CN114250389B - High-strength and high-toughness cast aluminum alloy and preparation method thereof - Google Patents
High-strength and high-toughness cast aluminum alloy and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a high-strength and high-toughness cast aluminum alloy, a heat treatment process and a preparation method thereof, wherein the aluminum alloy comprises the following components in percentage by weight: si: 5-8.5 wt%, Cu: 1-3 wt%, Mg:0.3 to 0.5 wt%, Zn: 0.5 to 1.0 wt%, Fe:0.1 to 0.2 wt%, Ti: 0.1 to 0.3 wt%, Cr:0.1 to 0.3 wt%, Zr:0.1 to 0.3 wt%, Sr: 0.02-0.06 wt%, mixed rare earth Re: 0.2-0.4 wt%, the total of other inevitable impurity elements is not more than 0.15 wt%, and the balance of aluminum. The aluminum alloy is specially treated by the heat treatment process of solid solution and aging, so that the obtained aluminum alloy has ultrahigh strength and toughness, the yield strength of the aluminum alloy exceeds 350MPa, the tensile strength of the aluminum alloy exceeds 400MPa, and the elongation of the aluminum alloy is more than 3%, and the problems of low strength and poor toughness of the conventional aluminum alloy can be effectively solved.
Description
Technical Field
The invention relates to the technical field of metal materials, in particular to a high-strength and high-toughness cast aluminum alloy, a heat treatment process and a preparation method thereof.
Background
In recent years, a clear 'carbon neutralization' target is provided in many countries and regions in the world, and the 'carbon dioxide emission strives to reach a peak value before 2030 years and strives to achieve carbon neutralization before 2060 years' is provided in 2020 in China. Under the background, the acceleration of decarburization becomes a large trend in the automobile industry, and the vigorous development of new energy vehicles also becomes a consensus of the vehicle enterprises. One of the routes for achieving "carbon neutralization" in the automotive industry is to use light-weight technology to reduce fuel consumption or electricity consumption per kilometer of automobiles, wherein replacement of traditional steel parts with aluminum alloy parts is the core of light-weight automobiles.
The largest consumption of aluminum alloy materials used for automobile chassis or related important stressed structural parts at present is A356(AlSi7Mg0.3), after the A356 is cast by gravity or cast at low pressure, T6 is adopted for heat treatment, the yield strength can reach 210MPa, the tensile strength can reach 290MPa, the elongation percentage can reach about 4%, and the aluminum alloy material is mainly used for a series of important parts such as automobile wheel hubs, front and rear auxiliary frames of the chassis, steering knuckles, control arms and the like. In addition, the demand that the brake caliper adopts the fixed calliper of integral type has begun to obviously increase, and this kind of fixed calliper of integral type if adopt the shaping of aluminum alloy casting mode, will be for the aluminium forging mode greatly reduced production manufacturing cost that warp. However, the method is limited by the limitation that the toughness of the existing A356 material is not high, obvious restrictions are caused on the weight reduction effect and the production and manufacturing of the parts, and the requirement of the new energy automobile on the comprehensive properties of the parts such as strength, complex geometric dimension, cost and the like cannot be met by using the A356 aluminum alloy alone, so that the ultrahigh-strength high-toughness heat treatment casting aluminum alloy suitable for the automobile field is urgently needed to be developed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a high-strength and high-toughness cast aluminum alloy, which solves the problems of low strength and poor toughness of the aluminum alloy material in the prior art.
Further provides a heat treatment process and a preparation method of the cast aluminum alloy.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows:
the high-strength and high-toughness cast aluminum alloy is characterized by comprising the following components in percentage by weight: si: 5-8.5 wt%, Cu: 1-3 wt%, Mg:0.3 to 0.5 wt%, Zn: 0.5 to 1.0 wt%, Fe: 0.1-0.2 wt%, Ti: 0.1 to 0.3 wt%, Cr:0.1 to 0.3 wt%, Zr:0.1 to 0.3 wt%, Sr: 0.02-0.06 wt%, mixed rare earth Re: 0.2-0.4 wt%, the total of other inevitable impurity elements is not more than 0.15 wt%, and the balance of aluminum.
Further, the mixed rare earth Re comprises La, Ce and Er.
Further, La: Ce: Er ═ 1:1: 1.
Further, the ratio of Cu to Mg is 3: 1-5: 1.
