A Cr + Mg + Ti composite aluminum-iron alloy modifier and its application

Abstract

The present invention discloses a Cr+Mg+Ti composite aluminum-iron alloy modifier and its application, wherein the composite aluminum-iron alloy modifier is composed of Cr, Mg and Ti; the content of Cr in the aluminum-iron alloy is 1.0-2.5wt%, the content of Mg in the aluminum-iron alloy is 0.2-0.6wt%, and the content of Ti in the aluminum-iron alloy is 0.1-0.5wt%; the aluminum-iron alloy is prepared by using the composite aluminum-iron alloy modifier. The primary crystal phase nucleation in the Al-8%Fe cast alloy structure prepared by adding the composite aluminum-iron alloy modifier of the present invention is easier, the primary crystal phase growth time increases less, the refinement effect is better, and the microstructure distribution is more uniform.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum-iron alloy modifiers, in particular to a Cr+Mg+Ti composite aluminum-iron alloy modifier and its application. Background Art

[0002] Hypereutectic Al-Fe (i.e., Fe content>1.8%) heat-resistant alloys contain primary iron-rich phases and dispersed hard particles, which make the alloys have high hardness, wear resistance and heat resistance, and can be stably used in the range of 150-350°C. Therefore, Al-Fe alloys have become highly competitive high-temperature lightweight structural materials in the aerospace and weapons industries, and can be used to manufacture heat-resistant parts such as rocket and missile shells, tail fins, aircraft skins, engine turbines, cylinders, pistons, heat sinks, and aluminum foil for cable coating.

[0003] Under normal casting conditions, when the iron content in Al-Fe alloy is greater than 1.8wt% (eutectic composition), lath-shaped, skeleton-shaped, Chinese character-shaped or even large-block primary iron-rich phase (Al 3 Fe), which is randomly distributed in the α-Al dendrites and (α-Al+Al 3 The study found that the coarse iron-rich phase seriously split the matrix, especially when the alloy was subjected to stress, these coarse, needle-like primary crystals of Al 3 Fe first becomes the crack source, seriously affecting the mechanical properties and plastic processing properties of the alloy, limiting the application range of the alloy.

[0004] The existing methods for improving the needle-like iron-rich phase in Al-Fe alloys can be summarized as follows: adding alloying elements to change the crystal structure and crystal morphology of the iron-rich phase, such as adding elements such as Mn, Co, Cr, Mo, and using composite alloys such as (Mn+Cr) or (Mo+S) or (Mn+Mo) to eliminate the needle-like iron-rich phase; adding rare earth elements to change Al 3 The nucleation and growth of Fe make the needle-like iron-rich phase transform into a spherical or petal-like shape; increase the cooling rate to inhibit the precipitation of the needle-like iron-rich phase or refine its size; use electromagnetic stirring, ultrasonic treatment and other methods to interfere with the growth of the needle-like iron-rich phase. Among the above methods, increasing the cooling rate is often difficult to achieve in actual production; electromagnetic stirring and ultrasonic treatment are not suitable for the production of large-sized and complex-shaped structural parts; adding alloy modification is an effective measure that can be truly used for large-scale production, but the existing modifiers have poor modification effects on Al-Fe alloys with high iron content, so it is necessary to find a suitable modifier. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a Cr+Mg+Ti composite aluminum-iron alloy modifier and its application, so as to solve the problem that the modification effect of the existing aluminum-iron alloy modifier is not ideal.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A Cr+Mg+Ti composite aluminum-iron alloy modifier consists of Cr, Mg and Ti elements; the content of Cr in the aluminum-iron alloy is 1.0-2.5wt%, the content of Mg in the aluminum-iron alloy is 0.2-0.6wt%, and the content of Ti in the aluminum-iron alloy is 0.1-0.5wt%.

[0008] In the above Cr+Mg+Ti composite aluminum-iron alloy modifier, the content of Cr element in the aluminum-iron alloy is 2.0wt%, the content of Mg element in the aluminum-iron alloy is 0.4wt%, and the content of Ti element in the aluminum-iron alloy is 0.3wt%.

