Metal matrix composite material and method for manufacturing the same

Abstract

The present invention provides a molybdenum-copper metal matrix composite material for use as an electrode tip for welding electrodes, which exhibits improved high-temperature hardness, improved machinability, and very low reactivity with the material being welded, i.e., very low tackiness, as well as a method for manufacturing the same. [Solution] A novel metal matrix composite material comprising copper in a volume percentage of 1% to 65% of the volume of the composite material, titanium nitride in a volume percentage of 1% to 25% of the volume of the composite material, and the remainder being molybdenum. This disclosure also relates to a method for manufacturing the metal matrix composite material disclosed herein. This disclosure also relates to a welding electrode tip made from the metal matrix composite material disclosed herein.

Description

Technical Field

[0001] The present invention relates to metal matrix composites, particularly those manufactured by sintering.

Background Art

[0002] Prior Art Molybdenum-copper composites are a known family of metal-metal composites similar to tungsten-copper composites, and due to a good combination of high thermal conductivity and low thermal expansion, they enable an optimal mechanical-thermal coupling with semiconductors in electronic devices, and are thus widely used as thermal management solutions for electrical conductors and semiconductors in resistance welding applications. As resistance welding electrodes, they are known for having a low tendency to adhere, in addition to a good compromise between toughness, machinability, electrical conductivity, and hardness. They are typically manufactured through a two-step process in which a powder of a refractory metal (molybdenum or tungsten) is pressed, sintered, or hot-pressed to create an open pore structure or scaffold. In the second step, copper is pressure-impregnated as a liquid through (and into) the open pore structure or scaffold.

[0003] Another method for manufacturing copper-molybdenum composites is suggested by US Patent No. 7,122,069 B2, which proposes generating appropriate powders of copper and molybdenum through the reduction of a CuMo-based composite oxide that has been reduced in hydrogen and prepared for pressure and sintering by liquid phase sintering.

[0004] Another, more advanced method is proposed in US 10,837,087 B2, in which a molybdenum-based or tungsten-based scaffold is impregnated with copper. The base molybdenum or tungsten scaffold is reinforced with one of B (boron), N (nitrogen), or C (carbon) to increase its hardness. In one embodiment, the resulting material is disclosed as a molybdenum-based or tungsten-based scaffold comprising one of the following: silicon (Si), silver (Ag), cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn), niobium (Nb), nickel (Ni), phosphorus (P), sulfur (S), tantalum (Ta), titanium (Ti), vanadium (V), and zirconium (Zr), where at least one of B, N, and C and at least one additional additive are present together in a total amount up to 25% by weight, based on the total weight of the material. The addition of additive elements with small atomic radii, such as B, N, or C, which tend to form a ceramic hard phase with molybdenum, is with the specific intention of strengthening the base molybdenum powder.

[0005] However, there are significant limitations to the microstructures and phases disclosed in such documents. Molybdenum carbides, nitrides, and borides are not as effective at reducing adhesion and friction as other ceramic phases. The high distribution of the refractory phase (scaffold) compared to the copper phase is a result of the need for liquid copper to properly impregnate the scaffold so that the molybdenum powder densifies during the liquid-phase sintering process, and therefore it must have an open porosity with a porosity value of 10-50%. These types of microstructures do not optimize the mechanical properties at high temperatures and are merely an inevitable consequence of the manufacturing methods used.

