NON-HEAT-TREATED HIGH-TOUGHNESS DIE-CASTING ALUMINUM-SILICON ALLOY AND PREPARATION METHOD THEREFOR

Abstract

This invention discloses a non-heat treatable die-cast aluminum-silicon (AlSi) alloy with high toughness and its preparation method. By controlling the Mn/Fe ratio to a specific value, the adverse effects of Fe in the alloy can be effectively suppressed. In addition, a certain proportion of rare earth elements are introduced into the alloy to effectively refine the Si and form high-temperature phases with elements such as Al and Cu, therefore improving the deformation resistance of the alloy when applied to one-piece die-cast large-scale structural parts. When taking specimens from the casting after die casting for testing, the specimens have the following properties: tensile strength 290 Mpa, yield strength 140 Mpa, and elongation 13%. The alloy also has excellent die-cast molding performance, and the energy used is clean, which meets low-carbon emission standards.

Claims

1. A non-heat treated die-cast AlSi alloy consisting of the following components, in percent by weight: Si: 6.3-8.3%; Fe: 0.07-0.45%; Cu: 0.05-0.5%; Mn: 0.5-0.8%; Mg: 0.15-0.35%; Ti: 0.01-0.2%; Sr 0.015-0.035%; rare earth elements: 0.04%-0.2%; Ni: 0.001-0.1%; Zn: 0.005-0.1%; Ga: 0.01-0.03%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al; and wherein the rare earth elements include at least one of La, Ce, and Sc.

2. The non-heat treated die-cast AlSi alloy according to claim 1, consisting of the following components (in percent by weight): Si: 6.3-7.0%; Fe: 0.2-0.4%; Cu: 0.35-0.45%; Mn: 0.5-0.8%; Mg: 0.25-0.35%; Ti: 0.1-0.2%; Sr 0.015-0.035%; rare earth elements: 0.04%-0.2%; Ni: 0.001-0.1%; Zn: 0.005-0.1%; Ga: 0.01-0.03%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al; and wherein the rare earth elements include at least one of La, Ce, and Sc.

3. The non-heat treated die-cast AlSi alloy according to claim 1, consisting of the following components (in percent by weight): Si: 6.4-7.1%; Fe: 0.10-0.25%; Cu: 0.05-0.28%; Mn: 0.5-0.8%; Mg: 0.25-0.35%; Ti: 0.03-0.16%; Sr 0.025-0.035%; rare earth elements: 0.04%-0.15%; Ni: 0.001-0.1%; Zn: 0.005-0.1%; Ga: 0.01-0.03%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al; and wherein the rare earth elements include at least one of La, Ce, and Sc.

4. The non-heat treated die-cast AlSi alloy according to claim 1, consisting of the following components (in percent by weight): Si: 7.0-7.7%; Fe: 0.15-0.3%; Cu: 0.2-0.35%; Mn: 0.6-0.8%; Mg: 0.2-0.3%; Ti: 0.05-0.2%; Sr 0.015-0.035%; rare earth elements: 0.04%-0.2%; Ni: 0.001-0.1%; Zn: 0.005-0.1%; Ga: 0.01-0.03%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al; and wherein the rare earth elements include at least one of La, Ce, and Sc.

5. The non-heat treated die-cast AlSi alloy with high toughness according to claim 1, is characterized in that the die-cast AlSi alloy consists of the following components (in percent by weight): Si: 7.7-8.3%; Fe: 0.07-0.2%; Cu: 0.05-0.2%; Mn: 0.6-0.8%; Mg: 0.15-0.3%; Ti: 0.01-0.15%; Sr: 0.015-0.035%; rare earth elements: 0.04%-0.2% (the rare earth elements include at least one of La/Ce/Sc); Ni: 0.001-0.1%; Zn: 0.005-0.1%; Ga: 0.01-0.03%; the total amount of other impurities shall be less than or equal to 0.2%, and the balance is Al.

