CN115141960B - High-strength and high-toughness cast aluminum alloy with low Si content and preparation method thereof - Google Patents

High-strength and high-toughness cast aluminum alloy with low Si content and preparation method thereof Download PDF

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CN115141960B
CN115141960B CN202210685285.1A CN202210685285A CN115141960B CN 115141960 B CN115141960 B CN 115141960B CN 202210685285 A CN202210685285 A CN 202210685285A CN 115141960 B CN115141960 B CN 115141960B
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王万林
曾杰
彭健飞
甘培原
曹佳艺
朱晨阳
黄道远
翼军宇
韦德仕
何俞松
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C22C21/04—Modified aluminium-silicon alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/026—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F3/00—Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention provides a casting aluminum alloy with high strength and toughness and low Si content and a preparation method thereof, wherein the aluminum-silicon alloy comprises the following components in percentage by mass: si:4.5 to 7 percent of Mg:0.4 to 0.7 percent, cu:0.2 to 0.5 percent, RE:0.1 to 0.4 percent, cr:0.15 to 0.35 percent, fe is less than or equal to 0.15 percent, ti:0.01 to 0.05 percent, sr:0.001 to 0.004 percent, B: 0.001-0.004%, wherein the rare earth element is selected from Ce and/or La, and the balance is aluminum and unavoidable impurities. The preparation method comprises the steps of placing a melt obtained by smelting raw materials on a permanent magnet stirring device, carrying out permanent magnet stirring treatment on the melt, and casting to obtain the cast aluminum alloy. According to the invention, the solidification structure of the alloy is regulated and controlled by regulating the element proportion in the alloy and adopting a magnetic field stirring technology with unique multielement metamorphic coupling, so that the problem of coarse precipitated phases in the aluminum-silicon alloy is solved, and the cast aluminum alloy with high strength and toughness Si content is further obtained. The method provided by the invention has the advantages of simple process, convenient operation, safety, reliability, low cost and wide application prospect.

Description

High-strength and high-toughness cast aluminum alloy with low Si content and preparation method thereof
Technical Field
The invention relates to a casting aluminum alloy with high strength and toughness and low Si content and a preparation method thereof, belonging to the technical field of aluminum alloy preparation.
Background
Research shows that 60% of the fuel consumption of the automobile is derived from dead weight, and the reduction of the dead weight of the automobile is an important way for reducing energy consumption and pollution emission. Light weight, high safety and greenization are important directions of development of the automobile industry. With the continuous and rapid development of new energy automobile industry in China, the demands of various domestic large passenger car manufacturers for light and high-strength new materials are gradually increased.
The aluminum-silicon alloy has the advantages of small density, high strength, good heat conduction performance, small thermal expansion coefficient and the like, and can reduce weight, abrasion, lubricating oil consumption and piston clearance, and meet the condition of replacing the traditional steel materials. However, the application of aluminum alloys is currently limited to stationary parts such as car bodies, cylinder blocks, cylinder heads, etc. For moving parts or important stressed structural parts, the requirements on mechanical properties such as strength, plasticity, fracture toughness and the like are high, and the materials commonly used at present are steel materials.
When the Si content in the aluminum-silicon alloy is too high, the Si phase is separated out firstly in the solidification process, and coarse primary Si phase is easy to appear in the alloy, so that the product performance is deteriorated. Correspondingly, the aluminum-silicon alloy with high silicon content has excellent wear resistance and can be used for parts such as automobile cylinders, pistons and the like. When the Si content in the aluminum-silicon alloy is lower than the eutectic point, si is usually precipitated as eutectic Si phase, the alloy has small linear shrinkage, low thermal cracking tendency and good air tightness, and can be used for producing middle-high strength automobile parts such as automobile hubs, engine frames, steering knuckles and the like, automobile gearbox shells, shock absorbers, shock absorber covers and the like. However, in untreated aluminum-silicon alloy, the eutectic Si phase is in a slender needle shape, so that the toughness of the alloy is greatly compromised, and the production and the utilization of the alloy are not facilitated.