[0006] A further drawback is associated with the use of tungsten in the refractory phase, which is known to be more expensive, have lower toughness, lower machinability, and lower availability compared to other metals for the refractory phase. Purpose of the invention An object of the present invention is to solve the above-mentioned technical problems. More specifically, an object of the present invention is to provide a molybdenum-copper metal matrix composite material that has improved high-temperature hardness, improved machinability, and very low reactivity with the material being welded, i.e., very low stickiness, particularly for use as electrode tips for welding electrodes. A further object of the present invention is to reduce the welding energy involved during welding when using electrode tips made of the molybdenum-copper metal matrix composite material. Yet another object of the present invention is to enable manufacturing using materials that are more widely available than tungsten. [Overview of the project]

[0007] The object of the present invention is achieved by a metal matrix composite material, a method for manufacturing it, and a welding electrode having the features described in the following claims, which form an integral part of the technical disclosure provided herein in connection with the present invention. [Brief explanation of the drawing]

[0008] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, which are provided purely as non-limiting examples. [Figure 1] This is an optical microscope image of a mixture of particle-form components used in the manufacturing method according to the present invention. [Figure 2] This is an optical microscope image of the Grade 1 material according to the present invention. [Figure 3] This is an enlarged view of Figure 2. [Figure 4] This is an XRD (X-ray diffraction) plot of the Grade 0 material according to the present invention. [Figure 5] This is an XRD (X-ray diffraction) plot of the Grade 1 material according to the present invention. [Figure 6] This is an image of a welding electrode tip made from the material according to the present invention. [Figure 7] This is an image of a welding electrode tip made from the material according to the present invention. [Figure 8]Adhesion test plot of a welding electrode tip made of the material according to the present invention. [Figure 9] Adhesion test plot of a welding electrode tip made of the material according to the present invention. [Figure 10] Image of an electrode tip material and an electrode for resistance welding according to an embodiment of the present invention. [Figure 11] Image of an electrode tip material and an electrode for resistance welding according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0009] Disclosed herein is a metal matrix composite material according to an embodiment of the present invention, comprising copper (Cu) in a volume percentage amount of 1% to 65% of the volume of the composite material, titanium nitride (TiN) in a volume percentage amount of 1% to 25% of the volume of the composite material, and the balance molybdenum (Mo), with the balance being such that it reaches 100% of the volume of the composite material.

[0010] More specifically, the volume fraction of each i-th phase, i.e., each of copper, titanium nitride, and molybdenum (where i = 1, 2, 3 in this specification)

Number

Number

Number

Number

[0011] To determine how much powder should be weighed to prepare the composite material, the starting point is δi = v i / m i is the definition of density as, where δ is g / m 3 in units or more frequently in g / cm 3 in units of density, from which the value of m, i.e., the powder amount in terms of weight, can be calculated.

[0012] The density (δ c ) of the composite material is obtained by applying the law of phases to the powder since there is little or no chemical interaction to form other phases, i.e.:

Number

[0013] As an example, the compositions of two notable grades (1 and 2) of the material according to the present invention are shown in the following table (both in terms of weight and volume percentages of the total weight and total volume of the material).

Table 1

Table 2

[0014] The microstructure and composition of the metal matrix composite material according to the present invention achieve very high machinability and low tackiness, along with high mechanical properties at high temperatures. It is manufactured through mechanical alloying starting from a very fine mechanical mixture of titanium nitride (TiN), molybdenum (Mo), and copper (Cu). Thus, a method for manufacturing the above metal matrix composite material is defined, which is: - The step of providing copper (Cu) in particulate form, i.e., as powder. - The step of providing titanium nitride in particulate form, i.e., as a powder, - A step of providing molybdenum in particulate form, i.e., as a powder. - A step of grinding at least the titanium nitride in particulate form and the molybdenum in particulate form, - Following the pulverization step, the method includes a step of solidifying a mixture of particulate copper, particulate titanium nitride, and particulate molybdenum into a metal matrix composite material by electric field-assisted sintering.

[0015] Considering the above and referring to Figure 1, according to an advantageous embodiment of the present invention, the ceramic phase (TiN) is preferably closely mixed with molybdenum and dispersed so well that, by optical microscopy, they constitute a single metallurgical phase. In particular, Figure 1 shows the aggregation of TiN and molybdenum after the preparation of a mixture of copper, titanium nitride, and molybdenum, before solidification by sintering. The white circles indicate islands of copper surrounded by what appears to be a single phase (white arrow), but it is actually a mechanical mixture of TiN and molybdenum. Figure 2 shows the microstructure of the solidified (sintered) metal matrix composite material of the present invention, which consists substantially of a nearly invisible copper binder surrounding the Mo-TiN composite. The close mechanical alloying of the Mo-TiN phase with copper is such that the copper is only discernible at high magnification and uniformly coats the Mo-TiN particles, as shown in the magnified view of Figure 3.

