Al-V-C grain refiner as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of nonferrous alloy metallurgy and casting, and particularly relates to an Al-V-C grain refiner and a preparation method and application thereof. Comprising the following steps that Al-10V powder and VC powder are mixed and then subjected to vacuum ball milling, and a mixture is obtained; after a container is preheated, pure aluminum is placed in the container and heated till the pure aluminum is melted to form aluminum melt, the aluminum foil wrapped with the mixture is immersed in the aluminum melt, and mixed melt is formed; raising the temperature of the mixed melt to 1190-1210 DEG C and keeping the temperature; then cooling to 790-810 DEG C, and keeping the temperature; and after the mixture is poured to be in a semi-solid state, continuous rheological extrusion forming is conducted, and the Al-V-C grain refiner is obtained. According to the grain refiner prepared through the method, VAl3 and VC phase distribution is more uniform, an Al matrix is introduced by adding the Al-V-C refiner, heterogeneous nucleation sites of Al are increased, the purpose of grain refinement is achieved, and the problem that the wettability of carbon and aluminum is poor is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous alloy metallurgy and casting, and specifically relates to an Al-VC grain refiner and a preparation method and application thereof. Background Art

[0002] With the continuous development of modern industry, the fields of vehicles, military defense, manned spaceflight, etc. have put forward higher requirements on the performance of aluminum and aluminum alloys. Grain refiners for aluminum and aluminum alloys play an important role in improving the mechanical properties of materials such as tensile strength and elongation. In non-ferrous metals or alloys, the finer the grains and the more grain boundaries, the higher the material strength. In addition, grain refinement can also significantly reduce shrinkage cavities, shrinkage porosity, thermal cracking, etc. of the material, and improve the air tightness and surface quality of castings.

[0003] The development of efficient new grain refiners is still the focus of research. Application number: CN202110443686.1, discloses an Al-VB master alloy and its preparation method and application, wherein the chemical element composition of the Al-VB master alloy is as follows: V: 1-3%, B: 10.2%, and the balance is Al. The Al-3V-3B refiner in the Al-VB refiner can refine the α-Al grain size to 450μm, but the distribution of the phases in the prepared Al-VB refiner is uneven, resulting in poor refinement effect. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an Al-VC grain refiner and its preparation method and application. The physical phase composition of the Al-VC grain refiner consists of VAl3 and VC physical phases; the distribution of VAl3 and VC physical phases in the Al-VC grain refiner is more uniform, and the second phase particles such as VAl3 and VC are introduced into the Al matrix by adding the Al-VC refiner, which can increase the heterogeneous nucleation sites of Al, thereby achieving the purpose of grain refinement.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The first object of the present invention is to provide a method for preparing an Al-VC grain refiner, comprising the following steps:

[0007] The Al-10V powder and the VC powder are mixed and then vacuum ball milled to obtain a mixture.

[0008] After preheating the container, pure aluminum is placed in the container and heated until the pure aluminum is melted to form an aluminum melt. The aluminum foil wrapped with the mixture is immersed in the aluminum melt and stirred to form a mixed melt.

[0009] The mixed melt is heated to 1190°C-1210°C and kept warm; then cooled to 790°C-810°C and kept warm with stirring every 8 minutes to reduce particle sedimentation and aggregation; then poured into a semi-solid state, continuous rheological extrusion molding is performed to obtain an Al-VC grain refiner.

[0010] Preferably, the mass percentages of chemical elements in the mixed melt are: Al: 97.8wt.% to 98.8wt.%, V: 1.0wt.% to 3.0wt.%, C: 0.2wt.%, and the mass percentages of each element add up to 100%.

[0011] Preferably, during continuous rheological extrusion molding, the extrusion ratio is 2 to 10, and the extrusion speed is 3 rad / min to 8 rad / min.

[0012] Preferably, the temperature is raised to 1190° C. to 1210° C. and kept for 20 minutes; then the temperature is lowered to 790° C. to 810° C. and kept for 1 hour to 1.5 hours.

[0013] Preferably, during the primary vacuum ball milling, the ball milling mixing time is 1h to 3h, the rotation speed is 120r / min to 200r / min, and the vacuum degree is 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1.

