A high-strength, high-toughness, environmentally friendly aluminum-silicon series high-pressure die-casting aluminum alloy and a manufacturing method thereof

Abstract

The invention discloses a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy and a manufacturing method thereof, and a formula comprising the following components and the weight percentage of each component: 6-10wt% Si, 0.05-0.6wt% Mg, 0.01-2.0wt% Cu, 0.1-0.25wt% Fe, 0.4-0.8wt% Mn, 0.01-0.5wt% Zn, 0.02-0.14wt% Ti, 0.001-0.05wt% Sr, 0.001-0.5wt% Er / Eu; no more than 0.15wt% of inevitable inclusions; and the balance of Al. Compared with the existing as-cast high-toughness aluminum-silicon die-cast aluminum alloy with a tensile strength of 250MPa, the present invention achieves more than 10% higher toughness while the as-cast tensile strength can exceed 300MPa, and is used for lightweight and low-cost environmentally friendly manufacturing of large and ultra-large die-cast aluminum alloy components; while achieving more than 10% higher toughness, the T6 heat-treated tensile strength can exceed 420MPa, and is used for lightweight and low-cost environmentally friendly manufacturing of small and medium-sized die-cast aluminum alloy components, and is widely used in the lightweighting of the entire chain of structural parts in key areas such as automobile transportation, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of metal casting, and in particular to a high-strength, high-toughness, environmentally friendly aluminum-silicon series high-pressure die-casting aluminum alloy and a manufacturing method thereof. Background Art

[0002] Aluminum alloys have the advantages of low density, high specific strength, good thermal conductivity, corrosion resistance, easy processing and molding, and recyclability. They have been successfully used in the fields of automobile transportation, aerospace, communications and electronics, mechanical equipment, and construction. Die casting, as a large-scale and high-efficiency manufacturing process, is particularly suitable for large-scale and high-efficiency manufacturing of automobiles. At present, lightweight aluminum-silicon die-cast aluminum alloys have become the most widely used die-cast aluminum alloys due to their good fluidity, and play an increasingly important role in automobile lightweighting. Since most automotive parts made of die-cast aluminum alloys are connected by riveting, higher requirements are placed on the toughness of the die-cast aluminum alloy itself. High-strength and high-toughness aluminum-silicon die-cast aluminum alloys have gradually become key materials for lightweighting automobiles.

[0003] In recent years, with the emergence of innovative automobile manufacturing technologies such as integrated die-casting, die-cast aluminum alloy automobile parts are developing towards super-large and integrated directions with sizes above meters. Super-large die-cast aluminum alloy automobile parts such as rear floors and front engine compartments have gradually emerged, greatly reducing the original dozens to hundreds of parts to a few super-large parts, and bringing about an increase in overall stiffness and overall lightweight effects.

[0004] Due to the large and difficult to control deformation during the T6 heat treatment, it is difficult to perform T6 heat treatment strengthening on super-large die-cast aluminum alloy parts. Currently, large and super-large aluminum-silicon die-cast aluminum alloy parts are mostly used in the cast condition. While achieving a high toughness of more than 10%, the cast yield strength is only about 120MPa and the cast tensile strength is only about 250MPa, which is a bottleneck problem of low cast strength.

[0005] At present, in order to solve the above problems, expensive single fine-grain strengthening elements such as V, Zr, and Mo are used to strengthen the fine-grain strengthening effect of the α-Al matrix phase in the cast aluminum-silicon die-cast aluminum alloy. However, there are problems such as high raw material cost and single strengthening effect. Therefore, it is urgent to develop low-cost, environmentally friendly, high-strength and high-toughness die-cast aluminum alloys.

[0006] In addition, for small and medium-sized aluminum-silicon die-cast aluminum alloy automotive parts that can be strengthened by T6 heat treatment, while achieving a high toughness of more than 10%, the tensile strength in the T6 heat-treated state is difficult to exceed 350MPa. Compared with the tensile strength of more than 400MPa of current high-strength extruded deformed aluminum alloy profiles for automobiles, there is still a bottleneck problem of low strength in the T6 heat-treated state.

