RU2711699C1 - METHOD OF PRODUCING COMPOSITE MATERIAL Ti/TiB - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to production of Ti/TiB composite material. Method comprises mixing titanium powder with average particle size of 25±10 mcm and titanium diboride powder, average particle size of which is equal to 4±1.5 mcm, in disk vibration mill at rotor rotational speed of 700 rpm for 60 minutes in medium of ethanol with cooling, and subsequent synthesis of composite material by spark plasma sintering at temperature of 1,000 °C, pressure 40 MPa, for 15 minutes. Mixing of titanium and titanium diboride powders is carried out for 30–60 minutes, while stirring during 50–60 minutes, the grinding set is cooled by liquid nitrogen. Received after spark plasma sintering workpiece of synthesized composite material is subject to deformation-thermal treatment by hot sheet rolling at double-rolling mill at accumulated degree of deformation of 50 % with reduction by one pass of 200 mcm at temperature from 900 to 1,000 °C.EFFECT: obtaining Ti/TiB composite material with high strength and wear resistance along with sufficient ductility at room temperature.1 cl, 8 ex, 3 dwg

Description

The invention relates to the field of powder metallurgy, in particular to the production of composite materials with a metal matrix, hardened reinforcing components. This invention can be used in the manufacture of cutting tools, including medical, operating in special conditions, for example, in aggressive environments, in a magnetic field.

Due to the complex of attractive properties (high specific strength, corrosion resistance, biocompatibility), titanium and titanium alloys are widely in demand in industry and medicine [Leyens, C. Titanium and Titanium Alloys. Fundamentals and Applications / C. Leyens, M. Peters // Wiley-VCH: Weinheim, Germany. 2003. P. 1-499]. However, the use of titanium and low alloy titanium alloys is often limited by their insufficiently high absolute strength, hardness and wear resistance. Hardening of titanium can be achieved by creating titanium-matrix composite materials using high-hardness compounds such as TiB ₂ , TiC, TiN as a reinforcing component [Godfrey, TMT Titanium particulate metal matrix composites-Reinforcement, production methods, and mechanical properties / TMT Godfrey, PS Goodwin, CM Ward-Close // Adv. Eng. Mater. 2000. V. 2. P. 85-91]. Moreover, in comparison with other hardeners, TiB ₂ has high stability at synthesis temperatures, density and thermal expansion coefficient close to titanium, and also has good crystallographic conjugation with a titanium matrix, thereby ensuring minimal residual stresses [Morsi, K. Processing and properties of titanium – titanium boride (TiBw) matrix composites - a review / K. Morsi, VV Patel // J. Mater. Sci. 42 (2007) 2037-2047]. In this case, a titanium metal matrix is used; the TiB ₂ compound acts as a hardener. To date, spark plasma sintering (hereinafter IPS) is one of the most promising methods for creating composite materials. IPS allows one to synthesize at a relatively low temperature compared to casting and in a short time, which, on the one hand, ensures high productivity of the method when almost 100% density of the workpieces is achieved, and on the other hand, does not lead to a significant increase in structural elements, allowing one to obtain a nanostructured state composite [Ragulya, AV Fundamentals of Spark Plasma Sintering, in Encyclopedia of Materials / AV Ragulya // Science and Technology (Eds. KH Jürgen Buschow et al.). 2010. P. 1-5.]. During spark plasma synthesis of a mixture of powders of titanium and titanium diboride (TiB ₂ ), the chemical reaction 2Ti + TiB ₂ = Ti + 2TiB takes place, as a result of which a strong TiB phase is formed in the titanium matrix [Feng, H. Growth Mechanism of In Situ TiB Whiskers in Spark Plasma Sintered TiB / Ti Metal Matrix Composites / H. Feng, Yu Zhou, D. Jia, Q. Meng, and J. Rao // Crystal Growth & Design. 2006. V. 7. P. 1626-1630.].

