RU2614356C1 - Titanium-based alloy and product made from it - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: titanium-based alloy contains, wt %: aluminium 1.5-4.5;. vanadium 13.5-19.0; chrome 2.0-5.0; tin 2.0-4.0; molybdenum 0.5-2.5; zirconium 0.5-2.5; niobium 0.01-0.40; yttrium 0.005-0.150; titanium and impurities - the rest.

EFFECT: alloy is characterized by high values of ductility, thermal stability, and creep strength in the thermally hardened condition, while keeping the fracture viscosity values.

5 cl, 2 tbl, 4 ex

Description

The invention relates to the field of non-ferrous metallurgy, and in particular to the creation of titanium alloys intended for use as a high-strength structural thermally hardened material. A wide range of deformed semi-finished products (sheets, tape, foil, plates, rods, stampings, etc.) can be made of alloy, which can be used in power structures of aviation and space technology, power plants and rockets, long-term operating at temperatures up to 350 ° C.

It is known from the prior art that alloying with rare metals (RM) and rare-earth metals (REM) is often used to increase the strength properties of alloys through predominantly dispersion hardening (the proportion of solid solution hardening is relatively small in a number of examples).

So, the known method of forming a directional texture in a titanium alloy alloyed with rare metals and rare-earth metals in an amount of up to 3 wt.%. The introduction of rare-earth metals such as erbium or yttrium in the specified amount allows to obtain at least 0.5 vol.% Stable and stable dispersed particles at temperatures above T _pp , which increases its strength and heat-resistant properties (US 5074907, C22C 14/00 , published on 12.24.1991).

The disadvantages of this method include the fact that the manufacture of semi-finished products requires the use of powder metallurgy methods, and the directional texture is characterized by a pronounced anisotropy of properties. The use of metal powders obtained by gas atomization, and the operation of their subsequent sintering, significantly increase the cost of products. It is known that deformed semi-finished products with a pronounced texture and anisotropy of properties have significantly lower values of plastic properties in the transverse direction, which reduces the guaranteed level of operational properties of the product.

Known alloy (GB 1479855, C22C 14/00, publ. 07/13/1977) based on titanium, having the following chemical composition, wt.%:

aluminum 1.0-6.0 vanadium 0.1-10.0 molybdenum 5.0-10.0 chromium 4.0-12.0 iron 0.1-4.0 nickel 0.3-4.0 oxygen <0.2 nitrogen <0.1 hydrogen <0.03 carbon <0.05 titanium rest

The disadvantage of the alloy is its low technological plasticity, which complicates its processing and the manufacture of semi-finished products.

Known alloy (JP 2004068146, C22C 14/00, publ. 04.03.2004) based on titanium, having the following chemical composition, wt.%:

aluminum 2.5-5.0 vanadium 15-25 tin 0.5-4.0 oxygen <0.2 titanium and impurities rest

A disadvantage of the known alloy is the duration of the hardening heat treatment, the insufficient level of operational properties, due to the predominant alloying with isomorphic β-stabilizers.

The closest analogue of the claimed technical solution is an alloy based on titanium (SU 1621543, C22C 14/00, publ. 08/15/1994), having the following chemical composition, wt.%:

aluminum 2.0-4.0 vanadium 14.0-20.0 chromium 2.0-5.0 tin 2.0-4.0 molybdenum 0.5-3.0 zirconium 0.3-2.0 niobium 0.01-0.40 titanium rest

A disadvantage of the known alloy is the insufficient level of ductility in a thermally hardened state and cyclic strength.

The technical task of the invention is the creation of a titanium alloy intended for the manufacture of semi-finished products of a wide assortment (sheets, plates, rods, forgings, stampings) with a high level of operational properties.

The technical result of the claimed invention is to increase the values of ductility, thermal stability and creep in a thermally hardened state while maintaining the values of fracture toughness.

The technical result is achieved using an alloy based on titanium containing aluminum, molybdenum, vanadium, chromium, zirconium, tin, niobium and yttrium, in the following ratio of components, wt.%:

aluminum 1,5-4,5 vanadium 13.5-19.0 chromium 2.0-5.0 tin 2.0-4.0 molybdenum 0.5-2.5 zirconium 0.5-2.5 niobium 0.01-0.40 yttrium 0.005-0.150 titanium and impurities rest

The alloy may additionally contain oxygen in an amount of from 0.04 to 0.16 wt.%.

The total content of tin and zirconium should be in the range from 2.6 to 6.1 wt.%.

The mutual ratio of aluminum and oxygen can be from 40/1 to 20/1 in wt. shares.