[0009] The invention discloses an application of a Cr+Mg+Ti composite aluminum-iron alloy modifier, wherein the Cr+Mg+Ti composite aluminum-iron alloy modifier is used for the preparation of aluminum-iron alloy.

[0010] In the application of the above Cr+Mg+Ti composite aluminum-iron alloy modifier, the content of Fe element in the aluminum-iron alloy is 3-8wt%.

[0011] In the application of the above Cr+Mg+Ti composite aluminum-iron alloy modifier, the content of Cr element in the aluminum-iron alloy is 2.0wt%, the content of Mg element in the aluminum-iron alloy is 0.4wt%, and the content of Ti element in the aluminum-iron alloy is 0.3wt%.

[0012] The application of the above Cr+Mg+Ti composite aluminum-iron alloy modifier and the preparation method of the aluminum-iron alloy include the following steps:

[0013] Step A: placing pure aluminum, aluminum-iron master alloy, aluminum-chromium master alloy and aluminum-titanium master alloy in a smelting furnace according to proportion and smelting until all the alloy raw materials are melted to obtain alloy liquid;

[0014] Step B: adding the aluminum-magnesium master alloy to the alloy liquid and continuing to smelt to obtain an alloy melt; the boiling point of magnesium is 1090°C, and it is easy to vaporize and lose at a high melting temperature. In addition, magnesium is easily oxidized, so adding it later can shorten the melting time of magnesium and avoid excessive burning;

[0015] Step C: Cooling the alloy melt, removing slag, and casting it into a mold to obtain a cast aluminum-iron alloy.

[0016] In the application of the above-mentioned Cr+Mg+Ti composite aluminum-iron alloy modifier, in step A, the purity of pure aluminum is greater than or equal to 99.7wt%, the iron content in the aluminum-iron master alloy is 20wt%, the chromium content in the aluminum-chromium master alloy is 10wt%, and the titanium content in the aluminum-titanium master alloy is 10wt%; in step B, the magnesium content in the aluminum-magnesium master alloy is 10wt%.

[0017] In the application of the above Cr+Mg+Ti composite aluminum-iron alloy modifier, in step A, the smelting temperature is 980-1100°C.

[0018] In the application of the above Cr+Mg+Ti composite aluminum-iron alloy modifier, in step B, the aluminum-magnesium master alloy is added and then the smelting is continued for 3 to 8 minutes.

[0019] In the application of the above Cr+Mg+Ti composite aluminum-iron alloy modifier, in step C, when the alloy melt is cooled to a temperature within the range of 890-950°C, the slag is stirred and removed; during casting, the mold is preheated to 180-220°C. The pouring temperature is generally 30-50°C higher than the liquidus, and for casting thin-walled parts or small parts, it can be 100°C higher than the liquidus; in the present invention, if the casting temperature is higher than 1000°C, the pouring temperature is too high, which is easy to increase shrinkage defects and cracks; pouring between 890-950°C can avoid the above problems.

[0020] The technical solution of the present invention achieves the following beneficial technical effects:

[0021] 1. The present invention uses Cr, Mg and Ti in the aluminum-iron alloy at the same time, and by adjusting the addition amount of the three elements, it can convert the primary iron-rich phase (Al2O3) in the aluminum-iron alloy with a high iron content (3-8wt%) into a lath-shaped, bone-shaped, Chinese character-shaped or even coarse needle-shaped phase. 3 Fe) is transformed into a flower-like or nearly spherical shape, which makes the aluminum-iron alloy structure significantly refined.