[0007] In summary, it is imperative to develop low-cost, environmentally friendly, cast-state high-strength and high-toughness aluminum-silicon die-cast aluminum alloys and their manufacturing methods for lightweighting large and extra-large die-cast aluminum alloy automobile parts, as well as low-cost, environmentally friendly, T6 heat-treated high-strength and high-toughness aluminum-silicon die-cast aluminum alloys and their manufacturing methods for lightweighting small and medium-sized die-cast aluminum alloy automobile parts. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems existing in the manufacturing process of the existing aluminum-silicon high-pressure die-cast aluminum alloy. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy and its manufacturing method of the present invention are different from the single α-Al phase fine grain strengthening and strengthening elements such as V, Zr, and Mo currently used. The present invention uses lower-cost Er and Eu elements to break through the comprehensive strengthening and toughening effects of α-Al phase fine grain strengthening, eutectic Si phase modification strengthening, and toughening composite strengthening. Among them, the costs of Er and Eu are approximately 7.4%, 73.9%, and 65.8% of V, Zr, and Mo, respectively, and an appropriate amount of Cu is used to achieve further strengthening, and an appropriate amount of Zn is used to improve corrosion resistance. The alloy not only has good fluidity, castability, It has good corrosion resistance and shows excellent toughness in the cast and heat-treated states. Compared with the 250MPa tensile strength of the existing cast high-toughness aluminum-silicon die-cast aluminum alloy, it achieves more than 10% higher toughness while the cast tensile strength can exceed 300MPa, which is used for lightweight and low-cost environmentally friendly manufacturing of large and ultra-large die-cast aluminum alloy components; while achieving more than 10% higher toughness, the T6 heat-treated tensile strength can exceed 420MPa, which is used for lightweight and low-cost environmentally friendly manufacturing of small and medium-sized die-cast aluminum alloy components, and is widely used in the lightweighting of the entire chain of structural parts in key areas such as automobile transportation, and has good application prospects.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy, comprising the following components and the weight percentage of each component:

[0011] 6-10wt% Si, 0.05-0.6wt% Mg, 0.01-2.0wt% Cu, 0.1-0.25wt% Fe, 0.4-0.8wt% Mn, 0.01-0.5wt% Zn, 0.02-0.14wt% Ti, 0.001-0.05wt% Sr, 0.001-0.5wt% Er / Eu;

[0012] Unavoidable inclusions not exceeding 0.15wt%;

[0013] and the balance Al.

[0014] Preferably, the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for cast form includes the following components and the weight percentage of each component:

[0015] 7-9wt% Si, 0.05-0.5wt% Mg, 0.01-1.0wt% Cu, 0.1-0.25wt% Fe, 0.5-0.65wt% Mn, 0.01-0.3wt% Zn, 0.06-0.14wt% Ti, 0.01-0.02wt% Sr, 0.001-0.4wt% Er / Eu;

[0016] Unavoidable inclusions not exceeding 0.15wt%;

[0017] and the balance Al.

[0018] Preferably, the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for cast form includes the following components and the weight percentage of each component:

[0019] 7-9wt% Si, 0.05-0.3wt% Mg, 0.05-0.8wt% Cu, 0.1-0.25wt% Fe, 0.5-0.65wt% Mn, 0.05-0.15wt% Zn, 0.06-0.14wt% Ti, 0.01-0.02wt% Sr, 0.1-0.4wt% Er / Eu;

[0020] Unavoidable inclusions not exceeding 0.15wt%;

[0021] and the balance Al.

[0022] Preferably, the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for heat treatment includes the following components and the weight percentage of each component:

[0023] 7-10wt% Si, 0.05-0.5wt% Mg, 0.01-2.0wt% Cu, 0.1-0.25wt% Fe, 0.5-0.65wt% Mn, 0.01-0.3wt% Zn, 0.06-0.14wt% Ti, 0.01-0.02wt% Sr, 0.001-0.4wt% Er / Eu;

[0024] Unavoidable inclusions not exceeding 0.15wt%;

[0025] and the balance Al.

[0026] Preferably, the mass ratio of Er to Eu in Er / Eu is in the range of 2:1 to 4:1.

[0027] Preferably, the Si raw material is provided in the form of Si powder or Al-Si master alloy; the Al, Mg, Cu, and Zn raw materials are provided in the form of pure metal blocks, wherein Cu is in the form of filament blocks; the Mn, Ti, Sr, Er, and Eu raw materials are provided in the form of Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy, and Al-Eu master alloy, respectively, and meet the weight percentage requirements of Al, Si, Mg, Cu, Fe, Mn, Zn, Ti, Sr, Er / Eu components in the high-strength, high-toughness, and environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy.

[0028] The manufacture of a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for cast form comprises the following steps:

[0029] Step (A1), weighing Al powder and Si powder according to a stoichiometric ratio or selecting an Al-Si master alloy according to a stoichiometric ratio, and performing a smelting treatment at 660-690° C. for 0.5-3 h to form an Al-Si melt;

[0030] Step (B1), weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, weighing thin wire blocks of Cu according to a stoichiometric ratio, and selecting Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy and Al-Eu master alloy according to a stoichiometric ratio to add to the Al-Si melt obtained in step (A1) to obtain a precast melt;

[0031] Step (C1), heating the precast melt obtained in step (B1) to 700-740°C, and refining the precast melt for 5-15 minutes in a nitrogen or argon atmosphere and a refining agent to remove gas and inclusions in the precast melt to obtain a purified cast melt, wherein the refining agent is 25% Na2SiF6 + 75% C2Cl6;

[0032] Step (D1), subjecting the purified cast melt obtained in step (C1) to die casting to obtain a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy in cast form.