The prior Chinese patent CN112143945A is a high-strength and high-toughness cast aluminum-silicon alloy with multiple composite rare earth elements and a preparation method thereof, and the plasticity and toughness of the Al-Si-Mg alloy are improved by adding the composite rare earth elements and multiple refiners, strengthening solution treatment and multistage aging treatment. The method obtains fine solidification structure and higher strength through modification and multiple heat treatments, and the process is complex. The prior Chinese patent CN103469028A is a rare earth praseodymium alloyed aluminum-silicon alloy and a preparation method thereof, the single rare earth is utilized to combine with ultrasonic treatment to denature the aluminum-silicon alloy, the silicon content is controlled to be 9.0-12.0%, the heat preservation is carried out for 31-180 min before melt casting, the heat preservation time is long, and the energy consumption is high. The existing Chinese patent CN108220703A is a cast aluminum-silicon alloy with the synergistic reinforcement of graphene and rare earth and a preparation method thereof, and the cast aluminum-silicon alloy performance is modified through the synergistic reinforcement of the graphene and the rare earth, but the graphene has extremely high cost and is not beneficial to industrial implementation.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention aims to provide a casting aluminum alloy with high strength and toughness and low Si content and a preparation method thereof. According to the invention, low-content Si is added into the aluminum alloy, a certain proportion of Mg, cu, cr, fe elements, trace amounts of Ti, sr and B elements are added, and the rare earth modification and permanent magnet stirring process are used for assisting in effectively controlling the solidification structure of the alloy.
The invention relates to a cast aluminum alloy with high strength and toughness and low Si content, which comprises the following components in percentage by mass: si:4.5 to 7 percent of Mg:0.4 to 0.7 percent, cu:0.2 to 0.5 percent, RE:0.1 to 0.4 percent, cr:0.15 to 0.35 percent, fe is less than or equal to 0.15 percent, ti:0.01 to 0.05 percent, sr:0.001 to 0.004 percent, B: 0.001-0.004%, RE (rare earth element) is selected from Ce and/or La, and the balance is aluminum and unavoidable impurities.
In a preferred embodiment, the impurity content is less than 0.2%.
According to the cast aluminum alloy disclosed by the invention, the alloy element Mg, cu, cr, fe is added, so that on one hand, mg, cu and Cr can be dissolved in an aluminum matrix to improve the matrix strength, and on the other hand, a magnesium-silicon phase, an aluminum-copper-magnesium-silicon phase and an iron-rich phase are formed and uniformly distributed in the matrix to realize precipitation phase strengthening. In addition, rare earth elements and trace Ti, sr and B elements are added, and heterogeneous nuclear phases such as Al are introduced 3 La、Al 4 Ce、Al 3 Ti、Ti 2 B and the like, refining an aluminum matrix; the aggregation of Sr and Re elements at the Si phase can also limit the growth of the Si phase, refine the Si phase and improve the toughness of the alloy, and finally, the cast aluminum alloy has excellent toughness under the cooperation of the above elements.
In a preferable mode, in the cast aluminum alloy, the mass ratio of Cr to Fe is 1-3.
The inventors found that the toughness of the final material can be optimized by controlling the mass ratio of Cr to Fe to be 1 to 3, because Cr is an effective neutralizing element of Fe and has a good deterioration effect on the coarse beta-Fe phase. However, if the Cr/Fe mass ratio is too low, mn has weak deterioration effect, a beta-Fe phase is easy to form, and the matrix is easy to tear to reduce the toughness of the alloy in a coarse needle shape or a space sheet shape. If the Cr/Fe mass ratio is too high, the Fe phase is well controlled, but the excessive Cr element can increase the quenching sensitivity and the preparation cost of the alloy.
In a preferable mode, in the cast aluminum alloy, the mass ratio of Ti to B is 5-10.
