CN115652120B - Method for preparing aluminum-based alloy refined material by two-step method - Google Patents
Method for preparing aluminum-based alloy refined material by two-step method Download PDFInfo
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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
Technical Field
The invention belongs to the technical field of manufacture of non-ferrous metals or alloys, particularly relates to processing and preparation of an aluminum alloy, and particularly relates to a method for preparing an aluminum-based alloy refining material by a two-step method.
Background
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, and excellent corrosion resistance and electrical conductivity. The addition of grain refiners to reduce grain size is the preferred method to increase both strength and plasticity of aluminum alloys.
Currently, in the industrial production of cast aluminum alloy, the common method for refining the grain size is to refine alpha-Al grains in a mode of adding A1-Ti-B intermediate alloy rods during smelting so as to improve the performance of the cast aluminum alloy. At present, the most widely used Al-5Ti-1B intermediate alloy refiner is used, but Al-5Ti-1B in the A356 alloy with higher Si content is difficult to achieve the refining effect of the national standard A type below 250 mu m. The reason is that the refined phase TiAl of Al-Ti-B 3 In particular TiB 2 TiAl on the surface of particles 3 The two-dimensional compound is easily corroded by the Si element. In industrial production, the dosage of Al-5Ti-1B needs to be increased to further reduce the A356 grain size. In order to overcome the problem of Si element poisoning of Al-5 Ti-1B. In recent years, al-Nb-B master alloy refiner appears, and Nb has similar action with Ti element to form NbAl 3 High phase stability and Si resistanceThe erosion of elements can play a refining role in casting the aluminum-silicon alloy. However, al-Nb-B is NbAl due to its second phase 3 、NbB 2 The alloy has large relative atomic mass, is easy to agglomerate and settle in an aluminum melt, has poor decay resistance, does not meet the process requirement of casting aluminum-silicon alloy for long heat preservation time, has high Nb element cost, and is difficult to be applied to industrial production.
Considering the similar atomic properties of Ti and Nb, the TiAl phase is refined 3 And NbAl 3 、TiB 2 And NbB 2 The crystal structures are the same, and TiB can be theoretically converted 2 The nucleation particles and the Nb element are added into the aluminum melt together, and the high-efficiency Al-Nb-TiB for casting aluminum alloy is prepared by combining the advantages of excellent Al-Ti-B refining effect and Al-Nb-B Si poisoning resistance 2 And (4) an intermediate alloy refiner. The traditional method is to melt all components simultaneously to prepare the refiner, but in practical application, the refiner obtained by the method is found to have Nb element pair TiB in the melting process 2 The surface modification of the nucleation particles is insufficient, and it is difficult to obtain good refining performance.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for preparing an aluminum-based alloy refining material by a two-step method. A two-step method is adopted: firstly, al-Nb melt pair TiB with higher Nb element concentration is used 2 The nucleation particles are modified to ensure that the Nb element is in TiB 2 Enriching and modifying effect on the surface of the nucleation particle, quantitatively supplementing Al element step by step, and fully exerting Al-Nb-TiB 2 The system has the characteristics of recession resistance and Si poisoning resistance, and the refining efficiency is improved.
In order to achieve the purpose, the complete technical scheme of the invention comprises the following steps:
a method for preparing an aluminum-based alloy refining material by a two-step method comprises the following steps:
step (1): smelting at a first temperature to obtain an Al-Nb melt, and keeping the temperature for a first time, wherein Nb has a first concentration in the Al-Nb melt;
step (2): adding TiB into the Al-Nb melt prepared in the step (1) 2 Particles and continuing to melt at a second temperature for a second time period to form TiB 2 Particle processModification;
and (3): modifying the TiB with modification obtained in the step (2) 2 Adding aluminum into the Al-Nb melt of the particles for dilution, and keeping the temperature at a third temperature for a third time to enable the concentration of Nb to reach a second concentration, wherein the second concentration is less than the first concentration;
and (4): and (4) casting the melt obtained in the step (3) at a fourth temperature to obtain the aluminum-based alloy refined material.
Further, in the step (1), the mass percent of Nb in the Al-Nb melt is not less than 5%.
Further, in the step (3), after aluminum is added and diluted, the mass percent of Nb in the melt is 1.5 to 3.5%.
