RU2324576C2 - Nanocristallic metal material with austenic structure possessing high firmness, durability and viscosity, and method of its production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used for production of bearing parts, gear transmissions and instruments utilised for heat processing and extrusion, as well as for a range of medical tools. The nanocristallic metal material is designed in the shape of an aggregate from the metal nanocristallic grains containing 0.4-5.0 % of the nitrogen mass. The powder components of the nanocristallic metal material are to be alloyed with the substance which becomes a source of nitrogen inside the centrifugal mill, obtaining consequently the small grained powders of the nanocristallic metal material with a high nitrogen composition in it. The powders of the nanocristallic material are then subjected to the condensed process selected from the heated pressing, the electrodischarge sintering, cogging in its cladding, formation of the condensed powders by way of extrusion and/or stamping with an explosion; and cogging of the formed metal material when it is shaped in an appropriate manner.

EFFECT: material obtained is noted for its increased durability and viscosity.

19 cl, 4 dwg, 5 tbl, 8 ex

Description

Technical field

The invention relates to metallic materials, in particular to nanocrystalline metallic materials with high hardness, strength and toughness and to a method for their manufacture.

State of the art

According to the Petch relation, the strength and hardness of the metal material increase with decreasing diameter D of the crystalline grain, and this ratio remains as long as D has a value of several tens of nm. Thus, reducing the diameter of crystalline grains to nanoscales becomes one of the most important means of hardening metallic materials.

On the other hand, when the diameters of crystalline grains are reduced to ultra-small, nanolevels, most metallic materials exhibit such a unique property as superplasticity in the temperature region above 0.5 TP, where TP is the melting point (K).

Using this phenomenon makes it possible to deform and process at relatively low temperatures even materials that are extremely difficult to plastic processing due to the high melting point.

There is some evidence that in magnetic elements such as iron, cobalt and nickel, with nanosized diameters D of the crystal grains of these metals, the coercive force decreases, and weak magnetism intensifies with a decrease in D, which does not occur with diameters D of micron sized crystal grains.

However, the crystal grain diameter D of most metallic materials produced by melting is usually in the range of several microns to several thousand microns, and D can hardly be reduced to nanoscale even with subsequent treatments. For example, even with controlled rolling, which is an important micro-treatment of crystalline grains of steel, the lowest possible grain diameter limit is at best 4-5 microns. In other words, using conventional methods, it is impossible to obtain materials with grain diameters reduced to nanoscale.

DETAILED DESCRIPTION OF THE INVENTION

The objective of the invention is to solve the above problems.

The invention is based on the use of mechanical grinding (MR) or mechanical alloying (MS) of mixtures of powders of metals or semimetals and powders of other metal additives. The obtained nanocrystalline powders are reduced to nanoscale by molding by sintering or by methods using superplasticity, thus obtaining a material having strength (high strength) and hardness (superhardness) close to the limits achieved at crystal diameters reduced to nanoscale, as well as high corrosion resistance. Further, the term "sintering" means "shaping by sintering"

Thus, this invention relates to nanocrystalline metallic materials and methods for their manufacture, below.

1. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, characterized in that between the crystalline grains and / or inside the crystalline grains contains metal oxide or semimetal, which serves as an inhibitor of the growth of nanocrystalline grains.

2. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, characterized in that between the crystalline grains and / or inside the crystalline grains contains metal nitride or semimetal, which serves as an inhibitor of the growth of nanocrystalline grains.

3. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, characterized in that between the crystalline grains and / or inside the crystalline grains contains metal carbide or semimetal, which serves as an inhibitor of the growth of nanocrystalline grains.

4. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, characterized in that between the crystalline grains and / or inside the crystalline grains contains a metal or semimetal silicide, which serves as an inhibitor of the growth of nanocrystalline grains.

5. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, characterized in that between the crystalline grains and / or inside the crystalline grains contains metal boride or semimetal, which serves as an inhibitor of the growth of nanocrystalline grains.

6. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, characterized in that between the crystalline grains and / or inside the crystalline grains contains at least two components selected from the group consisting of : a metal or semimetal oxide, a metal or semimetal nitride, a metal or semimetal carbide, a metal or semimetal silicide and a metal or semimetal boride that serve as growth inhibitors Nanocrystalline grains.

7. Nanocrystalline metal material according to any one of claims 1 to 6, containing 0.01-5.0 wt.% Nitrogen.

8. Nanocrystalline metal material according to any one of claims 1 to 6, containing 0.01 to 2.0 wt.% Nitrogen.

9. Nanocrystalline metal material according to any one of claims 1 to 8, containing oxygen in the form of a metal oxide in an amount of 0.01-1.0 wt.%.