The inventor finds that the mass ratio of Ti to B is controlled to be 5-10, so that the toughness of the final material is optimal, primary aluminum can be effectively refined by Ti element, and the refining effect of Ti can be enhanced by adding a proper amount of B element; if B element is added too much, deterioration of Sr is deteriorated.
In a preferable mode, in the cast aluminum alloy, the mass ratio of Sr to B is 1-2.
The inventors found that the mass ratio of Sr to B is controlled to be 1-2, the strengthening effect on the matrix is optimal finally, the addition of Sr can effectively refine Si phase, and the addition of B can refine the matrix. However, if the Sr/B mass ratio is too low, B reacts with Sr to produce Sr 6 And B, reducing the deterioration effect of Sr. If the Sr/B mass ratio is too high, the content of B is small, and the synergistic effect with Ti is weakened.
In a preferred scheme, the cast aluminum alloy comprises the following components in percentage by mass: si: 6-8%, mg:0.5 to 0.7 percent, cu:0.3 to 0.5 percent, RE:0.2 to 0.3 percent, cr:0.15 to 0.30 percent of Fe:0.1 to 0.15 percent, ti:0.02 to 0.04 percent, sr:0.003 to 0.004 percent, B: 0.003-0.004%, wherein RE is selected from Ce and/or La, and the balance is aluminum and unavoidable impurities.
Preferably, the RE is selected from La. RE is selected from La, and has better alloy performance.
The invention relates to a preparation method of a cast aluminum alloy with high strength and toughness Si content, which comprises the following steps: preparing an aluminum source, a silicon source, a magnesium source, a copper source, an iron source and a chromium source according to a design proportion, uniformly mixing to obtain a mixture, introducing argon to discharge air, smelting to obtain a melt A, starting a permanent magnet stirring device, and applying permanent magnet stirring treatment to the melt; then adding rare earth source, titanium source, strontium source and boron source, preserving heat to obtain melt B, cooling, stopping applying permanent magnet stirring treatment, stopping introducing argon, and casting to obtain the cast aluminum alloy.
According to the preparation process, through controlling the feeding sequence of elements in smelting and applying permanent magnet stirring in the smelting process, the alloy casting blank with even and refined structure is finally obtained, the precipitated phases are uniformly dispersed and distributed in the matrix, and the obtained cast aluminum alloy has excellent mechanical properties.
In a preferred scheme, the aluminum source is selected from at least one of pure aluminum blocks, regenerated aluminum and aluminum alloy blocks, and the aluminum alloy blocks are alloy blocks formed by at least one of aluminum and Si, cu, mg, fe, cr. Such as high-iron aluminum silicon alloy, secondary aluminum, aluminum copper alloy, aluminum magnesium alloy block and the like.
Preferably, the silicon source is selected from silicon alloy blocks, and the silicon alloy blocks are alloy blocks composed of at least one of silicon and Al, cu, mg, ti. Such as high-iron aluminum silicon alloys.
Preferably, the copper source is selected from at least one of pure copper blocks and copper alloy blocks, and the copper alloy blocks are alloy blocks composed of at least one of copper and Si, mg, al, fe. Such as aluminum copper alloys, etc.
In a preferred scheme, the magnesium source is selected from at least one of pure magnesium blocks and magnesium alloy blocks, and the magnesium alloy blocks are alloy blocks composed of at least one of magnesium and Si, cu, al, fe.
Preferably, the iron source is selected from iron alloy blocks, and the iron alloy blocks are alloy blocks composed of at least one of iron and Si, cu, al, mg. Such as high-iron aluminum silicon alloy, silicon iron alloy, etc.
Preferably, the chromium source is at least one selected from silicon-chromium alloy and ferrochrome.
Preferably, the smelting temperature is 800-850 ℃.
Further preferably, the smelting process is as follows: heating to 800-850 ℃, and preserving heat for 15-25 min after the mixture is completely melted to obtain a melt A.
Preferably, the rare earth source is at least one selected from aluminum lanthanum alloy, aluminum cerium alloy and lanthanum cerium alloy.
Preferably, the titanium source is at least one selected from aluminum-titanium alloy and aluminum-titanium-boron alloy.