[0016] The TiN phase should remain intact during the production of the composite powder (Mo+TiN in particle form, which is then pulverized) and during the solidification process. For this purpose, according to one aspect of the present invention, the titanium nitride in particle form has a particle size of 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. Generally, the smaller the size of the TiN particles in powder form, the better. However, according to the present invention, it is more difficult to maintain the TiN particles intact through the densification process without undesirable molybdenum diffusion and degradation to molybdenum nitride.

[0017] Regarding the grinding stage, it can be carried out by including all components (Cu, Mo, TiN) together regardless of the amount of copper, which is generally the preferred option, or it can be carried out in two subsequent stages depending on the amount of copper.

[0018] In embodiments in which the grinding step includes subsequent steps based on the amount of copper, when copper is present in a low to moderate amount (for example, when copper is present in less than 50% by volume), the grinding step includes grinding copper in particulate form together with and simultaneously grinding titanium nitride and molybdenum in particulate form. On the other hand, when copper is present in a high amount (for example, when copper is present in more than 50% by volume, up to a maximum of 65%), the grinding step includes, - First grinding of titanium nitride and molybdenum in particulate form, - This process includes a second grinding of copper in particulate form with pre-ground titanium nitride and molybdenum in particulate form from a first grinding, i.e., copper is ground together with a pre-ground mixture of TiN and molybdenum.

[0019] Grinding is preferably carried out by an attrita mill or a planetary ball mill.

[0020] As can be seen in the X-ray diffraction (XRD) spectra of Figures 4 and 5, each grade of the material of the present invention is unique (Grade 0 in Figure 4, Grade 1 in Figure 5), and no phases other than molybdenum, titanium nitride, and copper are present, neither in the particle form before grinding and solidification nor in the solidified material. More specifically, in a preferred embodiment of the present invention, the only phases constituting the material are face-centered cubic (FCC) copper, face-centered cubic (FCC) titanium nitride, and body-centered cubic (BCC) molybdenum, and thereafter the list of components and ranges disclosed above should be understood as consisting of copper as face-centered cubic copper, titanium nitride as face-centered cubic titanium nitride, and molybdenum as body-centered cubic molybdenum in such embodiments. FCC copper is associated with triangular markers in Figures 4 and 5, FCC titanium nitride is associated with star-shaped markers, and BCC molybdenum is associated with square-shaped markers. Figures 4 and 5 feature five individual plots (spectrums), specifically, i) Grade 0 / 1 - Sintered: XRD spectrum of solidified Grade 0 / 1 material, ii) Grade 0 / 1 - Powder: XRD spectrum of powder grade 0 / 1 material, i.e., having those constituent components in the particle form before solidification, iii) XRD spectrum of BCC molybdenum (molybdenum (MO-BCC)), iv) XRD spectrum of FCC TiN (Titanium Nitride (TiN-FCC)), v) XRD spectrum of FCC copper (copper (Cu)). During solidification, care must be taken with the combination of time / temperature / energy to avoid causing long-range diffusion, as long-range diffusion can convert titanium nitride particles into a core-shell ceramic having molybdenum nitride in the outer layer and titanium nitride in the inner layer, or induce the complete dissolution of molybdenum into titanium nitride to form a composite carbide, both of which are clearly undesirable in light of the above.

[0021] The effect of TiN particles in the composite material of the present invention can be considered to be triple, i) It increases high-temperature hardness by reducing plastic deformation, ii) It increases hardness retention after exposure to high temperatures, iii) It reduces the tendency for adhesion or welding to the materials being welded (adhesion reduction).