Further, the total content of Zr, Cr and Ti is less than 0.7wt%
The preparation method of the high-strength and high-toughness cast aluminum alloy is characterized by comprising the following preparation steps:
1) preparing materials: weighing industrial pure aluminum, Al-Si20 intermediate alloy, pure magnesium, pure zinc, Al-50Cu intermediate alloy, Al-20Fe intermediate alloy, Al-10Zr intermediate alloy, Al-10Cr intermediate alloy, Al-5Ti intermediate alloy, Al-Sr intermediate alloy, Al-Re intermediate alloy, aluminum deslagging, degassing and refining agent and the like according to the set chemical components according to the metering ratio, and drying the alloys and the raw materials for later use;
2) melting an aluminum ingot: putting an industrial pure aluminum ingot preheated to 150-180 ℃ into a smelting furnace for melting, wherein the melting temperature is 760-780 ℃, adding a deslagging agent accounting for 0.4-0.5% of the mass of the aluminum ingot after melting, stirring for 20-25 minutes by using a graphite rod, and preserving heat for 20-25 minutes after deslagging;
3) smelting and melt purification: cooling the melt obtained in the step 2) to 740-745 ℃, adding Al-Si20 intermediate alloy and Al-20Fe intermediate alloy, cooling to 720-725 ℃ after all the melt is melted, manually stirring for 5-6 minutes to make the components uniform, adding Al-10Zr intermediate alloy, Al-10Cr intermediate alloy, Al-5Ti intermediate alloy and Al-50Cu intermediate alloy, cooling to 690-700 ℃ after melting, adding magnesium and zinc, manually stirring for 5-6 minutes after melting, removing bottom sediment and surface scum with a filter screen after standing for 10-15 minutes, adding Al-Re intermediate alloy into the melt, manually stirring for 5-6 minutes, cooling to 690 ℃ after melting, removing bottom sediment and surface scum with the filter screen after standing for 10-15 minutes, then uniformly throwing an aluminum sodium-free covering agent on the surface of the melt according to the area reference dosage of 1/square meter, wrapping an aluminum refining agent by using a pure aluminum foil, then filling the aluminum refining agent into a graphite bell jar, wherein the using amount of the refining agent is 0.2-0.5% of the mass of aluminum liquid to be treated by mass, pressing the bell jar into the deep part of the aluminum liquid, which is about 10 cm away from the bottom of the furnace, horizontally moving the bell jar to each place in the furnace, carrying out reaction accompanied by the rolling of the aluminum liquid for about 4-6 minutes, and fishing floating slag and bottom sediment by using a filter screen or a slag ladle after the reaction is finished; after slagging is finished, reducing the temperature of the melt to 680-685 ℃, protecting the melt by using inert gas argon, adding an Al-Sr intermediate alloy, pressing the intermediate alloy into the bottom of a smelting furnace for melting, uniformly stirring the melt after melting, standing for 10-15 minutes, carrying out component analysis before the furnace, detecting the component content of the alloy melt, and enabling the component content of the melt with unqualified component content to reach the qualified range by a material supplementing or diluting mode;
4) degassing: heating the melt obtained in the step 3) to 700-720 ℃, introducing argon for 5-10 minutes for degassing, skimming after degassing, standing for 10-20 minutes and waiting for casting;
5) casting a tensile test bar: performing gravity casting on the melt obtained in the step 4), controlling the temperature of molten aluminum to be 670-680 ℃ and the temperature of a mold to be 220-250 ℃, uniformly and stably pouring molten aluminum into a mold gate during casting, enabling the molten aluminum not to flow out in the middle, cooling for 1-2 minutes after the molten aluminum of a riser is solidified after casting, and then opening the mold to avoid damage to a test rod caused by mold opening at high temperature;
6) and (3) heat treatment: carrying out solid solution and aging treatment on the aluminum alloy obtained in the step 5).
Further, solid solution parameters: keeping the temperature at 495 +/-1 ℃ for 10 +/-0.2 h, and keeping the quenching water at 70-90 ℃; aging parameters are as follows: keeping the temperature at 170 +/-1 ℃ for 8 +/-0.2 h.
Further, solid solution parameters: keeping the temperature at 480 +/-1 ℃ for 4 +/-0.2 h, keeping the temperature at 500 +/-1 ℃ for 6h, keeping the temperature at 525 +/-1 ℃ for 6h, and keeping the temperature at quenching water at 70-90 ℃; aging parameters are as follows: keeping the temperature at 175 plus or minus 1 ℃ for 7 plus or minus 0.2 h.