6. The non-heat treated die-cast AlSi alloy according to claim 1, wherein the die-cast AlSi alloy has a tensile strength greater than or equal to 270 Mpa, a yield strength greater than or equal to 130 Mpa, and an elongation greater than or equal to 11%.

7. A method for preparing the non-heat treatable treated die-cast AlSi alloy with high toughness according to claim 1, comprising the following ordered steps: heating and melting the components not easy to cause burning loss to obtain a molten aluminum alloy; de-slagging and refining the molten aluminum alloy before adding the components that are easy to cause burning loss; after the composition reaches the specified value, pouring the molten alloy into molds to obtain the die-cast AlSi alloy.

8. The method according to claim 7, wherein the molten alloy is die-cast at a die-casting temperature is of 680-720 C., a die-casting speed of 2.5-5 m/s, and a holding time is of 2-10 s.

9. The method according to claim 7, further comprising the following steps: after all of the components are completely melted, the molten aluminum alloy is stirred well, left to stand and then sampled and analyzed, and then adjusting the weight percentage of the components to the required composition range.

10. The method according to claim 7, further comprising using a refining agent that does not contain Na ions.

11. The non-heat treatable die-cast AlSi alloy according to claim 2, wherein the die-cast AlSi alloy has a tensile strength greater than or equal to 270 Mpa, a yield strength greater than or equal to 130 Mpa, and an elongation greater than or equal to 11%.

12. The non-heat treatable die-cast AlSi alloy according to claim 3, wherein the die-cast AlSi alloy has a tensile strength greater than or equal to 270 Mpa, a yield strength greater than or equal to 130 Mpa, and an elongation greater than or equal to 11%.

13. The non-heat treatable die-cast AlSi alloy according to claim 4, wherein the die-cast AlSi alloy has a tensile strength greater than or equal to 270 Mpa, a yield strength greater than or equal to 130 Mpa, and an elongation greater than or equal to 11%.

14. The non-heat treatable die-cast AlSi alloy according to claim 5, wherein the die-cast AlSi alloy has a tensile strength greater than or equal to 270 Mpa, a yield strength greater than or equal to 130 Mpa, and an elongation greater than or equal to 11%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By referring to the figures, the following embodiments, the above and other features, advantages and aspects of the embodiments of the present disclosure will become more distinct. In these figures, the same or similar marks indicate the same or similar elements. It shall be understood that the figures are only schematic and the originals and elements would not be plotted to scale.

[0028] FIG. 1 shows the microstructure metallographs of the die-cast aluminum alloy obtained in Embodiment 2, where Figure (a) is a 100 metallograph of microstructure, and Figure (b) is a 500 metallograph of microstructure.

[0029] FIG. 2 illustrates the fluidity test mold for the die-cast aluminum alloy obtained in Embodiment 2.

[0030] FIG. 3 shows the tensile stress-strain curves of the die-cast aluminum alloy obtained in Embodiment 2, Comparative example 1 and Comparative example 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] The embodiments of the present disclosure will be described in detail below by referring to the figures. Although certain embodiments of the disclosure are shown in the figures, it is important to understand that the disclosure may be implemented in various forms and shall not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided for a more thorough and complete understanding of the present disclosure. It is important to understand that the figures and embodiments of the present disclosure are merely exemplary in nature and are not intended to limit the scope of protection of the disclosure.

[0032] It is important to understand that the individual steps described in the method embodiments of the disclosure may be performed in a different order, and/or in parallel. In addition, the method embodiments may include additional steps and/or omit the illustration of some performed steps. The scope of the present disclosure is not limited in this regard.

[0033] The present disclosure provides a non-heat treatable die-cast AlSi alloy with high toughness and its preparation method. The embodiments of the present disclosure are described in detail as follows through Figures.