Currently, for the manufacture of cutting tools operating in aggressive environments, for example, in sea water or in surgery, corrosion-resistant steels are mainly used. Titanium alloys have a competitive advantage over steels in the field of their application in special conditions. For example, during the operation of a cutting tool made of steel in seawater, contact corrosion develops, as a result, the steel tool quickly collapses. The use of steel in surgical instruments has also become obsolete, as steel scalpels have a large specific weight, can cause allergies in patients, and also make it impossible to carry out surgical operations in a magnetic field. Technically pure titanium is devoid of these drawbacks, but there is a problem: the low hardness does not allow to make a cutting tool out of it. Therefore, it is necessary to solve the problem of creating a composite material based on a metal matrix with high hardness and wear resistance. One way to solve this problem is to strengthen titanium with high-strength compounds.

At the moment, several methods for producing composite materials with a metal matrix are known.

A known method of manufacturing a composite material with a metal matrix and nanosized reinforcing particles [RF Patent No. RU 2574534 C2 dated 06/17/2014 "Composite material with a metal matrix and nanosized reinforcing particles and the method of its manufacture"]. The objective of the technical solution is to increase the strength properties of the composite material while minimizing the volume fraction of reinforcing particles. In a composite material with a metal matrix and nanosized reinforcing particles in an agglomerated state made with a molten matrix, the content of nanosized reinforcing particles in the agglomerated state does not exceed 5% of the total volume of the nanoparticles, and the remaining nanosized reinforcing particles are in the non-agglomerated state. In this method, aluminum or copper acts as a matrix, and diamond or silicon carbide particles act as a hardener. To accomplish the task in this method, composite granules were prepared by mechanical alloying of initial mixtures of metal particles and hardening nanoparticles, then the granules were heated to full or partial melting and the products were molded or deformed in a liquid or semi-liquid state. According to the invention, the prepared composite granules are introduced into the melt of the matrix material or its component and mixed, while the temperature of the melt is maintained in the temperature range 1.01-1.3 of the melting temperature of the melt material. The disadvantage of this technical solution is that it does not indicate information confirming the increase in the strength properties of the obtained composites and does not describe their ability to work in aggressive environments and in a magnetic field.

A known method of producing a composite material by electropulse sintering [RF Patent No. RU 2495732 C1 of 09/20/2012 "Method for producing consolidated powder materials"]. This method can be used for the manufacture of workpieces with high strength characteristics, including composites. The technical solution consists of two stages: preliminary cleaning of the powder by heating it in a vacuum with a series of low-voltage DC pulses and subsequent consolidation by exposing the powder to a pressure of 50-500 MPa and passing through it a high-voltage current pulse with a density of 50-500 kA / cm ² and a duration of 10 -500 μs. As a result, this method allows to obtain powder materials with high strength and ductility while maintaining the original grain size of the powders. As an example, a method for producing a sample from a powder of alloy powder E-110 based on zirconium with a relative density that practically coincides with the theoretically possible (99.9%) is given. The disadvantage of this method is its high energy consumption, as well as the absence of specific examples of work in aggressive environments and in a magnetic field. And also the insufficiently high strength of the obtained composite, which prevents its use as cutting tools in medicine. However, there is no data on the possibility of using the obtained material in an aggressive marine environment.

A known method of producing a composite with a metal matrix based on titanium [RF Patent No. RU 2492256 C1 of 05.16.2012 “Nanostructured composite material based on pure titanium and method for its preparation]. This invention can be used in medicine for the manufacture of implants and surgical instruments. Composite nanostructured material contains a matrix of pure titanium with a grain size of ≤250 nm, dispersion hardened by thermally stable and chemically stable nanoscale particles of titanium carbide, boride or nitride with a particle size of 2-10 nm. The reinforcing particles are evenly distributed in the volume of the material, and their total share is 0.05-0.50 vol.%. The method includes obtaining a powder mixture containing pure titanium powder with a particle size of 40-200 μm and nanosized strengthening particles of titanium carbide, nitride or diboride, mechanical alloying of the mixture in a protective medium in a planetary ball mill with grinding cups and grinding balls made of zirconia, partially stabilized with yttrium, or alumina, with the formation of a mixture of composite particles, degassing, placement in a metal capsule, vibration compaction, evacuation, seal isation and subsequent hot pressing by the isostatic method. The method provides an increase in the strength properties of the material due to the increase in the level of the conditional yield strength, tensile strength, fatigue resistance and biological compatibility of the material.