Compared with the prior art, the invention has the following advantages:
1. compared with the conventional aluminum alloy, the aluminum alloy material has higher strength and elongation, the yield strength exceeds 350MPa, the tensile strength exceeds 400MPa, and the elongation is more than 3%. The aluminum alloy of the invention has the advantages that the microstructure of the material is compact, the crystal grains are fine and uniform, the modification effect of the eutectic silicon is excellent, and the heat treatment process parameters are reasonable through strict component proportion control and process requirements.
2. The invention controls the aspects of component control, metamorphism, melt purification, casting, heat treatment process and the like, so that the material achieves high strength and toughness. In the preparation process, the aluminum alloy material is smelted in multiple steps in the smelting process, so that the alloy elements are uniformly distributed, and meanwhile, the casting process and the strict and precise heat treatment parameter control in the heat treatment process are controlled in the casting process, so that the alloy elements in the material play the greatest role, and finally the material reaches the performance index of ultrahigh strength and toughness.
Drawings
FIG. 1 is a stress-strain-tensile curve diagram in examples 1 to 6 of the present invention;
FIG. 2 is a 100-fold photograph of the metallographic structure of the cast aluminum alloy according to example 1 of the present invention;
FIG. 3 is a 500-fold photograph of the metallographic structure of the cast aluminum alloy according to example 1 of the present invention.
Detailed Description
The present invention will be further described with reference to specific examples in order to better understand the technical solutions of the present invention for those skilled in the art, but the embodiments of the present invention are not limited thereto.
In theoretical research and experiments on aluminum alloy fluidity influencing factors, eutectic silicon modification, microalloying reinforcement, a smelting process, a heat treatment process and the like, the invention finds that the silicon content is strictly controlled within the range of 5-8.5%, magnesium, zinc and copper are added according to a certain proportion to serve as main reinforcing elements, meanwhile, crystal grains can be obviously refined by trace composite addition of transition group elements such as Zr, Cr and Ti, the toughness of the material can be improved, and excellent modification effect can be obtained by combined use of Sr and mixed rare earth, and the toughness of the material can also be improved by refining the crystal grains. In addition, through different heat treatment processes and proper solid solution temperature and time, second phases such as eutectic silicon and the like are fully dissolved in solid solution and spheroidized, stress concentration points in the material are reduced, the material components are more uniform, solid solution elements are properly dispersed and precipitated to strengthen the matrix through proper aging treatment, and finally the aluminum alloy material with yield strength of more than 350MPa, tensile strength of more than 400MPa and elongation of more than 3% is obtained.
The function and principle of part of alloy elements or alloy element combination in the invention are as follows:
the main function of silicon is to increase the fluidity of the alloy and simultaneously reduce the volume shrinkage rate during solidification, the silicon can also improve the strength of the alloy within a certain range, but the excessive silicon content can obviously reduce the plasticity of the material. For materials such as gravity casting, the inventor verifies that enough eutectic structures can be generated when the silicon content is between 5% and 8.5% according to a large amount of experiments, namely the eutectic reaction in the solidification process is sufficient, and the flowability of the materials can be ensured.
As for the strength of Al-Si-Cu-Mg series materials, the influence of copper is the largest, the influence of magnesium is the next, and the influence of silicon is the smallest, so that the invention can disperse and separate out beta phase (Mg) during aging treatment when simultaneously adding Mg and Cu and keeping the Cu content higher than the Mg content to a certain value 2 Si) and W phase (Al) 2 Si 5 CuMg 4 ) And the alloy strength is obviously improved. The inventor determines that the Cu-Mg range is 3: 1-5: 1, the strengthening effect is better, meanwhile, the material strength can be further improved by properly adding a trace amount of Zn, and MgZn can be formed in Mg-containing aluminum alloy by mainly utilizing Zn 2 The phase has good natural aging effect, and can further improve the strength of the material. However, when the Zn content exceeds a certain value, shrinkage porosity and shrinkage cavity tendency in the solidification process are likely to increase, so that the Zn content in the invention is controlled to be 0.5-1.0%.
