CN115652120B - A two-step method for preparing aluminum-based alloy refinement materials - Google Patents

Abstract

The invention belongs to the technical field of manufacture of non-ferrous metals or alloys, and particularly discloses a method for preparing an aluminum-based alloy refining material by a two-step methodSmelting to obtain an Al-Nb melt, and keeping the temperature for a first time to ensure that Nb has a first concentration; adding TiB2 particles into the prepared Al-Nb melt, and continuously smelting at a second temperature for a second time to modify the TiB2 particles; adding aluminum into the obtained Al-Nb melt with the modified TiB2 particles for dilution, and keeping the temperature at a third temperature for a third time to enable the Nb concentration in the Al-Nb melt to reach a second concentration, wherein the second concentration is less than the first concentration; then pouring to obtain Al-base alloy refined material, under the condition of high Nb concentration said method uses TiB ₂ A modified transition layer NbAl is formed on the (0001) surface ₃ ^’ Make TiB ₂ The particles are better dispersed in the Al-Nb melt, and the Al-Nb-TiB with homogeneous and stable quality is obtained ₂ The melt improves the use performance of the refined material.

Description

A two-step method for preparing aluminum-based alloy refinement materials

technical field

The invention belongs to the technical field of manufacturing non-ferrous metals or alloys, in particular to the processing and preparation of aluminum alloys, and in particular to a two-step method for preparing aluminum-based alloy refinement materials.

Background technique

Aluminum is widely used in many fields such as packaging, construction, transportation and electrical materials due to its abundant resources, light weight, good mechanical properties, excellent corrosion resistance and electrical conductivity. The addition of grain refiners to reduce the grain size is the preferred method to simultaneously improve the strength and ductility of aluminum alloys.

At present, in the industrial production of cast aluminum alloys, the usual practice of refining the grain size is to refine the α-Al grains by adding Al-Ti-B intermediate alloy rods during smelting, so as to improve the performance of cast aluminum alloys. Currently the most widely used Al-5Ti-1B master alloy refiner, but in the A356 alloy with high Si content, Al-5Ti-1B is difficult to achieve the refinement effect of the national standard A class below 250μm. The reason is that the fine phase TiAl ₃ of Al-Ti-B, especially the TiAl ₃ two-dimensional compound on the surface of TiB ₂ particles is easily corroded by Si element. In industrial production, it is necessary to increase the amount of Al-5Ti-1B to further reduce the grain size of A356. In order to overcome the Si element poisoning problem of Al-5Ti-1B. In recent years, Al-Nb-B master alloy refiner has appeared. Nb has similar effect with Ti element, and the formed NbAl ₃ phase has high stability, can resist the erosion of Si element, and can play a role in refinement in cast aluminum-silicon alloy. effect. However, due to the relative atomic mass of the second phase NbAl ₃ and NbB ₂ of Al-Nb-B, it is easy to agglomerate and settle in the aluminum melt, and its resistance to decay is poor. Moreover, the cost of Nb element is high, and it is difficult to be applied in industrial production.

Considering that the atomic properties of Ti and Nb are similar, and the crystal structure of the refined phase TiAl ₃ and NbAl ₃ , TiB ₂ and NbB ₂ is the same, it is theoretically possible to add TiB ₂ nucleation particles and Nb elements to the aluminum melt together, combining Al-Ti- The excellent refining effect of B and the advantages of Al-Nb-B anti-Si poisoning, the preparation of high-efficiency Al-Nb-TiB _master alloy refining agent for casting aluminum alloys. The traditional method is to melt all components at the same time to prepare the refiner, but in practical application, it is found that in the refiner obtained by the above method, the surface modification of TiB ₂ nucleation particles by Nb element during the smelting process Insufficient, it is difficult to obtain good thinning performance.

Contents of the invention

In order to solve the above technical problems, the present invention provides a two-step method for preparing aluminum-based alloy refined materials. A two-step method is adopted: first, the TiB ₂ nucleation particles are modified by using Al-Nb melt with a high concentration of Nb elements to ensure the enrichment and modification effect of Nb elements on the surface of TiB ₂ nucleation particles, and then quantitative supplementation is carried out step by step. Al element, give full play to the anti-recession and anti-Si poisoning characteristics of the Al-Nb-TiB ₂ system and improve the refining efficiency.