10. Nanocrystalline metal material according to any one of claims 1 to 9, which further comprises a metal element having a greater affinity for nitrogen than for nanocrystalline metal, to prevent denitrification of an aggregate of nanocrystalline grains during sintering.

11. Nanocrystalline metal material according to any one of claims 1 to 10, in which the component forming the nanocrystalline metal is at least one of the elements selected from the group consisting of aluminum, magnesium, zinc, titanium, calcium, beryllium, antimony, yttrium, scandium, indium, uranium, gold, silver, chromium, zirconium, tin, tungsten, tantalum, iron, nickel, cobalt, copper, niobium, platinum, vanadium, manganese, molybdenum, lanthanum, rhodium, carbon, silicon, boron, nitrogen and phosphorus.

12. Nanocrystalline metal material according to any one of claims 1 to 10, in which the component forming the nanocrystalline metal is an element of the platinum group used in dentistry.

13. The nanocrystalline metal material according to any one of claims 1 to 10, in which the nanocrystalline material is one, two or more intermetallic compounds selected from the group consisting of Ni ₃ Al, Fe ₃ Al, FeAl, Ti ₃ Al, TiAl, TiAl ₃ , ZrAl ₃ , NbAl ₃ , NiAl, Nb ₂ Al, Nb ₂ Al, MoSi ₂ , Nb ₅ Si ₃ , Ti ₅ Si ₃ , Nb ₂ Be ₁₇ , Co ₃ Ti, Ni ₃ (Si, Ti), SiC, Si ₃ N ₄ , AlN, TiNi, ZrB ₂ , HfB ₂ , Cr ₃ C ₂ , or Ni ₃ Al-Ni ₃ Nb.

14. Nanocrystalline metal material according to any one of claims 1 to 13, characterized in that the metal nanocrystalline grains obtained by mechanical grinding (MR) or mechanical alloying (MS) using a ball mill or similar device.

15. A method of manufacturing a nanocrystalline metal material, including:

- mechanical alloying (MS) of the powders of the components of the nanocrystalline metal material using a ball mill or similar device for the manufacture of thus fine-grained nanocrystalline metal powders; and

- processing of powders by sintering, for example, rolling in a shell, electric discharge sintering, extrusion, stamping by explosion, to obtain a metal material with high hardness, strength and viscosity.

16. A method of manufacturing a nanocrystalline metal material, including:

- mixing the powders of the components of the nanocrystalline metal material with a nitrogen source substance;

- mechanical alloying of the powders of the components of the nanocrystalline metal material using a ball mill or similar device for the manufacture of thus fine-grained powders of the nanocrystalline metal; and

- processing of powders by sintering, for example, rolling in a shell, electric discharge sintering, extrusion, stamping by explosion, to obtain a metal material with high hardness, strength and viscosity.

17. The method according to clause 16, in which the source material of nitrogen is a metal nitride.

18. The method according to clause 16, wherein the source of nitrogen is gaseous N ₂ or NH ₃ .

19. The method according to any of paragraphs.15-18, in which mechanical grinding or mechanical alloying is carried out in an atmosphere of a gas selected from the group consisting of an inert gas, for example argon, N ₂ , NH ₃ or a mixture of these gases.

20. The method according to claim 19, in which the atmosphere in which the mechanical grinding or mechanical alloying is carried out, contains a reducing agent, for example gaseous H ₂ .

21. The method according to any one of claims 15-16, wherein the medium in which the mechanical grinding or mechanical alloying is carried out is a vacuum with a reducing agent, for example gaseous H ₂ .

22. The method according to any one of paragraphs.16-21, including:

- mixing the powders of the components of the nanocrystalline metal material with 1-10 vol.% metal nitride or with 0.5-10 wt.% metal having a greater affinity with nitrogen than with nanocrystalline metal, and with a substance source of nitrogen;

- mechanical alloying of the resulting mixture with a ball mill or similar device for the manufacture of thus fine-grained nanocrystalline metal powders; and

- processing the powders by sintering, for example by rolling in a shell, by electric discharge sintering, by extrusion or by stamping by explosion, wherein the nitride is dispersed or the nitride or carbonitride precipitates or disperses during mechanical alloying or in the process of sintering of mechanically alloyed powders, resulting in a metal material having hardness, strength and toughness.

23. The method according to any one of claims 15-22, wherein the nanocrystalline metal mixture contains 0-40 wt.% Of another element, and sintering is carried out at a temperature of 10% below the melting point.