Further, in the step (2), tiB 2 The mass of the particles accounts for 4.3-8% of the mass of the Al-Nb melt obtained in the step (1).
Further, in the step (2), the second temperature is 850-900 ℃, and the second time is 60-120min.
Further, in step (2), in TiB 2 A modified transition layer NbAl is formed on the (0001) surface 3 ’ 。
Further, in the step (1), the first temperature is 850-900 ℃, and the first time is 30-60min; in the step (3), the third temperature is 750-800 ℃, and the third time is 30min; in the step (4), the fourth temperature is 720 ℃.
The aluminum-based alloy refining material prepared by the method comprises the following element components in percentage by mass: 94 to 96 percent of Al, 3~5 percent of Ti, 1.5 to 3.5 percent of Nb, 0.5 to 1.5 percent of B and 100 percent of the total.
Further, the aluminum-based alloy refined material contains an aluminum matrix and a second phase TiB 2 And NbAl 3 (ii) a Wherein TiB 2 The phase mass fraction is 3~4%, the size is below 3 μm, nbAl 3 The phase mass fraction is 5~7% and the size is below 10 μm.
Further, the second phase is dispersed throughout the aluminum matrix.
Al-Nb-Ti prepared by the inventionB 2 The refiner has obvious refining effect on Al-7 Si: adding Al-Nb-TiB 2 Then, under the optimal refining process (the addition of a refiner is 0.5wt.%, the refining temperature is 750 ℃, and the refining time is 10 min), the grain size is refined from the original 1400 mu m to 330.48 mu m; the technical scheme improves the refining efficiency of the Al-Nb-B refiner, avoids the problem that the Al-Ti-B refiner is poisoned by the cast aluminum-silicon alloy Si, takes the advantages of the two types of refiners into consideration, and has practical value for improving the alloy quality and performance of the cast aluminum-silicon alloy.
1. Al-Nb-TiB prepared by the invention 2 The refiner is TiB 2 The phase is nucleation particles, the high-efficiency refining effect of an Al-Ti-B system on the aluminum alloy is ensured, and Nb is introduced to TiB 2 Surface modification is carried out, and TiB is avoided 2 TiAl of surface 3 The two-dimensional compound is corroded by Si element and damaged.
2. Al-Nb-TiB prepared by the invention 2 The refiner can refine the aluminum-silicon alloy with the Si content of 7wt.% from 1400 mu m to 330.48 mu m, and the refining effect is better than 549.06 mu m of the commercial Al-5 Ti-1B.
3. Al-Nb-TiB prepared by the invention 2 Only 0.5wt.% of addition amount is needed to refine the aluminum-silicon alloy with the Si content of 7wt.% to 330.48 mu m, compared with the Al-Nb-TiB prepared conventionally 2 The thinning efficiency is higher.
4. The preparation process can realize TiB 2 In situ generation of nucleation particles, tiB 2 Surface modification of nucleation particles to obtain Al-Nb-TiB 2 The refiner has unique second phase structure and uniform component structure, and is beneficial to TiB 2 、NbAl 3 The refining effect is fully exerted.
Drawings
FIG. 1 is a metallographic structure diagram of an Al-2.8Nb-2.2Ti-1B master alloy refiner in inventive example 1.
FIG. 2 is a structural diagram of the α -Al grain refinement effect of Al-2.8Nb-2.2Ti-1B prepared in inventive example 1 on Al-7Si alloy at different refinement times.
FIG. 3 is a comparison of the α -Al grain refinement effect of Al-7Si alloy by Al-2.8Nb-2.2Ti-1B prepared in invention example 1 at different refinement times.
FIG. 4 is a graph of α -Al grain refinement for Al-2.8Nb-2.2Ti-1B versus Al-7Si alloy prepared by the conventional method in comparative example 1.
FIG. 5 is a structural diagram showing the α -Al grain refining effect of the Al-7Si alloy in comparative example 2 using a commercially available Al-5Ti-1B refiner.
FIG. 6 is a graph comparing the refining effect of Al-2.8Nb-2.2Ti-1B prepared by the two-step process in example 1 with Al-2.8Nb-2.2Ti-1B prepared conventionally in comparative example 1 and Al-5Ti-1B commercially available in comparative example 2 on Al-7Si alloy.
