RU2840530C1 - Aluminium composite material for laser melting - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: invention relates to powder metallurgy, particularly, to aluminium composite materials for laser melting. It can be used in various industries in the manufacture of products using additive laser technologies. Aluminium composite material for laser melting contains the following, wt.%: submicron ceramic particles SiC 8.5-13.5; particles of titanium alloy BT5 12-15 and powder of aluminium alloy Al-Si 71.5-79.5.

EFFECT: providing hardness at room temperature 164-213 HV_0.05 and temperature 200-400 °C 195-213 HV_0.05.

1 cl, 3 tbl, 8 ex

Description

The invention relates to the field of metallurgy associated with aluminum alloys having an ultrafine structure. In particular, it concerns aluminum matrix composite materials. Since at the moment the range of aluminum composite materials used in the field of additive technologies is extremely small, the presented compositions can be used in various industries and manufactured by laser melting, including additive laser technologies.

A metallic aluminum powder is known for use in additive technologies (CN 109317661 B, published 16.07.2021). The composite powder contains a base powder and particles of a strengthening phase, wherein the base powder is AlSi10Mg powder, the particles of the strengthening phase are TiN ceramic particles, which are uniformly distributed in the powder of the AlSi10Mg base alloy, and the mass fractions of the base powder and the particles of the strengthening phase are, respectively, as follows: AlSi10Mg 90-99%, TiN 1-10%. According to the invention, ceramic particles are used as a strengthening phase of the aluminum-based powder, due to which the laser absorption rate of the composite powder increases, formability during low-power printing is improved, and production costs are reduced. The strengthening phase retains the nanostructure after laser processing, so that fine-crystalline strengthening is formed, and the hardness and tensile strength of the material are increased. The base alloy powder and ceramic particles are pre-mixed in an ultrasonic vibrator (the vibration frequency is 10-30 kHz, and the vibration mode is continuous or pulsed; the dispersion and pre-mixing time by ultrasonic vibration is 20-60 min). Then, the powders were mixed in a planetary mill for 12 hours. After that, the powder particles with a size of 15-50 μm are sifted to obtain the powder of the required fraction for subsequent melting. Melting mode: laser power 80-100 W, scanning speed 200-600 mm / s, overlap 0.08-0.1 mm. In addition, in the process of selective laser melting and molding of the part, the direction of each layer of laser beams is rotated by an angle of 5-60 degrees, to reduce the stress in the 3D printed part. The tensile strength of the alloy reaches 310-400 MPa, and compared with the cast Al-Si alloy, the alloy has a significant improvement. The disadvantage of this composition is the insufficiently high tensile strength of the final material.

A metal composite aluminum powder used in additive technologies is known (CN 107812941 B, published on 18.08.2020). The composite powder contains aluminum powder as the main one and one or more Sc, Zr and Ti powders, the mass percentage of which does not exceed 6 mass%. The powder mixture is preliminarily ground in a planetary mill at a mode of 100-500 rpm and a processing time of 1-8 hours. Then the powder is sieved to obtain a particle size of no more than 75 μm. The parameters of the laser used to process the composite material workpiece: laser power 300-400 W, substrate heating temperature 100-200 ° C, scanning speed 600-1000 mm / s. As a result, the structure of the final material becomes finely dispersed, since the additives of Sc, Zr and Ti contribute to its grinding and change the shape of the grains from columnar to equiaxed. The disadvantage of this composition is the insufficient strength of the final material due to only dispersion hardening.

Metallic aluminum powder is known for its use in additive technologies (CN 105803271 B, published 07.07.2017). Composite material based on hypoeutectic silumin A1- Si, in which the silicon content does not exceed 10.5% with additives of rare earth metal particles in an amount of no more than 0.8 wt. %, as well as TiC / SiC powder particles. The total amount of reinforcing particles should not exceed 4-6 wt. %. The powder is pre-milled in a planetary mill in an argon atmosphere for 4-8 hours at a speed of 250-350 rpm. 3D printer printing parameters: Laser power is 100-130 W and powder layer thickness is 50 μm. The tensile strength of the resulting alloys is on average 389-471 MPa. The disadvantage of this method is the high cost of ceramic and rare earth particles, as well as the insufficient tensile strength.