24. A method of manufacturing a nanocrystalline steel having high hardness, strength and toughness, including:

- mechanical alloying of the powders of the components forming the steel using a ball mill or similar device to thereby obtain nanocrystalline powders forming the steel: and

- processing of powders forming steel by sintering, for example, rolling in a shell, electric-discharge sintering, extrusion or stamping by explosion at a temperature that causes superplasticity, or close to it.

25. A method of manufacturing a nanocrystalline cast iron having high hardness, strength and toughness, including:

- mechanical alloying of powders of components that make cast iron, using a ball mill or similar device for the manufacture of nanocrystalline powders that form cast iron in this way; and

- processing of powders forming cast iron by sintering, for example, rolling in a shell, electric discharge sintering, extrusion or stamping by explosion at a temperature that causes superplasticity, or close to it.

26. A method of manufacturing products from nanocrystalline steel having high hardness, strength and toughness, including:

- mechanical alloying of the powders of the components that make up the steel, using a ball mill or similar device, for the manufacture of thus nanocrystalline powders that make up the steel;

- processing of powders forming steel by sintering, for example by rolling in a shell, electric discharge sintering, extrusion or stamping by explosion, to obtain steel; and

- processing of steel at a temperature that causes superplasticity, or close to it.

27. A method of manufacturing articles of nanocrystalline cast iron having high hardness, strength and viscosity, including:

- mechanical alloying of powders of components that make cast iron, using a ball mill or similar device for the manufacture of nanocrystalline powders that form cast iron in this way;

- processing the powders of the components that form cast iron by sintering, for example by rolling in a shell, electric discharge sintering, extrusion or by stamping by explosion, to obtain cast iron; and

- processing cast iron at a temperature that causes superplasticity, or close to it.

According to this invention, when applying mechanical grinding (MR) or mechanical alloying (MS) to the powder material of one metal with the addition of another element, a powder with a structure of ultrafine crystalline grains is obtained. Sintering such powders at a temperature 10% below the melting temperature of these powders, it is easy to obtain a metal material.

By mechanical alloying (MS), mixtures of powders of virtually one metal, for example, iron, cobalt, nickel, aluminum, and added carbon, niobium, tantalum, or a similar element, produce a structure from even smaller, ultrafine crystalline grains. Sintering such powders, one obtains a material with a structure of nanocrystalline grains, which has higher strength and hardness than the material obtained by melting.

By selecting crystalline grain size, composition, and the like. supercriticality is imparted to the nanocrystalline material, and this phenomenon can be effectively used in the process of sintering of powders obtained by mechanical alloying (MS).

A brief description of the graphic materials

Figure 1 - the average diameter of the crystalline grains of each element after a 50-hour process of mechanical alloying (MS) of powders of iron, cobalt and nickel with another element (A) added in an amount of 15 at.%, In accordance with one example of the invention.

Figure 2 is a graph of the relationship between the diameter of the crystalline grain of iron D _Fe used in one example of the invention and the logarithm of logβ segregation coefficient β along the grain boundaries of the dissolved added element.

Figure 3 is a graph of the relationship between the diameter of the crystalline cobalt grain D _Co used in one example of the invention and the logarithm of logβ segregation coefficient β along the grain boundaries of the dissolved added element.

Figure 4 is a graph of the relationship between the diameter D of the crystalline grain of the sample used in one example of the invention and the amount of tantalum added (in at.%).

Preferred Embodiments

Some embodiments of the invention are described below. In one embodiment, the methods of mechanical grinding (MR) or mechanical alloying (MS) are applied to elementary powders of individual metals, for example, iron, cobalt, nickel, aluminum and copper, with or without other elements, using a ball mill or similar device, with room temperature in an argon atmosphere or other atmosphere.

Grain crystals by mechanical grinding or mechanical alloying of powders are easily reduced to a diameter of approximately 10-20 nanometers as a result of mechanical energy generated by grinding balls. For example, iron, whose grain diameter is reduced to approximately 25 nanometers, has a Vickers hardness of approximately 1000.

Then mechanically milled or mechanically alloyed powders are loaded under vacuum into a stainless steel pipe with an inner diameter of about 7 mm for sintering by rolling in a shell at a temperature that is at least 10% below the melting point. Thus, for example, it is possible to easily fabricate an iron sheet 1.5 mm thick with a conditional yield strength of at least 1.5 GPa.

If mechanical alloying (MS) is applied to a mixture of powders, including elementary powders of iron, cobalt, nickel, aluminum, copper and the like, with other elements, such as carbon, niobium and titanium, added to the above elements in an amount of about 0.5-15 wt.%, using a ball mill or similar device, the powders become ultrafine, that is, their crystalline grains have a size of several nm.