Detailed Description
The technical solutions of the present invention will be described in further detail below with reference to the drawings of the present invention, and it should be understood that the described embodiments are only illustrative and are not intended to limit the present application.
The invention discloses a method for preparing an aluminum-based alloy refining material by a two-step method, which comprises the following steps:
(1) Forming Al-Nb melt with high Nb concentration
(1a) Weighing raw materials: taking Al-10Nb intermediate alloy as a raw material, weighing 250-350g of Al-10Nb intermediate alloy, taking a pure aluminum ingot as a raw material, and weighing an aluminum ingot which is equal to the Al-10Nb alloy;
(1b) Alloying: putting the weighed metal raw materials into a graphite crucible, putting the graphite crucible and the graphite crucible into an induction melting furnace, and heating to 850-900 ℃; and (3) after the aluminum ingot is completely melted, keeping the temperature for 10 to 60min, and continuously stirring by using a graphite stirring rod during the period to accelerate the dissolution and uniform distribution of Nb. Adding 0.1wt.% of refining agent to refine the molten aluminum, and skimming dross on the surface of the molten aluminum to obtain a pure Al-Nb melt.
(2)TiB 2 Powder preparation and modification
(2a) Weighing raw materials: by average particle diameter D 50 (ii) TiB with a distribution width of 0.3 to 3.0 [ mu ] m and a distribution width of 2.5 to 20 [ mu ] m 2 The powder is used as a raw material, and a planetary ball mill is used for aligning TiB at the rotating speed of 200 to 400rpm 2 Ball milling the powder raw material for 2-4h to ensure TiB 2 The dispersion is uniform, and the agglomeration is reduced as much as possible. Selecting TiB with proper particle size distribution according to requirements 2 The powder raw material is taken as the introduced nucleation particles and is weighed according to the following components: tiB 2 The weight ratio is 30 to 40g.
(2b) Introduction of TiB 2 Nucleation particles: weighing TiB 2 Wrapping the powder with aluminum foil, preheating at 175 ℃ for 30min, adding into the Al-Nb melt obtained in (1 b) and keeping the temperature at 850-900 ℃, and simultaneously wrapping TiB with a graphite stirring rod 2 Pressing the powder aluminum foil block to the middle lower part of the melt, waiting for about 2min, and TiB after the aluminum foil is completely melted 2 And (4) dispersing the powder, and then continuously stirring for 60-120min by using a graphite stirring rod.
TiB 2 Poor wettability with aluminum melt, direct reaction of TiB 2 When pure aluminum melt is added, tiB tends to appear 2 The Al-Nb alloying needs to be finished first under the condition that the Al-Nb alloy is not uniformly dispersed in the aluminum melt due to bottom precipitation. TiB 2 In the Al-10Nb alloy with high Nb concentration, nbAl is used 3 With TiAl 3 Similar in structure, can be found in TiB 2 A modified transition layer NbAl is formed on the (0001) surface 3 ’ ，NbAl 3 ’ Can reduce TiB 2 Wetting angle with aluminium melt, 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 Melting the materials;
(3) Make-up solvent Al
And (3) supplementing Al to dilute the melt: selecting 99.7wt.% or more aluminum ingots as raw materials, weighing 200 to 400g of the aluminum ingots, and waiting for obtaining Al-Nb-TiB in the step (2 b) 2 Cooling the melt to 750 to 800 ℃, adding the weighed aluminum ingot into Al-Nb-TiB 2 In the melt, the concentration of Nb element is diluted, the melt is kept warm for 30min after the aluminum alloy is completely melted at 750 ℃, and a graphite stirring rod is used for stirring the melt during the process, so that the Al and Nb elements are uniformly distributed, and TiB is prevented 2 Settling the particles, adding 0.1wt.% of refining agent to refine the molten aluminum, skimming dross on the surface of the molten aluminum to obtain pure Al-Nb-TiB after Al dilution 2 And (4) melting the melt.
(4) Preparation by casting
Waiting for Al-Nb-TiB 2 Cooling the melt to 720 ℃, pouring the melt into a conical metal mold preheated at 175 ℃ for 1h, and cooling and solidifying to obtain Al-Nb-TiB 2 And (3) alloying. The used hot work die steel die is made of the following materials: h13 hot work die steelThe size of the conical die is phi 50mm multiplied by 80mm.