The trace compound addition of transition elements such as Zr, Cr and Ti can obviously refine grains and improve the toughness of the material, and the Zr element is separated out from the solid solution in the heat treatment process to form metastable Al 3 Zr phase is uniformly dispersed in the matrix, and can keep good coherent relation with the matrix, thereby improving the performance of the alloy. Meanwhile, Al 3 The Zr particles are fine, and alpha-Al can be attached to the small particles to form nuclei during the peritectic reaction, thereby playing the role of refining grains. Besides the solid solution strengthening effect on the matrix, the Cr element can be dispersed and precipitated in the aging stage and play a role in dispersion strengthening, meanwhile, part of massive Cr-rich compounds can be segregated in the grain boundary and easily form sigma and other dispersed phases with harmful elements such as Fe and the like to replace other harmful Fe-containing phases, the splitting effect of insoluble Fe-containing phases on the matrix is reduced, and finally the elongation of the material is obviously improved. Ti is a typical alpha dendrite refiner, and the invention finds that the beneficial effect of the combined use of Zr, Cr and Ti is obviously higher than that of the use of a single element through experiments. And the total content of Zr + Cr + Ti is less than 0.7 percent, otherwise excessive blocky phases are generated, and the elongation of the material is reduced.
The size of the crystal grains and the morphology of the second phase have a crucial influence on the mechanical property of the alloy, the smaller the crystal grains are, the better the mechanical property is, meanwhile, the second phase has the smallest fracture to the aggregate when existing in a fine spherical particle shape, the stress concentration caused is also the smallest, cracks are not easy to generate on a phase interface in the stress deformation process of the material, and finally, the toughness of the material is better. The rare earth elements can improve the strength of the aluminum alloy by inhibiting recrystallization, refining crystal grains, improving the appearance of eutectic silicon and influencing the aging precipitation process. The inventor discovers through a large number of cross experiments that the effect of the combined action of the lanthanum, cerium and erbium mixed rare earth is more obvious than that of the single rare earth element, and the effect is most obvious when the La to Ce to Er is 1 to 1. Meanwhile, the deterioration of strontium is reduced when the content of the misch metal exceeds 0.6%, so that the content of the misch metal is controlled to be 0.2-0.4% in the invention. The Sr content is controlled to be between 0.02 and 0.06 percent, the modification effect of the aluminum alloy material is most obvious, when the Sr content exceeds 0.08 percent, the surface of the solidified material has an obvious fine cracked surface state, an oxide film on the surface of the aluminum alloy is damaged due to the fact that the Sr content is too high, a Sr-containing second phase is formed when the Sr content is further increased to 1 percent, air absorption of the material is obvious, internal defects are increased, therefore, the Sr content is controlled to be between 0.02 and 0.06 percent, meanwhile, the Sr addition temperature is between 680 and 690 ℃, the too high Sr causes serious burning loss, the Sr is added after refining to avoid reaction loss with a refining agent, the temperature is kept for 20 to 25 minutes after the Sr is added, and casting is finished within 4 hours, otherwise, the modification effect of Sr is greatly reduced.
In general, Fe belongs to harmful impurity elements in Al alloy, but a small amount of iron element is inevitably present in industrial alloy, and the contact between iron tools in the smelting and casting processes also causes iron increase, so that the smelting process needs to be strictly controlled.
And (3) heat treatment:
the invention mainly carries out strengthening through T6 heat treatment, namely solid solution and aging, which are key steps for obtaining the final high strength and toughness performance.
Solid solution: the main purpose of the solution treatment is to re-dissolve the precipitated phase in the solidification process in the matrix alpha-Al at high temperature to form a supersaturated solid solution, so as to prepare for the aging treatment of the alloy. In the solid solution process, the phase change of silicon is large, and diffusion fusing and gradual graining of the silicon phase mainly occur, and if the solid solution time is too long, coarsening and other processes also occur. During the graining stage of the eutectic silicon phase, the eutectic silicon casting becomes round and transforms into a spherical shape or a sphere-like shape, and meanwhile, eutectic silicon continuously migrates to the inside of the crystal, so that the distribution of the silicon in the matrix is more uniform. In addition, the relevant copper-containing phase and the relevant strengthening phase such as magnesium are gradually dissolved into the matrix in the process of solid solution, and preparation is made for aging. The key point of the solution treatment is to select proper temperature and time, for example, the A356 alloy is generally treated by 535 ℃ and is kept for about 8 hours for solution treatment, but the aluminum alloy of the invention has high copper content, and by performing DSC curve analysis on the material, an endothermic exothermic peak exists at 509 ℃, and the material is found to be a copper-containing theta phase by phase analysis. The presence of this low-melting phase makes solution treatment difficult, on the one hand, if the temperature is raised directly to 535 ℃, this phase will melt, causing the serious drawback of overburning of the material, even a slightly overburnt material will seriously impair mechanical properties and be unusable.