Preferably, the strontium source is selected from aluminum strontium alloys.
Preferably, the boron source is at least one selected from aluminum-boron alloy and aluminum-titanium-boron alloy.
In a preferred scheme, the temperature is reduced to 750-800 ℃, a rare earth source, a titanium source, a strontium source and a boron source are added, and the temperature is kept for 10-20 min, so as to obtain a melt B.
In the preferred scheme, after the melt B is obtained, the temperature is reduced to 680-720 ℃, the permanent magnet stirring treatment is stopped, the argon is stopped being introduced, and the casting aluminum alloy is obtained.
In the actual operation process, small blocks of aluminum source, silicon source, magnesium source, copper source, iron source and chromium source are adopted, and are evenly mixed and then are placed in Al 2 O 3 Smelting in a vacuum furnace to obtain a melt A, starting a permanent magnet stirring device, applying alternating permanent magnet stirring treatment to the melt, adding a rare earth source, a titanium source, a strontium source and a boron source, preserving heat to obtain a melt B, cooling, closing permanent magnet stirring, stopping ventilation, and casting to obtain a finished product.
In a preferred scheme, the permanent magnet stirring treatment process comprises the following steps: firstly, the melt is rotated forward for 1 to 4 minutes and then rotated reversely for 1 to 4 minutes, so that the melt reciprocates; in the rotating process, the melt is made to perform lifting movement every 1-4 min.
In the permanent magnet stirring process, the movement mode of the magnetic field at the melt is continuously regulated by adopting the direction changing and displacement means, so that lorentz forces in different directions and sizes are excited, heat transfer and mass transfer of the melt can be effectively realized, smelting of intermediate alloy is promoted, solute elements are uniformly distributed, alloy solidification structures are refined, and alloy toughness is enhanced. The permanent magnet stirring process in the scheme realizes multi-level multi-element control of the magnetic field through the change of the rotating speed of the magnet and the position change treatment of the melt, and has obvious stirring effect and simple control means. Compared with the traditional single magnetic field movement mode, the melt moves along with the magnetic field in a single direction, such as horizontal rotation movement, the up-and-down homogenization of the melt is realized by means of turbulence formed by high rotation speed, the effect is limited, the same speed and the same direction movement are kept for a long time, and the precipitated phase in the melt is in a relatively static state along with the melt or weakened in relative movement, so that the stirring effect is weakened. Of course, even if the steering rotation is adopted, if the rotation time in the same direction is too short, the high-speed rotation time of the melt is reduced in consideration of the mechanical acceleration time and the deceleration time, so that the stirring effect is weakened, and the service life of the equipment is influenced by frequent steering.
In the present invention, the forward rotation and the reverse rotation are only opposite directions, and the forward rotation and the reverse rotation only represent direction changes. But is not specifically limited in direction.
Further preferably, the process of the permanent magnet stirring treatment is as follows: firstly, the melt is rotated forward for 3-4 min and then rotated backward for 3-4 min, so that the melt reciprocates; in the rotating process, the melt is made to perform lifting motion every 3-4 min. The inventors found that the properties of the finally obtained alloy material are optimal by stepwise redirection using this preferred scheme.
In a preferred scheme, the magnetic induction intensity is 500-3000 Gs, preferably 1500-3000 Gs, in the process of the permanent magnet stirring treatment.
In a preferred scheme, the rotating speed of the magnet is 80-300 rpm, preferably 150-250 rpm, in the process of the permanent magnet stirring treatment.