To achieve the above object, the complete technical solution of the present invention includes:

A two-step method for preparing aluminum-based alloy refined materials, comprising the steps of:

Step (1): Melting at a first temperature to obtain an Al-Nb melt and keeping it warm for a first time, wherein Nb has a first concentration in the Al-Nb melt;

Step (2): adding TiB ₂ particles into the Al-Nb melt prepared in step (1), and continuing to smelt at a second temperature for a second time to modify the TiB ₂ particles;

Step (3): adding aluminum to the Al-Nb melt with modified _TiB2 particles obtained in step (2) for dilution, and maintaining at a third temperature for a third time so that the concentration of Nb reaches the second concentration, the second concentration is less than the first concentration;

Step (4): pouring the melt obtained in step (3) at a fourth temperature to obtain the aluminum-based alloy refined material.

Further, in step (1), the mass percentage of Nb in the Al-Nb melt is not less than 5%.

Further, in step (3), after adding aluminum for dilution, the mass percentage of Nb in the melt is 1.5-3.5%.

Further, in step (2), the mass of TiB ₂ particles accounts for 4.3%-8% of the mass of the Al-Nb melt obtained in step (1).

Further, in step (2), the second temperature is 850°C-900°C, and the second time is 60-120min.

Further, in step (2), a modified transition layer NbAl ₃ ^′ is formed on the (0001) plane of TiB ₂ .

Further, in step (1), the first temperature is 850°C~900°C, and the first time is 30~60min; in step (3), the third temperature is 750°C~800°C, and the first time is 30~60min; The third time is 30 minutes; in step (4), the fourth temperature is 720°C.

The aluminum-based alloy refined material prepared by the method, the components and mass percentages of each element of the aluminum-based alloy refined material are as follows: Al is 94-96%, Ti is 3-5%, Nb is 1.5-3.5%, B 0.5~1.5%, the sum is 100%.

Further, the aluminum-based alloy refinement material contains an aluminum matrix and second phases TiB ₂ and NbAl ₃ ; wherein the TiB ₂ phase mass fraction is 3-4%, the size is below 3 μm, and the NbAl ₃ phase mass fraction is 5-7% %, the size is below 10 μm.

Further, the second phase is dispersed in the aluminum matrix.

The Al-Nb- _TiB refiner prepared by the present invention has a significant refinement effect on Al-7Si: after adding Al-Nb-TiB ₂ , under the best refinement process (refiner addition 0.5wt.% , refinement temperature 750°C, refinement time 10min), the grain size was refined from the original 1400μm to 330.48μm; The refining agent is poisoned by Si in cast aluminum-silicon alloy, taking into account the advantages of the two types of refining agents, it has practical value for improving the alloy quality and performance of cast aluminum-silicon alloy.

1. The Al-Nb- _TiB2 refining agent prepared by the present invention uses the _TiB2 phase as nucleation particles to ensure the efficient refining effect of the Al-Ti-B system on aluminum alloys, and Nb is introduced to modify the surface of _TiB2 . The problem that the TiAl ₃ two-dimensional compound on the surface of TiB ₂ is destroyed by Si element corrosion is avoided.

2. The Al-Nb-TiB ₂ refining agent prepared by the present invention can refine the aluminum-silicon alloy with a Si content of 7wt.% from 1400 μm to 330.48 μm, and the refining effect is better than that of the commercially available Al-5Ti-1B at 549.06 μm .

3. The Al-Nb-TiB ₂ prepared by the present invention only needs 0.5wt.% addition to refine the aluminum-silicon alloy with a Si content of 7wt.% to 330.48 μm. Compared with the conventionally prepared Al-Nb-TiB ₂ The refinement efficiency is higher.

4. The preparation process in the present invention can realize the in- _situ generation of _TiB2 nucleation particles and the surface modification of _TiB2 nucleation particles. Uniformity is good for TiB ₂ and NbAl ₃ phases to give full play to the refinement effect.

Description of drawings

Fig. 1 is a metallographic structure diagram of Al-2.8Nb-2.2Ti-1B master alloy refiner in Example 1 of the invention.

Fig. 2 is a structure diagram of the effect of Al-2.8Nb-2.2Ti-1B prepared in Invention Example 1 on the α-Al grain refinement effect of Al-7Si alloy at different refinement times.