[0022] On the other hand, the effects of copper include increasing the electrical conductivity of the composite material, as well as mechanically solidifying the Mo-TiN composite, thereby imparting higher toughness, strength, and better machinability.

[0023] By adjusting the amounts of such phases (TiN, Mo, Cu), the electrical (and consequently thermal) conductivity of the material can be designed to better suit the intended welding application, considering its use as a welding electrode tip material.

[0024] Generally, the highest possible amount of TiN is advantageous in reducing the tendency for sticking / adhesion during welding, but on the other hand, because TiN is a semiconductor, it reduces electrical conductivity. Furthermore, they significantly reduce toughness and the machinability of the material. A key advantage of material grades with a particularly high percentage of copper is the potential for both high-temperature mechanical resistance, machinability, and relatively low cost due to the high volume percentage of copper.

[0025] With respect to solidification, any high-speed electric field-assisted sintering method can be used in the manufacturing method of the present invention. Electro-sinter-forging (ESF) is a preferred choice in this respect. High-speed electric field-assisted sintering methods such as ESF or capacitor discharge sintering have the advantage of avoiding contamination of the solidified material and suppressing long-range diffusion (and thus suppressing the undesirable effects mentioned above in relation to long-range diffusion).

[0026] More specifically, a preferred option is any electric field-assisted sintering method in which the duration of the thermal cycle (heating, holding, and cooling) is 30 seconds or less, preferably 20 seconds or less, and more preferably 10 seconds or less.

[0027] In view of the above, in a preferred embodiment of the method of the present invention, the following is assumed: a) The step of grinding at least the titanium nitride and molybdenum in particulate form is carried out in an inert environment, such as argon, whether in a single step or two steps based on copper concentration, as disclosed above, but may be accompanied by the addition of a small amount of hydrogen (<4% by volume) to help deoxygenate and remove any residual oxygen present in the grinding atmosphere. Nitrogen is relatively stable but cannot be used as a protective gas because it tends to combine with molybdenum during the grinding process, thereby altering the powder's solidification tendency and profoundly changing both the microstructural and chemical properties of the starting powder. The grinding is then carried out in a high-energy system for preparing a very fine and homogeneous composite, including a planetary ball mill or attritor mill as described above.

[0028] A preferred output of the method of the present invention is to solidify the mixture (output of the grinding stage) into a cylindrical body, particularly a cylindrical electrode tip.

[0029] In light of its intended use as a welding electrode tip, the above includes further machining operations to achieve the desired / required shape of the electrode tip. Further details are provided in the detailed descriptions of the subsequent Examples #1 to #3.

[0030] Example #1 In one embodiment, with reference to Figures 6 and 7, this involves machining a cylindrical body to achieve a wall-like shape at one end. Reference numeral 1 in Figures 6 and 7 indicates a welding electrode tip configured for welding the collector of an electric motor. The electrode 1 comprises a cylindrical body 2 (generally hollow) having a longitudinal axis X2 and including an intermediate portion 4, a first end portion 6, and a second end portion 8. The intermediate portion 4 has a larger outer diameter than the end portions 6 and 8 and is positioned between them. The first end is slightly conical to fit into a socket of a standard welding electrode body, while the second end portion 8 has a wall-like shape including a circular arrangement of axially finger-shaped and evenly spaced projections 10, the distal end of which provides the welding surface. Such a shape is also commonly referred to as a “multi-pin” shape.

[0031] Prior art electrode tips, i.e. electrodes made from the material discussed at the beginning of this disclosure, have the same shape, but unlike those achieved by brazing finger-like projections 10 to the intermediate portion 4, the electrode tip 1 made from the material according to the present invention is machined from a billet, i.e., machined starting from a cylindrical body which is the output of solidification by electric field-assisted sintering. This results in much higher reliability and lower manufacturing costs. A typical use involves brazing 96.5%Sn-3.5%Ag coated copper wire onto a 97%Ag-3%Cu collector for an electric motor. When made from the Grade 1 material according to the present invention, such electrode tips have a higher resistivity that helps heat the solder material, thereby enabling a 13% reduction in energy consumption during soldering (from 4.8 kW / h to 4.2 kW / h) compared to prior art brazing (tungsten) solutions.