Embodiment 1

[0034] In this embodiment, a non-heat treatable die-cast AlSi alloy with high toughness produced from renewable energy for low carbon emission is provided, which consists of the following components (in percent by weight): Mg: 0.2%; Si: 6.5%; Fe: 0.15%; Cu: 0.1%; Mn: 0.5%; Ti: 0.03%; Sr: 0.025%; total amount of La and Ce: 0.05%; Ni: 0.005%; Zn: 0.006%; Ga: 0.015%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0035] In this embodiment, a method for preparing the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0036] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0037] (2) Dosing: prepare Al ingots, Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Then add these raw materials in the above proportions, taking into account the burning loss.

[0038] (3) Charge to the furnace for melting: first put the Al ingots into the furnace for melting, and the melting temperature is controlled at 760-790 C. After all the Al ingots are melted, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0039] (4) Refining and slagging off: the temperature of the molten aluminum alloy is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0040] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0041] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace for 30-50 min, and then leave to stand for 15-30 min.

[0042] (7) Casting or die-casting: once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Embodiment 2

[0043] In this embodiment, a non-heat treatable die-cast AlSi alloy with high toughness produced from renewable energy for low carbon emission is provided, which consists of the following components (in percent by weight): Mg: 0.3%; Si: 6.9%; Fe: 0.2%; Cu: 0.2%; Mn: 0.6%; Ti: 0.07%; Sr: 0.02%; La: 0.1%; Ni: 0.003%; Zn: 0.07%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0044] In this embodiment, a method for preparing the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0045] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0046] (2) Dosing: prepare Al ingots or aluminum scrap, Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Then add these raw materials in the above proportions, taking into account the burning loss.

[0047] (3) Charge to the furnace for melting: first put the Al ingots or aluminum scrap into the furnace for melting, and the melting temperature is controlled at 760-790 C. After all the Al ingots or aluminum scrap are melted, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0048] (4) Refining and slagging off: the temperature of the molten aluminum alloy is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0049] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0050] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0051] (7) Casting or die-casting: once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Embodiment 3

[0052] In this embodiment, a non-heat treatable die-cast AlSi alloy with high toughness produced from renewable energy for low carbon emission consists of the following components (in percent by weight): Mg: 0.35%; Si: 7.5%; Fe: 0.25%; Cu: 0.3%; Mn: 0.7%; Ti: 0.15%; Sr: 0.03%; Ce: 0.08%; Ni: 0.08%; Zn: 0.09%; Ga: 0.025%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0053] In this embodiment, a method for preparing the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0054] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0055] (2) Dosing: prepare Al ingots or aluminum scrap, Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Then add these raw materials in the above proportions, taking into account the burning loss.

[0056] (3) Charge to the furnace for melting: first put the Al ingots or aluminum scrap into the furnace for melting, and the melting temperature is controlled at 760-790 C. After all the Al ingots or aluminum scrap are melted, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0057] (4) Refining and slagging off: the temperature of the molten aluminum alloy is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0058] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0059] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0060] (7) Casting or die-casting: once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Embodiment 4

[0061] In this embodiment, a non-heat treatable die-cast AlSi alloy with high toughness produced from renewable energy for low carbon emission is provided, which consists of the following components (in percent by weight): Mg: 0.25%; Si: 7.8%; Fe: 0.35%; Cu: 0.4%; Mn: 0.8%; Ti: 0.2%; Sr-0.035%; Sc: 0.15%; Ni: 0.02%; Zn: 0.08%; Ga: 0.012%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0062] In this embodiment, a method for preparing the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0063] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0064] (2) Dosing: prepare Al ingots or aluminum scrap, Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Then add these raw materials in the above proportions, taking into account the burning loss.