[0033] Preferably, step (D1) obtains a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy in a cast state, which can be used for secondary processing of large and ultra-large die-cast aluminum alloy components:

[0034] Among them, the yield strength of 6.35mm thick-walled large and super-large die-cast aluminum alloy components is 140-165MPa, the tensile strength is 280-315MPa, and the elongation is 10-16%;

[0035] The yield strength of 2-4mm medium-thin-wall large and super-large die-cast aluminum alloy components is 145-180MPa, the tensile strength is 290-340MPa, and the elongation is 10-16%.

[0036] The manufacture of a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for heat treatment specifically comprises the following steps:

[0037] Step (A2), weighing Al powder and Si powder according to a stoichiometric ratio or selecting an Al-Si master alloy according to a stoichiometric ratio, and performing a smelting treatment at 660-690° C. for 0.5-3 h to form an Al-Si melt;

[0038] Step (B2), weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, weighing thin wire blocks of Cu according to a stoichiometric ratio, and selecting Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy and Al-Eu master alloy according to a stoichiometric ratio to add to the Al-Si melt obtained in step (A2) to obtain a prefabricated heat-treated melt;

[0039] Step (C2), heating the prefabricated heat-treated melt obtained in step (B2) to 700-740°C, and refining the melt for 5-15 minutes in a nitrogen or argon atmosphere and a refining agent to remove gas and inclusions in the prefabricated heat-treated melt to obtain a purified heat-treated melt, wherein the refining agent is 25% Na2SiF6 + 75% C2Cl6;

[0040] Step (D2), performing die casting on the purified heat-treated melt obtained in step (C2) to obtain a die-cast aluminum alloy to be heat-treated;

[0041] Step (E2), performing T6 heat treatment on the die-cast aluminum alloy to be heat treated obtained in step (D2), including solution treatment at 470-510°C for 15-45 minutes, hot water quenching at 60-80°C for 1-10 minutes, and aging treatment at 150-190°C for 4-20 hours, to obtain a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy in a heat-treated state.

[0042] Preferably, in step (E2), the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy in a heat-treated state can be used for secondary processing of medium and small die-cast aluminum alloy components:

[0043] Among them, the yield strength of 6.35mm thick-walled medium and small die-cast aluminum alloy components is 300-350MPa, the tensile strength is 400-450MPa, and the elongation is 10-16%;

[0044] The yield strength of 2-4mm medium and small thin-walled die-cast aluminum alloy components is 320-380MPa, the tensile strength is 420-480MPa, and the elongation is 10-16%.

[0045] The beneficial effects of the present invention are as follows: the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy and the manufacturing method thereof can produce lightweight, low-cost, environmentally friendly cast-state high-strength, high-toughness aluminum-silicon die-cast aluminum alloys required for large and super-large die-cast aluminum alloy automobile parts; and can also produce lightweight, low-cost, environmentally friendly T6 heat-treated state high-strength, high-toughness aluminum-silicon die-cast aluminum alloys required for small and medium-sized die-cast aluminum alloy automobile parts, and have the following characteristics:

[0046] (1) Existing aluminum-silicon high-toughness die-cast aluminum alloys use relatively expensive single fine-grain strengthening elements such as V, Zr, and Mo to enhance the fine-grain strengthening effect of the α-Al phase, which has the problems of high raw material cost and single strengthening effect. The present invention uses lower-cost Er and Eu elements to break through the comprehensive strengthening and toughening effect of α-Al phase fine-grain strengthening, eutectic Si phase modification strengthening and toughening composite strengthening. It has low cost and meets the requirements of green environmental protection. The cost of Er and Eu is approximately 7.4%, 73.9% and 65.8% of that of V, Zr and Mo, respectively, which is convenient for wide promotion.

[0047] (2) In view of the problem that the current technical path for achieving lightweighting by aluminum alloy die-casting in automobiles and other products is unclear, the present invention produces lightweight, low-cost, environmentally friendly cast high-strength and high-toughness aluminum-silicon die-cast aluminum alloys required for large and ultra-large die-cast aluminum alloy automobile parts, and can also produce lightweight, low-cost, environmentally friendly T6 heat-treated high-strength and high-toughness aluminum-silicon die-cast aluminum alloys required for small and medium-sized die-cast aluminum alloy automobile parts, thereby achieving full-chain lightweighting of die-cast aluminum alloy parts in automobiles and other products.

[0048] (3) In view of the problem that the current aluminum-silicon high-toughness die-cast aluminum alloy has insufficient strength, the present invention can realize a low-cost aluminum-silicon high-pressure die-cast aluminum alloy with high strength and toughness in both the cast and heat-treated forms, wherein the uses of various chemical elements are as follows: Si is used to improve fluidity; Mg is used to strengthen the alloy; Cu is used to strengthen the alloy; Fe is used to control the content of Fe to be above 0.1 to avoid high-purity aluminum configuration alloy and reduce the cost of alloy raw materials; it is controlled to be below 0.25 to reduce the content of long strip-shaped brittle β-Fe phase and ensure the high toughness of the alloy; Mn is used to improve the viscosity of the alloy and improve the morphology of the Fe phase; Zn is used to improve the corrosion resistance of the alloy; Ti is used to hinder grain growth and refine the grains; Sr is a metamorphic element that refines the eutectic Si phase, improves the morphology of the eutectic Si phase, and improves the strength and toughness of the alloy; Er / Eu, relatively low-cost Er and Eu, effectively and synergistically enhance the α-Al phase fine grain strengthening effect, enhance the eutectic Si phase modification strengthening and toughening effect, synergistically improve the strength and toughness of the alloy while reducing the cost of raw materials.