[0032] More specifically, the prior art manufacturing method (and materials) for achieving the electrode shapes shown in Figures 6 and 7 involves silver brazing seven thin electrodes made of tungsten or tungsten-copper onto a machined copper bushing with a diameter of 10 mm that serves as an electrode holder.

[0033] By using the material of the present invention (Example #1), a cylindrical body with a diameter of 10 mm and a height of 12 mm having a Grade 1 composition according to Tables 1 and 2 is manufactured in the following steps: -8.02 g of molybdenum powder with a -240 mesh size and 4.86 g of titanium nitride in particle form (powder) with a particle size distribution between 1 and 2 μm are placed in a steel jar of a planetary ball mill equipped with steel balls, at a ball-to-powder ratio of 46.5:1. The jar is emptied of air and filled with argon; - The powder is ground in 24 cycles, each cycle consisting of 15 minutes of grinding and 15 minutes of off-time for cooling. The rotation direction is reversed after each cycle. The total grinding time is 12 hours, with an effective grinding time of 6 hours. No other grinding media or grinding aids are added. Grinding speed (rotary): 350 rpm; -At the end of grinding, 17.12 g of copper powder is added to the jar. The ball-to-powder ratio is adjusted to 20:1, and grinding is carried out in an argon atmosphere at 200 RPM for 180 cycles, with 1 minute on and 1 minute off, for a total of 6 hours. The use and presence of nitrogen or oxygen during grinding degrades the mechanical and electrical properties and densifies the material. The resulting composite powder is then held and stored in an inert atmosphere such as argon or nitrogen (which can be used for storage purposes but not in the grinding stage). It should be noted that the quantities and details of the method described are merely illustrative, and many different grinding techniques and routes can be relied upon. The results are consistently those of a relatively coarse, flowable composite powder made from FCC copper, BCC molybdenum, and FCC titanium nitride. The composite material has a density of 8.225 g / cc. - To manufacture a cylinder with a diameter of 10 mm and a height of 12 mm, 7.752 g of the composite powder prepared according to the above is loaded into the ceramic die of an electric sintering forging machine. The powder is solidified in less than 10 seconds with an energy of approximately 7.8 kJ (specific energy input (SEI) of 1 kJ / g), a peak current of 44.9 kA, and a peak voltage of 22.2 V, along with an initial pressure of 55 MPa and a peak pressure of 290 MPa. The solidified cylindrical body is automatically ejected from the die by a lower punch (fixed matrix configuration). The cylinder is then machined into the shape shown in Figures 6 and 7 by a conventional mill.

[0034] Example #2 In another embodiment, this involves machining a cylindrical body to achieve a blunt or rounded shape at one end, which is particularly necessary in view of use as a brass welding electrode. More specifically, such a blunt or rounded shape is such that it imparts an OZ-like shape to the machined cylindrical body.

[0035] Preferably, electrodes for spot welding 0.5 mm thick brass sheets are manufactured from the Grade 1 material according to the present invention. The material preparation is the same as that described in Example #1. Further machining operations are required for the electrode tip to mate to a standard ISO welding tip, which is prior art.