[0065] (3) Charge to the furnace for melting: first put the Al ingots or aluminum scrap into the furnace for melting, and the melting temperature is controlled at 760-790 C. After all the Al ingots or aluminum scrap are melted, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0066] (4) Refining and slagging off: the temperature of the molten aluminum alloy is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0067] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0068] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0069] (7) Casting or die-casting: once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Embodiment 5

[0070] In this embodiment, a non-heat treatable die-cast AlSi alloy with high toughness produced from renewable energy for low carbon emission is provided, which consists of the following components (in percent by weight): Mg: 0.15%; Si: 8.3%; Fe: 0.45%; Cu: 0.5%; Mn: 0.65%; Ti: 0.15%; Sr: 0.03%; the total amount of La and Sc: 0.2%; Ni: 0.08%; Zn: 0.01%; Ga: 0.018%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0071] In this embodiment, a method for preparing the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0072] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0073] (2) Dosing: prepare Al ingots or aluminum scrap, Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Then add these raw materials in the above proportions, taking into account the burning loss.

[0074] (3) Charge to the furnace for melting: first put the Al ingots or aluminum scrap into the furnace for melting, and the melting temperature is controlled at 760-790 C. After all the Al ingots or aluminum scrap are melted, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0075] (4) Refining and slagging off: the temperature of the molten aluminum alloy is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0076] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0077] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0078] (7) Casting or die-casting: once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Embodiment 6

[0079] In this embodiment, a method using recycled aluminum scrap to prepare the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0080] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0081] (2) Dosing: the recycled aluminum scrap is sorted and processed. Then prepare Al ingots, Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Add these raw materials in the above proportions, taking into account the burning loss.

[0082] (3) Charge to the furnace for smelting: add Al ingots (40%) and aluminum scrap (60%) to the furnace in turn for smelting, and the melting temperature is controlled at 760-790 C. After all materials are completely melted, sample the molten alloy for analysis in order to adjust the contents of elements to the required composition. After that, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0083] (4) Refining and slagging off: the temperature of the molten aluminum alloy with qualified composition is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0084] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0085] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0086] (7) Casting or die-casting: the cast alloy consists of the following components at last (in percent by weight): Mg: 0.25%; Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Ti: 0.12%; Sr-0.028%; the total amount of La, Ce and Sc: 0.2%; Ni: 0.005%; Zn: 0.06%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al. Once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Embodiment 7

[0087] In this embodiment, a method using recycled aluminum scrap to prepare the non-heat treatable die-cast AlSi alloy is disclosed, which comprises the following steps:

[0088] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0089] (2) Dosing: the recycled aluminum scrap is sorted and processed. Then prepare Mg ingots, industrial Si, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, Cu or the intermediate alloy AlCu, Ni, Zn and Ga, the intermediate alloy AlSr, and the aluminum rare earth alloy as raw materials for the preparation of the aluminum alloy. Add these materials in the required proportions, taking into account the burning loss.

[0090] (3) Charge to the furnace for smelting: add aluminum scrap (100%) to the furnace for smelting, and the melting temperature is controlled at 760-790 C. After all materials are completely melted, sample the molten alloy for analysis in order to adjust the contents of elements to the required composition. After that, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, the intermediate alloy AlMn or Mn, Cu or the intermediate alloy AlCu, Ni, Zn and Ga are added for smelting.

[0091] (4) Refining and slagging off: the temperature of the molten aluminum alloy with qualified composition is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0092] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, the aluminum rare earth alloy, Mg, the intermediate alloy AlSr are added for alloy refinement and modification. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0093] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0094] (7) Casting or die-casting: the cast alloy consists of the following components at last (in percent by weight): Mg: 0.3%; Si: 7.7%; Fe: 0.15%; Cu: 0.3%; Mn: 0.7%; Ti: 0.15%; Sr: 0.035%; Ce: 0.08%; Ni: 0.1%; Zn: 0.1%; Ga: 0.03%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al. Once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Comparative Example 1

[0095] This comparative example is an adjustment based on the composition of Embodiment 2, with fewer Sr added than that in Embodiment 2, and no La added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 6.9%; Fe: 0.2%; Cu: 0.2%; Mn: 0.6%; Mg: 0.3%; Ti: 0.07%; Sr-0.008%; Ni: 0.003%; Zn: 0.07%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0096] A method for preparing the die-cast Al alloy provided in this comparative example comprises the following steps:

[0097] (1) Furnace preparation: clean the furnace hearth and start heating the furnace up until the furnace wall turns red. Dry and preheat all operating tools after they have been coated with graphite powder.