A metallic aluminum powder is known for its use in additive technologies (CN 107299239 B, published 03.09.2019). The composite material is based on the powder of the aluminum alloy AlSi10Mg, as well as graphene particles. The total proportion of graphene in the final mass of the composite material blank is 1-5 wt. %. First, the aluminum alloy and graphene powders are mixed separately with dehydrated alcohol and stirred in an ultrasonic mixer for 2-5 hours. Then both resulting solutions are placed in a planetary mill and ground for 0.5-1.5 hours at a temperature of 5-10 ° C and a speed of 150-250 rpm. Then the resulting powder is dried using a centrifuge, and then placed in a vacuum furnace to get rid of residual alcohol. When melting, the laser parameters are 180 W and a scanning speed of 1200 mm/s, each subsequent layer is printed with a 67° rotation of the laser beam. It is stated that the tensile strength increases by 80%, and the compressive strength by 20%. The disadvantage of this method is the high cost of graphene and the long time it takes to obtain a blank of the composite material.

A metallic aluminum powder is known for use in additive technologies (CN 109759578 B, published on 23.11.2021). The composite material contains aluminum alloy powder belonging to the silumin group, 2% TiB ₂ and 1-3% SiC. The aluminum alloy powder particles are spherical, the particle size is 15-53 μm, the TiB ₂ particles have a particle size of 20-100 nm and an average particle size of 50 nm; the size of ceramic SiC particles is 300-500 nm. After preparing the composite material blanks, the powder particles are ground in a planetary mill for at least 8 hours at a speed of 200-500 rpm. Then the powder is dried in a vacuum furnace at 60 ° and then used in printing. The main parameters of powder melting are: laser power of 180 W, scanning speed of 1000 mm/s and powder layer thickness of 30 μm, the microhardness of the obtained material reaches 160 HV0.3. The disadvantage of this method and composition is the insufficiently high hardness of the final material during the energy- and resource-intensive production process.

The objective of this invention is to increase the level of mechanical properties at room and elevated temperatures by forming carbides as products of the interaction of the initial components during laser melting and to reduce the cost of the composite material by using VT5 alloy powder instead of TiC powder.

The technical result of this invention is to provide a high level of hardness at room temperature (164-213 HV _0.05 ) and a temperature of 200-400°C (195-213 _HV0.05 ), which is achieved by passing an in-situ reaction between aluminum, titanium and silicon carbide with the formation of refractory carbides of the SiC and TiC types.

The specified technical result is achieved as follows.

The aluminum composite material for laser melting contains aluminum alloy powder Al-Si and submicron ceramic particles SiC, and it additionally contains particles of titanium alloy VT5 in the following ratio of components, mass %:

submicron ceramic particles SiC - 8.5-13.5;

titanium alloy grade VT5 - 12-15;

aluminum alloy Al-Si - 71.5-79.5.

The complex interaction of laser-melted ceramic particles of SiC and VT5 leads to the formation of dispersed intermetallic phases and eutectics consisting of carbides SiC, TiC, Al ₄ SiC ₄ , the formation of which occurs in-situ during the process of melting powders by a laser beam. At the same time, the energy consumption for melting the initial particles is reduced compared to similar compositions containing TiC.

The short lifetime of the melt and the high cooling rate during crystallization make it possible to obtain a very dispersed structure of the eutectic and intermetallics, which ensures the desired structure of the aluminum composite material with a high level of strength properties.

The laser beam melting technology allows to expand the classical range of aluminum alloying with SiC ceramic particles and VT alloy particles, adopted for the powder technology of obtaining composite materials, which is due to the high cooling rate. In turn, this allows to form a composite material with a homogeneous and very dispersed structure and to obtain a significant increase in strength characteristics.