[0014] Preferably, the method for preparing Al-10V powder comprises the following steps:

[0015] The Al-10V master alloy was subjected to secondary vacuum ball milling. The ball milling time was 24h to 48h, the speed was 500r / min, and the vacuum degree was 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1, and Al-10V powder is obtained.

[0016] Preferably, the method for preparing VC powder comprises the following steps:

[0017] The VC master alloy was subjected to secondary vacuum ball milling. The ball milling time was 24h to 48h, the speed was 500r / min, and the vacuum degree was 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1, and VC powder is obtained.

[0018] Preferably, after the secondary vacuum ball milling, the particle size of the Al-10V powder is 1 mm to 3 mm, and the particle size of the VC powder is 1 μm to 100 μm.

[0019] Preferably, the stirring rod used in the stirring process is a titanium alloy stirring rod, and the surface of the stirring rod is coated with titanium dioxide.

[0020] The second object of the present invention is to provide an Al-VC grain refiner prepared by the above preparation method, wherein the mass percentage of chemical elements is: Al: 97.8wt.%~98.8wt.%, V: 1.0wt.%~3.0wt.%, C: 0.2wt.%, and the mass percentage of each element totals 100%.

[0021] The third object of the present invention is to provide the use of the Al-VC grain refiner in casting aluminum and aluminum alloys, wherein the addition amount of the Al-VC grain refiner is 0.2wt.% to 1.2wt.%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention adopts a one-time vacuum ball milling method to add VC particles with controllable size to replace the existing VC particles, reduce the proportion of large-size VC phases, make the size of the VC phase more concentrated, which is beneficial to increase the number of effective nucleation cores and improve the refinement efficiency. The melting method can make V evenly melt into the interior of the A1 melt, and the reaction rate is increased by first heating to 1190°C to 1210°C for insulation; then cooling to 790°C to 810°C for insulation to ensure sufficient reaction, and by intermittent stirring to reduce particle sedimentation and aggregation, the distribution of VAl3 and VC phases can be more uniform. Second phase particles such as VAl3 and VC are introduced into the Al matrix by adding Al-VC refiner, which can increase the heterogeneous nucleation sites of Al, thereby achieving the purpose of grain refinement. After rheological extrusion, the Al-VC grain refiner phase distribution is more uniform and the size is more concentrated. It is helpful to solve the problem of low refinement efficiency and enable more VC phases to play a refining role, thereby achieving better aluminum or aluminum alloy grain refinement effect. The preparation method is simple, the cost is low, and large-scale industrial production can be carried out.

[0024] The Al-VC grain refiner provided by the present invention has a phase composition consisting of VAl3 and VC phases; the distribution of VAl3 and VC phases in the Al-VC grain refiner is more uniform, and second phase particles such as VAl3 and VC are introduced into the Al matrix by adding the Al-VC refiner, which can increase the heterogeneous nucleation sites of Al, thereby achieving the purpose of grain refinement. Since CV particles are directly introduced, the problem of poor wettability between carbon and aluminum is avoided, and at the same time, VC particles have excellent refining ability, thereby improving the grain refinement effect. CV particles provide additional nucleation points in liquid aluminum, so that aluminum grains can nucleate earlier and faster during the solidification process, thereby effectively reducing the grain size. After the Al-VC grain refiner is added to the aluminum liquid, the solidification characteristics of the alloy will be changed, the supercooling degree will be reduced, and the refinement will be further promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is the XRD diagram of the Al-VC grain refiner rod prepared in Example 1 of the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the Al-VC grain refiner rod prepared in Example 1 of the present invention.

[0027] Figure 3 This is the macroscopic morphology of pure aluminum refined by adding 0.2wt.% of Al-1V-0.2C grain refiner in Example 1 of the present invention. Figure 3 In the figure, (a) is a macroscopic image, and (b) is a local enlarged image of (a).

[0028] Figure 4 This is the macroscopic morphology of pure aluminum refined by adding 0.4wt.% of Al-1V-0.2C grain refiner in Example 1 of the present invention. Figure 4 In the figure, (a) is a macroscopic image, and (b) is a local enlarged image of (a).