[0098] (2) Dosing: prepare Al ingots, Mg ingots, industrial Si, Cu, the intermediate alloy AlMn or Mn, Fe, the intermediate alloy AlTi, and the intermediate alloy AlSr as raw materials for the preparation of the aluminum alloy. Then add these materials in the above proportions, taking into account the burning loss.

[0099] (3) Charge to the furnace for smelting: first put the Al ingots into the furnace for smelting, and the melting temperature is controlled at 670-690 C. After all the Al ingots are melted, the temperature is increased and controlled at 760-780 C. Then the industrial Si, Fe, Cu, and the intermediate alloy AlMn or Mn are added for smelting.

[0100] (4) Refining and slagging off: the temperature of the molten aluminum alloy with qualified composition is controlled at 740-760 C. for stirring well. Refining agent special for aluminum alloy is then added for primary injection refining and secondary injection refining, and the time interval between two refinements is controlled at 50-60 min. Perform slagging off after each refining to remove the flux and dross from the hearth.

[0101] (5) Add other metallic elements: when the molten alloy temperature is 740-760 C., the intermediate alloy AlTi, Mg, and the intermediate alloy AlSr are added for smelting. After the materials are fully melted, the molten aluminum alloy is sampled for analysis.

[0102] (6) Furnace degassing: when the melting temperature is maintained at 740-760 C., degas the furnace with nitrogen for 30-50 min, and then leave to stand for 15-30 min.

[0103] (7) Casting or die-casting: once the composition analysis results of on-the-spot sample are qualified, cast into finished ingots at casting temperature or perform high pressure casting through die casting process to obtain non-heat treatable die castings.

Comparative Example 2

[0104] This comparative example is an adjustment based on the composition of Embodiment 2, with more Sr added than that in Embodiment 2, and no La added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 6.9%; Fe: 0.2%; Cu: 0.2%; Mn: 0.6%; Mg: 0.3%; Ti: 0.07%; Sr: 0.05%; Ni: 0.003%; Zn: 0.07%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0105] The preparation method of this comparative example is the same as that of Comparative example 1.

Comparative Example 3

[0106] This comparative example is an adjustment based on the composition of Embodiment 6, and in this comparative example, the elements La, Ce, Sc, Zn, Ni and Ga are not added. The alloy provided in this comparative example consists of the following components (in percent by weight):

[0107] Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Mg: 0.25%; Ti: 0.12%; Sr-0.028%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0108] The preparation method of this comparative example is the same as that of Comparative example 1.

Comparative Example 4

[0109] This comparative example is an adjustment based on the composition of Embodiment 6, and in this comparative example, the elements La, Ce and Sc are not added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Mg: 0.25%; Ti: 0.12%; Sr: 0.028%; Ni: 0.06%; Zn: 0.005%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0110] The preparation method of this comparative example is the same as that of Comparative example 1.

Comparative Example 5

[0111] This comparative example is an adjustment based on the composition of Embodiment 6, and in this comparative example, a high content of La, Ce and Sc are added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Mg: 0.25%; Ti: 0.12%; Sr: 0.028%; La: 0.2; Ce: 0.2; Sc: 0.2; Ni: 0.06%; Zn: 0.005%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0112] The preparation method of this comparative example is the same as that of Comparative example 1.

Comparative Example 6

[0113] This comparative example is an adjustment based on the composition of Embodiment 6, and in this comparative example, a high content of La is added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Mg: 0.25%; Ti: 0.12%; Sr: 0.028%; La: 1.0; Ni: 0.06%; Zn: 0.005%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0114] The preparation method of this comparative example is the same as that of Comparative example 1.