[0022] 2. When adding modifiers to the Al-8%Fe alloy, compared with no modifiers or other combinations of modifiers, the primary crystal phase nucleation in the Al-8%Fe cast alloy prepared by adding Cr+Mg+Ti as modifiers is easier, the primary crystal phase growth time increases less, the refinement effect is better, and the microstructure distribution is more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1a Microscopic morphology of the cast Al-8%Fe alloy without adding a modifier in the embodiment of the present invention (200 μm);

[0024] Figure 1b Microscopic morphology of the cast Al-8%Fe alloy with Cr as a modifier in the embodiment of the present invention (200μm);

[0025] Figure 1c Microscopic morphology of the cast Al-8%Fe alloy with Cr+Ti as a modifier in the embodiment of the present invention (200μm);

[0026] Figure 1d Microscopic morphology of the cast Al-8%Fe alloy with Cr+Mg+Ti as modifier in the embodiment of the present invention (200μm);

[0027] Figure 1e Microscopic morphology of the cast Al-8%Fe alloy with Cr+Mn+Mg+Ti as modifier in the embodiment of the present invention (200μm);

[0028] Figure 1f Microscopic morphology of the cast Al-8%Fe alloy with Cr+Ce+Ti as modifier in the embodiment of the present invention (200μm);

[0029] Figure 1g Microscopic morphology of the cast Al-8%Fe alloy with Mn+(Al+5%Ti+1%B) as a modifier in the embodiment of the present invention (200μm);

[0030] Figure 2a Microstructure diagram of the as-cast Al-8%Fe alloy without adding a modifier in the embodiment of the present invention (50 μm);

[0031] Figure 2b Microstructure diagram (50 μm) of the as-cast Al-8% Fe alloy with 1.6% Cr+0.2% Mg+0.1% Ti as a modifier in the embodiment of the present invention;

[0032] Figure 2c Microstructure diagram (50 μm) of the as-cast Al-8% Fe alloy with 2% Cr+0.4% Mg+0.3% Ti as a modifier in the embodiment of the present invention;

[0033] Figure 2d Microstructure diagram (50 μm) of the as-cast Al-8% Fe alloy with 2.5% Cr+0.6% Mg+0.5% Ti as a modifier in the embodiment of the present invention;

[0034] Figure 3a Energy spectrum of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention;

[0035] Figure 3b Figure 3a EDS analysis at A in the middle;

[0036] Figure 3c Figure 3a EDS analysis at B in the middle;

[0037] Figure 3d Figure 3a EDS analysis at center C;

[0038] Figure 4a Surface scanning diagram of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention;

[0039] Figure 4b Surface scanning diagram of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention (Al element);

[0040] Figure 4c Surface scanning diagram of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention (Fe element);

[0041] Figure 4d Surface scanning diagram of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention (Cr element);

[0042] Figure 5a XRD spectrum of the cast Al-8%Fe alloy without adding a modifier in the embodiment of the present invention;

[0043] Figure 5b XRD spectrum of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention;

[0044] Figure 6 DSC curve of the cast Al-8%Fe alloy without adding a modifier in the embodiment of the present invention;

[0045] Figure 7 DSC curve of the cast Al-8%Fe alloy with 2%Cr+0.4%Mg+0.3%Ti as a modifier in the embodiment of the present invention;

[0046] Figure 8 DSC curve of the cast Al-8%Fe alloy with 2.5%Cr+0.6%Mg+0.5%Ti as the modifier in the embodiment of the present invention. DETAILED DESCRIPTION

[0047] 1 Experiment

[0048] 1.1 Experimental plan

[0049] In this embodiment, Cr, Cr+Ti, Cr+Mg+Ti, Cr+Mn+Mg+Ti, Cr+Ce+Ti and Mn+(Al+5%Ti+B) are added as modifiers to Al-8%Fe alloy to compare the effects of different modifiers on the microstructure of Al-8%Fe alloy. The addition range of each element in each modifier [if not otherwise specified, all element addition amounts in this embodiment are indicated as mass percentage wt% of aluminum-iron alloy] is: Cr: 1.0-2.5wt%; Mg: 0-0.5wt%; Ti: 0.1-1wt%; Mn: 0.5-2wt%; Ce: 0.5-2wt%; Al+5Ti+B: 0.05-0.4wt%; This embodiment designs the above additives in different proportions of composite addition test, in which the alloy elements are added in the form of intermediate alloys, a total of 40 samples, numbered 1# to 40#.

