Abstract:
The present invention provides an aluminum alloy refiner, which is characterized by being an amorphous alloy comprising 40 to 60 parts of Zr, 25 to 45 parts of Cu, 1 to 15 parts of Al, 1 to 10 parts of Pd and 1 to 10 parts of Nb in terms of mass fraction. The refiner provided by the present invention can be used to favorably refine crystal grains as well as improve the mechanical property of the aluminum alloy to a certain extent. Moreover, the intermediate alloy improves the strength and plasticity of the alloy, and a refined A356 aluminum alloy is very suitable for the manufacturing of automobile wheels.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to the field of smelting of aluminum alloys, and in particular to an alloy refiner material for refining an aluminum alloy. 
       BACKGROUND ART 
       [0002]    Aluminum is the most abundant metal element reserved in the earth crust, has the characteristics of small density, high plasticity, good ductility and excellent casting performance and is good in corrosion resistance due to a dense oxidiation film for surface protection. Cast aluminum alloy is prepared by adding other metal or non-metal elements on the basis of pure aluminum, not only maintaining the basic properties of the pure aluminum, but also possessing excellent comprehensive performance due to the effects of alloying and thermal treatment. Al-Si cast alloy takes Si as a major secondary element, with the Si content controlled to be 4% to 22%. Al-Si based alloy has good casting properties (such as liquidity, shrinkage percentage, thermal cracking resistance, and air tightness). A356 alloy belongs to Al-Si based alloy and is widely applied to casting of various casing parts, automobile wheels, aircraft pumps, aircraft accessories, automobile transmissions, car chassis accessories and the like due to the excellent comprehensive performance thereof. 
         [0003]    At present, A356 aluminum alloy has been often adopted in the international automobile industry to cast various wheels. A356 aluminum alloy is an Al-Si-Mg based alloy, with primary α-Al and an eutectic structure as a major structure (α-Al+eutectic Si), wherein eutectic silicon takes a coarse acicular shape, and a structure taking the coarse acicular shape will severely split a matrix and reduce the mechanical property of the alloy. Therefore, modification treatment is needed to improve the structure form thereof to further improve the mechanical property of the alloy. The present invention is intended to develop a novel modifier. Accordingly, at present, there is an urgent need of a refiner, which meets the chemical requirements of A356.2 alloy and is capable of improving the structure as well as the mechanical property of the A356.2 alloy to meet the requirement of wheel production. 
       SUMMARY OF THE INVENTION 
       [0004]    Therefore, an object of the present invention is to provide a refiner, which meets the chemical requirements of A356.2 alloy, and is capable of improving the structure as well as the mechanical property of the A356.2 alloy to meet the requirement of wheel production. 
         [0005]    In order to achieve the object described above, the present invention provides a technical solution as follows. 
         [0006]    In one aspect of the present invention, an aluminum alloy refiner is provided, which is characterized by being an amorphous alloy comprising 40 to 60 parts of Zr, 25 to 45 parts of Cu, 1 to 15 parts of Al, 1 to 10 parts of Pd and 1 to 10 parts of Nb in terms of mass fraction. 
         [0007]    In one preferable aspect of the present invention, the aluminum alloy refiner comprises 50 parts of Zr, 35 parts of Cu, 7 parts of Al, 5 parts of Pd and 3 parts of Nb in terms of mass fraction. 
         [0008]    In one preferable aspect of the present invention, the aluminum alloy refiner is prepared through rapid cooling. 
         [0009]    In one preferable aspect of the present invention, the rapid cooling is to melt Zr, Cu, Al, Pd and Nb at the temperature of 900 to 1000° C. and the refiner is prepared by a single-roll melt spinner. 
         [0010]    In one preferable aspect of the present invention, the aluminum alloy refiner is prepared with a method including the following steps: 
         [0011]    (1) mixing pure metals of Zr, Cu, Al, Pd and Nb according to a certain proportion, pre-vacuumizing a vacuum electric arc furnace to be below 10 −3 Pa, charging an argon gas (preferably under a partial pressure of 0.02 to 0.05 MPa) for smelting, and repeatedly smelting 5 times to prepare a master alloy with even components; and 
         [0012]    (2) breaking the master alloy from the step (1) into small lumps, placing the small lumps into a quartz tube, pre-vacuumizing a single-roll melt spinner to be below 10 −3 Pa, charging the argon gas (preferably under a partial pressure of 0.05 to 0.1 MPa) to melt the master alloy in the quartz tube through induction heating, with the temperature of molten alloy of 900 to 1000° C., regulating the rotation speed of a copper roll to be 3000 to 4000 r/min, and spraying the molten alloy out to the surface of the copper roll by using the argon gas, thereby preparing an amorphous alloy ribbon. 
         [0013]    In another aspect of the present invention, a method for preparing the foregoing aluminum alloy refiner described is also provided, characterized by comprising the following steps: 
         [0014]    (1) mixing pure metals of Zr, Cu, Al, Pd and Nb according to a certain proportion, pre-vacuumizing a vacuum electric arc furnace to be below 10 −3 Pa, charging an argon gas (preferably under a partial pressure of 0.02 to 0.05 MPa) for smelting, and repeatedly smelting 5 times to prepare a master alloy with even components; and 
         [0015]    (2) breaking the master alloy from step (1) into small lumps, placing the small lumps into a quartz tube, prevacuumizing the single-roll melt spinner to be below 10 −3 Pa, charging the argon gas (preferably under a partial pressure of 0.05 to 0.1 MPa) to melt the master alloy in the quartz tube through induction heating, with the temperature of molten alloy of 900 to 1000° C., regulating the rotation speed of a copper roll to be 3000 to 4000 r/min, and spraying the molten alloy out to the surface of the copper roll by using the argon gas, thereby preparing an amorphous alloy ribbon. 