If the amount of oxygen in the form of metal oxide or semimetal, which inevitably gets into powders subjected to mechanical alloying (MS), adjust, as a rule, to approximately 0.5 wt.%. it can further prevent coarsening of crystalline grains during sintering. To enhance the effect of preventing coarsening, it is advisable to add to powders subjected to mechanical alloying, 1-10 vol.%, Preferably 3-8 vol.% Dispersant, for example AlN and NbN.

In this invention, mechanical grinding (MR) or mechanical alloying (MS) is applied to powders of individual metals, for example, iron, cobalt, nickel, aluminum, copper, with or without other elements, to obtain powders with a structure of crystalline nanoscale grains . Then, after forming the metal powders by sintering, for example, by rolling in a shell or by extrusion, the amount of oxygen in the form of a metal oxide, which inevitably forms during mechanical grinding (MR) or mechanical alloying (MS), is controlled to approximately 0.5 wt% the most constrained is the enlargement of crystalline grains as a result of the effect of fixing this oxide along the boundaries of crystalline grains. Thus, it is possible to efficiently produce nanocrystalline materials.

Examples

Below with reference to graphic materials are examples of carrying out the invention.

Example 1

Figure 1 shows the changes in the average diameter of the crystalline grain of each element subjected to mechanical alloying, that is, iron, cobalt and nickel, with a 50-hour mechanical alloying (MS) of a powder mixture with the composition M ₈₅ A ₁₅ (at.%) (M - iron, cobalt or nickel), which additionally contained 15 at.% carbon (C), niobium (Nb), tantalum (Ta), titanium (Ti), etc. as other elements (A).

In Fig. 1, D _Fe , D _Co, and D _Ni are the average crystal grain diameter (in nm) of mechanically alloyed iron, cobalt, and nickel, respectively. Figure 1 shows that the reduction in the diameter of the crystalline grains of each of the elements - iron, cobalt and nickel can be promoted more efficiently by mechanical alloying with the addition of carbon, niobium, tantalum, titanium, etc., while the crystal grains of all three of the above elements reduced to nanoscale.

It was also established that the addition of other elements also contributes to the reduction of the crystal grains of copper, aluminum, and titanium, and that carbon, phosphorus, and boron are especially effective. It should be noted here that other elements used include carbon (C), niobium (Nb), tantalum (Ta), phosphorus (P), boron (B) or a similar element, and that the data regarding nitrogen (N) apply only to iron.

Figure 2 shows a graph of the relationship between the diameter of the crystalline grain of iron D _Fe used in one of the examples and the logarithm of logβ segregation coefficient β along the grain boundaries of the added element A in iron.

The added element A, for example, may be carbon (C), nitrogen (N), tantalum (Ta) and vanadium (V).

From figure 2 it can be seen that the larger the value of logβ, the stronger the effect of a decrease in crystalline grains in the MS process.

Figure 3 shows a graph of the relationship between the diameter of the crystalline cobalt grain D _Co and the logarithm logβ of the segregation coefficient β along the grain boundaries of the added element A in cobalt.

The added element A, for example, may be carbon (C), nitrogen (N) and tantalum (Ta).

From figure 2 it can be seen that the larger the value of logβ, the stronger the effect of a decrease in crystalline grains in the MS process.

Example 2

Figure 4 shows a graph of the relationship between the average diameter of the crystalline grain D (in nm) of a mixture of Fe _64-y Cr ₁₈ Ni ₈ Tay ₁₀ (in at.%), Where y = 0-15, obtained after 100-hour MS processing a powder mixture of elements: iron, nickel and tantalum with the addition of iron nitride and tantalum in the amount of y (at.%).

Figure 4 shows that the noted effect of the added elements A having a large segregation coefficient β along the grain boundaries on the decrease in grain sizes in binary materials consisting of Fe and A is also noted in multicomponent materials based on Fe.

Example 3

A powder sample of Fe _99.8 Co _0.2 (wt.%) Was obtained by mechanical alloying (MS) of a powder mixture of iron and carbon for 200 hours. Then the sample was placed under vacuum in a stainless steel tube. The compaction (i.e., sintering) of the powder placed in the tube was carried out by rolling in a shell (PO) at a temperature of 900 ° C and the material obtained is shown in table 1.

Table 1
The average diameter of the crystalline grain D, the Vickers hardness index Hv and the amount of oxygen after analysis of the material Fe _99.8 Co _0.2 (wt.%), Obtained by rolling in the shell (PO) mechanically alloyed at 900 ° С powders of iron and carbon Sample D (nm) Hv Oxygen (wt.%) Material obtained by MS * 23 980 0.485 * - the D value was calculated according to the Scherrer equation, and the * symbol means that the material thickness was approximately 1.4 mm.

