CN107400803A - Ti-Al alloy material and preparation method thereof - Google Patents

Abstract

The invention discloses a titanium-aluminum alloy material and a preparation method thereof, wherein the titanium-aluminum alloy material is composed of a base material, a toughening phase and a reinforcement phase; wherein, the base material includes the following parts by mass: Ti 70-72.5; Al 25 ; Mo 1; the toughening phase includes the following mass fractions: HfC 0.8~1.5; Ta 0.5; VN 0.2~2; the reinforcing phase is graphene, and the mass fraction is 0~1.5. According to the invention, the strength and toughness of the titanium-aluminum alloy material are relatively high.

Description

Titanium-aluminum alloy material and preparation method thereof

technical field

The invention relates to a titanium-aluminum alloy material and a preparation method thereof.

Background technique

Titanium aluminum is an intermetallic compound. Due to its good mechanical properties and relatively low density, it can replace the traditional nickel-based high-temperature alloy (the density is only about half of that of nickel-based alloys). Titanium-aluminum alloy has excellent properties such as high elastic modulus, creep resistance, oxidation resistance, wear resistance and high temperature resistance. As a lightweight heat-resistant structural material, it has always attracted the attention of researchers and has great development and application potential. Excellent properties are widely used in important fields such as aviation, aerospace, military and machinery.

Alloying is an effective method to improve the room-temperature plasticity, wear resistance and oxidation resistance of titanium-aluminum alloys below 800 °C. Yu Hongbao and others studied the microstructure and properties of titanium-aluminum-based alloys, and added Cr, Nb, B, etc. to the titanium-aluminum-based alloy matrix to prepare hard phase dispersion, fine and uniform TiAl composite structure nano-alloy powders. At present, the research on the application of graphene in metal matrix composites (Cu, Al, Ni) has found that the addition of graphene will greatly improve the mechanical properties and friction properties of the material, but there are few research reports on titanium-aluminum alloy as the matrix. The high strength and toughness of graphene can prepare titanium-aluminum matrix composites with low friction coefficient and high wear resistance, which has broad prospects for the application of titanium-aluminum matrix composites.

At present, the treatment methods used to improve the mechanical properties of titanium-aluminum alloys are mainly realized through appropriate heat treatment. However, heat treatment can only improve the alloy texture to a certain extent, and the material itself has not changed, or there are inherent deficiencies, and heat treatment The resulting alloy texture transforms back very easily during use.

In some implementations, in order to obtain better mechanical properties, by increasing the amount of titanium, the amount of titanium added is as high as 91% to 96%, which will cause the cost of titanium-aluminum alloy to be high.

In some implementations, no less than 30% of the total weight of niobium is added to the titanium-aluminum alloy to improve the strength and toughness of the titanium-aluminum alloy. However, the price of niobium is much higher than that of titanium (about 10 times), which will greatly Increase the price of Titanium Aluminum Alloy.

Contents of the invention

The object of the present invention is to provide a nano-particle reinforced and toughened titanium-aluminum alloy material, and the present invention also provides a preparation method of the titanium-aluminum alloy material.

According to an embodiment of the present invention, a titanium-aluminum alloy material is provided, which is composed of a matrix material, a toughening phase and a reinforcing phase;

Wherein, the base material includes the following parts by mass:

Ti 70~72.5;

Al 25;

Mo 1;

The toughening phase includes the following parts by mass:

HfC 0.8~1.5;

Ta 0.5;

VN 0.2~2;

The reinforcing phase is graphene, and the mass fraction is 0-1.5.

For the above-mentioned titanium-aluminum alloy material, optionally, the mass fraction of Ti is preferably 72.

Optionally, the HfC mass fraction is preferably 1;

The mass fraction of VN is preferably 0.5.

Optionally, the mass fraction of graphene is 0.25-0.90.