[0049] (4) Existing aluminum-silicon high-toughness die-cast aluminum alloys have the problem of insufficient as-cast strength. While achieving a high toughness of more than 10%, the as-cast yield strength is only 120 MPa and the tensile strength is only 250 MPa. The alloy manufactured by the present invention can achieve a high toughness of more than 10% while the as-cast tensile strength can exceed 300 MPa, and can be used for lightweight manufacturing of large and ultra-large die-cast aluminum alloy components.

[0050] (5) Existing aluminum-silicon high-toughness die-cast aluminum alloys have the problem of insufficient strength in the heat-treated state. While achieving a high toughness of more than 10%, the tensile strength in the heat-treated state is difficult to exceed 350 MPa, which is not as good as the tensile strength of more than 400 MPa of high-strength extruded aluminum alloy profiles for automobiles. The alloy manufactured by the present invention can achieve a high toughness of more than 10% and a tensile strength of more than 420 MPa in the T6 heat-treated state, which can be used for lightweight manufacturing of small and medium-sized die-cast aluminum alloy components. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is the effect diagram of α-Al phase grain refinement under normal conditions.

[0052] Figure 2 This is a diagram showing the grain refinement and strengthening effect of the α-Al phase based on the composite of Er and Eu.

[0053] Figure 3 This is a diagram showing the modification and refinement effect of the eutectic Si phase under normal conditions.

[0054] Figure 4 This is a diagram showing the modification, refinement and strengthening effect of the eutectic Si phase based on the composite of Er and Eu.

[0055] Figure 5It is a specific manufacturing flow chart of the present invention regarding the die-cast aluminum alloy components in two forms, namely, the cast state and the heat-treated state. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with the accompanying drawings.

[0057] The high-strength, high-toughness and environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy of the present invention comprises the following components and the weight percentage of each component: 6-10wt% Si, 0.05-0.6wt% Mg, 0.01-2.0wt% Cu, 0.1-0.25wt% Fe, 0.4-0.8wt% Mn, 0.01-0.5wt% Zn, 0.02-0.14wt% Ti, 0.001-0.05wt% Sr, 0.001-0.5wt% Er / Eu; no more than 0.15wt% of unavoidable inclusions; and the balance Al.

[0058] The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy suitable for cast form (the lightweight, low-cost, environmentally friendly cast high-strength, high-toughness aluminum-silicon die-cast aluminum alloy required for large and super-large die-cast aluminum alloy automobile parts) includes the following components and the weight percentage of each component:

[0059] 7-9wt% Si, 0.05-0.5wt% Mg, 0.01-1.0wt% Cu, 0.1-0.25wt% Fe, 0.5-0.65wt% Mn, 0.01-0.3wt% Zn, 0.06-0.14wt% Ti, 0.01-0.02wt% Sr, 0.001-0.4wt% Er / Eu; not more than 0.15wt% unavoidable inclusions; and the balance Al;

[0060] Further optimization selection, 7-9wt% Si, 0.05-0.3wt% Mg, 0.05-0.8wt% Cu, 0.1-0.25wt% Fe, 0.5-0.65wt% Mn, 0.05-0.15wt% Zn, 0.06-0.14wt% Ti, 0.01-0.02wt% Sr, 0.1-0.4wt% Er / Eu; no more than 0.15wt% unavoidable inclusions; and the balance Al.

[0061] A high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for heat treatment (a lightweight, low-cost, environmentally friendly T6 heat-treated high-strength, high-toughness aluminum-silicon die-casting aluminum alloy required for small and medium-sized die-casting aluminum alloy automobile parts) includes the following components and the weight percentage of each component: 7-10wt% Si, 0.05-0.5wt% Mg, 0.01-2.0wt% Cu, 0.1-0.25wt% Fe, 0.5-0.65wt% Mn, 0.01-0.3wt% Zn, 0.06-0.14wt% Ti, 0.01-0.02wt% Sr, 0.001-0.4wt% Er / Eu; no more than 0.15wt% of unavoidable inclusions; and the balance Al.