[0050] In this embodiment, the above-mentioned elements are selected to be compounded as the modifier, mainly considering:

[0051] Cr in Al 3 The solubility of Fe in the phase is very large, dissolving into Al 3 Fe phase is followed by Al 3 (CrFe) phase. The solidification process after adding Cr is as follows: first, primary Al crystals are crystallized from the alloy liquid. 3 (CrFe), and then the peritectic reaction occurs, making Al 3 The morphology of the Fe phase changes to hollow spheres, small blocks and small flowers, which can improve the brittleness of intermetallic compounds and enhance the plastic deformation ability.

[0052] Ti is adsorbed around the primary Fe-rich phase, hindering the migration of Fe atoms and increasing the concentration gradient in the liquid phase at the interface front, resulting in a large component supercooling. 3 The Fe phase is wrapped by the later nucleated iron-rich phase before it has time to branch, and grows into small pieces and granules. 3 Ti may affect the primary Al 3 Nucleation and growth mode of Fe phase.

[0053] Mg in primary Al 3 The Fe phase is enriched around it, causing a certain amount of supercooling, making the primary Al 3 The Fe phase branches. In addition, the enrichment at the front of the needle-like iron-rich phase also inhibits the growth of the primary phase. The iron-rich phase changes from coarse needle-like to dendrite-like, short rod-like, and small block-like.

[0054] Mn is soluble in Al 3 Fe phase increases the kinetic supercooling during crystal growth, changing the growth mode from small plane to non-small plane. Mn can also form Al 6Mn phase, iron in the alloy can be dissolved in it to form complex compounds, reducing Al 3 The formation and growth rate of Fe phase.

[0055] Ce is adsorbed around the iron-rich phase, hindering the migration of Fe atoms and increasing the concentration gradient in the liquid phase at the interface front, resulting in supercooling of the composition. When the Ce content is high, Al can be formed in the melt. 4 Compound phases such as Ce may affect the primary Al 3 Nucleation and growth mode of Fe phase.

[0056] Al+Ti+B is a commonly used refiner for aluminum alloys, which can refine α-Al dendrites and part of the second phase.

[0057] 1.2 Experimental process

[0058] The Al-8%Fe alloy used in this embodiment is prepared by industrial pure aluminum and Al-20wt%Fe master alloy in proportion. The master alloys of various alloy elements are placed in a graphite crucible (except Al-Mg master alloy) according to the proportion, and smelted in an induction melting furnace. The heating temperature is 1000°C. After the alloy in the crucible is completely melted, Al-10wt%Mg is finally added in proportion, and the insulation time is 5min. After that, the crucible containing the alloy melt is taken out from the induction furnace, and the temperature is measured by a thermocouple. After the Al-Fe alloy melt reaches 900°C, it is quickly stirred and slag-scraped with a graphite rod, and poured into a metal mold preheated at 200°C to obtain a 20mm×100mm cast sample. By changing the proportion of each alloy element, a cast Al-8%Fe alloy sample with different modifiers and different amounts of modifier additives is prepared.

[0059] 1.3 Experimental Results

[0060] Among the 40 specimens, the microstructures of some Al-8%Fe alloys with different kinds of alloying elements added are as follows: Figure 1a to Figure 1g shown.

[0061] By comparing the metallographic structures, it can be seen that when no modifiers such as Cr, Mg, and Ti are added, the primary Al in the Al-8%Fe alloy 3 The Fe phase is mostly coarse lamellar and long needle-like structures and is randomly distributed in the matrix (see Figure 1a ); After adding alloying elements, the morphology of the primary iron-rich phase is significantly improved and the size is smaller. Among these composite added elements, the group of Cr+Mg+Ti additions has the best modification effect, such as Figure 1dAs shown. Focusing on this alloy element combination, this implementation also conducted experiments on different ratios of Cr+Mg+Ti, and finally determined the optimal modifier ratio and addition amount. After that, for a group of partial samples of Cr+Mg+Ti (see Table 1), the cast samples were cut and metallographic analysis was performed after grinding and polishing to explore the effect of the composite addition of Cr+Mg+Ti on the microstructure. Then, the microstructure morphology was observed under an S-3400N scanning electron microscope, and the distribution of alloying elements in the alloy was analyzed by energy spectrum. The effect of the addition of Cr, Mg and Ti elements on the phase composition was analyzed by X-ray diffractometer, and the formation process of each phase was analyzed by SETARAM thermal analyzer.