The preparation idea of the refined material is to firstly obtain Al-Nb melt with high Nb concentration and add TiB 2 Particles of, for TiB in an Nb-rich environment 2 Fully modifying the particles, adding Al for dilution to obtain Al-Nb-TiB with a target component 2 Refining the material, in the process, a first concentration of Nb, and adding TiB 2 The relation between the particles and the mass ratio and the modification time have an important relation, and the too low Nb concentration can cause insufficient modification and influence the refining effect; however, the excessively high Nb concentration can significantly increase the cost, and the Nb element has high specific gravity, which can cause agglomeration and sedimentation in the aluminum melt in the refining process, and also influence the refining effect. Therefore, the present invention analyzes the above relationship in each step, and preferably adopts the following relationship:w 1 =k(w t ) n in the formula (I), wherein,w 1 the mass percent of Nb in the initially prepared Al-Nb melt, i.e. the first concentration,w t for adding TiB 2 The mass of the particles accounts for the mass percent of the Al-Nb melt prepared initially,nis an index factor, the value range is 0.5 to 0.8,kthe value range is 0.18 to 0.22.
The Al-based alloy refined material obtained by the method is Al-Nb-TiB 2 The alloy comprises the following element components in percentage by mass: 94 to 96 percent of Al, 3~5 percent of Ti, 1.5 to 3.5 percent of Nb and 0.5 to 1.5 percent of B, and the total is 100 percent. The alloy contains a second phase of TiB 2 、NbAl 3 。TiB 2 The phase mass fraction is 3~4%, the size is below 3 mu m, nbAl 3 The phase mass fraction is 5~7%, the size is below 10 μm, and all the second phases are uniformly dispersed in the aluminum matrix.
Example 1: al-Nb-TiB for preparing cast aluminum-silicon alloy by two-step method 2 A refiner comprising the steps of:
step 1: taking Al-10Nb master alloy as a raw material, and weighing 260g of Al-10Nb master alloy and 260g of pure aluminum ingot; putting the weighed metal raw materials into a graphite crucible, putting the graphite crucible and the graphite crucible into an induction smelting furnace, and heating to 900 ℃; and (3) after the aluminum ingot is completely melted, keeping the temperature for 30min, and continuously stirring by using a graphite stirring rod during the period to accelerate the dissolution and uniform distribution of Nb. Adding 0.1wt.% of refining agent to refine the molten aluminum, and skimming dross on the surface of the molten aluminum to obtain a pure Al-5Nb melt.
And 2, step: by average particle diameter D 50 TiB of =0.3 μm, distribution width σ =20 μm 2 Powder as raw material, using a planetary ball mill at 400rpm for TiB 2 Ball milling the powder raw material for 4h to ensure TiB 2 The dispersion is uniform, and the agglomeration is reduced as much as possible. Selecting TiB with proper particle size distribution according to requirements 2 The powder raw material is taken as the introduced nucleation particles and is weighed according to the following components: tiB 2 Was 30g.
And step 3: weighing TiB 2 Wrapping the powder with aluminum foil, preheating at 175 deg.C for 30min, adding into the 900 deg.C heat-insulating Al-5Nb melt obtained in step 1, and wrapping with TiB with graphite stirring rod 2 Pressing the powder aluminum foil block to the middle lower part of the melt, waiting for about 2min until the aluminum foil is completely melted, and TiB 2 The powder was allowed to come out and then stirred continuously for 120min using a graphite stirring rod. TiB 2 Poor wettability with aluminum melt, direct reaction of TiB 2 With the addition of pure aluminum melt, tiB tends to occur 2 The Al-Nb alloying needs to be finished first under the condition that the Al-Nb alloy is not uniformly dispersed in the aluminum melt due to bottom precipitation. TiB 2 In the Al-10Nb alloy with high Nb concentration, nbAl is used 3 With TiAl 3 Similar in structure, can be found in TiB 2 A modified transition layer NbAl is formed on the (0001) surface 3 ’ ，NbAl 3 ’ Can reduce TiB 2 Wetting angle with aluminium melt, 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 Melting the materials;
and 4, step 4: selecting 99.7wt.% or more aluminum ingots as raw materials, weighing 380g of aluminum ingots, and waiting for the Al-Nb-TiB obtained in step (1 d) 2 Cooling the melt to 750 ℃, adding the weighed aluminum ingot into Al-Nb-TiB 2 In the melt, the concentration of Nb element is diluted, the melt is kept warm for 30min after the aluminum alloy is completely melted at 750 ℃, and a graphite stirring rod is used for stirring the melt during the process, so that the Al element and the Nb element are uniformly distributedUniform and simultaneous prevention of TiB 2 Settling the particles, adding 0.1wt.% of refining agent to refine the molten aluminum, skimming dross on the surface of the molten aluminum to obtain pure Al-Nb-TiB after Al dilution 2 And (3) cooling the melt to 720 ℃, pouring the melt into a conical metal mold preheated at 175 ℃ for 1h, and cooling and solidifying to obtain the Al-2.8Nb-2.2Ti-1B alloy, wherein the metallographic structure of the alloy is shown in figure 1.