It can be seen from Example 3 and Table 1 that in accordance with the invention, the Vickers hardness Hv of the obtained material increased as a result of the reduction of the crystal grains to nanoscale and exceeded the hardness of the hardened material having the martensitic structure of high-carbon steel.

Example 4

The powders of alloys (a) Fe ₈₆ Cr ₁₃ N ₁ (wt.%) And (b) Fe _69.25 Cr ₂₀ Ni ₈ Ta ₂ N _0.75 (wt.%) _Were prepared by mechanical alloying (MS) of powder mixtures, including powders of iron, chromium, nickel and tantalum, as well as iron nitride (containing 8.51 wt.% nitrogen) in an argon atmosphere using a ball mill.

Then these powders were placed in a graphite matrix with an internal diameter of 40 mm and the matrix was placed in vacuum for electric discharge sintering (IPA) at 900 ° C, after which the sintered material was hot rolled at the same temperature, annealed at 1150 ° C for 15 minutes, and finally cooled with water. Table 2 shows the average crystal grain diameter d, hardness Hv, tensile strength σB, elongation δ, and the amount of oxygen and nitrogen after analysis of the rolled / annealed products.

table 2
The average crystal grain diameter d, hardness Hv, tensile strength σB, elongation δ, and the amount of oxygen and nitrogen after analysis of the resulting materials (spark plasma sintering (vacuum, 900 ° C) plus rolling (vacuum, 900 ° C) plus annealing (1,150 ° C × 15 min / cooling in water) obtained from mechanically alloyed powder samples of (a) Fe ₈₆ Cr ₁₃ N ₁ (wt.%) And (b) Fe _69.25 Cr ₂₀ Ni ₈ Ta ₂ N _0.75 (wt.%) Sample d (nm) Hv σВ, MPa δ,
% Oxygen, wt.% Nitrogen, wt.% BUT AT but twenty 200 770 2200 fifteen 0.502 1,02 b 17 150 680 2050 twenty 0.544 0.746 A is a sample of mechanically fused powder,
B is a sample of the obtained material,
* - the amount of oxygen in powders up to MS was 0.23-0.28 wt.%.

From Table 2 it can be seen that although a significant increase in crystalline grain is observed both during sintering and during annealing, both samples obtained still retain a structure of crystalline nanoscale grains. This could be due to the fixation at the boundaries of crystalline grains of metal or semimetal oxides formed by oxygen, which was contained in mechanically alloyed powders.

It was also found that, due to the solid solution of nitrogen and the ultra-small sizes of crystalline grains, the hardness Hv and the tensile strength σB of both alloys were much improved.

In order to use the superplasticity caused by sintering in powder materials, it is very important to reduce crystalline grains to ultrafine sizes and to minimize crystalline grain growth during deformation due to superplasticity.

According to this invention, sintering processes using superplasticity are easy to carry out, since powders with ultrafine, nanosized crystalline grains are quite easy to produce by mechanical alloying (MS) of the initial powders and due to the fact that metal oxides inevitably result from mechanical alloying (MS), prevent grain growth during sintering.

The following are examples of sintering using the superplasticity in accordance with the invention, with reference to Tables 3, 4 and 5.

Example 5

In accordance with this invention, the sintering process using superplasticity was effectively carried out on powders obtained by mechanical alloying (MS) of a carbon steel material with a hypereutectoid steel composition, in particular with a carbon content of 0.765-2.14 wt.%. The following is one example.

Powders of an alloy having the composition of the hypereutectoid steel Fe _96.1-x1.5 Cr _1.7 Mn _0.5 N _0.2 Si _x (wt.%), Where x = 1-3, were prepared in a ball mill by mechanical alloying (MS, argon atmosphere) a mixture of powders of carbon, chromium, manganese and silicon with iron nitride with a nitrogen content of 8.51 wt.%. The powders were placed in a graphite matrix with an inner diameter of 40 mm for 15 minutes of hot pressing in vacuum at 750 ° C and a pressure of 60 MPa, and a pre-sintered mass was thus obtained in the form of a preform of 40 mm in diameter and approximately 5 mm thick.

Then, the workpiece was subjected to a compressive load at 800 ° C and a strain rate of 10 ^-4 / s for 30 minutes in the direction of its thickness to obtain a sintering product. Table 3 shows the average crystalline grain diameter d, hardness Hv, tensile strength σB, elongation δ, and the amount of oxygen and nitrogen obtained by analyzing the resulting product at different concentrations of Si (x, y wt.%).

It should be noted that nitrogen was included in this alloy sample to increase its strength.

From the data of Table 3 and the values of hardness Hv at ordinary temperature it is seen that the sintering process of these samples at 800 ° C becomes more efficient at a Si concentration of 2 wt.% Or higher.