The disadvantage of this method is the low content of the reinforcing component, which does not provide the necessary hardness for the production of, for example, a cutting tool, the high technical complexity of obtaining starting materials with the required dimensions in the nanoscale.

Closest to the invention in the manufacturing process of the composite is a method of synthesis of a composite with a metal matrix based on titanium and a reinforcing component TiB ₂ from the source [M. Ozerov, M. Klimova, A. Kolesnikov, N. Stepanov, S. Zherebtsov, Deformation behavior and microstructure evolution of a Ti / TiB metal-matrix composite during high temperature compression tests, Materials & Design 112 (2016) 17-26] . This method is adopted as a prototype. According to the method described in this article, titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm, is mixed in a disk vibration mill at a rotor speed of 700 rpm for one hour in ethyl alcohol. In this case, the reaction 2Ti + TiB ₂ = Ti + 2TiB is carried out. The weight fraction of titanium diboride in the initial mixture is 10%, which provides 17% TiB in the composite after the reaction. To prevent heating of the mixture during mixing, the grinding bowl is cooled with liquid nitrogen at T = - 196 ° C. Then, the Ti / TiB composite is synthesized by spark plasma sintering (IPA) at a temperature of 1000 ° C, a pressure of 40 MPa, and a holding time of 15 min. The microstructure of the Ti / TiB composite consists of TiB whiskers that are not uniformly distributed in the titanium matrix. The diameter of TiB fibers varies in a wide range from des ± 35 nm. Also, unreacted TiB ₂ particles are observed in the composite structure. Their volume fraction was 2%. Porosity does not exceed 0.5%. The hardness of the composite is 59-60 HRC. The advantage of the prototype is not only a sufficiently high hardness of the composite material, but also the use of spark plasma sintering (IPS) for the synthesis of the composite, when pulsed direct current with a high current strength is passed through the powder and external pressure is applied at the same time, due to which the workpiece is heated from the inside, thereby ensuring high uniformity of heating. A very high heating rate up to 1000 ° C / min and a significant applied pressure allows synthesis at significantly lower temperatures and in a significantly shorter time compared to other powder metallurgy methods, for example, HIP. [M. Selva Kumar et al. Characterization of titanium – titanium boride composites processed by powder metallurgy techniques. Mater. Charact. 73 (2012) pp. 43-51.].

The disadvantage of this method is the low ductility of the obtained composite Ti / TiB - the elongation at room temperature is zero.

SUMMARY OF THE INVENTION

The objective of the invention is the ability to obtain a composite material based on titanium with high strength and wear resistance, along with sufficient ductility at room temperature, allowing to produce a cutting tool for working in special conditions, for example, in aggressive environments, in a magnetic field.

The technical result of the invention is to obtain a composite material Ti / TiB with high strength and wear resistance along with sufficient ductility at room temperature for the manufacture of a cutting tool, due to the introduction of additional deformation-heat treatment by hot rolling of the blanks of the obtained composite material.

The objective of the invention is solved by the method of producing a Ti / TiB composite, comprising mixing titanium powders with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm in a disk vibration mill at a rotor speed of 700 rpm for 60 minutes in ethanol with cooling, followed by synthesis of the composite by spark plasma sintering (IPA) at a temperature of 1000 ° C, a pressure of 40 MPa, for 15 minutes, which introduced new features:

- mixing of powders of titanium and titanium diboride is carried out for 30-60 minutes, and with stirring for 50-60 minutes, cooling of the grinding set is additionally used with liquid nitrogen;

- finished samples of the synthesized composite are subjected to sheet rolling on a two-roll rolling mill for an accumulated degree of deformation of 50%, with compression in one pass of 200 μm, at a temperature of 900 to 1000 ° C, which provides ductility at room temperature equal to 5%.