[0062] The other samples in No. 1# to No. 40# in this embodiment are prepared by changing one or several types of elements and their addition amounts in the combination of Cr+Mg+Ti, and repeatedly testing the morphology improvement effect of the prepared Al-8%Fe aluminum-iron alloy structure (due to the large amount of test data, they are no longer listed one by one in this embodiment). The test found that if any one of the three elements Cr, Mg and Ti is missing or the necessary content is not reached, the effect of improving the morphology of the Al-8%Fe aluminum-iron alloy structure is not ideal. Theoretically, when the three elements Cr, Mg and Ti are used as modifiers for Al-8%Fe aluminum-iron alloy, the Ti element mainly affects the nucleation process, but if there is no specific content of Cr element to change the crystallographic properties and interfacial energy, or if there is no specific content of Mg element to enrich and form a gradient and purification effect, Al-8%Fe aluminum-iron alloy structure will not be improved. 3 The Fe phase will still grow into coarse needle-like or short needle-like shapes, and the modification effect is not good. Therefore, when Cr, Mg and Ti are used to improve the crystal phase structure of Al-8%Fe aluminum-iron alloy, the three play a synergistic role and none of them can be missing.

[0063] Table 1

[0064]

[0065] 2. Experimental results analysis

[0066] 2.1 Cast microstructure of Al-8%Fe alloy with composite addition of Cr+Mg+Ti

[0067] Figure 2a to Figure 2d The microstructure of Al-8%Fe cast alloy with different contents of Cr+Mg+Ti is shown in Figure 2. Figure 2a It can be seen that when Cr+Mg+Ti is not added, the primary Al in the Al-8%Fe alloy 3Fe phase is mostly coarse flake and long needle-like structure; when 1.6% Cr+0.2% Mg+0.1% Ti ("%" represents the mass fraction of the element in the aluminum-iron alloy, the same below) is added, the coarse needle-like structure is significantly reduced, and part of it is transformed into short needle-like, dot-like and small block-like structure, and the size is significantly reduced, but the structure is still uneven (see Figure 2b ); When 2%Cr+0.4%Mg+0.3%Ti is added, Al 3 Fe changes from flake to small blocks, nearly spherical, and the structure is evenly distributed (see Figure 2c When 2.5% Cr+0.6% Mg+0.5% Ti was added, the structure coarsened again and larger needle-like Al 3 Fe phase (see Figure 2d The above results show that the addition of appropriate amount of Cr+Mg+Ti composite addition significantly changes the primary Al 3 The morphology of Fe phase is best when 2%Cr+0.4%Mg+0.3%Ti is added in combination.

[0068] 2.2 Distribution of elements in alloys

[0069] In order to study the mechanism of action of each element, we must first understand the distribution of each element in the alloy. Figure 3a to Figure 3d This is the energy spectrum of Al-8%Fe alloy after adding 2%Cr+0.4%Mg+0.3%Ti. From EDS analysis, we can see that the solid solubility of Cr element in Al-Fe phase is large. Combined with the element content at the punctuation point in Table 2, we can see that the atomic ratio of Al and Fe+Cr is about 4.5:1, which is close to XRD ( Figure 5b ) 3 The atomic ratio of Fe phase is due to the fact that part of Cr is dissolved in Al 3 Fe forms Al 3 CrFe) phase, so with Al 3 The atomic ratio of the Fe phase is somewhat different, indicating that the iron-rich phase in the organization may be a complex structure of Al 3 (CrFe) phase.