[0062] In the above-mentioned high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy formulas, the mass ratio of Er to Eu in Er / Eu ranges from 2:1 to 4:1. This is because the existing aluminum-silicon high-toughness die-casting aluminum alloys use relatively expensive single fine-grain strengthening elements such as V, Zr, and Mo to enhance the α-Al phase fine-grain strengthening effect, which has the problems of high raw material cost and single strengthening effect. The present invention uses lower-cost Er and Eu elements to break through the comprehensive strengthening and toughening effect of α-Al phase fine-grain strengthening, eutectic Si phase modification strengthening and toughening composite strengthening, which is low in cost and meets the requirements of green environmental protection. Figure 1 and 2 As shown: Figure 1 This is the effect diagram of α-Al phase grain refinement under normal conditions. Figure 2 This is a diagram showing the grain refinement and strengthening effect of the α-Al phase based on the composite of Er and Eu; Figure 3 and 4 As shown: Figure 3 This is the modification and refinement effect diagram of eutectic Si phase under normal conditions. Figure 4The figure shows the modification and refinement effect of the eutectic Si phase based on the Er and Eu composite. The addition of Er and Eu has obvious effects on the grain refinement of the α-Al phase and the modification and refinement of the eutectic Si phase. The more specific description is as follows: the addition of Er can form Al3Er particles in the Al melt, which have the same cubic structure as Al, and its lattice constant of 0.4212 nm is very close to that of Al, which is 0.4049 nm. It can serve as a heterogeneous nucleation center of the α-Al phase, promote the nucleation of the α-Al phase, and then refine the α-Al phase. The addition of Er and Eu can form clusters rich in Er and Eu in the Al-Si melt, which are adsorbed on the growth steps of the eutectic Si phase, hindering the eutectic Si phase from growing from the steps to coarse and brittle lamellar shapes, and the eutectic Si phase grows into fine and tougher fibers; at the same time, the addition of Er and Eu can form a large number of fine Al2Si2Er and Al2Si2Eu particles in the Al-Si melt, further hindering the growth of the eutectic Si phase; thereby achieving the metamorphic strengthening and toughening of the eutectic Si phase. In particular, the present invention can find that Er can simultaneously achieve the fine grain strengthening of the α-Al phase, the metamorphic strengthening and toughening of the eutectic Si phase; Eu's ability to refine the α-Al phase is not as good as Er, but Eu's ability to metamorphically strengthen and toughen the eutectic Si phase is higher than Er. Therefore, the present invention selects Er and Eu for synergistic addition, thereby effectively and synergistically strengthening the fine grain strengthening effect of the α-Al phase and the metamorphic strengthening and toughening effect of the eutectic Si phase.

[0063] The specific selection and effects of other metal elements in the present invention are explained as follows: the addition of Si can reduce the viscosity of Al liquid and thus improve fluidity; the addition of Mg can be dissolved in the Al matrix to achieve solid solution strength, and at the same time form Mg-Si, Al-Si-Mg-Cu compounds to achieve second phase strengthening; the addition of Cu can be dissolved in the Al matrix to achieve solid solution strength, and at the same time form Al-Cu, Al-Si-Mg-Cu compounds to achieve second phase strengthening; the addition of Fe is controlled to be above 0.1 to avoid high-purity aluminum configuration alloy and reduce the cost of alloy raw materials; it is controlled to be below 0.25 to reduce the content of long strip-shaped brittle β-Fe phase and ensure the high toughness of the alloy; the addition of Mn can improve the viscosity of the alloy, and at the same time improve the morphology of the Fe phase and improve the toughness of the alloy; the addition of Zn can form a nano-scale passivation film, thereby improving the corrosion resistance of the alloy; the addition of Ti can hinder the growth of α-Al grains, thereby refining the α-Al grains; the addition of Sr can refine the eutectic Si phase, improve the morphology of the eutectic Si phase, and improve the strength and toughness of the alloy.

[0064] Preferably, the sources of the above-mentioned metal elements are as follows: the Si raw material is provided in the form of Si powder or Al-Si master alloy; the Al, Mg, Cu, and Zn raw materials are provided in the form of pure metal blocks, wherein Cu is in the form of filament blocks, and Cu is refractory, so filament blocks are selected; the Mn, Ti, Sr, Er, and Eu raw materials are provided in the form of Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy, and Al-Eu master alloy, respectively, and meet the requirements of Al, Si, Mg, Cu, Fe, Mn, Zn, Ti, Sr, and Er in high-strength, high-toughness, and environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy. The weight percentage requirements of each Er / Eu component, the grades of the Al-Si master alloy, Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy, and Al-Eu master alloy can be selected from the corresponding raw material grades in the prior art, as long as the Al master alloy contains relevant metal elements and meets the weight percentage requirements of each component.