[0029] Figure 5 This is the macroscopic morphology of pure aluminum refined by adding 1.2wt.% of Al-1V-0.2C grain refiner in Example 1 of the present invention. Figure 5 In the figure, (a) is a macroscopic image, and (b) is a local enlarged image of (a).

[0030] Figure 6 This is the macroscopic morphology of pure aluminum refined by adding 0.2wt.% Al-2V-0.2C grain refiner in Example 2 of the present invention. Figure 6 In the figure, (a) is a macroscopic image, and (b) is a local enlarged image of (a).

[0031] Figure 7 This is the macroscopic morphology of pure aluminum refined by adding 0.2wt.% of Al-3V-0.2C grain refiner in Example 3 of the present invention. Figure 7 In the figure, (a) is a macroscopic image, and (b) is a local enlarged image of (a).

[0032] Figure 8 This is the macroscopic morphology of pure aluminum without adding refiner in the present invention. Figure 8 In the figure, (a) is a macroscopic image, and (b) is a local enlarged image of (a). DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0035] Application number: CN202110443686.1, discloses an Al-VB master alloy and its preparation method and application, wherein the chemical element composition of the Al-VB master alloy is as follows by mass percentage: V: 1-3%, B: 10.2%, and the balance is Al. The Al-3V-3B refiner in the Al-VB refiner can refine the α-Al grain size to 450μm, but the distribution of the physical phase in the prepared Al-VB refiner is uneven, resulting in poor refining effect.

[0036] Based on the above problems, the present invention provides a method for preparing an Al-VC grain refiner, comprising the following steps:

[0037] S1. Al-10V powder and VC powder are mixed and then vacuum ball milled to obtain a mixture.

[0038] S2. After preheating the container, pure aluminum is placed in the container and heated until the pure aluminum is melted to form an aluminum melt. The aluminum foil wrapped with the mixture is immersed in the aluminum melt and stirred to form a mixed melt.

[0039] S3. The mixed melt is heated to 1190°C-1210°C and kept warm; then the mixed melt is cooled to 790°C-810°C and kept warm and stirred every 8 minutes to reduce particle sedimentation and aggregation; then the mixed melt is poured into a semi-solid state and continuously subjected to rheological extrusion molding to obtain an Al-VC grain refiner.

[0040] The present invention firstly performs high-energy ball milling on Al-10V raw materials, and then mixes them with pure Al powder and nano VC particles by ball milling to make them evenly distributed. The existing VC particles are replaced by VC particles with controllable sizes by ball milling, so as to reduce the proportion of large-sized VC phases and make the sizes of VC phases more concentrated, which is beneficial to increase the number of effective nucleation cores and improve the refinement efficiency.

[0041] After the container is preheated, the present invention shortens the subsequent melting time of Al and improves the efficiency. Aluminum foil is used to wrap Al-10V powder and VC powder. In order to prevent oxidation of V and enable V to be uniformly integrated into the Al melt, the temperature is first raised to 1190°C-1210°C for insulation; then the temperature is lowered to 790°C-810°C for insulation to increase the reaction rate and ensure sufficient reaction. Interval stirring is performed to reduce particle sedimentation and aggregation, so that VAl3 and VC phases can be distributed more evenly. Second phase particles such as VAl3 and VC are introduced into the Al matrix by adding an Al-VC refiner, which can increase the heterogeneous nucleation sites of Al, thereby achieving the purpose of grain refinement. The melting method is used to solve the problem of uneven distribution of the VC phase.

[0042] The present invention adopts continuous rheological extrusion as the extrusion molding technology for producing Al-VC refiners. After rheological extrusion, the Al-VC refiners have more uniform phase distribution and more concentrated sizes. A continuous rheological extrusion molding preparation method is provided, which is low in cost and can be industrialized on a large scale.

[0043] In some specific embodiments, the mass percentages of chemical elements in the mixed melt are: Al: 97.8wt.% to 98.8wt.%, V: 1.0wt.% to 3.0wt.%, C: 0.2wt.%, and the mass percentages of each element total 100%.

[0044] In some specific embodiments, in some embodiments, during continuous rheological extrusion molding, the extrusion ratio is 2 to 10, and the extrusion speed is 3 r / min to 8 r / min.