[0036] A medium-frequency welding apparatus was used while measuring current and voltage to evaluate welding efficiency. The current is supplied over a specific welding time, which is one of the welding machine's parameters. Table 3 below shows examples of experimentally recorded welding current-welding time pairs (I = current, t = time): [Table 3] Table 3 - Welding current-welding time pair in Example #2 Effective welding was achieved from 12.4 kA up to 16 kA. At 17 kA, the brass sheet material liquefied and was ejected away from the welding area. Despite the ejection, the welding tip remained undamaged and did not adhere to the material being welded, demonstrating the robustness and durability of brass in welding applications. The adhesion of the sheet to the tip was assessed by the operator using a semi-subjective evaluation, and the description is given in Table 4 below. [Table 4] Table 4 - Perceptual Adhesion Rating Values ​​higher than 3 are considered unacceptable due to the force required to separate the tip from the sheet. Values ​​between 1.5 and 3 are barely acceptable. Values ​​below 1.5 are acceptable. Figure 8 shows the perceived tackiness rating of Grade 1 electrode tips as a function of the number of subsequent welds (number of welds) compared to the commercial welding electrode material Cu-W 25-75. The material of the present invention behaves better than or equivalent to Cu-W, while also eliminating the need for tungsten.

[0037] Example #3 Electrodes for spot welding 0.5 mm thick copper sheets are manufactured using Grade 1 material, Grade 0 material, tungsten, molybdenum, and tungsten-copper 75-25 according to the present invention. The preparation of Grade 1 and Grade 0 materials is the same as that described in Example #1. The tested tungsten and tungsten-copper are commercial materials that have been machined like new materials and mounted on standard welding electrodes.

[0038] Adhesion was evaluated according to the same criteria as in Example 2, and Figure 9 shows the behavior of the four materials tested. The plots in Figure 9 are again of the perceived adhesion rating - weld count type.

[0039] More specifically, the Grade 1 material and W-Cu according to the present invention cease to function after a very small number of welds due to excessive stickiness. Tungsten and molybdenum are considered state-of-the-art for this application. The Grade 2 material according to the present invention performed better than tungsten and molybdenum. The average perceived stickiness values ​​were 1.44±0.68, 1.41±0.54, and 0.58±0.49 for tungsten, molybdenum, and Grade 2, respectively, indicating that the material according to the present invention exhibits significantly lower stickiness and more homogeneous behavior (from a lower standard deviation) than known and proven solutions.

[0040] Example #4 Referring to Figures 10 and 11, an electrode tip 10 for spot welding 0.5 mm thick copper sheets is manufactured from Grade 1 material according to the present invention. The electrode tip 10 comprises an electrode tip body including a nose portion 12 and a buffer portion 14, the nose portion being substantially the original buffer portion, machined into a tapered shape including two tapered sidewalls 16 (shown in the figures as tapering according to a nonlinear profile) and converging to a tip surface 18 intended to contact each copper sheet to be welded. The electrode tip body of the electrode tip 10 has a polygonal cross-section (e.g., rectangular or square as shown in the figures), the cross-section progressively decreasing from the buffer portion 14 towards the tip surface 18.

[0041] The electrode tip 10 is suitable for multiple dressings, which are intended to restore the shape of the tip portion 12 while gradually eroding the material of the buffer portion 14, which becomes shorter as the number of tip dressings progresses.

[0042] Referring to Figure 11, the electrode tip body of electrode tip 10 has an aspect ratio L / d that is between 1 and 50 (including the endpoints), more preferably between 10 and 27 (including the endpoints), where L is the length of the electrode tip body and d is the lateral dimension relative to the length L (d can be any lateral dimension relative to L, notwithstanding the dimensions specifically noted in Figure 11).

[0043] The material preparation for Grade 1 is identical to that described in Example #1. The powder is fed into a well-designed die with a rectangular cross-section and a cavity with dimensions of 80 × 3 mm. The final shape and size of the electrode is a rectangular cross-section with dimensions of 80 × 5 × 3 mm.

[0044] Elongated shapes of refractory materials such as W, Mo, and similar materials, or shapes with a high aspect ratio (length / lateral dimension), are conventionally manufactured by pressurization, sintering, and extrusion, or by Green's extrusion and sintering in a conventional hot oven or hot isostatic pressurization. Such shapes with a high aspect ratio cannot be easily manufactured by electric field-assisted sintering techniques, and the only way to manufacture elongated shapes is to use a rectangular or square cross section and densify / pressurize the part along either an 80mm × 5mm or 80mm × 3mm dimension (in the embodiments of Figures 10 and 11, the length is 80mm and the rectangular cross section is 3mm × 5mm). In the embodiment, the die cavity is 80mm × 3mm, thereby densifying the electrode 10 along the 5mm direction.