And 5: putting 530g of weighed pure aluminum ingot and 460g of Al-15Si alloy into a crucible, putting the crucible and the pure aluminum ingot into a resistance smelting furnace, heating to 750 ℃, and controlling the components of the aluminum alloy as follows: al-7Si; after the aluminum alloy is completely melted at 750 ℃, preserving heat for 30min, adding 0.1wt.% of refining agent to refine the aluminum liquid, and skimming dross on the surface of the aluminum liquid; pouring the molten metal into a conical metal mold preheated at 175 ℃ for 1h to obtain unrefined Al-7Si alloy;
step 6: putting the weighed Al-7Si alloy into a crucible, putting the crucible and the Al-7Si alloy into a resistance smelting furnace, heating to 750 ℃, adding the prepared Al-2.8Nb-2.2Ti-1B intermediate alloy into an aluminum melt, wherein the addition is 0.5 wt% of the Al-7Si alloy, manually stirring the melt for 2min by using a graphite stirring rod, and respectively preserving heat at 750 ℃ for 10min,30min,60min and 120min; pouring the molten metal reaching the corresponding heat preservation time into a conical metal mold preheated at 175 ℃ for 1h, and cooling and solidifying to obtain Al-2.8Nb-2.2Ti-1B refined Al-7Si alloy with refining time of 10min,30min,60min and 120min respectively. Cutting a casting sample at a position 3cm away from the bottom of the sample, carrying out anodic film coating treatment, and observing by using a polarizing microscope, wherein as shown in fig. 2, fig. 2 is a refining effect structure diagram of Al-2.8Nb-2.2Ti-1B on Al-7Si alloy under different refining time, and the refining time is as follows: FIG. 2 (a) is 10min; FIG. 2 (b) is 30min; FIG. 2 (c) is 60min; FIG. 2 (d) shows 120min. FIG. 3 shows the Al-7Si alloy refining effects of Al-2.8Nb-2.2Ti-1B at different refining times, which are 10min,30min,60min and 120min from left to right. When the aluminum crystal grains are measured by using a line cutting method specified in the national standard GB/T3246.1-2012, the refining effect is best when the refining time is 10min, and the average size of alpha-Al crystal grains in Al-7Si is 330.48 mu m. The anti-fading property is good, and even if the thinning time reaches 120min, the prepared Al-2.8Nb-2.2Ti-1B still has the thinning effect of 412.87 mu m on alpha-Al crystal grains in Al-7 Si.