[0045] In some specific embodiments, during the vacuum ball milling, the ball milling time is 1h to 3h, the speed is 120r / min to 200r / min, and the vacuum degree is 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1.

[0046] In some specific embodiments, the method for preparing Al-10V powder comprises the following steps:

[0047] The Al-10V master alloy was subjected to secondary vacuum ball milling. The ball milling time was 24h to 48h, the speed was 500r / min, and the vacuum degree was 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1, and Al-10V powder is obtained.

[0048] In some specific embodiments, the method for preparing VC powder comprises the following steps:

[0049] The VC master alloy was subjected to secondary vacuum ball milling. The ball milling time was 24h to 48h, the speed was 500r / min, and the vacuum degree was 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1, and VC powder is obtained.

[0050] In some embodiments, before the secondary vacuum ball milling, the purity of Al-10V is ≥99.0%, and after the primary vacuum ball milling, the particle size of Al-10V powder is 1 mm to 3 mm, and the particle size of VC powder is 1 μm to 100 μm.

[0051] In the present invention, the vacuum ball milling method is used to prevent oxidation of the alloy during the ball milling process. The purpose of the secondary vacuum ball milling is to crush and mix the Al-10V master alloy and the VC master alloy mixture, and then perform a vacuum ball milling to improve the uniformity of the mixture. The ball milling method is used to add VC particles with controllable size to replace the existing VC particles, which solves the problem that the size distribution of the VC phase generated by the fluoride salt method is a logarithmic normal distribution, reduces the proportion of large-sized VC phases, and makes the size of the VC phase more concentrated, which is conducive to increasing the number of effective nucleation cores and improving the refinement efficiency.

[0052] In some embodiments, the mixture is wrapped with aluminum foil, and cryolite is added as a solvent, and dried at 150° C. for 1 to 2 hours to remove moisture. The amount of cryolite as a solvent is 5 wt.% of the mixture.

[0053] In some embodiments, a titanium alloy stirring rod and weighed high-purity aluminum are placed in a drying oven together at 150°C for 1 hour to 2 hours to remove moisture; the stirring rod used in the stirring process is a titanium alloy stirring rod, and the surface of the stirring rod is coated with titanium dioxide as a protective layer; and the titanium alloy middle cover and titanium alloy colander used in the melting and stirring process are coated with titanium dioxide as a protective layer, and the container used for melting is a clay crucible coated with titanium dioxide as a protective layer; the titanium alloy middle cover, titanium alloy colander and clay crucible all need to be placed in a drying oven at 150°C for 1 hour to 2 hours to remove moisture.

[0054] In summary, the Al-VC grain refiner of the present invention and its preparation method and application make the size of the VC phase controllable and the distribution more uniform, which is conducive to solving the problem of low refinement efficiency, allowing more VC phases to play a refining role, thereby achieving better aluminum or aluminum alloy grain refinement effect.

[0055] The invention is further described below through specific examples.

[0056] Example 1

[0057] The invention provides an Al-1V-0.2C grain refiner, which comprises the following chemical elements by mass percentage: V: 1.0wt.%, C: 0.2wt.%, and the balance is Al, and the mass percentages of the various elements add up to 100%.

[0058] The preparation method of the Al-1V-0.2C grain refiner comprises the following steps:

[0059] S1. Put the block Al-10V master alloy (purity ≥ 99.0%) into a high-energy ball mill for 24 hours at a speed of 500 r / min and a vacuum degree of 2×20 -2 Pa, ball-to-material ratio 3:1; reduce the particle size of Al-10V master alloy to 2mm to obtain Al-10V particles; put the nano-VC particles into a high-energy ball mill for 24h, the speed is 500r / min, the vacuum degree is 2×20 -2 Pa, ball-to-material ratio 3:1; reduce the particle size of VC particles to 0.5μm.

[0060] S2. Weigh Al-10V particles and nano-VC particles according to the mass percentage of chemical elements.

[0061] S3, the weighed Al-10V particles were mixed with the nano-VC particles, and the mixture was put into a ball mill for 2 h, with a rotation speed of 200 r / min and a vacuum degree of 2×20 -2 Pa, the ball-to-material ratio is 3:1, and a mixture is obtained. 5.0wt.% cryolite is added to the total amount of the mixture and mixed evenly. It is wrapped into a cake shape with aluminum foil and then heated at 150°C to dry for 2 hours to remove moisture.