According to an embodiment of the present invention, there is also provided a method for preparing the aforementioned titanium-aluminum alloy material, comprising the following steps:

1) Material preparation: Weigh a given amount of matrix material, toughening phase and reinforcing phase powder to obtain the material;

2) Ball milling and mixing: Put the material weighed in step 1) into a ball mill for ball milling to obtain a mixture with a given particle size;

3) Molding: Fill the mixture into a given mold for molding.

The preparation method according to claim 5, characterized in that, in step 2), before the materials are put into the ball mill, the rest of the materials except the reinforcing phase are mixed and premixed to obtain a premix.

In the above preparation method, optionally, when performing ball milling in a ball mill, the premixed material is ball milled for a first time, then put into the reinforcement phase, and then ball milled for a second time.

Optionally, the first time is 150min, and the second time is 120min;

The rotational speed of the ball mill was 200 rpm/min.

Optionally, the mold is a graphite mold, and the inner diameter of the configured graphite mold sleeve is 40mm.

Optionally, step 3) molding has:

The first forming method: the first forming method is cold press forming, the pressure of cold press forming is 35MPa, and the holding time is 20s;

The second molding method: the second molding method is hot pressing molding, and the hot pressing molding pressure is 30MPa;

The formed blank is sintered at a temperature of 1250°C and a holding time of 30 minutes. The sintering must be completed in a vacuum chamber with a vacuum degree of 1×10 ^-2 Pa.

The titanium-aluminum alloy according to the embodiment of the present invention has relatively high mechanical properties, which are superior to traditional high-temperature alloys such as stainless steel and Ni-based. Conventional titanium-aluminum alloys have insufficient room temperature shaping, wear resistance, and oxidation resistance at high temperatures of 800°C; graphene is a new type of two-dimensional material discovered in 2004 that is currently the thinnest, strongest, and has a large specific surface area. Carbon nanomaterials with a planar structure have excellent properties. When added to the titanium-aluminum matrix, the effects of fine-grain strengthening and transfer shear stress strengthening can improve the performance of titanium-aluminum alloys. In TiAl alloy, the addition of Mo can improve the high-temperature strength of the material. After adding Mo with a body-centered cubic structure, it can inhibit the growth of the α-phase of Ti, significantly refine the β-phase and reduce the grain size, thereby improving the strength of titanium-aluminum alloy. The addition of HfC has the effect of precipitation and dispersion, which significantly improves the high temperature strength of the material; the addition of Ta improves the ductility and toughness of the material; the driving force of VN is easy to form fine dispersed particles, which can inhibit the coarsening of particles, and can improve the hardness and ductility of the material .

detailed description

In the embodiments of the present invention, the content of each component of the titanium-aluminum alloy material is represented by mass fraction. The matrix materials in the various embodiments of the present invention include Ti (titanium), Al (aluminum) and Mo (molybdenum); the toughening phase includes HfC (hafnium carbide), Ta (tantalum) and VN (vanadium nitride); the reinforcement phase for graphene.

Example 1:

The titanium-aluminum alloy material in this embodiment consists of the following mass parts: 72 (parts, omitted in other embodiments) Ti, 25 parts Al, 1 part Mo, 1 part HfC, 0.5 part Ta, 0.5 part VN. As a comparison, no graphene is added in this embodiment.

Graphene can enhance the mechanical properties of titanium-aluminum alloy materials, and the addition of graphene can effectively improve the alloy structure and improve the mechanical properties of composite materials.

The preparation method of titanium-aluminum alloy in the present embodiment is as follows:

1) Material preparation. The titanium-aluminum alloy material according to this embodiment is originally prepared, and each component material prepared is a powder material, which is called a material as a whole.

2) Put the weighed material and the steel ball into the pre-cleaned stainless steel ball mill tank according to the ratio of the mass ratio of the ball to the material: 8:1 (the diameter of the steel ball is 10mm, 6mm or 3mm). Mechanical ball milling on a ball mill and uniform mixing to obtain a pretreated mixed powder.