Preferably, the concentration of Si is in the range of 2.0-3.5 wt.%.

Table 3
The relationship between the Si concentration in samples with Fe _{96.1-x 1.5} Cr _1.7 Mn _0.5 N _0.2 Si _x (wt.%, Where x = 1-3) obtained by mechanical alloying and compaction during molding by sintering, and mechanical properties of the obtained samples The concentration of Si (x, wt.%) 1,0 1,5 2.0 2,5 3.0 d * (nm) 4,400 3,200 290 240 210 Hv 200 230 570 610 650 σВ (MPa) - - 1,220 1,350 1,430 δ (%) - - 24 fifteen 12 Oxygen (wt.%) 0.445 0.506 0.496 0.431 0.543 Nitrogen (wt.%) 0.202 0.198 0,207 0.210 0.204 * means that mechanically fused powders at each concentration x have an average grain diameter of 7-20 nm.

Example 6

According to this invention, the sintering process using superplasticity was effectively carried out on powders obtained by mechanical alloying (MS) of a material with the composition of cast iron or white cast iron with a carbon content of 2.2-4.3 wt.%. The following is one example.

As in Example 5, powders with the composition of cast iron Fe _94.3 C _3.5 Cr ₂ N _0.2 (wt.%) Were obtained by mechanical alloying (MS) of a mixture of powders of iron, carbon, chromium and iron nitride with a nitrogen content of 8 51 wt.%. The powders were placed in a graphite matrix with an inner diameter of 40 mm for 15 minutes of hot pressing in vacuum at 700 ° C and a pressure of 60 MPa to obtain thus pre-sintered mass in the form of a preform of 40 mm in diameter and about 5 mm thick. Then, the workpiece was subjected to a compressive load with a strain rate of 10 ^-4 / s for 30 minutes in the direction of its thickness at temperatures of 550 ° C, 600 ° C, 650 ° C, 700 ° C and 750 ° C to obtain a sintering product. Table 4 shows: average crystalline grain diameter d, hardness Hv, tensile strength σB, elongation δ and the amount of oxygen and nitrogen in the resulting product at different sintering temperatures.

Table 4
The molding temperature of the sintering obtained as a result of mechanical fusion (MS) of a powder of Fe _94.3 C _3.5 Cr ₂ N _0.2 (wt.%) And the mechanical properties of the obtained products T (° C) 550 600 650 700 750 d * (nm) 2,080 2,510 150 230 270 Hv 145 210 810 740 690 σВ (MPa) - - 1,610 1,530 1,380 δ (%) - - 10 17 23 Oxygen (wt.%) 0.503 0.469 0.457 0.432 0.425 Nitrogen (wt.%) 0.205 0.208 0.201 0.204 0,207

From the data of Table 4 and hardness indicators at ordinary temperature, it was found that the efficiency of the sintering process of each sample increases at temperatures of 650 ° C and above.

Example 7

As in Example 6, alloy powders (a) Ti ₈₈ Ta ₆ Nb ₄ Fe ₂ (wt.%), (B) Ti ₈₈ Nb ₆ Zr ₄ Fe ₂ (wt.%) And (c) Ti ₈₈ Zr ₆ Ta ₄ Fe ₂ (wt.%) Was obtained by mechanical alloying (MS) of a mixture of elementary powders of titanium, tantalum, niobium, zirconium, and iron. The powders were placed in a graphite matrix with an inner diameter of 40 mm for 15 minutes of hot pressing in vacuum at 700 ° C and a pressure of 60 MPa to obtain thus pre-sintered mass in the form of a preform of 40 mm in diameter and about 5 mm thick.

Then, the workpiece was subjected to a compressive load with a strain rate of 10 ^-4 / s for 30 minutes in the direction of its thickness, changing the temperature to determine the temperature T _SP , at which superplasticity appears and the hardness of the pre-sintered material sharply increases at normal temperature. The results are shown in Table 5.

Table 5
Mechanical properties of molded articles obtained from mechanically alloyed powders (a) Ti ₈₈ Ta ₆ Nb ₄ Fe ₂ (wt.%), (B) Ti ₈₈ Nb ₆ Zr ₄ Fe ₂ (wt.%) And (c) Ti ₈₈ Zr ₆ Ta ₄ Fe ₂ (wt.%), And the temperature of the appearance of superplasticity during molding Samples d * (nm) Hv σВ (MPa) δ (%) T (° C) Oxygen BUT 150 720 1,700 10 910 0.551 AT 190 650 1,610 fourteen 890 0.603 FROM 240 590 1,540 22 850 0.675 * - means that the average diameter of the crystalline grain in mechanically alloyed powders was 14-20 nm.