[0065] The manufacturing method of the high-strength, high-toughness and environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for the cast state of the present invention comprises the following steps:

[0066] Step (A1), weighing Al powder and Si powder according to a stoichiometric ratio or selecting an Al-Si master alloy according to a stoichiometric ratio, and performing a smelting treatment at 660-690° C. for 0.5-3 h to form an Al-Si melt;

[0067] Step (B1), weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, weighing thin wire blocks of Cu according to a stoichiometric ratio, and selecting Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy and Al-Eu master alloy according to a stoichiometric ratio to add to the Al-Si melt obtained in step (A1) to obtain a precast melt;

[0068] Step (C1), heating the precast melt obtained in step (B1) to 700-740°C, and refining the precast melt for 5-15 minutes in a nitrogen or argon atmosphere and a refining agent to remove gas and inclusions in the precast melt to obtain a purified cast melt, wherein the refining agent is 25% Na2SiF6 + 75% C2Cl6, and the refining agent can absorb gas and slag in the aluminum liquid to enhance the degassing and deslagging effects;

[0069] Step (D1), subjecting the purified cast melt obtained in step (C1) to die-casting to obtain a cast high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy, which can be used for secondary processing of large and ultra-large die-cast aluminum alloy components: wherein the yield strength of 6.35 mm thick-walled large and ultra-large die-cast aluminum alloy components is 140-165 MPa, the tensile strength is 280-315 MPa, and the elongation is 10-16%; the yield strength of 2-4 mm medium-thin-walled large and ultra-large die-cast aluminum alloy components is 145-180 MPa, the tensile strength is 290-340 MPa, and the elongation is 10-16%.

[0070] The manufacturing method of the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy suitable for heat treatment state of the present invention specifically comprises the following steps:

[0071] Step (A2), weighing Al powder and Si powder according to a stoichiometric ratio or selecting an Al-Si master alloy according to a stoichiometric ratio, and performing a smelting treatment at 660-690° C. for 0.5-3 h to form an Al-Si melt;

[0072] Step (B2), weighing pure metal blocks of Mg and Zn according to a stoichiometric ratio, weighing thin wire blocks of Cu according to a stoichiometric ratio, and selecting Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy and Al-Eu master alloy according to a stoichiometric ratio to add to the Al-Si melt obtained in step (A2) to obtain a prefabricated heat-treated melt;

[0073] Step (C2), heating the prefabricated heat-treated melt obtained in step (B2) to 700-740°C, and refining the melt for 5-15 minutes in a nitrogen or argon atmosphere and a refining agent to remove gas and inclusions in the prefabricated heat-treated melt to obtain a purified heat-treated melt, wherein the refining agent is 25% Na2SiF6+ 75% C2Cl6, and the refining agent can absorb gas and slag in the aluminum liquid to enhance the degassing and deslagging effects;

[0074] Step (D2), performing die casting on the purified heat-treated melt obtained in step (C2) to obtain a die-cast aluminum alloy to be heat-treated;

[0075] Step (E2), performing T6 heat treatment on the die-cast aluminum alloy to be heat treated obtained in step (D2), including solution treatment at 470-510°C for 15-45min, hot water quenching at 60-80°C for 1-10min, and aging treatment at 150-190°C for 4-20h, to obtain a high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-cast aluminum alloy in a heat-treated state, which can be used for secondary processing of medium and small die-cast aluminum alloy components: wherein the yield strength of 6.35mm thick-walled medium and small die-cast aluminum alloy components is 300-350MPa, the tensile strength is 400-450MPa, and the elongation is 10-16%; the yield strength of 2-4mm medium and thin-walled medium and small die-cast aluminum alloy components is 320-380MPa, the tensile strength is 420-480MPa, and the elongation is 10-16%.

[0076] like Figure 5 As shown, the present invention is a flowchart of the whole chain (small, medium, large and extra-large) of the manufacturing method of high-strength and high-toughness aluminum-silicon series high-pressure die-casting aluminum alloy in both cast and heat-treated forms, which is used to make die-casting aluminum alloy parts lightweight, low-cost and environmentally friendly.

[0077] The following describes the specific embodiments and test results of the high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy and its manufacturing method according to the present invention:

[0078] 1. About the Cast Tensile Properties Test

[0079] Example 1: Die-cast aluminum alloy component with a wall thickness of 3 mm, alloy weight percentage composition (unit: wt%):

[0080] 7.2Si, 0.15Mg, 0.1Cu, 0.15Fe, 0.6Mn, 0.1Zn, 0.12Ti, 0.015Sr, 0.15(Er,Eu), balance Al.

[0081] Example 2: Die-cast aluminum alloy component with a wall thickness of 6.35 mm, alloy weight percentage composition (unit: wt%):

[0082] 7.4Si, 0.15Mg, 0.15Cu, 0.15Fe, 0.6Mn, 0.1Zn, 0.12Ti, 0.015Sr, 0.15(Er,Eu), balance Al.

[0083] Example 3: Die-cast aluminum alloy component with a wall thickness of 3 mm, alloy weight percentage composition (unit: wt%):

[0084] 8.7Si, 0.25Mg, 0.5Cu, 0.15Fe, 0.6Mn, 0.1Zn, 0.12Ti, 0.015Sr, 0.25(Er,Eu), balance Al.