3) After the ball-milled powder is returned to room temperature, use a 200-mesh sieve to sieve it, and then fill it into a graphite mold. The graphite mold is slowly placed on a universal testing machine for compression molding, and the holding time is set to 20s.

4) Place the cold-pressed billet after pressing in a vertical vacuum hot-pressing sintering machine to sinter the sample.

The sintering process: from room temperature to 600°C, the heating rate is 10°C/min, holding for 10 minutes; from 600°C to 900°C, the heating rate is 5°C/min, holding for 15 minutes; from 900°C to 1250°C, the heating rate is 5°C/min , holding time is 30min, sintering pressure is 35MPa.

It is necessary to avoid oxidation of the mixture during sintering, and a vacuum chamber is provided, and the vacuum degree of the vacuum chamber is 10 ^-2 Pa.

The mechanical properties of the titanium-aluminum alloy material prepared through the above steps are: tensile strength 456MPa, yield strength 364MPa, hardness 37HV.

Before ball milling, the materials can be premixed. Although the required man-hours increase, it can make the mixture after ball milling more uniform.

During ball milling, the speed of the ball mill is 200rpm/min, and the ball milling time needs to be controlled within an appropriate range. The total ball milling time should not be less than 200min. If graphene is added, the other components except graphene should be ball milled first Time, and then put in graphene and then ball mill for a second time.

Wherein, the first time is preferably 150 minutes, and the second time is preferably 120 minutes.

When ball milling is carried out in two time periods, the total ball milling time shall not be less than 250 minutes.

Example 2:

The titanium-aluminum alloy material in this embodiment includes the following materials in parts by mass: 72 Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, which are recorded as mixed powder.

Graphene is added as a reinforcing phase, and 0.08 parts of graphene is weighed ("parts" are omitted in the following examples), and it becomes a mixture together with the above-mentioned mixed powder.

During preparation, due to the addition of graphene, as mentioned above, the mixed powder needs to be ball milled for the first time, and then graphene is added for further ball milling for the second time.

The remaining steps of the preparation method of the titanium-aluminum alloy material in this example are the same as those in Example 1.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 467MPa, yield strength 369MPa, hardness 37HV.

Example 3:

The titanium-aluminum alloy material in this embodiment includes the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, and 0.5VN, which are recorded as mixed powder; graphene is further added to the mixed powder, and the added graphene is for strengthening Phase, the consumption of graphene is 0.25 part, is called compound with the mixed powder as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 512MPa, yield strength 384MPa, hardness 45HV.

Example 4:

The titanium-aluminum alloy material of this embodiment includes the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, and these components are recorded as mixed powder; Add 0.4 part of graphene, and above-mentioned mixed powder is called compound as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 579MPa, yield strength 445MPa, hardness 44HV.

Example 5:

The titanium-aluminum alloy material of this embodiment includes the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, and these components are recorded as mixed powder; The graphene that adds is 0.56 part, is called compound with above-mentioned mixed powder as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 565MPa, yield strength 448MPa, hardness 42HV.

Embodiment 6:

The titanium-aluminum alloy material of this embodiment includes the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, and these components are recorded as mixed powder; The graphene that adds is 0.72 parts, is called compound with above-mentioned mixed powder as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 460MPa, yield strength 394MPa, hardness 40HV.

Embodiment 7:

The titanium-aluminum alloy material of this embodiment includes the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, and these components are recorded as mixed powder; The graphene that adds is 0.44 parts, is called compound with above-mentioned mixed powder as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 493MPa, yield strength 390MPa, hardness 40HV.

Embodiment 8:

The titanium-aluminum alloy material of this embodiment is composed of the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, and record these components as mixed powder; The graphene that adds is 1.05 parts, is called compound with above-mentioned mixed powder as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 454MPa, yield strength 376MPa, hardness 37HV.