In particular, Table 5 shows the following data: average crystalline grain diameter d, hardness Hv, tensile strength σB, elongation δ and the amount of oxygen in the molded product obtained at a given compressive load, a temperature 50 ° C higher than the temperature T _SP and strain rates of 10 ^-4 / s for 30 minutes.

From Example 5 (Table 3), Example 6 (Table 4), and Example 7 (Table 5), it can be seen that for sintered products that consist of nanocrystals, there is a certain temperature at which superplasticity appears, depending on size, composition and other characteristics of crystalline grains, and that the superplasticity that arose at such a temperature or close to it makes it possible to more efficiently combine nanocrystalline grains during sintering, which makes it possible to obtain material that at normal temperature has a very high hardness.

From example 5 (Table 3) it is seen that at a Si concentration of more than 2%, the sintering process can proceed more efficiently, since the presence of Si leads to a noticeable prevention of grain growth under the influence of a compressive load.

It can be seen from Example 7 (Table 5) that according to the invention, even alloys having a high melting point, for example titanium alloys, can be pulverized by mechanical alloying into powders consisting of crystalline nanoscale grains, and materials can be obtained by molding by sintering at relatively low temperatures.

Example 8

Powders of alloys of (a) Al _93.5 Cu ₆ Zr _0.5 (wt.%), (B) Cu ₈₇ Al ₁₀ Fe ₃ (wt.%) And (c) Ni _48.25 Cr ₃₉ Fe ₁₀ T _{1, 75} Al ₁ (wt.%) Obtained by mechanical alloying (MS) exhibit superplasticity at a temperature equal to or approaching 430 ° C, 750 ° C and 770 ° C, respectively, and each temperature was approximately 50 ° C lower temperature at which superplasticity of the alloy obtained by melting occurs.

The main reasons for this may be that the crystalline grains in the proposed nanocrystalline material are reduced to ultra-small sizes, and the metal oxide or similar compound present between and / or in the nanocrystalline grains behaves as an effective grain growth inhibitor.

According to the invention, difficult to process materials, for example cast iron, materials with a high melting point or titanium alloys, the use of which is limited due to their brittleness, can be converted into materials having high hardness, strength and toughness by manufacturing nanocrystalline powders by mechanical alloying (MS) and sintering using superplasticity, which could not be achieved by known methods. Thus, this invention makes it possible to obtain a completely new material with high hardness, strength and viscosity (in the form of an aggregate of nanocrystalline grains), as shown in examples 6 and 7.

Possible application of the invention in industry

Nanocrystalline metallic materials obtained in accordance with this invention, it is most advisable to apply in the following areas.

(1) bearings

When using the proposed nanocrystalline metal material for the rotating parts of the bearings, it is possible to significantly reduce the amount of material used due to its strength, which will not only save the material used, but will also significantly reduce energy during operation of the bearing due to a significant decrease in the centrifugal force of the moving bearing part.

(4) Gears

The metal materials used for the manufacture of most gears must have conflicting properties: wear resistance of the surface (surface of the tooth head) and internal strength. Therefore, to provide additional hardness, surface treatment is necessary and complex technologies have to be applied, including, for example, cementing the surface of the tooth head, hardening and tempering. However, if we use the proposed superhard nanocrystalline material produced by extrusion for these purposes, we can do without additional special processing.

(3) Tools for hot processing and extrusion

Hardened and tempered materials, which are often used in tools for cutting at high temperatures, for example, molybdenum steels for high-speed cutting, have the property of quickly softening at temperatures above 400 ° C due to the fact that the material matrix consists of a tempered martensitic phase, which becomes unstable with increasing temperature. The proposed nanocrystalline metal material, due to the fact that its matrix itself is a stable phase and therefore does not soften at high temperatures, is a more suitable material for tools designed for hot processing.

The proposed nanocrystalline metal material, due to the fact that its matrix is relatively heat-resistant, can be more effectively used for extrusion tools that undergo significant thermal changes during use.

(4) Medical and similar instruments

Unlike nickel-chromium austenitic stainless steels, titanium-based materials or high-nitrogen chromomanganese austenitic steels do not cause skin inflammation or skin disease and therefore can be used as material for surgical scalpels, medical low-temperature instruments, sharp-edged instruments, such as knives, instruments, etc. .P. general purpose.