Comparative example 1: al-7Si is refined by conventionally preparing Al-2.8Nb-2.2Ti-1B intermediate alloy, and the method comprises the following steps:
step 1: taking Al-10Nb master alloy as an Nb source, and weighing the following raw materials in percentage by weight: 200g of Al-10Nb master alloy and 520g of pure aluminum ingot. Placing the weighed alloy ingot into a crucible, placing the crucible and the alloy ingot into an induction smelting furnace, and heating to 900 ℃; after the aluminum ingot is completely melted, preserving the heat for 10min, adding 0.1wt.% of refining agent to refine the aluminum liquid, and skimming dross on the surface of the aluminum liquid to obtain a homogeneous and stable Al-2.8Nb melt;
step 2: by average particle diameter D 50 TiB of =0.3 μm, distribution width σ =20 μm 2 Powder as raw material, using a planetary ball mill at 400rpm for TiB 2 Ball milling the powder raw material for 4h to ensure TiB 2 The dispersion is uniform, and the agglomeration is reduced as much as possible. Selecting TiB with proper particle size distribution according to requirements 2 The powder raw material is taken as the introduced nucleation particles and is weighed according to the following components: tiB 2 23.8g;
and step 3: weighing TiB 2 Wrapping the powder with aluminum foil, preheating at 175 deg.C for 30min, adding into 900 deg.C heat-insulating Al-2.8Nb melt obtained in step 1, and wrapping with TiB with graphite stirring rod 2 Pressing the powder aluminum foil block to the middle lower part of the melt, waiting for about 2min, and TiB after the aluminum foil is completely melted 2 Dispersing the powder, continuously stirring for 120min by using a graphite stirring rod to obtain a homogeneous and stable Al-2.8Nb-2.2Ti-1B melt, pouring the melt into a conical metal mold preheated at 175 ℃ for 1h after the melt is cooled to 720 ℃, and cooling and solidifying to obtain Al-2.8Nb-2.2Ti-1B alloy;
and 4, step 4: putting the weighed Al-7Si alloy into a crucible, putting the crucible and the Al-7Si alloy into a resistance smelting furnace, heating to 750 ℃, adding the conventionally prepared Al-2.8Nb-2.2Ti-1B intermediate alloy into an aluminum melt, wherein the addition is 0.5wt.% of the Al-7Si alloy, manually stirring the melt for 2min by using a graphite stirring rod, and preserving the heat for 10min at 750 ℃; pouring the molten metal into a metal mold preheated at 175 ℃ for 1h, and cooling and solidifying to obtain Al-2.8Nb-2.2Ti-1B refined Al-7Si alloy with refining time of 10 min. Cutting a casting sample at a position 3cm away from the bottom of the sample, carrying out anodic coating treatment, observing by using a polarization microscope, and as shown in FIG. 4, FIG. 4 shows the refining effect of Al-2.8Nb-2.2Ti-1B on Al-7Si alloy, and measuring aluminum crystal grains by using a line cutting method specified in the national standard GB/T3246.1-2012, wherein when the refining time is 10min, the average size of alpha-Al crystal grains in Al-7Si is 580.37 mu m.
Comparative example 2: the refining effect of the commercial Al-5Ti-1B intermediate alloy on Al-7Si comprises the following steps:
step 1, placing weighed Al-7Si into a crucible, placing the crucible and the weighed Al-7Si into a crucible type resistance smelting furnace, and heating to 750 ℃; after the aluminum ingot is completely melted, preserving the heat for 30min, adding 0.1wt.% of refining agent to refine the aluminum liquid, and skimming dross on the surface of the aluminum liquid; adding a commercially available Al-5Ti-1B intermediate alloy into an Al-7Si melt, wherein the addition amount is 0.5wt.% of Al-7Si, stirring the melt by using a graphite stirring rod, and keeping the temperature at 750 ℃ for 10min;
and 2, pouring the aluminum melt into a conical metal mold preheated at 175 ℃ for 1h, and cooling and solidifying to obtain an Al-7Si sample refined by the Al-5Ti-1B intermediate alloy. The sample at a position 3cm away from the bottom of the sample is cut out, anodic coating treatment is carried out, observation is carried out by a polarization microscope, as shown in figure 5, and aluminum crystal grains are measured by using a line cutting method specified in the national standard GB/T3246.1-2012, when the refining time is 10min, the refining effect of the commercial Al-5Ti-1B intermediate alloy on alpha-Al crystal grains in Al-7Si is limited, and the average size of the alpha-Al crystal grains is 549.06 mu m.
Comparing Al-2.8Nb-2.2Ti-1B prepared by the two-step method in the embodiment 1 and the comparative examples 1 and 2, al-2.8Nb-2.2Ti-1B prepared conventionally and Al-5Ti-1B sold commercially, as shown in FIG. 6, al-2.8Nb-2.2Ti-1B prepared by the invention still has the thinning effect of about 412.87 μm on Al-7Si after the heat preservation for 120min, while Al-2.8Nb-2.2Ti-1B prepared directly conventionally can only thin alpha-Al in Al-7Si to 580.37 μm even when the heat preservation is 10 min. Compared with the Al-2.8Nb-2.2Ti-1B prepared by the invention, the refining effect is far better than that of the Al-2.8Nb-2.2Ti-1B prepared by the conventional method. And the refining effect of the commercially available Al-5Ti-1B on Al-7Si is also poor under the refining time of 10min, which is 549.06 mu m, which is far less than 330.48 mu m achieved by Al-2.8Nb-2.2Ti-1B prepared by the invention. Therefore, the Al-4Ti-1Nb-1B prepared by the invention has better refining effect and excellent decay resistance on Al-7 Si.