The invention also relates to a product of the claimed titanium-based alloy.

The authors found that the regulated content of oxygen and aluminum provides an increase in the creep limit. Zirconium forms a continuous series of solid solutions with both titanium modifications (α and β), and with increasing zirconium content in the alloy, the tensile strength increases, and its addition significantly increases the long-term strength and creep resistance of the alloy. In addition, zirconium in small quantities modifies the structure of the alloy, changing the nature of the intragranular structure and reducing the grain size. Alloying titanium with tin and zirconium, subject to the established mutual ratio of these elements, significantly increases the set of mechanical properties at room and elevated temperatures (for example, heat resistance and creep limit). Also, alloying the alloy with tin in the indicated concentration makes it possible to increase the ductility and accelerate the decay of the β-solid solution during aging, which leads to a reduction in the complexity and energy consumption during heat treatment. The introduction of niobium into the alloy provides an increase in the level of ductility and fracture toughness. The introduction of the rare-earth metal yttrium in the indicated amount allows one to realize the effect of modifying and refining the microvolumes of the alloy, to provide a more uniform and uniform decay of the β phase during aging, due to a decrease in the critical size of the nucleus of α-phase particles. Yttrium further improves the structural stability of grain boundaries, thereby increasing thermal stability and creep strength of the alloy.

Alloying titanium alloys with molybdenum and vanadium provides the ability to achieve a high level of strength characteristics and the effectiveness of hardening heat treatment. Joint alloying of the alloy with these elements in the specified amount contributes to moderate ductility with moderately high strength properties due to moderate solid solution hardening.

The selected chromium content is due to the fact that this element well strengthens titanium alloys and is a strong β-stabilizer. But when alloying the alloy with chromium more than the maximum limits established in this invention, embrittlement intermetallic compounds (TiCr ₂ ) can be formed with long isothermal exposures, and the formation of chemical inhomogeneities is very likely during ingot smelting.

The optimal combination of α- and β-stabilizers (aluminum, molybdenum, vanadium, chromium and niobium) makes it possible to carry out step-by-step heat treatment in vacuum and argon-vacuum furnaces, and to increase the plasticity and thermal stability characteristics in the thermally hardened state.

Examples of implementation

Example 1. The proposed alloy (in accordance with table No. 1) in the form of ingots was smelted using the triple vacuum-arc remelting. Then, the ingots were subjected to deformation processing by comprehensive forging under ordinary or quasi-isothermal conditions for pimps (40-45) × 180-220 × L mm. The resulting stoops were prepared for rolling by planing on all surfaces “as clean”. The rolling of the resulting slides was carried out sequentially in several stages: hot rolling to an intermediate prefabricated sheet, then warm and cold rolling. The intermediate sheet semi-finished products between the rolling operations were subjected to hardening for the β-phase, sandblasting and etching. Finished sheets were subjected to hardening heat treatment. Strength properties were determined by tensile tests at room temperature.

Examples 2-4 are similar to example 1.

Table 1 shows the content of the alloying elements of the smelted ingots, the mechanical properties of the proposed alloy and the prototype alloy (table 2).

In the claimed alloy in a thermally hardened state, the ductility (elongation) values increased by 15-20%, the creep limit - increased by 7-10.5% while maintaining the values of fracture toughness. The thermal stability after exposure at 400 ° C for 500 h exceeds the similar characteristics of the prototype alloy.

Using the proposed alloy based on titanium allows to produce various structural elements of the power structures of aviation and space technology, operating at temperatures up to 350 ° C, which allows to increase the level of operational properties and reliability compared to traditionally used titanium alloys.

Claims (6)

1. An alloy based on titanium containing aluminum, molybdenum, vanadium, chromium, zirconium, tin, niobium, characterized in that it additionally contains yttrium as an alloying element in the following ratio of components, wt.%: aluminum  1,5-4,5 vanadium  13.5-19.0 chromium  2.0-5.0 tin  2.0-4.0 molybdenum  0.5-2.5 zirconium  0.5-2.5 niobium  0.01-0.40 yttrium  0.005-0.150 titanium and impurities  rest 2. The alloy according to claim 1, characterized in that it additionally contains oxygen in an amount of from 0.04 to 0.16 wt.%. 3. The alloy according to claim 1, characterized in that the total content of tin and zirconium is 2.6-6.1 wt.%. 4. The alloy according to claim 2, characterized in that the mutual ratio of aluminum and oxygen is from 40/1 to 20/1 in wt. shares. 5. A product made of an alloy based on titanium, characterized in that it is made of an alloy according to claim 1.