[0062] S4. Coat the experimental tools with titanium dioxide as a protective layer: titanium alloy stirring rod, titanium alloy middle cover, titanium alloy colander and clay crucible; put them into a drying oven together with the weighed high-purity aluminum (purity ≥ 99.99%) at 150°C for 2 hours to remove moisture.

[0063] S5. Place a clay crucible in a box-type resistance furnace and preheat it to 300°C. Then place high-purity aluminum inside the crucible and heat it to 850°C until the high-purity aluminum melts to form an aluminum melt. Immerse the aluminum foil wrapped with the mixture into the aluminum melt, stir it thoroughly to form a mixed melt, and then keep it warm for 20 minutes. At this time, the mass percentage of chemical elements in the mixed melt is: V: 1.0wt.%, C: 0.2wt.%, and the remainder is Al, and the mass percentage of each element totals 100%.

[0064] S6. Raise the temperature of the mixed melt to 1200°C and keep it warm for 20 minutes, then cool the mixed melt to 800°C and keep it warm for 1 hour. The reaction rate is increased by heating and keeping warm to ensure sufficient reaction. During the cooling process of the mixed melt, stir it every 8 minutes for 2 minutes each time to reduce particle sedimentation and aggregation.

[0065] S7. Use a titanium alloy colander to remove salt slag on the surface of the mixed melt, pour it into a semi-solid continuous rheological extruder with an extrusion ratio of 3 and an extrusion speed of 3r / min to prepare Al-1V-0.2C grain refiner rod.

[0066] Example 2

[0067] The invention provides an Al-2V-0.2C grain refiner, which comprises the following chemical elements by mass percentage: V: 2.0wt.%, C: 0.2wt.%, and the balance is Al, and the mass percentages of the various elements add up to 100%.

[0068] The preparation method of the Al-2V-0.2C grain refiner comprises the following steps:

[0069] S1. Put the block Al-10V master alloy (purity ≥ 99.0%) into a high-energy ball mill for 30 hours at a speed of 500 r / min and a vacuum degree of 3×20 -2 Pa, ball-to-material ratio 3:1; reduce the particle size of Al-10V master alloy to 2mm to obtain Al-10V particles; put the nano-VC particles into a high-energy ball mill for 30h, the speed is 500r / min, the vacuum degree is 3×20 -2 Pa, ball-to-material ratio 3:1; reduce the particle size of VC particles to 0.3μm.

[0070] S2. Weigh the Al-10V particles and the nano-VC particles according to the mass percentage of the chemical elements.

[0071] S3, the weighed Al-10V particles were mixed with the nano-VC particles, and the mixture was put into a ball mill for 1 hour at a speed of 150 r / min and a vacuum degree of 3×20 -2 Pa, the ball-to-material ratio is 3:1, and a mixture is obtained. 5.0wt.% cryolite is added to the total amount of the mixture and mixed evenly. It is wrapped into a cake shape with aluminum foil and then heated at 150°C to dry for 2 hours to remove moisture.

[0072] S4. Coat the experimental tools with titanium dioxide as a protective layer: titanium alloy stirring rod, titanium alloy middle cover, titanium alloy colander and clay crucible; put them into a drying oven together with the weighed high-purity aluminum (purity ≥ 99.99%) at 150°C for 1 hour to remove moisture.

[0073] S5. Place a clay crucible in a box-type resistance furnace and preheat it to 300°C. Then place high-purity aluminum inside the crucible and heat it to 850°C until the high-purity aluminum melts to form an aluminum melt. Immerse the aluminum foil wrapped with the mixture into the aluminum melt and stir it thoroughly to form a mixed melt. Then keep it warm for 20 minutes. At this time, the mass percentage of chemical elements in the mixed melt is: V: 2.0wt.%, C: 0.2wt.%, and the remainder is Al. The mass percentage of each element totals 100%.