DETAILED DESCRIPTION OF THE INVENTION

Titanium powders with an average particle size of 25 ± 10 μm and titanium diboride (TiB ₂ ), the average particle size of which is 4 ± 1.5 μm, are mixed in a Retsch RS200 disk vibratory disk mill at a rotor speed of 700 rpm for 30- 60 min in ethyl alcohol. The weight fraction of titanium diboride in the initial mixture is 10%. The weight of the sample is 100 g. Since during the mixing in the mill the powder heats up and the surface of the particles becomes juvenile, accompanied by its agglomeration and sticking to the walls of the grinding set, ethanol is added to the powder mixture. With stirring for 50-60 minutes, cooling of the grinding set with liquid nitrogen is additionally used. This allows to reduce the heating of the powder mixture and significantly increase the structural uniformity of the final workpiece. Next, spark plasma sintering of Ti and TiB ₂ powders is carried out, in which the reaction 2Ti + TiB2 = Ti + 2TiB proceeds. Spark sintering is carried out at a temperature of 1000 ° C with a pressure of 40 MPa and a holding time of 15 minutes using the Technology SPS10-3 installation. Get the workpiece with a diameter of 20-100 mm and a height of 25 mm In order to increase the mechanical properties of the obtained Ti / TiB composite, mainly ductility, the samples are subjected to hot deformation by sheet rolling on a Hankook M-TechIndustries twin roll mill to an accumulated degree of deformation of 50% at a temperature of from 900 to 1000 ° C. Compression in one pass is 200 microns. Before each pass, the sample is heated in a Nabertherm muffle furnace to the required temperature; the temperature is controlled by an infrared pyrometer.

The mixing conditions of the initial mixture of Ti and TiB ₂ powders are essential. The duration of mixing monotonously affects the quality of the resulting Ti / TiB preforms. Stirring under these conditions for 15 minutes does not provide sufficient uniformity of the final mixture. An increase in the mixing time in the mill up to 2-4 hours reduces the fraction of residual diboride in the sintered blanks, but it significantly reduces the ductility of the composite and leads to the appearance of cracks with a length of 9 ± 5 μm. The optimal duration of mixing is 30-60 minutes, because more time leads to partial mechanical activation of the mixture and subsequent embrittlement of the synthesized preform, and a decrease in time reduces the uniformity of the structure.

The optimal TiB ₂ content in the initial mixture is 10 (weight)%, which corresponds to 17 (vol.)% TiB in the structure of the Ti / TiB composite after synthesis [Huang, LJ Effects of volume fraction on the microstructure and tensile properties of in situ TiBw / Ti6Al4V composites with novel network microstructure / LJ Huang, L. Geng, B. Wang, LZ Wu // Mater. Design 2013. V. 45. P. 532-538]. The selected amount of the reinforcing component provides a strengthening effect close to the maximum, while a further increase in its amount does not give a noticeable increase in hardness, but leads to a sharp decrease in ductility [Morsi, K. Processing and properties of titanium – titanium boride (TiBw) matrix composites - a review / K. Morsi, VV Patel // J. Mater. Sci. 42 (2007) 2037-2047].