Fig. 3 is a comparison chart of the refining effect of Al-2.8Nb-2.2Ti-1B prepared in Example 1 on the α-Al grain refinement of Al-7Si alloy under different refining times.

FIG. 4 is a microstructure diagram of α-Al grain refinement of Al-2.8Nb-2.2Ti-1B and Al-7Si alloy prepared by the conventional method in Comparative Example 1. FIG.

Fig. 5 is a microstructure diagram of the α-Al grain refinement effect of the Al-7Si alloy using a commercially available Al-5Ti-1B refiner in Comparative Example 2.

Fig. 6 is the Al-2.8Nb-2.2Ti-1B prepared by the two-step method of Example 1 and the conventionally prepared Al-2.8Nb-2.2Ti-1B of Comparative Example 1, and the commercially available Al-5Ti-1B of Comparative Example 2 to Al Comparison of refinement effect of -7Si alloy.

Detailed ways

The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only for illustration and are not intended to limit this application.

The two-step method for preparing aluminum-based alloy refinement materials disclosed by the present invention comprises the following steps:

(1) Formation of Al-Nb melt with high Nb concentration

(1a) Weighing raw materials: use Al-10Nb master alloy as raw material, weigh 250~350g of Al-10Nb master alloy, use pure aluminum ingot as raw material, weigh aluminum ingot equivalent to Al-10Nb alloy;

(1b) Alloying: Put the weighed metal raw material into the graphite crucible and put it into the induction melting furnace together with the crucible, and raise the temperature to 850~900°C; after the aluminum ingot is completely melted, keep it warm for 10~60min, during which graphite The stirring bar is continuously stirred to accelerate the dissolution and uniform distribution of Nb. Add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum to obtain a pure Al-Nb melt.

(2) Preparation and modification of TiB ₂ powder

(2a) Weighing raw materials: using TiB _{2 powder} with average particle size D ₅₀ =0.3~3.0μm and distribution width σ=2.5~20μm as raw material, use a planetary ball mill at a speed of 200~400rpm to carry out 2- 4h ball milling to ensure uniform dispersion of TiB ₂ and minimize agglomeration. Select _TiB2 powder raw material with suitable particle size distribution as the nucleation particles introduced as required, and weigh according to the following composition: _TiB2 is 30~40g.

(2b) Introduce _TiB2 nucleation particles: Wrap the weighed _TiB2 powder with aluminum foil, preheat at 175°C for 30min, and then add it into the Al-Nb melt kept at 850~900°C obtained in (1b), At the same time, use a graphite stirring rod to press the aluminum foil block wrapped with TiB ₂ powder to the middle and lower part of the melt, wait for about 2 minutes, until the aluminum foil is completely melted and the TiB ₂ powder is scattered, and then use a graphite stirring rod to continue stirring for 60~120 minutes.

TiB ₂ has poor wettability with aluminum melt. If TiB ₂ is directly added to pure aluminum melt, TiB ₂ will sink to the bottom and cannot be evenly dispersed in aluminum melt. Therefore, Al-Nb alloying needs to be completed first. TiB ₂ in the Al-10Nb alloy with high concentration of Nb, due to the similar structure of NbAl ₃ and TiAl ₃ , can form a modified transition layer NbAl ₃ ^' on the (0001) surface of TiB ₂ , and NbAl ₃ ^' can reduce the relationship between TiB ₂ and aluminum The wetting angle of the melt enables better dispersion of TiB ₂ particles in the Al-Nb melt, resulting in a homogeneous and stable Al-Nb-TiB ₂ melt;

(3) Supplementary solvent Al

Supplement Al dilution melt: select 99.7wt.% and above aluminum ingots as raw materials, weigh 200~400g aluminum ingots, and lower the temperature of the Al-Nb-TiB ₂ melt obtained in (2b) to 750~800°C, Add the weighed aluminum ingot into the Al-Nb-TiB ₂ melt to dilute the Nb element concentration. After the aluminum alloy is completely melted at 750°C, keep it warm for 30 minutes. During this period, use a graphite stirring rod to stir the melt to ensure that Al, The Nb element is evenly distributed, while preventing the _TiB2 particles from settling, then adding 0.1wt.% refining agent to refine the molten aluminum, and then skimming off the scum on the surface of the molten aluminum to obtain pure Al-Nb- _TiB2 molten aluminum diluted with Al body.