[0070] Table 2

[0071]

[0072] Figures 4a to 4d This is a surface scan photo of Al+8%Fe+2%Cr+0.4%Mg+0.3%Ti alloy. Figure 4b The white part is where the Al element appears in the matrix, and the black part is where the Al-Fe phase appears. Figure 4c The green part is where the Fe element exists in the alloy. The solid solubility of Fe in the Al matrix is ​​very small, so the content of Fe in the matrix is ​​relatively small. Figure 4d The red part is the location of Cr in the matrix. The solid solubility of Cr in the matrix is ​​small, so the content in the matrix is ​​small, and the number of red points is sparse. 3 There is a large amount of Cr element dissolved in Fe, and the red dots are dense. As can be seen from 4d, Cr element is more easily dissolved in Al 3 Due to the small amount of Mg and Ti added, the SEM energy spectrum analysis did not find the location and existence form of Mg and Ti elements.

[0073] 2.3 Effect of Cr+Mg+Ti addition on phase composition

[0074] The addition of Cr+Mg+Ti changes the primary Al 3 The morphology of the Fe phase has also changed. 3 The composition of the Fe phase was determined by XRD analysis of the Al+8%Fe+2%Cr+0.4%Mg+0.3%Ti alloy (e.g. Figure 5a and Figure 5b As shown in Figure 5, it can be found that after adding 2% Cr + 0.4% Mg + 0.3% Ti, a very small amount of Al 13 Cr 2 (PDF#29-0014) phase, but no Al-Fe-Cr ternary phase was formed. XRD showed that no intermetallic compounds of Al and Mg, Al and Ti or other ternary phases were formed. Mg and Ti should be dissolved in the matrix or Al 3 Fe.

[0075] From the perspective of electronegativity, the reason is that the electronegativity of Al and Cr is slightly different, and the atomic radius of Al is The atomic radius of Fe is The atomic radius of Cr is The Cr element will dissolve in the iron-rich phase in the form of substitutional solid solution, and it is not easy to form a compound but easy to form a solid solution.

[0076] 2.4 Crystallization process

[0077] The Al 3 The crystallization and growth process of Fe phase, 2mm×1mm slices were taken from the cast sample as DSC samples, and the phase change process of the alloy was tested by SETARAM thermal analyzer under the protection of argon. The heating rate was 15℃ / min, heated to 1000℃, kept warm for 5min, and cooled at a rate of 15℃ / min. Finally, the DSC curves of Al-8%Fe alloy cooling before and after Cr+Mg+Ti addition were obtained as shown in Figures 6 to 8As shown in the figure, during the solidification process of Al-8%Fe alloy, there are only two exothermic peaks, A and B, which represent the eutectic transformation process and the primary crystal transformation process respectively. After adding alloy elements, there are three exothermic peaks, A, B, and C, during the solidification process of the alloy, among which A represents the eutectic transformation, and B and C represent two primary crystal transformations. Combined with the phase diagram, it can be seen that peak B represents the primary crystal Al 3 The transformation process of the Fe phase has a crystallization starting temperature of 850.82°C, and the existence of peak C indicates that the alloy has undergone other transformations after the primary crystal transformation and before the eutectic transformation, and this transformation releases heat at around 778.83°C.

[0078] Combining the calculated phase diagram and XRD results, it is speculated that the exothermic peak corresponds to Al 13 Cr 2 The extrapolated starting point temperature of the exothermic peak is the transformation temperature, and the absolute area of ​​the exothermic peak can be obtained by baseline integration as the crystallization enthalpy of the transformation. Table 3 shows the changes in the crystallization temperature and crystallization enthalpy of the alloy before and after the addition of alloying elements Cr+Mg+Ti. The width of the two-phase zone is the difference between the initial crystallization temperature and the eutectic starting temperature.