The method for producing a composite material for laser melting involves mixing the initial powders of the Al-Si aluminum alloy with a particle size of 15-45 μm, with ceramic particles of SiC with a size of 5 μm, and particles of the VT5 alloy with a size of 5-10 μm using a pneumatic mixer. The pneumatic mixer is a sealed device in which the process of mixing powders in a fluidized bed occurs using an argon flow, which is fed into the chamber under a pressure of 2 atm using a compressor with a receiver (the compressor pumps argon into the chamber and creates the required pressure). Mixing occurs for 20 minutes. The powder mixing chamber is an acrylic tube with an internal diameter of 46 mm, a wall thickness of 2 mm and a total length of 500 mm. The design of the upper unit is a housing that is put on the pipe. The housing is fastened to the pipe by a nut and a rubber seal between the nut and the housing. The nut ensures the seal is pressed to the pipe. When the nut is tightened, the conical part of the seal is pressed tightly to the inner chamfer of the housing, resulting in a decrease in the internal diameter of the seal, which in turn ensures a mechanical connection of the unit to the pipe. The design of the lower unit is a sealed housing that is put on the pipe and allows you to hold the powder inside the mixer and has the ability to connect an air compressor to create an air flow. The connection of the lower unit to the unit is carried out by two rubber rings. In the lower part of the unit there is a 3/4 inch pipe thread designed to attach the adapter to the pneumatic collet fitting. After assembling and securing the unit on the tripod, the air compressor tube with the receiver is connected to the lower unit.

Laser melting of the obtained composite material is carried out by a Nd:YAG laser with a radiation wavelength of 1064 nm under the following parameters: laser supply voltage of 200-240 V, pulse duration of 10 ms, scanning speed of 0.25 mm/s, overlap of 0.1 mm. Focal length is 10 cm. High-purity argon (grade 5.5) is used as a protective atmosphere.

The structure after laser melting of the composite material is characterized by high homogeneity and dispersion of structural components. Due to the melting of the VT5 alloy powder particles, an ultra-fine TiC phase is formed, which leads to a significant increase in strength characteristics. Silicon carbide (SiC) contributes to the formation of a needle phase enriched with silicon, titanium and aluminum, up to 5 μm long. High dispersion of structural components and their uniform distribution throughout the volume of the composite material ensures a high level of hardness. Homogeneity of the structure and purity of the powder are ensured by uniform mixing of the original components using a pneumatic mixer in an argon environment.

Example 1

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name A. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 200 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at room temperature. The structure of the material after laser melting is characterized by high dispersion, but the boundaries of the melt pool are visible on the track, which does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is less than 1 μm. TiC phase particles are uniformly distributed throughout the volume, their size is about 0.5 μm.

The hardness was determined directly after laser melting without preliminary annealing. The hardness of the aluminum composite material is 213 HV _0.05 .

Example 2

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name A. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 200 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at room temperature. The structure of the material after 12-hour annealing at a temperature of 400 °C after laser melting is characterized by slightly lower dispersion compared to the structure before annealing. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is more than 1 μm. TiC phase particles are uniformly distributed throughout the volume.

The hardness was determined immediately after laser melting and 12-hour annealing at 400°C. The hardness of the aluminum composite material is 159 HV _0.05 .

Example 3

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name A. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 300 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at a temperature of 400 °C. The structure of the material after laser melting is characterized by high dispersion, but the boundaries of the melt pool are visible on the track, which does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is 1 μm. Due to the high temperature of the substrate during laser melting, a decrease in the cooling rate is achieved, which leads to an increase in the volume fraction and average size of TiC particles synthesized during the in-situ reaction.

The hardness was determined directly after laser melting without preliminary annealing. The hardness of the aluminum composite material is 157 HV _0.05 .