(4) Pouring preparation

After the Al-Nb-TiB ₂ melt is cooled to 720°C, the melt is poured into a conical metal mold preheated at 175°C for 1 hour, and the Al-Nb-TiB ₂ alloy is obtained after cooling and solidification. The material of the hot work die steel mold used is: H13 hot work die steel, and the size of the tapered die is Φ50mm×80mm.

The idea of preparing the refined material of the present invention is to firstly obtain Al-Nb melt with high Nb concentration, and add _TiB2 particles, after fully modifying _TiB2 particles in Nb-rich environment, add Al to dilute, so as to obtain the target Composition of Al-Nb- _TiB2 refinement material, in the process, there is an important relationship between the first concentration of Nb element, the relationship between the added _TiB2 particles and the mass ratio, and the modification time, too low Nb concentration It will lead to insufficient modification and affect the refinement effect; but too high Nb concentration will significantly increase the cost, and the Nb element has a large proportion, which will lead to agglomeration and settlement in the aluminum melt during the refinement process, which also affects the refinement effect. Therefore, the present invention analyzes the above-mentioned relationship in each step, and preferably adopts the following relationship: w ₁ =k ( w _t ) ⁿ , where w ₁ is the mass percentage of Nb in the initially prepared Al-Nb melt, that is, the first Concentration, wt _is the mass percentage of the added TiB ₂ particles in the initial prepared Al-Nb melt, n is the exponential factor, the value range is 0.5~0.8, k is the coefficient, the value range is 0.18~0.22.

The refined aluminum-based alloy material obtained by the method is an Al-Nb- _TiB alloy, and the components and mass percentages of each element are as follows: Al is 94-96%, Ti is 3-5%, and Nb is 1.5-3.5% %, B is 0.5~1.5%, and the sum is 100%. The alloy contains secondary phases TiB ₂ , NbAl ₃ . The mass fraction of TiB ₂ phase is 3~4%, the size is below 3μm, the mass fraction of NbAl ₃ phase is 5~7%, the size is below 10μm, and all the second phases are uniformly dispersed in the aluminum matrix.

Embodiment 1: a kind of two-step method prepares Al-Nb- _TiB refiner for cast aluminum-silicon alloy, comprises the following steps:

Step 1: Using Al-10Nb master alloy as raw material, weigh 260g of Al-10Nb master alloy and 260g of pure aluminum ingot; put the weighed metal raw material into a graphite crucible and put it into an induction melting furnace together with the crucible , the temperature was raised to 900 ° C; after the aluminum ingot was completely melted, it was kept for 30 minutes, and a graphite stirring rod was used to continuously stir during this period to accelerate the dissolution and uniform distribution of Nb. Add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum to obtain a pure Al-5Nb melt.

Step 2: Using TiB 2 powder with average particle size D ₅₀ =0.3 μm and distribution width σ=20 μm as the raw material, use a planetary ball mill to mill the TiB ₂ powder raw material at a speed of 400 rpm for 4 hours to ensure uniform dispersion of TiB ₂ and minimize _{agglomeration} . Select _TiB2 powder raw material with suitable particle size distribution as the nucleation particles introduced as required, and weigh according to the following composition: _TiB2 is 30g.

Step 3: Wrap the weighed TiB ₂ powder with aluminum foil, preheat it at 175°C for 30 minutes, then add it into the Al-5Nb melt at 900°C obtained in Step 1, and use a graphite stirring rod to wrap the TiB ₂ Press the powdered aluminum foil agglomerate to the middle and lower part of the melt, wait for about 2 minutes, until the aluminum foil is completely melted, and the TiB ₂ powder is scattered, then use a graphite stirring rod to continue stirring for 120 minutes. TiB ₂ has poor wettability with aluminum melt. When TiB ₂ is directly added to pure aluminum melt, TiB ₂ sinks to the bottom and cannot be evenly dispersed in aluminum melt. Therefore, Al-Nb alloying needs to be completed first. TiB ₂ in the Al-10Nb alloy with high concentration of Nb, due to the similar structure of NbAl ₃ and TiAl ₃ , can form a modified transition layer NbAl ₃ ^' on the (0001) surface of TiB ₂ , and NbAl ₃ ^' can reduce the relationship between TiB ₂ and aluminum The wetting angle of the melt enables better dispersion of TiB ₂ particles in the Al-Nb melt, resulting in a homogeneous and stable Al-Nb-TiB ₂ melt;