The invention provides two heat treatment solid solution schemes aiming at the difficulty of heat treatment of similar copper-containing aluminum-silicon alloy:
1) the method is characterized by comprising the following steps of (1) carrying out solid solution at 495 ℃ for 10 hours, carrying out hot water quenching (with the water temperature of 70-90 ℃), ensuring that the material does not have overburning risk when the temperature is lower than 509 ℃, and enabling the eutectic silicon in a casting state to be remarkably refined through material alloying design although the dissolution of the eutectic silicon is slightly lower than 535 ℃, so that the eutectic silicon is high in structure uniformity and can still obtain a good effect when solid solution is carried out at 495 ℃, and the method is simple and stable and is suitable for most use scenes;
2) the method comprises the steps of (1) carrying out graded solid solution, namely, firstly carrying out heat preservation at 480 ℃ for 6 hours, heating to 500 ℃ for 4 hours to fully dissolve a theta phase with a melting point of 509 ℃, granulating most of eutectic silicon and the like, then heating to 525 ℃ for heat preservation for 6 hours, then carrying out hot water quenching (with the water temperature of 70-90 ℃), further dissolving the eutectic silicon, and finally fully dissolving a related alloy phase under the condition of avoiding overburning of materials, wherein the solid solution process needs strict temperature and time control and is long in total use time and suitable for being adopted when higher requirements on toughness are met, and although the total solid solution time is up to 16 hours, the process has the effects of refining grains and preventing recrystallization and growth of the related alloy components, so that the mechanical property cannot be reduced due to the fact that the grains are coarse;
artificial aging: age hardening of aluminum alloys is a very complex process, related to alloy structure, aging process, and internal dislocation distribution. In general, age-hardening is the effect of inhibiting the movement of dislocations in the surrounding elastic stress field by the second phase precipitates in the matrix, so that the resistance of dislocations in passing through the dispersed precipitates is increased, thereby causing a strengthening effect. The most important temperature and time control of artificial aging is high temperature and high aging speed, but too high temperature can cause precipitation phase to grow up and lose coherent relation with a matrix, and finally the material is softened. After a large amount of research and tests, the invention establishes that different aging processes are adopted for materials under different solid solution conditions, namely, 170 +/-1 ℃ and 8 +/-0.2H artificial aging is adopted when single-stage solid solution is carried out for 495 +/-1 ℃ and 10 +/-0.2 hours, and 175 +/-1 ℃ and 7 +/-0.2H artificial aging is adopted when three-stage solid solution is carried out for 480 ℃, 4 hours, 500 ℃, 6 hours, 525 ℃ and 6 hours (temperature fluctuation range +/-1 ℃ and time range +/-0.2 hours).
The quenching water temperature should be controlled to be 70-90 ℃, too low quenching can cause too severe quenching to cause severe deformation of a sample, and too high quenching can cause slow cooling speed of parts, and the final performance is not influenced by the solid solution effect.
Example 1
The high-toughness cast aluminum alloy of the embodiment comprises the following components in percentage by weight: 6.0 percent of Si, 1.5 percent of Cu, 0.4 percent of Mg, 0.6 percent of Zn, 0.2 percent of Ti, 0.15 percent of Cr, 0.1 percent of Zr, 0.25 percent of Re, 0.02 percent of Sr and 0.15 percent of Fe; the sum of other impurities is less than 0.15 percent, and the balance is Al.