Claims (19)

1. Nanocrystalline metal material having high hardness, strength and viscosity, made in the form of an aggregate of metal nanocrystalline grains, which contains 0.4-5.0 wt.% Nitrogen. 2. The nanocrystalline metal material according to claim 1, in which the aggregate of metal nanocrystalline grains contains 0.4 to 2.0 wt.% Nitrogen. 3. The nanocrystalline metal material according to claim 1 or 2, which further comprises a metal element having a greater affinity for nitrogen than the nanocrystalline metal, and preventing denitrification of an aggregate of nanocrystalline grains during sintering. 4. The nanocrystalline metal material according to claim 1, in which the component that serves to form the metal material is at least one of the elements selected from the group consisting of aluminum, magnesium, zinc, titanium, calcium, beryllium, antimony, yttrium , scandium, indium, uranium, gold, silver, chromium, zirconium, tin, tungsten, tantalum, iron, nickel, cobalt, copper, niobium, platinum, vanadium, manganese, molybdenum, lanthanum, rhodium, carbon, silicon, boron, nitrogen and phosphorus. 5. Nanocrystalline metal material according to any one of claims 1 to 3, in which the component used to form the metal material is an element of the platinum group used in dentistry. 6. The nanocrystalline metal material according to any one of claims 1 to 3, in which the nanocrystalline material is one or two or more intermetallic compounds selected from the group consisting of Ni ₃ Al, Fe ₃ Al, FeAl, Ti ₃ Al, TiAl, TiAl ₃ , ZrAl ₃ , NbAl ₃ , NiAl, Nb ₂ Al, MoSi ₂ , Nb ₅ Si ₃ , Ti ₅ Si ₃ , Nb ₂ Be ₁₇ , Co ₃ Ti, Ni ₃ (Si, Ti), SiC, Si ₃ N ₄ , AlN, TiNi, ZrB ₂ , HfB ₂ , Cr ₃ C ₂ , or Ni ₃ Al-Ni ₃ Nb. 7. Nanocrystalline metal material according to any one of claims 1 to 3, in which metal nanocrystalline grains are obtained by mechanical grinding or mechanical alloying using a ball mill. 8. A method of manufacturing a nanocrystalline metal material, including mechanical alloying of the components of the nanocrystalline metal material with a substance that becomes a nitrogen source, using a ball mill to obtain fine-grained powders of nanocrystalline metal material with a high nitrogen content, densifying the processing of nanocrystalline material powders by a method selected from the group which consists of hot pressing, electric discharge sintering, rolling shell, and combinations of two or more techniques, molding obtained by sintering a metal material compacted powders by extrusion and / or stamping explosion rolling molded sintered metal material, if necessary imparting a predetermined shape to obtain a metal material having high hardness, strength and toughness. 9. The method according to claim 8, in which the substance, which becomes a source of nitrogen, is metal nitride. 10. The method according to claim 8, in which the substance, which becomes a source of nitrogen, is gaseous N ₂ or NH ₃ . 11. The method of claim 8, in which the mechanical alloying is carried out in an atmosphere of a gas selected from the group consisting of an inert gas, such as argon, N ₃ , NH ₃ , or a mixture of at least two of these gases. 12. The method according to claim 11, in which the atmosphere in which the mechanical alloying is carried out, contains a reducing agent, such as gaseous H ₂ . 13. The method of claim 8, in which the medium in which the mechanical alloying is carried out is a vacuum, a vacuum with a reducing agent, such as gaseous H ₂ , or a reducing atmosphere. 14. The method according to any one of claims 8 to 13, comprising mixing the powders of the components of the nanocrystalline metal material with 1-10 vol.% Metal nitride or with 0.5-10 wt.% Metal having a greater affinity for nitrogen than the nanocrystalline metal, and with a substance that becomes a source of nitrogen, mechanical alloying of the resulting mixture using a ball mill, thereby producing fine-grained nanocrystalline metal powders and densification processing of the powder and sintering according to claim 8, resulting in di nitride is dispersed, or nitride or carbonitride is precipitated or dispersed in the process of mechanical alloying, in the process of densification processing or in the molding process by sintering of said powders. 15. The method according to any one of claims 8 to 13, in which the mixture of nanocrystalline metal contains 0.5-40 wt.% Another element, and molding by sintering according to claim 8 is carried out at a temperature that is at least 10% below the melting point or the melting temperature of the nanocrystalline material. 16. The method of claim 8, wherein the sintering of powders that form a metal material in the form of steel is carried out at temperatures that cause superplasticity or close to them. 17. The method according to claim 8, in which the metal material obtained in the form of sintering in the form of steel is processed at or near superplastic temperatures. 18. The method of claim 8, wherein the sintering of powders that form a metallic material in the form of cast iron is carried out at or near superplastic temperatures. 19. The method of claim 8, wherein the resulting sintering of a metal material in the form of cast iron is processed at or near superplastic temperatures.

Images