The invention firstly aims at the problem that the refining effect of the Al-Ti-B refiner is reduced due to Si poisoning. When the Si content of the aluminum-silicon alloy is more than 3wt.%, si atoms are aligned with TiB in the Al-Ti-B alloy 2 TiAl of surface 3 The two-dimensional compound is corroded and modified to form TiAlSi phase, so that alpha-Al and TiB are formed 2 The free energy and mismatching degree of the interface are improved, and alpha-Al aluminum grains are difficult to be in TiB 2 Nucleation of the upper heterogeneous phase results in the weakening of the refining effect of the Al-Ti-B refiner. NbB in Al-Nb-B 2 NbAl of the surface 3 The layer stability is higher than that of TiAl 3 Is not easy to be corroded by Si atoms and is simultaneously caused by NbAl 3 Crystal structure and TiAl 3 Same, nbAl 3 Can be in TiB 2 Surface segregation and modification to form NbAl 3 ’ The structure makes the refiner have the capability of resisting Si poisoning.
The invention simultaneously aims at Al-Nb-TiB 2 TiB in preparation of intermediate alloy 2 Difficult to add. Due to TiB 2 The particles have general wettability with Al melt, and the direct addition of the particles easily causes TiB 2 Agglomeration, precipitation, etc. The invention adopts mechanical pre-alloying to reduce the agglomeration of Nb powder and improve the TiB by using Nb element 2 The wettability with Al melt is beneficial to the subsequent alloying process, and finally the Al-Nb-TiB with stable homogeneity is obtained 2 And (3) intermediate alloy.
The invention simultaneously solves the problems of Al-Nb-TiB 2 TiB in preparation of intermediate alloy 2 The problem of Nb modification. At present, the academic world considers that the characteristics of high refining efficiency of Al-5Ti-1B and Si poisoning resistance of Al-Nb-B depend on the specific element enrichment condition on the surface of nucleation particles. However, directly in Al-Nb melts to TiB 2 The modification process is difficult to ensure the Nb modification effect. The invention adopts two steps of mechanical pre-alloying and alloying of alloy melt, namely TiB 2 The environment of Nb element is always provided, and the Nb element in TiB is improved 2 Enrichment of the surfaceIncrease Al-Nb-TiB 2 The Si poisoning resistance of the master alloy.
The above applications are only some embodiments of the present application. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the inventive concept herein, and it is intended to cover all such modifications and variations as fall within the scope of the invention.
Claims (2)
1. A method for preparing an aluminum-based alloy refining material by a two-step method is characterized by comprising the following steps:
step (1): smelting at a first temperature to obtain an Al-Nb melt, and keeping the temperature for a first time, wherein the mass percent of Nb in the Al-Nb melt is not lower than 5%; the first temperature is 850-900 ℃, and the first time is 30-60min;
step (2): adding TiB into the Al-Nb melt prepared in the step (1) 2 Particles and continuing to melt at a second temperature for a second time period to TiB 2 Modifying the particles; tiB 2 The mass of the particles accounts for 4.3-8% of the mass of the Al-Nb melt obtained in the step (1); the second temperature is 850-900 ℃, and the second time is 60-120min;
and (3): modifying the TiB with modification obtained in the step (2) 2 Adding aluminum into the Al-Nb melt of the particles for dilution, and keeping the temperature at a third temperature for a third time, wherein the mass percent of Nb in the melt is 1.5 to 3.5 percent; the third temperature is 750-800 ℃, and the third time is 30min;
and (4): and (3) pouring the melt obtained in the step (3) at a fourth temperature to obtain the aluminum-based alloy refined material, wherein the fourth temperature is 720 ℃.
2. The method for preparing Al-based alloy refined material by two-step method according to claim 1, wherein in step (2), in TiB 2 A modified transition layer NbAl is formed on the (0001) surface 3 ’ 。
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