It was found that during spark sintering, titanium boride is formed in the form of whiskers - fibers, sprouting from the boundary between titanium and titanium diboride into titanium grains. The volume fraction of TiB in the structure of the obtained composite according to x-ray diffraction analysis is 17.1%, and TiB ₂ is 2.9% if the initial mixture contains TiB ₂ 10 (weight)%. The porosity of the synthesized preform in this state does not exceed 1%. A sufficiently complete conversion of diboride to titanium boride depends on the TiB ₂ content in the mixture and sintering temperature. For example, at 850 ° C the TiB ₂ content is more than 10 (weight)%. leads to the formation of a pronounced layer of residual TiB ₂ between the grains of titanium, which negatively affects the mechanical properties of the composite, because TiB ₂ does not have a good bond with the titanium matrix, in contrast to that formed during the synthesis of TiB, and leads to embrittlement of the composite. With an increase in the synthesis temperature to 900 ° C, the presence of a layer of unreacted TiB ₂ is observed only in the case of a proportion of TiB ₂ in the mixture of 20 wt%. When sintering at temperatures of 830 and 850 ° C, i.e. below the temperature of the polymorphic transformation of titanium equal to 882 ° C, in the structure of the composite, individual cracks with a length of about 10 μm and an increase in the amount of residual titanium diboride up to 5-15%, depending on the amount of diboride in the initial mixture, are observed. The latter fact can increase porosity to several percent due to poor conjugation of the Ti / TiB boundaries and the presence of pores along the boundaries of TiB ₂ and alpha titanium. In the course of research, the optimum sintering temperature was determined, which ranges from 900 to 1000 ° C. The highest values of the microhardness of the composite are shown by the state after sintering at 1000 ° C. An increase in the synthesis time to 30 min allows for a more complete reaction 2Ti + TiB ₂ = Ti + 2TiB and increases the amount of reacted TiB _{2 by} about 5%. However, an increase in sintering time leads to the growth of grains of the titanium matrix. A longer exposure time from 30 minutes to 1 hour leads to cracking and coarsening of the structure, and less than 15 minutes to an insufficiently complete reaction. The use of a pressure of more than 40 MPa during spark plasma sintering is similar to an increase in the synthesis temperature, but it allows the use of a shorter holding time and to prevent coarsening of the structure. At the same time, large working pressures significantly reduce the operating time of expensive graphite tooling. As a result, the optimal parameters for the synthesis are a pressure of 40 MPa, a temperature of 1000 ° C, and a holding time of 15 minutes for IPS.

Evaluation of the mechanical properties of samples of the Ti / TiB composite after IPA shows in all states an extremely low ductility, which does not allow us to evaluate the basic mechanical characteristics during tensile tests. The samples are brittlely destroyed, not reaching the flow stress, i.e. plastic deformation of not more than 0.1%. Measurement of microhardness values shows its increase with increasing TiB content in samples synthesized at a temperature of 1000 ° C and, conversely, a decrease in microhardness with increasing TiB in samples obtained below the polymorphic transformation temperature. The highest microhardness values of 686 ± 39 HV or 59-60 HRC show the state after IPA at 1000 ° C. Also in this case, the minimum residual TiB ₂ content was found in the structure.

The deformation-heat treatment of samples of the Ti / TiB composite by hot rolling on a two-roll rolling mill to an accumulated degree of deformation of 50% at temperatures from 900 to 1000 ° C with compression in one pass of 200 μm allows to increase the ductility of the composite material to about 5% at room temperature . This is confirmed by a study of the mechanical properties of composite samples, for which, after deformation, a flat sample is cut in the direction of rolling for uniaxial tensile tests at elevated temperatures and rectangular samples 4 × 4 × 6 mm in size are used for uniaxial compression tests at room temperature. After tensile tests at 400 ° C, the composite sample in the initial state shows zero ductility, while samples rolled at a temperature of 900 ° C and 1000 ° C show 20 and 22% ductility, respectively. After compression tests at room temperature, the ductility of the samples subjected to rolling at a temperature of 900 and 1000 ° C reaches about 5%, while in the initial, not subjected to deormation state, the composite sample is destroyed in the elastic region.

Thus, hot rolling has a significant effect on the mechanical properties of the Ti / TiB composite. The increase in ductility as a result of rolling also manifests itself in a shift in the temperature of the brittle-viscous transition of the Ti / TiB composite from ~ 500 ° C to ~ 300 ° C.

The invention is illustrated by the following materials:

FIG. 1 - Images of titanium powder (a) and titanium diboride powder (b) obtained by scanning electron microscopy (SEM).