[0074] S6. Raise the temperature of the mixed melt to 1200°C and keep it for 20 minutes, then cool the mixed melt to 800°C and keep it for 1.5 hours. The reaction rate is increased by heating and keeping the temperature to ensure sufficient reaction. During the cooling process of the mixed melt, stir it every 8 minutes for 2 minutes each time to reduce particle sedimentation and aggregation.

[0075] S7. Use a titanium alloy colander to remove salt slag on the surface of the mixed melt, pour it into a semi-solid continuous rheological extruder with an extrusion ratio of 3 and an extrusion speed of 3r / min to prepare Al-2V-0.2C grain refiner rod.

[0076] Example 3

[0077] The invention provides an Al-3V-0.2C grain refiner, which comprises the following chemical elements by mass percentage: V: 3.0wt.%, C: 0.2wt.%, and the balance is Al, and the mass percentages of the various elements add up to 100%.

[0078] The preparation method of the Al-3V-0.2C grain refiner comprises the following steps:

[0079] S1. Put the block Al-10V master alloy (purity ≥ 99.0%) into a high-energy ball mill for 48 hours at a speed of 500 r / min and a vacuum degree of 8×20 -2 Pa, ball-to-material ratio 3:1; reduce the particle size of Al-10V master alloy to 1mm to obtain Al-10V particles; put the nano-VC particles into a high-energy ball mill for 48h, the speed is 500r / min, the vacuum degree is 8×20 -2 Pa, ball-to-material ratio 3:1; reduce the particle size of VC particles to 0.3μm.

[0080] S2. Weigh Al-10V particles and nano-VC particles according to the mass percentage of chemical elements.

[0081] S3, the weighed Al-10V particles were mixed with the nano-VC particles, and the mixture was put into a ball mill for 1 hour, the speed was 120r / min, and the vacuum degree was 8×20 -2Pa, the ball-to-material ratio is 3:1, and a mixture is obtained. 5.0wt.% cryolite is added to the total amount of the mixture and mixed evenly. It is wrapped into a cake shape with aluminum foil and then heated to 150°C and dried for 1.5 hours to remove moisture.

[0082] S4. Coat the experimental tools with titanium dioxide as a protective layer: titanium alloy stirring rod, titanium alloy middle cover, titanium alloy colander and clay crucible; put them into a drying oven together with the weighed high-purity aluminum (purity ≥ 99.99%) at 150°C for 1.5 hours to remove moisture.

[0083] S5. Place a clay crucible in a box-type resistance furnace and preheat it to 300°C. Then place high-purity aluminum inside the crucible and heat it to 850°C until the high-purity aluminum melts to form an aluminum melt. Immerse the aluminum foil wrapped with the mixture into the aluminum melt, stir it thoroughly to form a mixed melt, and then keep it warm for 20 minutes. At this time, the mass percentage of chemical elements in the mixed melt is: V: 3.0wt.%, C: 0.2wt.%, and the remainder is Al, and the mass percentage of each element totals 100%.

[0084] S6. Raise the temperature of the mixed melt to 1200°C and keep it for 20 minutes, then cool the mixed melt to 800°C and keep it for 1.5 hours. The reaction rate is increased by heating and keeping the temperature to ensure sufficient reaction. During the cooling process of the mixed melt, stir it every 8 minutes for 2 minutes each time to reduce particle sedimentation and aggregation.

[0085] S7. Use a titanium alloy colander to remove salt slag on the surface of the mixed melt, pour it into a semi-solid continuous rheological extruder with an extrusion ratio of 5 and an extrusion speed of 5 r / min to prepare an Al-3V-0.2C grain refiner.

[0086] The morphology and structure of the Al-VC grain refiners prepared in Examples 1 to 3 were tested, and their refinement effects on pure aluminum were analyzed with the comparative example. The results are as follows:

[0087] Figure 1 This is the XRD pattern of the Al-VC grain refiner prepared in Example 1 of the present invention. Figure 1 As shown,

[0088] The prepared Al-VC grain refiner contains three phases of Al, VAl3 and VC, so this method can achieve the effective addition of VAl3 and VC phases. In the grain refinement process, the VC phase can serve as the nucleation core of α-Al, but because VC is face-centered cubic, and the lattice constant of VC (a=0.4327nm) is very close to the lattice constant of α-Al (a=0.4172nm), it provides a favorable surface, so that the aluminum crystals in the aluminum alloy can grow on it, thereby achieving grain refinement. Therefore, the VC phase is easy to serve as the nucleation core of α-Al. The VAl3 phase decomposes in the aluminum melt to release V atoms, which promotes grain refinement.