[0045] Naturally, while the principle of the present invention remains the same, the details of the configuration and embodiments can vary widely with respect to those described and illustrated purely as examples, without departing from the scope of the invention.

Claims

1. A metal matrix composite material comprising copper in an amount of 1% to 65% of the volume of the metal matrix composite material, titanium nitride in an amount of 1% to 25% of the volume of the metal matrix composite material, and the remainder being molybdenum.

2. The metal matrix composite material according to claim 1, wherein the copper is made of face-centered cubic copper, the titanium nitride is made of face-centered cubic titanium nitride, and the molybdenum is made of body-centered cubic molybdenum.

3. The metal matrix composite material according to claim 1 or 2, wherein the titanium nitride has a particle size of 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less.

4. The step of providing copper in particle form, The steps include providing titanium nitride in particulate form, The steps of providing molybdenum in particulate form, The steps include grinding at least the titanium nitride in particulate form and the molybdenum in particulate form, Following the pulverization step, the mixture of copper in particulate form, titanium nitride in particulate form, and molybdenum in particulate form is solidified into the metal matrix composite material by electric field-assisted sintering. A method for producing a metal matrix composite material according to claim 1 or 2, comprising:

5. The method according to claim 4, wherein the step of grinding at least the titanium nitride and molybdenum in particulate form further comprises the step of grinding copper in particulate form together with and simultaneously with the titanium nitride and molybdenum in particulate form.

6. At least the step of grinding titanium nitride in particulate form and molybdenum in particulate form is First grinding of titanium nitride in the particle form and molybdenum in the particle form, A second grinding of copper in particle form, which is obtained by combining the titanium nitride in particle form and the molybdenum in particle form obtained from the first grinding. The method according to claim 4, including the method described in claim 4.

7. The method according to claim 4, wherein the electric field-assisted sintering includes electrosintering forging.

8. The method according to claim 4, wherein the electric field-assisted sintering has a thermal cycle duration of 30 seconds or less, preferably 20 seconds or less, and more preferably 10 seconds or less.

9. The method according to claim 8, wherein the thermal cycle includes heating, holding, and cooling.

10. The method according to claim 4, wherein the step of solidifying the mixture of copper in particulate form, titanium nitride in particulate form, and molybdenum in particulate form into the metal matrix composite material by electric field-assisted sintering, following the pulverizing step, includes the step of solidifying the mixture into a cylindrical body, particularly a cylindrical electrode tip.

11. The method according to claim 10, further comprising the step of machining the cylindrical body to achieve a blunt or rounded shape at one end thereof.

12. The method according to claim 10, further comprising the step of machining the cylindrical body to achieve a castle wall-like shape at one end thereof.

13. The method according to claim 4, wherein the step of grinding at least the titanium nitride in particulate form and the molybdenum in particulate form includes the step of adding argon or helium and optionally up to 4% by volume of hydrogen to the grinding environment.

14. A welding electrode tip made of the metal matrix composite material according to claim 1 or 2, wherein the welding electrode tip is A cylindrical electrode tip with a blunt or rounded shape at one end, An electrode tip including an electrode tip body having a polygonal cross-section including a nose portion and a buffer portion, wherein the buffer portion can be machined into a tapered shape to provide the nose portion, and One end of it is a cylindrical hollow electrode tip with a castle-wall-like shape. One example is the welding electrode tip.

15. The welding electrode tip according to claim 14, wherein the electrode tip body having a polygonal cross-section has an aspect ratio L / d that falls between 1 and 50, preferably between 10 and 27, where L is the length of the electrode tip body and d is the lateral dimension relative to the length.

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