[0079] Table 3

[0080]

[0081] From the perspective of phase transition temperature, compared with the case where no alloying elements were added, after adding 2% Cr + 0.4% Mg + 0.3% Ti, the initial crystallization temperature increased by 10.96°C, the eutectic starting temperature increased by 7.02°C, and the width of the two-phase zone increased by 3.94°C. Such changes mean that the nuclei of the primary crystal phase are easier to form, and a large number of nuclei can be formed in a short time, but the width of the two-phase zone does not increase much, and the growth time of the primary iron-rich phase is limited. Therefore, the organization is refined. After continuing to increase the addition of alloying elements to 2.5% Cr + 0.6% Mg + 0.5% Ti, the initial crystallization temperature increased by 18.37°C, and the width of the two-phase zone increased by 10.2°C. The increase in the width of the two-phase zone of the alloy may be a factor leading to the coarsening of its organization. From the perspective of the crystallization enthalpy of phase transition, the size of the crystallization enthalpy can be used to express the volume fraction of the phase. With the increase in the addition of alloying elements, the volume fraction of the primary crystal phase continues to increase.

[0082] 3. Conclusion

[0083] (1) Adding 2% Cr+0.4% Mg+0.3% Ti to Al-8% Fe alloy can make the primary Al 3 The Fe phase changes from coarse needle-like to small blocks, flower-like and nearly spherical, and the alloy structure is significantly refined.

[0084] (2) The content of Cr in Al matrix is ​​relatively small. 3Fe has more solid solution, and Cr element will be dissolved in the iron-rich phase in the form of substitution solid solution, changing the Al 3 The solidification mode of Fe changes Al 3 The morphology of Fe phase. Mg and Ti do not form compounds but exist in the alloy in the form of solid solution.

[0085] (3)DSC analysis results show that the addition of 2% Cr + 0.4% Mg + 0.3% Ti makes the nucleation of the primary phase of the Al-8% Fe alloy easier, increases the growth time less, and refines the structure.

[0086] (4) When adding modifiers to the Al-8%Fe alloy, compared with no modifiers or other combinations of modifiers, the Al-8%Fe cast alloy prepared by adding Cr+Mg+Ti as modifiers has easier nucleation of the primary crystal phase, less increase in the primary crystal phase growth time, better primary crystal phase refinement effect, and more uniform distribution.

Claims

1. Application of a Cr+Mg+Ti composite aluminum-iron alloy modifier, It is characterized in that The Cr+Mg+Ti composite aluminum-iron alloy modifier is used to prepare an aluminum-iron alloy with an Fe content of 8wt%. The Cr+Mg+Ti composite aluminum-iron alloy modifier is composed of Cr, Mg and Ti elements; the content of Cr in the aluminum-iron alloy is 2.0wt%, the content of Mg in the aluminum-iron alloy is 0.4wt%, and the content of Ti in the aluminum-iron alloy is 0.3wt%; The preparation method of aluminum-iron alloy comprises the following steps: Step A: placing pure aluminum, aluminum-iron master alloy, aluminum-chromium master alloy and aluminum-titanium master alloy in a smelting furnace according to proportion and smelting until all the alloy raw materials are melted to obtain alloy liquid; Step B: adding the aluminum-magnesium master alloy to the alloy liquid and continuing to smelt to obtain an alloy melt; Step C: Cooling the alloy melt, removing slag, and casting it into a mold to obtain a cast aluminum-iron alloy.

2. The use of the Cr+Mg+Ti composite aluminum-iron alloy modifier according to claim 1, It is characterized in that In step A, the purity of pure aluminum is greater than or equal to 99.7wt%, the iron content in the aluminum-iron master alloy is 20wt%, the chromium content in the aluminum-chromium master alloy is 10wt%, and the titanium content in the aluminum-titanium master alloy is 10wt%; in step B, the magnesium content in the aluminum-magnesium master alloy is 10wt%; In step A, the melting temperature is 980 ~ 1100 ℃; In step B, the aluminum-magnesium master alloy is added and the melting is continued for 3 to 8 minutes; In step C, when the alloy melt is cooled to a temperature in the range of 890 to 950° C., the slag is removed by stirring; during casting, the mold is preheated to 180 to 220° C.

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