The heat treatment process and the preparation method of the high-toughness cast aluminum alloy of the embodiment comprise the following steps:
1) preparing materials: weighing industrial pure aluminum, Al-Si20 intermediate alloy, pure magnesium, pure zinc, Al-50Cu intermediate alloy, Al-20Fe intermediate alloy, Al-10Zr intermediate alloy, Al-10Cr intermediate alloy, Al-5Ti intermediate alloy, Al-Sr intermediate alloy, Al-Re intermediate alloy, aluminum deslagging, degassing and refining agent and the like according to the set chemical components according to the metering ratio, and drying the alloys and the raw materials for later use;
2) melting an aluminum ingot: putting an industrial pure aluminum ingot preheated to 150 ℃ into a smelting furnace for melting, wherein the melting temperature is 760 ℃, adding a deslagging agent accounting for 0.4 percent of the mass of the aluminum ingot after melting, stirring for 20 minutes by using a graphite rod, deslagging and preserving heat for 20 minutes;
3) smelting and melt purification: cooling the melt obtained in the step 2) to 740 ℃, adding Al-Si20 intermediate alloy and Al-20Fe intermediate alloy, cooling to 720 ℃ after all the melt is melted, manually stirring for 5 minutes to ensure that the components are uniform, cooling to 690-700 ℃ after the melt is melted, adding magnesium and zinc, manually stirring for 5 minutes after the melt is melted, removing bottom sediment and surface scum with a filter screen after standing for 10 minutes, then adding Al-Re intermediate alloy into the melt, manually stirring for 5 minutes, cooling to 690 ℃ after the melt is melted, manually stirring for 10 minutes to remove the bottom sediment and the surface scum with the filter screen, uniformly throwing an aluminum sodium-free covering agent on the surface of the melt according to the area reference amount of 1 kg/square meter, filling the melt into a graphite bell jar after an aluminum foil refining agent is wrapped with a pure aluminum foil, the using amount of the refining agent is 0.2 percent of the mass of the aluminum liquid to be treated by mass, the bell jar is pressed into the depth of the aluminum liquid to be about 10 centimeters away from the furnace bottom, the bell jar is horizontally moved to each part in the furnace, the aluminum liquid rolls in the reaction, the reaction time is about 4 minutes, and after the reaction is finished, scum and bottom sediment are fished clean by a filter screen or a scum spoon; after slagging is finished, reducing the temperature of the melt to 680 ℃, protecting the melt by using argon as an inert gas, adding an Al-Sr intermediate alloy, pressing the intermediate alloy into the bottom of a smelting furnace for melting, uniformly stirring the melt after melting, standing for 10 minutes, carrying out component analysis in front of the furnace, detecting the component content of the alloy melt, and enabling the component content of the melt with unqualified component content to reach the qualified range in a material supplementing or diluting way;
4) degassing: heating the melt in the step 3) to 700 ℃, introducing argon for 5 minutes for degassing, skimming after degassing, and standing for 10 minutes for casting;
5) casting a tensile test bar: performing gravity casting on the melt obtained in the step 4), controlling the temperature of molten aluminum at 670 ℃ and the temperature of a mold at 220 ℃, uniformly and stably pouring molten aluminum into a pouring gate of the mold during casting, enabling the middle of the molten aluminum not to be cut off, cooling for 1 minute after the casting is finished and the molten aluminum on a riser is solidified, and then opening the mold to avoid damage to a test bar caused by mold opening at high temperature;
6) and (3) heat treatment:
solid solution parameters: 495 ℃ and 10h (quenching water temperature 70 ℃)
Aging parameters are as follows: 170 ℃ for 8h
FIG. 1 is a stress-strain-elongation graph of examples 1 to 6 of the present invention, which shows that the overall strength is higher, and the elongation of the heat treatment method 2 is higher than that of the heat treatment method 1.
FIG. 2 is a 100-fold photograph of the metallographic structure of example 1 of the present invention. As can be seen from the figure, the metallographic structure of the material mainly comprises a matrix alpha-Al and a eutectic Si phase, and the related structure is fine and uniform in size and distribution, so that the material strength and plasticity are improved.
FIG. 3 is a 500-fold photograph of the metallographic structure of the cast aluminum alloy according to example 1 of the present invention. As can be seen from the figure, the metallographic structure of the alloy consists of a matrix alpha-Al, a eutectic Si phase and a small amount of alloy complex phases containing copper, magnesium and the like, and the eutectic silicon is in a round spherical particle shape and is beneficial to improving the elongation of the material.
Examples 2-3 the ingredients are shown in Table 1, and the preparation method is the same as example 1
Example 4
The high-toughness cast aluminum alloy of the embodiment comprises the following components in percentage by weight: 7.0 percent of Si, 2 percent of Cu, 0.3 percent of Mg, 0.8 percent of Zn, 0.2 percent of Ti, 0.25 percent of Cr, 0.2 percent of Zr, 0.3 percent of Re, 0.04 percent of Sr and 0.15 percent of Fe; the sum of other impurities is less than 0.15 percent, and the balance is Al.