FIG. 2 - Images of the microstructure of the Ti / TiB composite (a - scanning electron microscopy (SEM), b - transmission electron microscopy TEM.

FIG. 3 - Stress-strain curves obtained during uniaxial precipitation tests at room temperature of Ti / TiB composite samples in the initial state and after rolling.

The possibility of carrying out the invention is illustrated by examples to evaluate the influence of various parameters of the technological process of producing a composite on the structure and properties of Ti / TiB samples.

Example 1

For research using titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm. The weight fraction of titanium diboride in the initial mixture is 5%. The weight of the sample is 100 g. The mixing of the powders is carried out in a disk vibration mill at a rotor speed of 700 rpm for 30 minutes in ethanol. The Ti / TiB composite is synthesized by spark plasma sintering (IPS) technology at the Thermal Technology SPS10-3 unit at a temperature of 850 ° C with a pressure of 40 MPa and a holding time of 5 min.

The microhardness value is 510 ± 30 HV.

Example 2

For research using titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm. The weight fraction of titanium diboride in the initial mixture is 10%. The weight of the sample is 100 g. The mixing of the powders is carried out in a disk vibration mill at a rotor speed of 700 rpm for 40 minutes in ethanol. The Ti / TiB composite is synthesized using spark plasma sintering (IPS) technology at the Thermal Technology SPS10-3 unit at a temperature of 850 ° C with a pressure of 40 MPa and a holding time of 5 min.

The microhardness value is 580 ± 30 HV. This example shows that an increase in the content of TiB ₂ in the mixture to 10% allows to obtain an increase in microhardness by 15% compared with the content of TiB ₂ 5%.

Example 3

For research using titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm. The weight fraction of titanium diboride in the initial mixture is 10%. The weight of the sample is 100 g. The mixing of the powders is carried out in a disk vibratory mill at a rotor speed of 700 rpm for 50 min in ethanol. To prevent heating of the mixture during mixing, the grinding bowl is cooled with liquid nitrogen (T = -196 ° C). The Ti / TiB composite is synthesized using spark plasma sintering (IPS) technology at the Thermal Technology SPS10-3 unit at a temperature of 1000 ° C with a pressure of 40 MPa and a holding time of 5 min.

The microhardness value is 640 ± 30 HV. This example shows that an increase in the synthesis temperature to 1000 ° C allows one to obtain an increase in microhardness by 10% compared with the state after IPA at 850 ° C.

Example 4

For research using titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm. The weight fraction of titanium diboride in the initial mixture is 10%. The weight of the sample is 100 g. The mixing of the powders is carried out in a disk vibration mill at a rotor speed of 700 rpm for 60 minutes in ethanol. To prevent heating of the mixture during mixing, the grinding bowl is cooled with liquid nitrogen (T = -196 ° C). The Ti / TiB composite is synthesized by spark plasma sintering (IPS) technology on a Thermal Technology SPS10-3 unit at a temperature of 1000 ° C with a pressure of 40 MPa and a holding time of 15 min.

The microhardness value is 686 ± 39 HV OR 59-60 HRC. This example shows that the increase in exposure time during the IPA to 15 minutes provides hardness that allows you to sharpen the material and produce a cutting tool. Also in the structure of this state, the minimum content of residual TiB _{2 was found} , which does not have a good bond with the titanium matrix, and leads to embrittlement of the composite.

Example 5

For research using titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm. The weight fraction of titanium diboride in the initial mixture is 10%. The weight of the sample is 100 g. The mixing of the powders is carried out in a disk vibratory mill at a rotor speed of 700 rpm for 2 hours in ethanol. To prevent heating of the mixture during mixing, the grinding bowl is cooled with liquid nitrogen (T = -196 ° C). The Ti / TiB composite is synthesized by spark plasma sintering (IPS) technology on a Thermal Technology SPS10-3 unit at a temperature of 1000 ° C with a pressure of 40 MPa and a holding time of 15 min.