Principle and advantages
The high strength and toughness of the cast aluminum alloy provided by the invention are as follows: 1: on one hand, cu, mg and Cr can be dissolved in an aluminum matrix to improve the matrix strength, and on the other hand, an aluminum copper phase, an aluminum copper magnesium silicon phase and an iron-rich phase are formed and uniformly distributed in the matrix to realize precipitation phase strengthening. 2: adopts Re, ti, sr, B multielement synergistic modification treatment, on one hand introduces heterogeneous nuclear phase such as Al 3 La、Al 4 Ce、Al 3 Ti、Ti 2 B, on one hand, the refined aluminum matrix can be enriched near a silicon phase and an iron-rich phase, and the precipitated phases such as silicon are refined by changing the modification of a structure supercooling and precipitated phase growth mode and the like. 3: by a unique permanent-magnet stirring treatment, which is continuously changedThe magnetic field, rather than a single moving magnetic field, excites the lorentz force in each direction in the melt, effectively avoids the 'relative static' state caused by the inertial movement of the melt, and greatly improves the heat and mass transfer in the melt; in addition, the lorentz force in each direction effectively avoids the aggregation of alloy elements, improves the distribution of nucleation sites, further refines the solidification structure of the alloy and strengthens the toughness of the alloy.
Compared with the prior art, the invention has the beneficial effects that: the element proportion in the aluminum alloy is reasonably regulated and controlled, multielement modification treatment is adopted, and a unique permanent magnet stirring process is combined, so that the refining of the precipitated phases of the aluminum alloy is effectively realized, and the toughness of the alloy is greatly improved.
Detailed Description
Example 1:
alloy composition: 6% Si,0.5% Mg,0.3% Cu,0.2% La,0.2% Cr,0.1% Fe,0.03% Ti,0.003% Sr,0.003% B, the balance being aluminum and unavoidable impurities, the impurity content being less than 0.2%. The alloy comprises aluminum ingot, al-20% Si, magnesium ingot, al-10% Cu, al-10% La, al-10% Cr, al-5% Fe, al-5% Ti-1% B, al-10% Ti and Al-10% Sr.
The preparation method comprises the following steps: the small blocks of aluminum source, silicon source, magnesium source, copper source, iron source and chromium source which are weighed according to the component proportion are alternately arranged in Al 2 O 3 The crucible is vertically placed in a tube furnace. Introducing high-purity argon for 15min, starting a tube furnace, heating to 830 ℃, and preserving heat for 20min after the high-purity argon is completely melted; starting a permanent magnet stirring device and applying alternating permanent magnet stirring treatment; adding a rare earth source, a titanium source, a strontium source and a boron source into the alloy melt in proportion, and preserving heat for 15min; cooling to 700 ℃, closing the permanent magnet stirring device to stop ventilation, taking out the melt for casting, and obtaining the aluminum alloy. The alternating permanent magnet stirring treatment is as follows: forward rotating for 3min and then reverse rotating for 3min so as to reciprocate; in the rotating process, lifting movement is carried out through the telescopic rod every 3min, the stirring speed of the magnet is 200rpm, and the magnetic induction intensity is 1500-2500 Gs (along with lifting variation). And taking out the cast ingot after the melt is solidified. The tensile strength of the aluminum alloy obtained by test detection is 271MPa, and the elongation is 11.8%.
Example 2:
alloy composition: 7% Si,0.5% Mg,0.3% Cu,0.2% La,0.2% Cr,0.15% Fe,0.03% Ti,0.003% Sr,0.003% B, the balance being aluminum and unavoidable impurities, the impurity content being less than 0.2%. The alloy comprises aluminum ingot, al-20% Si, magnesium ingot, al-10% Cu, al-10% La, al-10% Cr, al-5% Fe, al-5% Ti-1% B, al-10% Ti and Al-10% Sr.
The preparation method comprises the following steps: the small blocks of aluminum source, silicon source, magnesium source, copper source, iron source and chromium source which are weighed according to the component proportion are alternately arranged in Al 2 O 3 The crucible is vertically placed in a tube furnace. Introducing high-purity argon for 15min, starting a tube furnace, heating to 830 ℃, and preserving heat for 20min after the high-purity argon is completely melted; starting a permanent magnet stirring device and applying alternating permanent magnet stirring treatment; adding a rare earth source, a titanium source, a strontium source and a boron source into the alloy melt in proportion, and preserving heat for 15min; cooling to 700 ℃, closing the permanent magnet stirring device to stop ventilation, taking out the melt for casting, and obtaining the aluminum alloy. The alternating permanent magnet stirring treatment is as follows: forward rotation is carried out for 4min and then reverse rotation is carried out for 4min, so that the reciprocating motion is carried out; in the rotating process, lifting movement is carried out through the telescopic rod every 3min, the stirring speed of the magnet is 150rpm, and the magnetic induction intensity is 1500-2500 Gs (along with lifting variation). And taking out the cast ingot after the melt is solidified. The tensile strength of the aluminum alloy obtained by test detection is 263MPa, and the elongation is 10.5%.