Embodiment 9:

The titanium-aluminum alloy material of this embodiment includes the following materials in parts by mass: 72Ti, 25Al, 1Mo, 1HfC, 0.5Ta, 0.5VN, and these components are recorded as mixed powder; The graphene that adds is 1.2 parts, is called compound with above-mentioned mixed powder as a whole.

The preparation method of the titanium-aluminum alloy material in this embodiment is the same as that in Embodiment 2.

The mechanical properties of the prepared titanium-aluminum alloy material are: tensile strength 478MPa, yield strength 385MPa, hardness 38HV.

The above experimental results show that the addition of graphene is evenly distributed in the matrix, and the existence of graphene can effectively prevent the nucleation rate and growth rate of titanium-aluminum alloy grains through hot-pressing sintering, and play a role in fine-grain strengthening. ; Graphene, as a reinforcing material, exists in the matrix in the form of a second phase, which produces an obvious strengthening effect. The super large specific surface area of graphene is easy to bond with the interface of the matrix, and can inhibit the movement of dislocations and lattice distortion during the stress of the material; The extremely high strength of graphene can disperse plastic deformation, reduce the stress on the titanium-aluminum matrix, and improve the mechanical properties of the material. However, the graphene content is too much, it is difficult to mix evenly with the matrix, and it is easy to agglomerate, and there are many cavities in the prepared sample, which reduces the mechanical properties of the material. Therefore, a certain content of graphene can improve the mechanical properties of the material.

Claims (10)

1. a kind of Ti-Al alloy material, it is characterised in that by matrix material, toughness reinforcing phase and enhancing phase composition；

Wherein, matrix material includes following mass fraction：

Ti 70~72.5；

Al 25；

Mo 1；

Toughness reinforcing mutually includes following mass fraction：

HfC 0.8~1.5；

Ta 0.5；

VN 0.2~2；

Enhancing is mutually graphene, matches somebody with somebody mass fraction for 0 ~ 1.5.

2. Ti-Al alloy material according to claim 1, it is characterised in that Ti mass fraction is preferably 72.

3. Ti-Al alloy material according to claim 1 or 2, it is characterised in that HfC mass fractions are preferably 1；

VN mass fractions are preferably 0.5.

4. Ti-Al alloy material according to claim 1 or 2, it is characterised in that the mass fraction of graphene be 0.25 ~ 0.90。

5. one kind prepares the preparation method of the Ti-Al alloy material as described in claim 1 ~ 4 is any, it is characterised in that including with Lower step：

1）Stock：Matrix material, toughness reinforcing phase and the enhancing phase powder of specified rate are weighed, obtains material；

2）Ball milling mixing：By step 1）The material input ball mill of weighing carries out ball milling, obtains the compound of given granularity；

3）Shaping：The compound is inserted and is molded to fixed mold.

6. preparation method according to claim 5, it is characterised in that in step 2）In, before material is put into ball mill, Mixed premix first is carried out to the rest materials in addition to phase is strengthened, obtains premix.

7. preparation method according to claim 6, it is characterised in that when ball milling is carried out in ball mill, first to premix The ball milling very first time is carried out, then puts into enhancing phase again, further the time of ball milling second.

8. preparation method according to claim 7, it is characterised in that very first time 150min, the second time is 120min；

Drum's speed of rotation is 200rpm/min.

9. according to any described preparation method of claim 5 ~ 8, it is characterised in that the mould is graphite jig, is configured Graphite jig sleeve diameter is 40mm.

10. according to any described preparation method of claim 5 ~ 8, it is characterised in that step 3）Shaping has：

First forming method：First forming method is cold moudling, and the pressure of cold moudling is 35MPa, and the dwell time is 20s；

Second forming method：Second forming method is hot-forming, and hot-forming pressure is 30MPa；

Blank after shaping is sintered, and sintering temperature is 1250 DEG C, soaking time 30min, is needed in a vacuum chamber during sintering Complete, the vacuum of vacuum chamber is 1 × 10^-2Pa。