The preparation method of the high-toughness cast aluminum alloy comprises the following steps:
1) preparing materials: weighing industrial pure aluminum, Al-Si20 intermediate alloy, pure magnesium, pure zinc, Al-50Cu intermediate alloy, Al-20Fe intermediate alloy, Al-10Zr intermediate alloy, Al-10Cr intermediate alloy, Al-5Ti intermediate alloy, Al-Sr intermediate alloy, Al-Re intermediate alloy, aluminum deslagging, degassing and refining agent and the like according to the set chemical components according to the metering ratio, and drying the alloys and the raw materials for later use;
2) melting an aluminum ingot: putting an industrial pure aluminum ingot preheated to 150 ℃ into a smelting furnace for melting, wherein the melting temperature is 760 ℃, adding a deslagging agent accounting for 0.4 percent of the mass of the aluminum ingot after melting, stirring for 20 minutes by using a graphite rod, deslagging and preserving heat for 20 minutes;
3) smelting and melt purification: cooling the melt obtained in the step 2) to 740 ℃, adding Al-Si20 intermediate alloy and Al-20Fe intermediate alloy, cooling to 720 ℃ after all the melt is melted, manually stirring for 5 minutes to ensure that the components are uniform, cooling to 690-700 ℃ after the melt is melted, adding magnesium and zinc, manually stirring for 5 minutes after the melt is melted, removing bottom sediment and surface scum with a filter screen after standing for 10 minutes, then adding Al-Re intermediate alloy into the melt, manually stirring for 5 minutes, cooling to 690 ℃ after the melt is melted, manually stirring for 10 minutes to remove the bottom sediment and the surface scum with the filter screen, uniformly throwing an aluminum sodium-free covering agent on the surface of the melt according to the area reference amount of 1 kg/square meter, filling the melt into a graphite bell jar after an aluminum foil refining agent is wrapped with a pure aluminum foil, the using amount of the refining agent is 0.2 percent of the mass of the aluminum liquid to be treated by mass, the bell jar is pressed into the depth of the aluminum liquid to be about 10 centimeters away from the furnace bottom, the bell jar is horizontally moved to each part in the furnace, the aluminum liquid rolls in the reaction, the reaction time is about 4 minutes, and after the reaction is finished, scum and bottom sediment are fished clean by a filter screen or a scum spoon; after slagging is finished, reducing the temperature of the melt to 680 ℃, protecting the melt by using argon as an inert gas, adding an Al-Sr intermediate alloy, pressing the intermediate alloy into the bottom of a smelting furnace for melting, uniformly stirring the melt after melting, standing for 10 minutes, carrying out component analysis in front of the furnace, detecting the component content of the alloy melt, and enabling the component content of the melt with unqualified component content to reach the qualified range in a material supplementing or diluting way;
4) degassing: heating the melt in the step 3) to 700 ℃, introducing argon for 5 minutes for degassing, skimming after degassing, and standing for 10 minutes for casting;
5) casting a tensile test bar: performing gravity casting on the melt obtained in the step 4), controlling the temperature of molten aluminum at 670 ℃ and the temperature of a mold at 220 ℃, uniformly and stably pouring molten aluminum into a pouring gate of the mold during casting, enabling the middle of the molten aluminum not to be cut off, cooling for 1 minute after the casting is finished and the molten aluminum on a riser is solidified, and then opening the mold to avoid damage to a test bar caused by mold opening at high temperature;
6) and (3) heat treatment:
solid solution parameters: 480 ℃, 4h, 500 ℃, 6h, 525 ℃ and 6h (quenching water temperature 70 ℃)
Aging parameters are as follows: 175 ℃ for 7h
Components of examples 5 to 6 are shown in Table 1, and the preparation method is the same as that of example 4
TABLE 1 (mass fraction wt%)
TABLE 2 as-cast Properties and T6 Heat treatment parameters
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.
Claims (4)
1. The high-strength and high-toughness cast aluminum alloy is characterized by comprising the following components in percentage by weight: si: 5-8.5 wt%, Cu: 1-3 wt%, Mg:0.3 to 0.5 wt%, Zn: 0.5 to 1.0 wt%, Fe: 0.1-0.2 wt%, Ti: 0.1 to 0.3 wt%, Cr:0.1 to 0.3 wt%, Zr:0.1 to 0.3 wt%, Sr: 0.02-0.06 wt%, mixed rare earth RE: 0.2-0.4 wt%, the total of other inevitable impurity elements is not more than 0.15 wt%, and the balance of aluminum;
the mixed rare earth RE comprises three elements of La, Ce and Er, and the mass ratio of La to Ce to Er =1 to 1;
the yield strength of the aluminum alloy is more than 350MPa, the tensile strength is more than 400MPa, and the elongation is more than 3%.
2. The high-toughness cast aluminum alloy according to claim 1, wherein the ratio of Cu to Mg is 3:1 to 5: 1.
3. The high strength cast aluminum alloy of claim 1, wherein the sum of the Zr, Cr, and Ti contents is less than 0.7 wt%.