Example 4

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name A. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 300 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at a temperature of 400 °C. The structure of the material after 12-hour annealing at a temperature of 400 °C is characterized by a slightly lower dispersion compared to the structure before annealing, but this does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is 2-3 μm. Due to the high temperature of the substrate during laser melting, a decrease in the cooling rate is achieved, which leads to an increase in the volume fraction and average size of TiC particles synthesized during the in-situ reaction.

The hardness was determined immediately after laser melting and 12-hour annealing at 400°C. The hardness of the aluminum composite material is 157 HV _0.05 .

Example 5

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name F. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 200 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at room temperature. The structure of the material after laser melting is characterized by high dispersion, but the boundaries of the melt pool are visible on the track, which does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is less than 1 μm. TiC phase particles are uniformly distributed throughout the volume, their size is about 1 μm.

The hardness was determined directly after laser melting without preliminary annealing. The hardness of the aluminum composite material is 162 HV _0.05 .

Example 6

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name F. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 300 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at a temperature of 400 °C. The structure of the material after 12-hour annealing at a temperature of 400 °C is characterized by a slightly lower dispersion compared to the structure before annealing, but this does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is 2-3 μm. Due to the high temperature of the substrate during laser melting, a decrease in the cooling rate is achieved, which leads to an increase in the volume fraction and average size of TiC particles synthesized during the in-situ reaction.

The hardness was determined immediately after laser melting and 12-hour annealing at 400°C. The hardness of the aluminum composite material is 153 HV _0.05 .

Example 7

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name F. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 300 V, a pulse duration of 10 ms, a scanning speed of 0.25 mm/s, and an overlap of 0.1 mm. The melting process took place at a temperature of 400 °C. The structure of the material after laser melting is characterized by high dispersion, but the boundaries of the melt pool are visible on the track, which does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is 3 μm. TiC phase particles are uniformly distributed throughout the volume, their size is about 2-3 μm. However, due to the reduced crystallization rate, the size of the structural components is larger than in the previous example of a similar composition, which leads to a decrease in the hardness values of the material.

The hardness was determined directly after laser melting without preliminary annealing. The hardness of the aluminum composite material is 185 HV _0.05 .

Example 8

The chemical composition of the aluminum alloy Al-Si used to obtain the aluminum matrix composite is given in Table 1. The composition of the aluminum matrix composite is given in Table 2 under the name F. The composition of the VT5 alloy used is given in Table 3. The composite material was obtained using the technology described above.

The obtained powder was subjected to laser melting at a laser radiation power of 300 V, a pulse duration of 12 ms, a scanning speed of 1 mm/s, and an overlap of 0.2 mm. The melting process took place at a temperature of 400 °C. The structure of the material after 12-hour annealing at a temperature of 400 °C is characterized by a slightly lower dispersion compared to the structure before annealing, but this does not affect the uniform and complete melting of refractory carbide particles. The latter is achieved due to uniform mixing of the original powders in a pneumatic mixer. The primary silicon phase is uniformly distributed throughout the volume of the material and its size is 2-5 μm. Due to the high temperature of the substrate during laser melting, a decrease in the cooling rate is achieved, which leads to an increase in the volume fraction and average size of TiC particles synthesized during the in-situ reaction.

The hardness was determined immediately after laser melting and 12-hour annealing at 400°C. The hardness of the aluminum composite material is 130 HV _0.05 .

These examples also show the economic benefit of using VT5 grade powder in the aluminum composite material, since its cost is almost 2 times less than the cost of TiC powder. It is also energetically more advantageous to use VT5 alloy powder, the melting point of which is 1668°C, while the melting point of TiC is 3260°C.

Claims (2)

An aluminum composite material for laser melting, containing aluminum alloy powder Al-Si and submicron ceramic particles SiC, characterized in that it additionally contains particles of titanium alloy VT5, with the following ratio of components, wt.%: submicron ceramic particles SiC 8.5-13.5 titanium alloy grade VT5 12-15 aluminum alloy Al-Si 71.5-79.5