The microhardness value is 696 ± 39 HV (61-62 HRC). It was found that increasing the mixing time leads to embrittlement of the composite and the appearance of cracks.

Example 6

For research using titanium powder with an average particle size of 25 ± 10 μm and titanium diboride, the average particle size of which is 4 ± 1.5 μm. The weight fraction of titanium diboride in the initial mixture is 10%. The weight of the sample is 100 g. The mixing of the powders is carried out in a disk vibration mill at a rotor speed of 700 rpm for 30 minutes in ethanol. The Ti / TiB composite is synthesized by spark plasma sintering (IPS) technology on a Thermal Technology SPS10-3 unit at a temperature of 1000 ° C with a pressure of 40 MPa and a holding time of 15 min.

The microhardness value is 686 ± 39 HV or 59-60 HRC. The obtained microhardness of the composite is equivalent to a hardness of about 60 HRC, which, in turn, is close to the hardness of hardened steel (55-60 HRC) used to make the cutting tool.

Example 7

Next, the samples obtained in example 4, are subjected to sheet rolling on a two-roll mill Hankook M-TechIndustries for the accumulated degree of deformation of 50% at a temperature of 900 ° C with compression in one pass of 200 microns. Before each pass, the sample is heated in a Nabertherm muffle furnace to the required temperature; the temperature is controlled by an infrared pyrometer. To study the mechanical properties of the composite, a flat sample is cut out after rolling in the direction of rolling for uniaxial tensile testing at elevated temperatures. The microhardness value is 680 ± 40 HV or 60 ± 2 HRC. The increase in ductility as a result of rolling manifests itself in a shift in the temperature of the brittle-viscous transition of the Ti / TiB composite from 500 ° C to 300 ° C. Also, after compression tests at room temperature, the plasticity of the samples subjected to rolling at 900 ° C reaches ~ 5%, while in the initial state, the composite sample is destroyed in the elastic region.

Example 8

Next, the samples obtained in example 6, are subjected to sheet rolling on a two-roll mill Hankook M-TechIndustries for the accumulated degree of deformation of 50% at a temperature of 1000 ° C with compression in one pass of 200 microns. Before each pass, the sample is heated in a Nabertherm muffle furnace to the required temperature; the temperature is controlled by an infrared pyrometer. To study the mechanical properties of the composite, a flat sample is cut out after rolling in the direction of rolling for uniaxial tensile testing at elevated temperatures. The microhardness value is 680 ± 40 HV or 60 ± 2 HRC. The increase in ductility as a result of rolling manifests itself in a shift in the temperature of the brittle-viscous transition of the Ti / TiB composite from 500 ° C to 300 ° C. Also, after compression tests at room temperature, the plasticity of the samples subjected to rolling at 1000 ° C reaches ~ 5%, whereas in the initial state, the composite sample is destroyed in the elastic region.

From this it follows that the Ti / TiB composite can be considered as a promising material for the production of cutting tools, including medical supplies, operating under special conditions, for example, in aggressive environments, in a magnetic field.

Claims (1)

A method of obtaining a composite material Ti / TiB, comprising mixing titanium powder with an average particle size of 25 ± 10 μm and titanium diboride powder, the average particle size of which is 4 ± 1.5 μm, in a disk vibratory mill at a rotor speed of 700 rpm for 60 minutes in ethanol with cooling, and subsequent synthesis of the composite material by spark plasma sintering at a temperature of 1000 ° C, a pressure of 40 MPa, for 15 minutes, characterized in that the mixing of titanium powders and titanium diboride is carried out for 30-60 minutes, while stirring for 50-60 minutes, the grinding set is cooled with liquid nitrogen, and the obtained after synthesized plasma sintering of the synthesized composite material blanks is subjected to heat-deformation processing by hot sheet rolling on a two-roll rolling mill for the accumulated degree of deformation 50% with compression in one pass of 200 microns at a temperature of from 900 to 1000 ° C.

Images