[0085] Example 4: Die-cast aluminum alloy component with a wall thickness of 6.35 mm, alloy weight percentage composition (unit: wt%):

[0086] 8.7Si, 0.2Mg, 0.3Cu, 0.15Fe, 0.6Mn, 0.1Zn, 0.12Ti, 0.015Sr, 0.25(Er,Eu), balance Al;

[0087] The formulas of existing process 1 (wall thickness 3 mm) and existing process 2 (wall thickness 6.35 mm) are 7.0Si, 0.2Mg, 0.15Fe, 0.62Mn, 0.1Ti, 0.014Sr, 0.3V, and the balance Al (unit: wt%).

[0088]

[0089] 2. About the tensile properties of heat-treated state

[0090] Example 5: Die-cast aluminum alloy component with a wall thickness of 3 mm, alloy weight percentage composition (unit: wt%):

[0091] 8.5Si, 0.3Mg, 1.4Cu, 0.15Fe, 0.6Mn, 0.3Zn, 0.12Ti, 0.015Sr, 0.2(Er,Eu), balance Al;

[0092] T6 heat treatment process: solution treatment at 480ºC@30Min, hot water quenching at 70ºC, aging at 180ºC@10h.

[0093] Example 6: Die-cast aluminum alloy component with a wall thickness of 6.35 mm, alloy weight percentage composition (unit: wt%):

[0094] 8.7Si, 0.3Mg, 1.2Cu, 0.15Fe, 0.6Mn, 0.3Zn, 0.12Ti, 0.015Sr, 0.2(Er,Eu), balance Al;

[0095] T6 heat treatment process: solution treatment at 500ºC@30Min, hot water quenching at 70ºC, aging at 180ºC@10h.

[0096] Existing process 1 (wall thickness 3 mm) and existing process 2 (wall thickness 6.35 mm) alloy weight percentage composition (unit wt%): 10.0Si, 0.3Mg, 0.15Fe, 0.65Mn, 0.13Ti, 0.018Sr, and the balance Al.

[0097] T6 heat treatment process is slightly advanced: solution treatment 525ºC@30Min, 70ºC hot water quenching, aging 170ºC@10h.

[0098]

[0099] As shown in Table 1 and Table 2, the tensile properties of the cast state of Examples 1-4 and the existing process 1-2 of the present invention; the tensile properties of the T6 heat-treated state of Examples 5-6 and the existing process 1-2, compared with the 250MPa tensile strength of the existing cast high-toughness aluminum-silicon die-cast aluminum alloy, the cast tensile strength can exceed 300MPa while achieving more than 10% high toughness, which is used for lightweight and low-cost environmentally friendly manufacturing of large and ultra-large die-cast aluminum alloy components; while achieving more than 10% high toughness, the tensile strength of the T6 heat-treated state can exceed 420MPa, which is used for lightweight and low-cost environmentally friendly manufacturing of small and medium-sized die-cast aluminum alloy components, and is widely used in the lightweighting of the entire chain of structural parts in key areas such as automobile transportation, and has the following characteristics:

[0100] (1) The existing aluminum-silicon series high-toughness die-cast aluminum alloys use relatively expensive single fine-grain strengthening elements such as V, Zr, and Mo to enhance the fine-grain strengthening effect of the α-Al phase, which has the problems of high raw material cost and single strengthening effect. The present invention uses lower-cost Er and Eu elements to break through the comprehensive strengthening and toughening effect of α-Al phase fine-grain strengthening, eutectic Si phase modification strengthening and toughening composite strengthening. It has low cost, meets the requirements of green environmental protection, and is easy to promote widely.

[0101] (2) In view of the problem that the current technical path for achieving lightweighting by aluminum alloy die-casting in automobiles and other products is unclear, the present invention produces lightweight, low-cost, environmentally friendly cast high-strength and high-toughness aluminum-silicon die-cast aluminum alloys required for large and ultra-large die-cast aluminum alloy automobile parts, and can also produce lightweight, low-cost, environmentally friendly T6 heat-treated high-strength and high-toughness aluminum-silicon die-cast aluminum alloys required for small and medium-sized die-cast aluminum alloy automobile parts, thereby achieving full-chain lightweighting of die-cast aluminum alloy parts in automobiles and other products.

[0102] (3) In view of the problem that the current aluminum-silicon high-toughness die-cast aluminum alloy has insufficient strength, the present invention can realize a low-cost aluminum-silicon high-pressure die-cast aluminum alloy with high strength and toughness in both the cast and heat-treated forms, wherein the uses of various chemical elements are as follows: Si is used to improve fluidity; Mg is used to strengthen the alloy; Cu is used to strengthen the alloy; Fe is used to control the content of Fe to be above 0.1 to avoid high-purity aluminum configuration alloy and reduce the cost of alloy raw materials; it is controlled to be below 0.25 to reduce the content of long strip-shaped brittle β-Fe phase and ensure the high toughness of the alloy; Mn is used to improve the viscosity of the alloy and improve the morphology of the Fe phase; Zn is used to improve the corrosion resistance of the alloy; Ti is used to hinder grain growth and refine the grains; Sr is a metamorphic element that refines the eutectic Si phase, improves the morphology of the eutectic Si phase, and improves the strength and toughness of the alloy; Er / Eu, relatively low-cost Er and Eu, effectively and synergistically enhance the α-Al phase fine grain strengthening effect, enhance the eutectic Si phase modification strengthening and toughening effect, synergistically improve the strength and toughness of the alloy while reducing the cost of raw materials.