Example 3:
alloy composition: 7% Si,0.6% Mg,0.4% Cu,0.3% Ce,0.25% Cr,0.1% Fe,0.03% Ti,0.004% Sr,0.004% B, the balance being aluminum and unavoidable impurities, the impurity content being less than 0.2%. The alloy comprises aluminum ingot, al-20% Si, magnesium ingot, al-10% Cu, al-10% Ce, al-10% Cr, al-5% Fe, al-5% Ti-1% B, al-10% Ti and Al-10% Sr.
The preparation method comprises the following steps: the small blocks of aluminum source, silicon source, magnesium source, copper source, iron source and chromium source which are weighed according to the component proportion are alternately arranged in Al 2 O 3 The crucible is vertically placed in a tube furnace. Introducing high-purity argon for 15min, starting a tube furnace, heating to 850 ℃, and preserving heat for 20min after the high-purity argon is completely melted; starting a permanent magnet stirring device and applying alternating permanent magnet stirring treatment; adding rare earth source and titanium source into alloy melt in proportionPreserving the temperature of the strontium source and the boron source for 10min; cooling to 700 ℃, closing the permanent magnet stirring device to stop ventilation, taking out the melt for casting, and obtaining the aluminum alloy. The alternating permanent magnet stirring treatment is as follows: forward rotation is carried out for 4min and then reverse rotation is carried out for 4min, so that the reciprocating motion is carried out; in the rotating process, lifting movement is carried out through the telescopic rod every 4min, the stirring speed of the magnet is 200rpm, and the magnetic induction intensity is 1500-2500 Gs (along with lifting variation). And taking out the cast ingot after the melt is solidified. The tensile strength of the aluminum alloy obtained by test detection is 264MPa, and the elongation is 9.8%.
Example 4:
alloy composition: 7% Si,0.6% Mg,0.4% Cu,0.3% Ce,0.2% Cr,0.1% Fe,0.02% Ti,0.004% Sr,0.004% B, the balance being aluminum and unavoidable impurities, the impurity content being less than 0.2%. The alloy comprises aluminum ingot, al-20% Si, magnesium ingot, al-10% Cu, al-10% Ce, al-10% Cr, al-5% Fe, al-5% Ti-1% B, al-10% Ti and Al-10% Sr.
The preparation method comprises the following steps: the small blocks of aluminum source, silicon source, magnesium source, copper source, iron source and chromium source which are weighed according to the component proportion are alternately arranged in Al 2 O 3 The crucible is vertically placed in a tube furnace. Introducing high-purity argon for 15min, starting a tube furnace, heating to 800 ℃, and preserving heat for 20min after the high-purity argon is completely melted; starting a permanent magnet stirring device and applying alternating permanent magnet stirring treatment; adding a rare earth source, a titanium source, a strontium source and a boron source into the alloy melt in proportion, and preserving heat for 10min; cooling to 700 ℃, closing the permanent magnet stirring device to stop ventilation, taking out the melt for casting, and obtaining the aluminum alloy. The alternating permanent magnet stirring treatment is as follows: forward rotation is carried out for 4min and then reverse rotation is carried out for 4min, so that the reciprocating motion is carried out; in the rotating process, lifting movement is carried out through the telescopic rod every 4min, the stirring speed of the magnet is 150rpm, and the magnetic induction intensity is 1500-2500 Gs (along with lifting variation). And taking out the cast ingot after the melt is solidified. The tensile strength of the aluminum alloy obtained by test detection is 258MPa, and the elongation is 9.5%.