Comparative Example 7

[0115] This comparative example is an adjustment based on the composition of Embodiment 6, and in this comparative example, a high content of Sc is added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Mg: 0.25%; Ti: 0.12%; Sr: 0.028%; Sc: 0.5; Ni: 0.06%; Zn: 0.005%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0116] The preparation method of this comparative example is the same as that of Comparative example 1.

Comparative Example 8

[0117] This comparative example is an adjustment based on the composition of Embodiment 6, and in this comparative example, a high content of Sc is added. The alloy provided in this comparative example consists of the following components (in percent by weight): Si: 7.0%; Fe: 0.35%; Cu: 0.25%; Mn: 0.6%; Mg: 0.25%; Ti: 0.12%; Sr: 0.028%; La: 0.01; Sc: 0.01; Ni: 0.06%; Zn: 0.005%; Ga: 0.02%; the total amount of other impurities is less than or equal to 0.2%, and the balance is Al.

[0118] The preparation method of this comparative example is the same as that of Comparative example 1.

[0119] Table 1 shows the aluminum alloy compositions for embodiments 1 to 7 and comparative example 1 to 8.

TABLE-US-00001 TABLE 1 Alloy composition Element Si Fe Cu Mn Mg Ti Sr La Ce Sc Zn Ni Ga Embodiment 1 6.5 0.15 0.1 0.5 0.2 0.03 0.025 0.02 0.03 / 0.006 0.005 0.015 Embodiment 2 6.9 0.2 0.2 0.6 0.3 0.07 0.02 0.1 / / 0.07 0.003 0.02 Embodiment 3 7.5 0.25 0.3 0.7 0.35 0.15 0.03 / 0.08 / 0.09 0.08 0.025 Embodiment 4 7.8 0.35 0.4 0.8 0.25 0.2 0.035 / / 0.15 0.08 0.02 0.012 Embodiment 5 8.3 0.45 0.5 0.65 0.15 0.15 0.03 0.15 / 0.05 0.01 0.08 0.018 Embodiment 6 7.0 0.35 0.25 0.6 0.25 0.12 0.028 0.05 0.1 0.05 0.06 0.005 0.02 Embodiment 7 7.7 0.15 0.3 0.7 0.3 0.15 0.035 / 0.08 / 0.1 0.1 0.03 Comparative 6.9 0.2 0.2 0.6 0.3 0.07 0.008 / / / 0.07 0.003 0.02 example 1 Comparative 6.9 0.2 0.2 0.6 0.3 0.07 0.05 / / / 0.07 0.003 0.02 example 2 Comparative 7.0 0.35 0.25 0.6 0.25 0.12 0.028 / / / / / / example 3 Comparative 7.0 0.35 0.25 0.6 0.25 0.12 0.028 / / / 0.06 0.005 0.02 example 4 Comparative 7.0 0.35 0.25 0.6 0.25 0.12 0.028 0.2 0.2 0.2 0.06 0.005 0.02 example 5 Comparative 7.0 0.35 0.25 0.6 0.25 0.12 0.028 1.0 / / 0.06 0.005 0.02 example 6 Comparative 7.0 0.35 0.25 0.6 0.25 0.12 0.028 / / 0.5 0.06 0.005 0.02 example 7 Comparative 7.0 0.35 0.25 0.6 0.25 0.12 0.028 0.01 / 0.01 0.06 0.005 0.02 example 8

[0120] Table 2 shows the tensile properties at room temperature of the F-state specimens and the specimens which have been held in furnace at 180 C. for 30 min as well as the fluidity. These specimens are taken from the Al alloy castings provided in Embodiments 1 to 7 and Comparative examples 1 to 8.