[0103] (4) Existing aluminum-silicon high-toughness die-cast aluminum alloys have the problem of insufficient as-cast strength. While achieving a high toughness of more than 10%, the as-cast yield strength is only 120 MPa and the tensile strength is only 250 MPa. The alloy manufactured by the present invention can achieve a high toughness of more than 10% while the as-cast tensile strength can exceed 300 MPa, and can be used for lightweight manufacturing of large and ultra-large die-cast aluminum alloy components.

[0104] (5) Existing aluminum-silicon high-toughness die-cast aluminum alloys have the problem of insufficient strength in the heat-treated state. While achieving a high toughness of more than 10%, the tensile strength in the heat-treated state is difficult to exceed 350 MPa, which is not as good as the tensile strength of more than 400 MPa of high-strength extruded aluminum alloy profiles for automobiles. The alloy manufactured by the present invention can achieve a high toughness of more than 10% and a tensile strength of more than 420 MPa in the T6 heat-treated state, which can be used for lightweight manufacturing of small and medium-sized die-cast aluminum alloy components.

[0105] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy, characterized in that: Its components by mass percentage are as follows: Si 6~10wt%, Mg 0.05~0.6wt%, Cu 0.01~2.0wt%, Fe 0.1~0.25wt%, Mn 0.4~0.8wt%, Zn 0.01~0.5wt%, Ti 0.02~0.14wt%, Sr 0.001~0.05wt% Er and Eu 0.001~0.5wt%, Unavoidable inclusions not exceeding 0.15wt%; The balance is Al; Among them, the mass ratio between Er and Eu is 2:1 to 4:

1.

2. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy according to claim 1 is characterized in that: The aluminum alloy composition includes: The raw material of Si is Si powder or Al-Si master alloy; The raw materials of Al, Mg, Cu and Zn are pure metal blocks; The raw materials of Fe, Mn, Ti, Sr, Er and Eu are respectively Al-Fe master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-Sr master alloy, Al-Er master alloy and Al-Eu master alloy.

3. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy according to claim 2 is characterized in that: When the die-cast aluminum alloy is a cast aluminum alloy, its components are as follows by mass percentage: Si 7~9wt%, Mg 0.05~0.5wt%, Cu 0.01~1.0wt%, Fe 0.1~0.25wt%, Mn 0.5~0.65wt%, Zn 0.01~0.3wt%, Ti 0.06~0.14wt%, Sr 0.01~0.02wt% Er and Eu 0.001~0.4wt%, Unavoidable inclusions not exceeding 0.15wt%; The balance is Al.

4. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy according to claim 3 is characterized in that: When the die-cast aluminum alloy is a cast aluminum alloy, its components are as follows by mass percentage: Si 7~9wt%, Mg 0.05~0.3wt%, Cu 0.05~0.8wt%, Fe 0.1~0.25wt%, Mn 0.5~0.65wt%, Zn 0.05~0.15wt%, Ti 0.06~0.14wt%, Sr 0.01~0.02wt% Er and Eu 0.001~0.4wt%, Unavoidable inclusions not exceeding 0.15wt%; The balance is Al.

5. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy according to claim 3 or 4, characterized in that: The cast aluminum alloy, For large and super-large pressed aluminum alloy components with a thickness of 6.35 mm, the yield strength is 140-165 MPa, the tensile strength is 280-315 MPa, and the elongation is 10-16%; For large and extra-large pressed aluminum alloy components with a thick wall of 2 to 4 mm, the yield strength is 145 to 180 MPa, the tensile strength is 290 to 340 MPa, and the elongation is 10 to 16%.

6. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy according to claim 2, characterized in that: When the die-cast aluminum alloy is in a heat-treated state, its components are as follows by mass percentage: Si 7~10wt%, Mg 0.05~0.5wt%, Cu 0.01~2.0wt%, Fe 0.1~0.25wt%, Mn 0.5~0.65wt%, Zn 0.01~0.3wt%, Ti 0.06~0.14wt%, Sr 0.01~0.02wt% Er and Eu 0.001~0.4wt%, Unavoidable inclusions not exceeding 0.15wt%; The balance is Al.

7. The high-strength, high-toughness, environmentally friendly aluminum-silicon high-pressure die-casting aluminum alloy according to claim 6, characterized in that: The heat-treated aluminum alloy, For medium and small aluminum alloy components with a thickness of 6.35mm, the yield strength is 300-350MPa, the tensile strength is 400-450MPa, and the elongation is 10-16%; For medium and small aluminum alloy components with a thick wall of 2 to 4 mm, the yield strength is 320 to 380 MPa, the tensile strength is 420 to 480 MPa, and the elongation is 10 to 16%.

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