Step 4: Select aluminum ingots with 99.7wt.% or more as raw materials, weigh 380g of aluminum ingots, cool down the Al-Nb-TiB ₂ melt obtained in (1d) to 750°C, and place the weighed aluminum ingots Add it to the Al-Nb-TiB ₂ melt to dilute the concentration of Nb elements. After the aluminum alloy is completely melted at 750°C, keep it warm for 30 minutes. During this period, use a graphite stirring rod to stir the melt to ensure that the Al and Nb elements are evenly distributed, and at the same time prevent TiB ₂ particles settle down, then add 0.1wt.% refining agent to refine the molten aluminum, then skim off the scum on the surface of the molten aluminum to obtain pure Al-Nb-TiB ₂ melt after Al dilution, and wait for the melt to cool to At 720°C, the melt was poured into a conical metal mold preheated at 175°C for 1h, and after cooling and solidification, the Al-2.8Nb-2.2Ti-1B alloy was obtained, and its metallographic structure is shown in Figure 1.

Step 5: Put 530g of pure aluminum ingot and 460g of Al-15Si alloy weighed into the crucible and put them into the resistance melting furnace together with the crucible, raise the temperature to 750°C, and control the composition of the aluminum alloy to be: Al-7Si; After the alloy is completely melted at 750°C, keep it warm for 30 minutes, add 0.1wt.% refining agent to refine the molten aluminum, and then skim off the scum on the surface of the molten aluminum; pour the molten metal into a conical metal mold preheated at 175°C for 1 hour , to obtain unrefined Al-7Si alloy;

Step 6: Put the weighed Al-7Si alloy into the crucible and put it into the resistance melting furnace together with the crucible, raise the temperature to 750°C, and add the prepared Al-2.8Nb-2.2Ti-1B master alloy into the aluminum melt , the addition amount is 0.5wt.% of the Al-7Si alloy, the melt is artificially stirred with a graphite stirring rod for 2 minutes, and kept at 750°C for 10, 30, 60, and 120 minutes respectively; the molten metal that reaches the corresponding holding time is poured into In a conical metal mold preheated at 175°C for 1 hour, after cooling and solidification, Al-2.8Nb-2.2Ti-1B refined Al-7Si alloys with refining times of 10, 30, 60 and 120 minutes were obtained. Cut the casting sample at the position 3cm from the bottom of the sample, carry out anodic coating treatment, and observe it with a polarizing microscope, as shown in Figure 2. Figure 2 shows the effect of Al-2.8Nb-2.2Ti-1B on Al Microstructure diagram of -7Si alloy, refining time: (a) in Figure 2 is 10min; (b) in Figure 2 is 30min; (c) in Figure 2 is 60min; (d) in Figure 2 ) is 120min. Figure 3 shows the refinement effect of Al-2.8Nb-2.2Ti-1B on Al-7Si alloy under different refinement times, which are 10min, 30min, 60min and 120min from left to right. The aluminum grains were measured using the intercept method specified in the national standard GB/T 3246.1-2012. The refining effect was the best when the refining time was 10 minutes. The average size of α-Al grains in Al-7Si was 330.48 μm. The anti-fading performance is good. Even if the refining time reaches 120min, the prepared Al-2.8Nb-2.2Ti-1B still has a refining effect of 412.87μm on the α-Al grains in Al-7Si.

Comparative Example 1: The conventional preparation of Al-2.8Nb-2.2Ti-1B master alloy to refine Al-7Si includes the following steps:

Step 1: Al-10Nb master alloy is used as Nb source, and the raw materials are weighed according to the following composition ratio: 200g of Al-10Nb master alloy and 520g of pure aluminum ingot. Place the weighed alloy ingot in the crucible and put it into the induction melting furnace together with the crucible, and raise the temperature to 900°C; after the aluminum ingot is completely melted, keep it warm for 10 minutes, and add 0.1wt.% refining agent to refine the aluminum liquid , and then skim off the scum on the surface of the molten aluminum to obtain a homogeneous and stable Al-2.8Nb melt;