Comparative example 1:
other experimental conditions were exactly the same as in example 1, except that the iron element ratio was increased to 1% and the chromium element was unchanged. The tensile strength of the aluminum alloy obtained by test detection is 162MPa, and the elongation is 5.6%.
As can be seen from the comparison of the data of comparative example 1 with that of example 1, too high an iron content and too low a Cr/Fe ratio resulted in coarse iron-containing phases, which deteriorated the elongation properties of the alloy, although strengthening the matrix hardness.
Comparative example 2:
other experimental conditions were exactly the same as in example 1, except that no rare earth element was added and no permanent magnet stirring was applied. The tensile strength of the aluminum alloy obtained by test detection is 158MPa, and the elongation is 6.4%.
Comparative example 3:
other experimental conditions were exactly the same as in example 1, except that no rare earth element was added. The tensile strength of the aluminum alloy obtained by test detection is 194MPa, and the elongation is 6.8%.
Comparative example 4:
other experimental conditions were exactly the same as in example 1, except that the rare earth was 0.02% la. The tensile strength of the aluminum alloy obtained by test detection is 213MPa, and the elongation is 7.3%. As can be seen from comparative example 4, when the rare earth content is low, the rare earth deterioration effect is weak, and the alloy strengthening effect is correspondingly weak.
Comparative example 5:
other experimental conditions were exactly the same as in example 1, except that the rare earth was 3.0% la. The tensile strength of the aluminum alloy obtained by test detection is 217MPa, and the elongation is 7.9%. As can be seen from comparative example 5, when the rare earth content is high, the rare earth aggregates with each other and reacts with the alloy element to generate brittle or long-strip intermetallic compounds, which correspondingly lower the alloy performance to some extent.
As can be seen from the comparison of the data of comparative examples 2 to 5 and example 1, the rare earth addition significantly affects the deterioration effect of the alloy, and when the rare earth addition is too low or 0, the deterioration effect of the rare earth is not significantly insufficient; when the addition amount of rare earth is too high, coarse rare earth compounds appear in the alloy, and tear the matrix to play a role in reaction.
Comparative example 6:
other experimental conditions were exactly the same as in example 1, except that no permanent magnet stirring was applied. The tensile strength of the aluminum alloy obtained by test detection is 189MPa, and the elongation is 6.4%.
Comparative example 7:
other experimental conditions were exactly the same as in example 1, except that the permanent magnet stirring speed was 30rpm. The tensile strength of the aluminum alloy obtained by test detection is 218MPa, and the elongation is 7.2%.
As can be seen from comparative example 7, the permanent magnet stirring process parameters also have a certain influence on the performance of the cast ingot, when the permanent magnet stirring speed is smaller, the excited Lorentz force is smaller, the formed vortex is smaller, the stirring effect is correspondingly weakened, the growth restriction on the precipitated phase is weaker, and the strengthening effect is poor.
Comparative example 8:
other experimental conditions were exactly the same as in example 1, except that the speed direction was not changed during the permanent magnet stirring. The tensile strength of the aluminum alloy obtained by test detection is 209MPa, and the elongation is 8.2%.
Comparative example 9:
other experimental conditions were exactly the same as in example 1, except that no lifting bar was moved during the application of the permanent magnet stirring. The tensile strength of the aluminum alloy obtained by test detection is 213MPa, and the elongation is 8.6%.
Comparative example 10:
other experimental conditions were exactly the same as in example 1, except that in the application of permanent magnetic stirring, the lifting movement of the lifting rod was once every 6 min. The tensile strength of the aluminum alloy obtained by test detection is 221MPa, and the elongation is 8.9%. As can be seen from comparative example 10, when the moving frequency of the telescopic rod is low, the moving magnetic field is relatively slow, and due to the rapid movement in the horizontal direction, precipitated phases in the melt are gathered to a certain extent, so that the structure is coarsened, and the alloy performance is correspondingly reduced.