[0089] Figure 2 This is a scanning electron microscope image of the Al-VC grain refiner prepared in Example 1 of the present invention. Figure 2 As shown in the figure, the VAl3 phase is larger in size and is in light gray block shape. The nano-VC phase is locally enriched around the VAl3 phase, and the remaining VC phase is dispersed in the Al matrix.

[0090] The Al-VC grain refiner prepared in Examples 1 to 3 is used for pure aluminum, specifically comprising the following steps:

[0091] Step 1: put pure aluminum into a crucible and heat it to 750° C. until the pure aluminum melts to form a melt.

[0092] Step 2, respectively add the Al-1V-0.2C grain refiner rod prepared in Example 1, the Al-2V-0.2C grain refiner rod prepared in Example 2 and the Al-3V-0.2C grain refiner rod prepared in Example 1 into 1000g of pure aluminum melt, wherein the amount of Al-1V-0.2C grain refiner is 0.2wt.%, 0.4wt.% and 1.2wt.% of the total amount of pure aluminum melt, the amount of Al-2V-0.2C grain refiner is 0.2wt.% of the total amount of pure aluminum melt, and the amount of Al-3V-0.2C grain refiner is 0.2wt.% of the total amount of pure aluminum melt; stir thoroughly until the grain refiner melts, and mix all the materials evenly to form a uniform mixed melt.

[0093] Step 3: Keep the mixed melt at 750°C for 15 minutes, stir it every 3 minutes for 2 minutes, and then pour it into a steel mold to form an ingot; the ingot is polished and corroded to observe the grains. Figure 3-7 shown.

[0094] A pure aluminum melt without grain refiner was used as a control example. After stirring, it was kept warm for 10 minutes, poured, corroded, and its grain size was measured. Figure 8 shown.

[0095] Figure 3 This is the macroscopic morphology of pure aluminum refined by adding 0.2wt.% of Al-1V-0.2C grain refiner in Example 1 of the present invention. Figure 3 In the figure, (a) is a macroscopic image, and (b) is a partial enlarged image of (a). Figure 3 As shown, the ingot was observed under a stereo microscope and the average grain size of the ingot was 390±20μm.

[0096] Figure 4 This is the macroscopic morphology of pure aluminum refined by adding 0.4wt.% of Al-1V-0.2C grain refiner in Example 1 of the present invention. Figure 4 In the figure, (a) is a macroscopic image, and (b) is a partial enlarged image of (a). Figure 4 As shown, the ingot was observed under a stereo microscope and the average grain size of the ingot was 320±20μm.

[0097] Figure 5 This is the macroscopic morphology of pure aluminum refined by 1.2wt.% Al-1V-0.2C grain refiner in Example 1 of the present invention. Figure 5 In the figure, (a) is a macroscopic image, and (b) is a partial enlarged image of (a). Figure 5 As shown, the ingot was observed under a stereo microscope and the average grain size of the ingot was 195±20μm.

[0098] Figure 6 This is the macroscopic morphology of pure aluminum refined by adding 0.2wt.% Al-2V-0.2C grain refiner in Example 2 of the present invention. Figure 6 In the figure, (a) is a macroscopic image, and (b) is a partial enlarged image of (a). Figure 3 As shown, the ingot was observed under a stereo microscope and the average grain size of the ingot was 280±20μm.

[0099] Figure 7 This is the macroscopic morphology of the refined pure aluminum in Example 3Al-3V-0.2C of the present invention with a grain refiner addition amount of 0.2wt.%. Figure 7 In the figure, (a) is a macroscopic image, and (b) is a partial enlarged image of (a). Figure 7 As shown, the ingot was observed under a stereo microscope and the average grain size of the ingot was 263±20μm.