TABLE-US-00002 TABLE 2 Mechanical properties Specimen Tensile Yield thickness, Specimen strength, strength, Elongation, Example mm state MPa MPa % Fluidity Embodiment 3 F-state 290 130 15.1 Excellent 1 3 Baked 310 153 12.6 / Embodiment 3 F-state 287 139 13.3 Excellent 2 3 Baked 316 167 12.2 / Embodiment 3 F-state 300 145 13.0 Excellent 3 3 Baked 320 178 11.5 / Embodiment 3 F-state 300 138 12.3 Excellent 4 3 Baked 320 165 10.8 / Embodiment 3 F-state 295 133 12.4 Excellent 5 3 Baked 310 159 10.3 / Embodiment 3 F-state 285 143 12.6 Excellent 6 3 Baked 306 166 11.0 / Embodiment 3 F-state 297 149 13.2 Excellent 7 3 Baked 313 180 11.1 / Comparative 3 F-state 265 113 9.1 Good example 1 3 Baked 275 125 8.2 / Comparative 3 F-state 264 122 8.4 Good example 2 3 Baked 278 155 6.5 / Comparative 3 F-state 253 118 9.3 Good example 3 3 Baked 268 136 8.4 / Comparative 3 F-state 255 120 9.0 Good example 4 3 Baked 270 138 8.1 / Comparative 3 F-state 250 125 7.8 Good example 5 3 Baked 261 133 6.5 / Comparative 3 F-state 245 127 7.5 Good example 6 3 Baked 258 136 6.2 / Comparative 3 F-state 256 123 8.5 Good example 7 3 Baked 266 131 7.3 / Comparative 3 F-state 260 128 8.4 Good example 8 3 Baked 268 126 6.9 /

[0121] According to Tables 1 and 2, the content of Sr in Comparative example 1 is much lower than that in Embodiment 2; and moreover, when no rare earth element is added, the yield strength is reduced by 26 Mpa and the elongation is reduced by 4.2%. Compared with Embodiment 2, the content of Sr in Comparative example 2 is much higher than that in Embodiment 2; and moreover, when no rare earth element is added, the yield strength is reduced by 17 Mpa and the elongation is reduced by 4.9%. Compared with Embodiment 6, when rare earth elements, Zn, Ni and Ga are not added in Comparative example 3, the yield strength is reduced by 25 Mpa and the elongation is reduced by 3.3%. Compared with Embodiment 6, when rare earth elements are not added in Comparative example 4, the yield strength is reduced by 23 Mpa and the elongation is reduced by 3.6%. Compared with Embodiment 6, when the rare earth elements La, Ce and Sc are added in Comparative example 5 with a total amount of 0.6%, the yield strength is reduced by 18 Mpa and the elongation is reduced by 4.8%. Compared with Embodiment 6, when the rare earth element La is added in Comparative example 6 with a total amount of 1.0%, the yield strength is reduced by 16 Mpa and the elongation is reduced by 5.1%. Compared with Embodiment 6, when the rare earth element Sc is added in Comparative example 7 with a total amount of 0.5%, the yield strength is reduced by 20 Mpa and the elongation is reduced by 4.1%. Compared with Embodiment 6, when the rare earth elements La and Sc are added in Comparative example 8 with a total amount of 0.02%, the yield strength is reduced by 16 Mpa and the elongation is reduced by 4.2%. In summary, only when Sr and the rare earth elements La, Ce and Sc are included in the scope of this invention, the mechanical properties can be excellent. When the content of Sr and the rare earth elements La, Ce and Sc is too low or too high, the mechanical properties are not satisfied.

[0122] The above describes in detail the preferred embodiments of the invention. However, the invention is not limited thereto. Within the scope of the technical concept of the invention, various simple variants can be made for the technical solution of the invention, including the combination of individual technical features in any other suitable manner. Such simple variants and combinations shall also be considered as part of the content disclosed by the invention and are within the scope of protection of the invention.