As can be seen from comparative examples 6-10 and example 1, the stirring effect is reduced at a lower magnetic field rotation speed, a lower lifting frequency and a constant magnetic field rotation speed direction in the magnetic field control process, and the alloy performance cannot be optimized well.
As can be seen from the comparison of the data in comparative examples 2-10 and example 1, the alloy can be strengthened to a certain extent by utilizing the rare earth modification and the permanent magnet stirring technology, the permanent magnet stirring technology is superior to the rare earth modification, and the combined moving magnetic field stirring technology effect is better; the permanent magnet stirring coupling rare earth modification technology can obviously improve the tensile strength and the elongation of the alloy and obviously improve the toughness of the aluminum alloy.
The method is feasible by the examples and the comparison examples, and has certain practical value and industrial application potential. The above embodiments are provided for illustrating the present invention and not for limiting the present invention, and various changes and modifications may be made by one skilled in the relevant art without departing from the spirit and scope of the present invention, and thus all equivalent technical solutions should be defined by the claims.

Claims (6)

1. A preparation method of a casting aluminum alloy with high strength and toughness and low Si content is characterized by comprising the following steps: the method comprises the following steps: preparing an aluminum source, a silicon source, a magnesium source, a copper source, an iron source and a chromium source according to a design proportion, uniformly mixing to obtain a mixture, introducing argon to discharge air, smelting to obtain a melt A, starting a permanent magnet stirring device, and applying permanent magnet stirring treatment to the melt; then cooling, adding a rare earth source, a titanium source, a strontium source and a boron source, preserving heat to obtain a melt B, cooling, stopping applying permanent magnet stirring treatment, stopping introducing argon, and casting to obtain the cast aluminum alloy;
the process of the permanent magnet stirring treatment comprises the following steps: firstly, the melt is rotated forward for 1 to 4 minutes and then rotated reversely for 1 to 4 minutes, so that the melt reciprocates; in the rotating process, the melt is made to perform lifting movement once every 1-4 min;
the cast aluminum alloy comprises the following components in percentage by mass: si:4.5 to 7 percent of Mg:0.4 to 0.7 percent, cu:0.2 to 0.5 percent, RE:0.1 to 0.4 percent, cr:0.15 to 0.35 percent, fe is less than or equal to 0.15 percent, ti:0.01 to 0.05 percent, sr:0.001 to 0.004 percent, B: 0.001-0.004%, the rest is aluminum and unavoidable impurities;
in the cast aluminum alloy, the mass ratio of Cr to Fe is 1-3;
in the cast aluminum alloy, the mass ratio of Ti to B is 5-10;
in the cast aluminum alloy, the mass ratio of Sr to B is 1-2.
2. The method for preparing the cast aluminum alloy with high strength and toughness and low Si content according to claim 1, which is characterized in that: the smelting process comprises the following steps: heating to 800-850 ℃, and preserving heat for 15-25 min after the mixture is completely melted to obtain a melt A.
3. The method for preparing the cast aluminum alloy with high strength and toughness and low Si content according to claim 1, which is characterized in that: cooling to 750-800 ℃, adding a rare earth source, a titanium source, a strontium source and a boron source, and preserving heat for 10-20 min to obtain a melt B.
4. The method for preparing the cast aluminum alloy with high strength and toughness and low Si content according to claim 1, which is characterized in that: and after the melt B is obtained, cooling to 680-720 ℃, stopping applying permanent magnet stirring treatment, stopping introducing argon, and casting to obtain the cast aluminum alloy.
5. The method for preparing the cast aluminum alloy with high strength and toughness and low Si content according to claim 1, which is characterized in that: in the process of the permanent magnet stirring treatment, the magnetic induction intensity is 500-3000 Gs.
6. The method for preparing the cast aluminum alloy with high strength and toughness and low Si content according to claim 1, which is characterized in that: in the process of the permanent magnet stirring treatment, the rotating speed of the magnet is 80-300 rpm.
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