[0100] Figure 8 This is the macroscopic morphology of pure aluminum without adding grain refiner in the present invention. Figure 8 In the figure, (a) is a macroscopic image, and (b) is a partial enlarged image of (a). Figure 8 As shown, the aluminum grains without adding grain refiner are not refined, the aluminum grain size is poorly uniform, and the size is large.

[0101] In summary, the Al-VC grain refiner provided by the present invention has a phase composition consisting of VAl3 and VC phases; the distribution of VAl3 and VC phases in the Al-VC grain refiner is more uniform, and the second phase particles such as VAl3 and VC are introduced into the Al matrix by adding the Al-VC refiner, which can increase the heterogeneous nucleation sites of Al, thereby achieving the purpose of grain refinement. Due to the direct introduction of CV particles, the problem of poor wettability between carbon and aluminum is avoided. At the same time, VC particles have excellent refining ability and improve the grain refinement effect. CV particles provide additional nucleation points in liquid aluminum, so that aluminum grains can nucleate earlier and faster during the solidification process, thereby effectively reducing the grain size. After adding Al-VC grain refiner to aluminum liquid, the solidification characteristics of the alloy will be changed, the supercooling degree will be reduced, and the refinement will be further promoted.

[0102] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0103] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing an Al-VC grain refiner, characterized in that: The following steps are involved: Al-10V powder and VC powder are mixed and then vacuum ball milled to obtain a mixture; After preheating the container, pure aluminum is placed in the container and heated until the pure aluminum is melted to form an aluminum melt, and the aluminum foil wrapped with the mixed material is immersed in the aluminum melt and stirred to form a mixed melt; The mixed melt is heated to 1190°C-1210°C and kept warm; then cooled to 790°C-810°C and kept warm with stirring every 8 minutes to reduce particle sedimentation and aggregation; then poured into a semi-solid state, continuous rheological extrusion molding is performed to obtain an Al-VC grain refiner.

2. The method for preparing the Al-VC grain refiner according to claim 1, characterized in that: The mass percentages of chemical elements in the mixed melt are: Al: 97.8wt.% to 98.8wt.%, V: 1.0wt.% to 3.0wt.%, C: 0.2wt.%, and the mass percentages of each element add up to 100%.

3. The method for preparing the Al-VC grain refiner according to claim 1, characterized in that: During continuous rheological extrusion molding, the extrusion ratio is 2 to 10, and the extrusion speed is 3 rad / min to 8 rad / min.

4. The method for preparing the Al-VC grain refiner according to claim 1, characterized in that: Raise the temperature to 1190℃~1210℃ and keep warm for 20min; then lower the temperature to 790℃~810℃ and keep warm for 1h~1.5h.

5. The method for preparing the Al-VC grain refiner according to claim 1, characterized in that: During the first vacuum ball milling, the ball milling mixing time is 1h~3h, the speed is 120r / min~200r / min, and the vacuum degree is 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:

1.

6. The method for preparing the Al-VC grain refiner according to claim 1, characterized in that: Preparation method of Al-10V powder, The following steps are involved: The Al-10V master alloy was subjected to secondary vacuum ball milling. The ball milling time was 24h to 48h, the speed was 500r / min, and the vacuum degree was 2×20 -2 Pa~8×20 -2 Pa, ball-to-material ratio is 3:1, and Al-10V powder is obtained; The preparation method of VC powder comprises the following steps: The VC master alloy was subjected to secondary vacuum ball milling. The ball milling time was 24h to 48h, the speed was 500r / min, and the vacuum degree was 2×20 -2 Pa~8×20 -2 Pa, the ball-to-material ratio is 3:1, and VC powder is obtained.

7. The method for preparing the Al-VC grain refiner according to claim 6, characterized in that: After the secondary vacuum ball milling, the particle size of the Al-10V powder is 1 mm to 3 mm, and the particle size of the VC powder is 1 μm to 100 μm.

8. The method for preparing the Al-VC grain refiner according to claim 1, characterized in that: The stirring rod used in the stirring process is a titanium alloy stirring rod, and the surface of the stirring rod is coated with titanium dioxide.

9. An Al-VC grain refiner prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Al-VC grain refiner according to claim 9 in casting aluminum and aluminum alloys, characterized in that: The addition amount of the Al-VC grain refiner is 0.2wt.% to 1.2wt.%.

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