Step 2: Using TiB 2 powder with average particle size D ₅₀ =0.3 μm and distribution width σ=20 μm as the raw material, use a planetary ball mill to mill the TiB ₂ powder raw material at a speed of 400 rpm for 4 hours to ensure uniform dispersion of TiB ₂ and minimize _{agglomeration} . Select _TiB2 powder raw material with suitable particle size distribution as the nucleation particles introduced as required, and weigh according to the following composition: _TiB2 is 23.8g;

Step 3: Wrap the weighed TiB ₂ powder with aluminum foil, preheat it at 175°C for 30min, then add it into the Al-2.8Nb melt at 900°C obtained in step 1, and use a graphite stirring rod to wrap the TiB _2. Press the powdered aluminum foil agglomerate to the middle and lower part of the melt, wait for about 2 minutes, until the aluminum foil is completely melted, and the TiB ₂ powder is scattered, then use a graphite stirring rod to continue stirring for 120 minutes to obtain a homogeneous and stable Al-2.8Nb-2.2Ti-1B Melt, after the melt is cooled to 720°C, pour the melt into a conical metal mold preheated at 175°C for 1 hour, and obtain Al-2.8Nb-2.2Ti-1B alloy after cooling and solidification;

Step 4: Put the weighed Al-7Si alloy into the crucible and put it into the resistance melting furnace together with the crucible, raise the temperature to 750°C, add the conventionally prepared Al-2.8Nb-2.2Ti-1B master alloy into the aluminum melting % of the Al-7Si alloy, artificially stir the melt with a graphite stirring rod for 2 minutes, and keep it at 750°C for 10 minutes; pour the molten metal into a metal mold preheated at 175°C for 1 hour After cooling and solidification, the Al-2.8Nb-2.2Ti-1B refined Al-7Si alloy with a refining time of 10min was obtained. Cut the casting sample at the position 3cm away from the bottom of the sample, carry out anodic coating treatment, and observe it with a polarizing microscope, as shown in Figure 4, Figure 4 is the microstructure of Al-2.8Nb-2.2Ti-1B on Al-7Si alloy The refinement effect was measured, and the aluminum grains were measured using the intercept method specified in the national standard GB/T 3246.1-2012. When the refinement time was 10 minutes, the average size of α-Al grains in Al-7Si was 580.37 μm.

Comparative example 2: The refinement effect of commercially available Al-5Ti-1B master alloy on Al-7Si, including the following steps:

Step 1. Put the weighed Al-7Si in the crucible and put it into the crucible-type resistance melting furnace together with the crucible, and heat up to 750°C; after the aluminum ingot is completely melted, keep it warm for 30 minutes, and then add 0.1wt.% refining agent Refining the molten aluminum, then skimming off the scum on the surface of the molten aluminum; adding the commercially available Al-5Ti-1B master alloy to the Al-7Si melt, the addition amount is 0.5wt.% of Al-7Si, and using a graphite stirring rod Stir the melt and keep it warm at 750°C for 10 minutes;

Step 2. Pouring the aluminum melt into a conical metal mold preheated at 175°C for 1 hour, cooling and solidifying to obtain a refined Al-7Si sample of the Al-5Ti-1B master alloy. Cut the sample at a position 3cm from the bottom of the sample, carry out anodic coating treatment, observe with a polarizing microscope, as shown in Figure 5, and use the intercept method specified in the national standard GB/T 3246.1-2012 to analyze the aluminum grains. According to measurements, the commercially available Al-5Ti-1B master alloy has a limited refining effect on α-Al grains in Al-7Si when the refining time is 10 min, and the average size of α-Al grains is 549.06 μm.

Comparing Example 1 with the Al-2.8Nb-2.2Ti-1B prepared by the two-step method in Comparative Example 1 and 2, the conventionally prepared Al-2.8Nb-2.2Ti-1B, the commercially available Al-5Ti-1B to Al-7Si The refinement effect of the alloy, as shown in Figure 6, the Al-2.8Nb-2.2Ti-1B prepared by the present invention still has a refinement effect of about 412.87 μm on Al-7Si after 120 minutes of heat preservation, while the conventionally prepared Al- 2.8Nb-2.2Ti-1B can only refine α-Al in Al-7Si to 580.37μm even when it is held for 10 minutes. In contrast, the Al-2.8Nb-2.2Ti-1B prepared by the present invention not only has a far better refinement effect than the conventionally prepared Al-2.8Nb-2.2Ti-1B. And for commercially available Al-5Ti-1B, the refinement effect on Al-7Si is also poor at 549.06 μm under the refinement time of 10 minutes, which is far inferior to the 330.48 μm achieved by the preparation of Al-2.8Nb-2.2Ti-1B in the present invention. Therefore, the Al-4Ti-1Nb-1B prepared according to the present invention not only has a better refining effect on Al-7Si, but also has excellent decay resistance.