4. A preparation method of a high-toughness cast aluminum alloy is characterized by adopting the components of the aluminum alloy in any one of claims 1 to 3 for preparation, and comprises the following preparation steps:
1) preparing materials: weighing industrial pure aluminum, Al-Si20 intermediate alloy, pure magnesium, pure zinc, Al-50Cu intermediate alloy, Al-20Fe intermediate alloy, Al-10Zr intermediate alloy, Al-10Cr intermediate alloy, Al-5Ti intermediate alloy, Al-Sr intermediate alloy, Al-RE intermediate alloy and aluminum deslagging, degassing and refining agent according to the set chemical components according to the metering ratio, and drying the alloys and the raw materials for later use;
2) melting an aluminum ingot: putting an industrial pure aluminum ingot preheated to 150-180 ℃ into a smelting furnace for melting, wherein the melting temperature is 760-780 ℃, adding a deslagging agent accounting for 0.4-0.5% of the mass of the aluminum ingot after melting, stirring for 20-25 minutes by using a graphite stick, and preserving heat for 20-25 minutes after deslagging;
3) smelting and melt purification: cooling the melt obtained in the step 2) to 740-745 ℃, adding Al-Si20 intermediate alloy and Al-20Fe intermediate alloy, cooling to 720-725 ℃ after all the melt is melted, manually stirring for 5-6 minutes to make the components uniform, adding Al-10Zr intermediate alloy, Al-10Cr intermediate alloy, Al-5Ti intermediate alloy and Al-50Cu intermediate alloy, cooling to 690-700 ℃ after melting, adding magnesium and zinc, manually stirring for 5-6 minutes after melting, removing bottom sediment and surface scum with a filter screen after standing for 10-15 minutes, adding Al-RE intermediate alloy into the melt, manually stirring for 5-6 minutes, cooling to 690 ℃ after melting, removing bottom sediment and surface scum with the filter screen after standing for 10-15 minutes, uniformly throwing an aluminum sodium-free covering agent on the surface of the melt according to the area reference dosage of 1/square meter, wrapping an aluminum refining agent by using a pure aluminum foil, then filling the aluminum refining agent into a graphite bell jar, wherein the using amount of the refining agent is 0.2-0.5% of the mass of aluminum liquid to be treated by mass, pressing the bell jar into the deep part of the aluminum liquid, which is about 10 cm away from the bottom of the furnace, horizontally moving the bell jar to each place in the furnace, carrying out reaction accompanied by the rolling of the aluminum liquid for 4-6 minutes, and fishing floating slag and bottom sediment by using a filter screen or a slag ladle after the reaction is finished; after slagging is finished, reducing the temperature of the melt to 680-685 ℃, protecting the melt by using inert gas argon, adding an Al-Sr intermediate alloy, pressing the intermediate alloy into the bottom of a smelting furnace for melting, uniformly stirring the melt after melting, standing for 10-15 minutes, carrying out component analysis before the furnace, detecting the component content of the alloy melt, and enabling the component content of the melt with unqualified component content to reach the qualified range by a material supplementing or diluting mode;
4) degassing: heating the melt in the step 3) to 700-720 ℃, introducing argon for 5-10 minutes for degassing, skimming after degassing, standing for 10-20 minutes, and waiting for casting;
5) casting a tensile test bar: performing gravity casting on the melt obtained in the step 4), controlling the temperature of molten aluminum to be 670-680 ℃ and the temperature of a mold to be 220-250 ℃, uniformly and stably pouring molten aluminum into a mold gate during casting, enabling the molten aluminum not to flow out in the middle, cooling for 1-2 minutes after the molten aluminum of a riser is solidified after casting, and then opening the mold to avoid damage to a test rod caused by mold opening at high temperature;
6) and (3) heat treatment: carrying out solid solution and aging treatment on the aluminum alloy obtained in the step 5);
the parameters of the solid solution and the aging treatment are any one of the following parameters:
(1) solid solution parameters: keeping the temperature at 495 +/-1 ℃ for 10 +/-0.2 h, and keeping the quenching water at 70-90 ℃; aging parameters are as follows: keeping the temperature at 170 +/-1 ℃ for 8 +/-0.2 h;
(2) solid solution parameters: keeping the temperature at 480 +/-1 ℃ for 4 +/-0.2 h, keeping the temperature at 500 +/-1 ℃ for 6h, keeping the temperature at 525 +/-1 ℃ for 6h, and keeping the temperature at quenching water at 70-90 ℃; aging parameters are as follows: keeping the temperature at 175 plus or minus 1 ℃ for 7 plus or minus 0.2 h.
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