saw-tooth chips more easily formed and the shear bands are narrower in the machining of BTi-6431S; (3) SEM and EDS observations of the worn tools indicate that more cobalt elements diffuse into the workpiece from tool inserts during machining of BTi-6431S alloy, which significantly aggravates tool wear rate. The experimental results indicate that the machinability of BTi-6431S near alpha titanium alloy is significantly lower than Ti-6Al-4V alloy.

Current Research Situation and Development of Titanium Alloy in China in Recent Five Years

2005 ◽  
Vol 475-479 ◽  
pp. 563-568
Author(s):  
Yong Qing Zhao ◽  
Lian Zhou
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
High Strength ◽  
Basic Theory ◽  
Ti Alloys ◽  
Developing Directions ◽  
Research Situation

China pays great attentions to the development of titanium alloys and their basic theory because of their excellent properties. New titanium alloys and their new basic theories developed in China in recent five years were reviewed, for example, high temperature Ti alloys, burn resistant titanium alloys, high strength and middle strength titanium alloys and so on. The developing directions in the next 5 to 10 years were forecast.

Effect of a High-Temperature Hydrogen Treatment on a Microstructure and Surface Fracture in Titanium Ti-6Al-4V Alloy

2012 ◽  
Vol 191 ◽  
pp. 243-248
Author(s):  
Maria Sozańska
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Hydrogen Gas ◽  
Hydrogen Treatment ◽  
Surface Fracture ◽  
Two Phase ◽  
Hydrogen Corrosion ◽  
Gas Atmosphere ◽  
Three Stages

Influence of hydrogen on the structure of titanium alloys is a complex phenomenon, depending on the circumstances, may be negative or positive [1,2]. The presence of hydrogen in titanium alloys usually results in degradation of their microstructure and properties, as well promote some undesirable effects such as hydrogen corrosion and hydrogen embrittlement [3]. Positive nature of the effects of hydrogen on the properties of titanium alloys is manifested in the high temperature hydrogen treatment (HTM - Hydrogen Treatment of Materials), where hydrogen is temporary alloying component [4-9]. This is possible because of the high values of diffusion coefficients can be easily introduced into the titanium and it just as easily removed. Titanium and its alloys show the absorbability of almost 60 at. % of hydrogen at 600°C. The limit hydrogen of solubility in Tiα is very low and does not exceed 0.05 at. % at room temperature. The limit hydrogen of solubility in Tiβ is much higher and its maximum value is 48 at. %. Since the beginning of the titanium industry, a great deal of attention has been paid to control the hydrogen content at titanium products – above 0.2 ppm. The paper presents the results of the possibilities of hydrogen using as a temporary alloying element in Ti-6Al-4V alloy. Treatment of hydrogen alloy consisted of three stages: hydrogenation in hydrogen gas atmosphere at 650 °C, a cyclic hydrogen-treatment (3 cycles 650 °C to 250 °C) and a dehydrogenation in vacuum (550 °C). It was shown that hydrogen affects appreciably changes the microstructure of surface layer of the tested titanium alloy. The aim of this study is thus to determine the effect of hydrogen on the two-phase microstructure, hardness, and surface fracture of the titanium alloy Ti-6Al-4V due to high-temperature hydrogen treatment.

Oxidation of Experimental Ti-Si-Al Based Alloys

2016 ◽  
Vol 258 ◽  
pp. 391-394
Author(s):  
Serhii Tkachenko ◽  
Oleg Datskevich ◽  
Zdeněk Spotz ◽  
Karel Dvořák ◽  
Leonid Kulak ◽  
...  
Keyword(s):  
High Temperature ◽  
Titanium Alloys ◽  
Oxide Scale ◽  
Oxidation Kinetics ◽  
High Strength ◽  
X Ray Diffraction ◽  
Scale Thickness ◽  
Alpha Case ◽  
Good Potential ◽  
Experimental Findings