The present invention first aims at the problem that the refining effect of the Al-Ti-B refining agent is reduced due to Si poisoning. When the Si content of the aluminum-silicon alloy is greater than 3wt.%, Si atoms will erode and modify the TiAl ₃ two-dimensional compound on the surface of TiB ₂ in the Al-Ti-B alloy, forming a TiAlSi phase, making the interface between α-Al and TiB ₂ The free energy and the degree of mismatch increase, and it is difficult for α-Al aluminum grains to nucleate heterogeneously on TiB ₂ , which leads to the weakening of the refining effect of Al-Ti-B refiner. The NbAl ₃ layer on the surface of NbB ₂ in Al-Nb-B is more stable than TiAl ₃ , and is not easily corroded by Si atoms. At the same time, because the crystal structure of NbAl ₃ is the same as that of TiAl ₃ , NbAl ₃ can be segregated and modified on the surface of TiB ₂ , The NbAl ₃ ^' structure is formed, so that the refiner has the ability to resist Si poisoning.

The invention also aims at the problem that TiB ₂ is difficult to add in the preparation of Al-Nb-TiB ₂ master alloy. Since the wettability of TiB ₂ particles and Al melt is average, direct addition is likely to cause problems such as TiB ₂ agglomeration and precipitation. The invention adopts mechanical pre-alloying to reduce the agglomeration of Nb powder, and uses Nb element to improve the wettability of _TiB2 and Al melt, which is helpful to the subsequent alloying process, and finally obtains a homogeneous and stable Al-Nb- _TiB2 intermediate alloy.

The invention simultaneously solves the problem of Nb modification of _TiB2 in the preparation of Al-Nb- _TiB2 master alloy. At present, the academic circles believe that both the high refinement efficiency of Al-5Ti-1B and the anti-Si poisoning characteristics of Al-Nb-B depend on the specific element enrichment on the surface of nucleation particles. However, it is difficult to ensure the effect of Nb modification in the process of directly modifying _TiB2 in Al-Nb melt. The present invention adopts two steps of mechanical pre-alloying and alloy melt alloying to provide _TiB2 with an environment of Nb elements all the time, improve the enrichment of Nb elements on the surface of _TiB2 , and improve the Si poisoning resistance of Al-Nb- _TiB2 master alloy ability.

The above applications are only some embodiments of the present application. Those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present application, and these all belong to the protection scope of the present application.

Claims (2)

1. A two-step method for preparing aluminum-based alloy refinement materials, characterized in that, comprises the steps: Step (1): Melting at a first temperature to obtain an Al-Nb melt and keeping it warm for a first time, the mass percentage of Nb in the Al-Nb melt is not less than 5%; the first temperature is 850°C ~900°C, the first time is 30~60min; Step (2): Add TiB ₂ particles to the Al-Nb melt prepared in step (1), and continue smelting at a second temperature to modify the TiB ₂ particles for a second time; the mass of TiB ₂ particles accounts for the mass of the step ( 1) 4.3%-8% of the mass of the Al-Nb melt obtained in the method; the second temperature is 850°C~900°C, and the second time is 60~120min; Step (3): For the Al- _Nb melt with modified TiB particles obtained in step (2), add aluminum to dilute, and keep it at a third temperature for a third time, and the mass percentage of Nb in the melt is 1.5~3.5%; the third temperature is 750°C~800°C, and the third time is 30min; Step (4): Casting the melt obtained in step (3) at a fourth temperature to obtain the aluminum-based alloy refined material, the fourth temperature being 720° C. 2. A two-step method for preparing aluminum-based alloy refined materials according to claim 1, characterized in that, in step (2), a modified transition layer NbAl ₃ is formed on the (0001) surface of TiB ₂ ^' .

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