Despite the fact that conventional high temperature titanium alloys possess a good combination of low weight, high strength and good corrosion resistance, their operational temperatures do not exceed 540-600 °C, since at higher temperatures they suffer from extensive oxidation, scaling and formation of a brittle oxygen-reach diffusion layer on their surface, so-called ‘apha-case’. The alloying with silicon was regarded as a promising way to raise the working temperatures of titanium alloys, since silicon is known to improve oxidation resistance, oxide scale adherence and high temperature creep behavior of titanium without noticeable deterioration of its ductility. The present paper was focused on studying of the oxidation kinetics and the formation of oxide scale and alpha-case layers on a series of experimental Ti−Al−Si based alloys, additionally alloyed with zirconium and tin. The oxidation kinetics of the experimental alloys upon exposure in air at 700 °С for up to 240 hours was examined and compared with that of commercially available Ті−6242 alloy. The oxide scale thickness, its phase composition and crystal morphology were characterized using X-ray diffraction and scanning electron microscopy (SEM), while the alpha-case layer was analyzed using SEM and microhardness measurements. According to the experimental findings, the experimental Ti−Al−Si based alloys demonstrated a good potential for their use at high temperatures.

scholarly journals Non-Isothermal Oxidation Behavior and Mechanism of a High Temperature Near-α Titanium Alloy

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2141 ◽  
Author(s):  
Peixuan Ouyang ◽  
Guangbao Mi ◽  
Peijie Li ◽  
Liangju He ◽  
Jingxia Cao ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Oxidation Behavior ◽  
Oxidation Mechanism ◽  
Isothermal Oxidation ◽  
Pure Oxygen ◽  
Oxygen Barrier ◽  
Barrier Effect ◽  
Oxide Formation

Non-isothermal oxidation is one of the important issues related to the safe application of high-temperature titanium alloys, so this study focuses on the non-isothermal oxidation behavior and mechanism of near-α titanium alloys. The thermogravimetry-differential scanning calorimetry (TGA/DSC) method was used to study the non-isothermal oxidation behavior of TA29 titanium alloy heated from room temperature to 1450 °C at a heating rate of 40 °C/min under pure oxygen atmosphere. The results show that non-isothermal oxidation behavior can be divided into five stages, including no oxidation, slow oxidation, accelerated oxidation, severe oxidation and deceleration oxidation; for the three-layer TiO2 scale, Zr, Nb, Ta are enriched in the intermediate layer, while Al is rich in the inner layer and Sn is segregated at the oxide-substrate interface, which is related to their diffusion rates in the subsurface α case. The oxidation mechanism for each stage is: oxygen barrier effect of a thin compact oxide film; oxygen dissolution; lattice transformation accelerating the dissolution and diffusion of oxygen; oxide formation; oxygen barrier effect of recrystallization and sintering microstructure in outer oxide scale. The alloying elements with high valence state and high diffusion rate in α-Ti are favorable to slow down the oxidation rate at the stage governed by oxide formation.

Determining High-Temperature Oxidation Resistance of Ti-Al-Cr-Si-N Based Nitride Thin Coatings Deposited on Titanium Alloys

2020 ◽  
Vol 1013 ◽  
pp. 41-45
Author(s):  
Konstantins Savkovs ◽  
Darja Andrejeva
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Heat Resistance ◽  
Titanium Alloys ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Main Element ◽  
Temperature Oxidation ◽  
Thin Coatings

This article considers the possibility of applying thin Ti-Al-Cr-Si-N based nitride thin coatings (up to 10 microns) for increasing the heat-resistance of titanium alloy blades without altering their aerofoil. It presents the results of testing samples, which were coated by using different ratios of the parameters of main element deposition simultaneously from various sputtering sources, as well as an assessment of the efficiency of these coatings in terms of oxidation at temperatures of 750–850°С.

Ti-6Al-4V

Alloy Digest ◽  
1992 ◽  
Vol 41 (9) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Heat Treating ◽  
Zero Temperature ◽  
Beta Titanium Alloy ◽  
Temperature Performance ◽  
Beta Titanium ◽  
Alpha Beta

Abstract Ti-6A1-4V and its modification Ti-6A1-4V ELI are moderately age-hardenable titanium alloys, the latter containing extra low interstitials to impart additional toughness at sub-zero temperature. This alloy is the most widely used of all titanium alloys and a great wealth of data exists. Ti-6A1-4V is characterized as an alpha rich alpha-beta titanium alloy. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ti-66. Producer or source: Timet. Originally published July 1972, revised September 1992.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

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