         [0016]    In other aspects of the present invention, a technical solution is also provided as follows: 
         [0017]    In one aspect of the present invention, a method for smelting an aluminum alloy is provided, characterized by comprising a step of treating the aluminum alloy with a refiner, wherein the refiner is a Zr-Cu-Al-Pd-Nb amorphous alloy, which is characterized by comprising 40 to 60 parts of Zr, 25 to 45 parts of Cu, 1 to 15 parts of Al, 1 to 10 parts of Pd and 1 to 10 parts of Nb in terms of mass fraction; preferably, the amorphous alloy comprises 50 parts of Zr, 35 parts of Cu, 7 parts of Al, 5 parts of Pd and 3 parts of Nb in terms of mass fraction. 
         [0018]    In one preferable aspect of the present invention, the Zr-Cu-Al-Pd-Nb amorphous alloy is prepared through rapid cooling; and preferably, the rapid cooling is to melt Zr, Cu, Al, Pd and Nb at the temperature of . and prepare the refiner by a single-roll melt spinner. 
         [0019]    In one preferable aspect of the present invention, the Zr-Cu-Al-Pd-Nb amorphous alloy is prepared with a method including the following steps: 
         [0020]    (1) mixing pure metals of Zr, Cu, Al, Pd and Nb according to a certain proportion, pre-vacuumizing a vacuum electric arc furnace to be below 10 −3 Pa, charging an argon gas (under a partial pressure of 0.02 to 0.05 MPa) for smelting, and repeatedly smelting 5 times to prepare a master alloy with even components; and 
         [0021]    (2) breaking the master alloy from the step (1) into small lumps, placing the small lumps into a quartz tube, pre-vacuumizing a single-roll melt spinner to be below 10 −3 Pa, charging the argon gas (under a partial pressure of 0.05 to 0.1 MPa) to melt the master alloy in the quartz tube through induction heating, with the temperature of molten alloy as 900 to 1000° C., regulating the rotation speed of a copper roll to be 3000 to 4000 r/min, and spraying the molten alloy out to the surface of the copper roll by using the argon gas, thereby preparing an amorphous alloy ribbon. 
         [0022]    In one preferable aspect of the present invention, the Zr-Cu-Al-Pd-Nb amorphous alloy is added according to 0.15 to 0.80 wt % of the weight of the aluminum alloy to be treated during refining treatment. 
         [0023]    In one preferable aspect of the present invention, the refining treatment comprises the following steps: (1) melting the aluminum alloy to be treated at 750 to 800° C. and deslagging and degassing; and (2) adding the Zr-Cu-Al-Pd-Nb amorphous alloy according to 0.15 to 0.80 wt % of the weight of the aluminum alloy to be treated, holding the heat for 5 to 120 min, and degassing. 
         [0024]    In one preferable aspect of the present invention, the melting temperature in the step (1) is 790° C., and in the step (2), the Zr-Cu-Al-Pd-Nb amorphous alloy is added according to 0.20 wt % of the weight of the aluminum alloy to be treated. 
         [0025]    In one preferable aspect of the present invention, the melting temperature in the step (1) is 790° C., and in the step (2), the Zr-Cu-Al-Pd-Nb amorphous alloy is added according to 0.60 wt % of the weight of the aluminum alloy to be treated. 
         [0026]    In one preferable aspect of the present invention, the heat is held for 5 to 120 min in the step (2), for example, the heat is held for 5, 10, 30, 45 or 60 min. 
         [0027]    In other aspects of the present invention, an aluminum alloy prepared according to the foregoing method as described is also provided. 
         [0028]    In other aspects of the present invention, an application of the foregoing aluminum alloy as described to a cast aluminum alloy wheel is also provided. 
         [0029]    In other aspects of the present invention, a technical solution is provided as follows. 
         [0030]    In one aspect of the present invention, a technological method for modification treatment of an A356 aluminum alloy by adding a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is provided, characterized by comprising the following steps: 
         [0031]    Step 1, preparing of a Zr-Cu-Al-Pd-Nb amorphous ribbon by using a single-roll melt spinner, to be specific, preparing raw materials according to 40% to 60% of Zr, 25% to 45% of Cu, 1% to 15% of Al, 1% to 10% of Pd and 1% to 10% of Nb in terms of atomic percentage, smelting the raw materials in a nonconsumable electric arc smelting furnace for smelting at first, and then placing the smolten alloy into the single-roll melt spinner to prepare the Zr-Cu-Al-Pd-Nb amorphous ribbon; 
         [0032]    Step 2, smelting and refining, to be specific, with A356 aluminum alloy (chemical components of which are as shown in Table 1) as an alloy raw material and the Zr-Cu-Al-Pd-Nb amorphous ribbon prepared in Step 1 as an intermediate alloy, placing the A356 aluminum alloy into a resistance furnace for smelting at the smelting temperature of 750 to 800° C., adding the alloy raw material at the smelting temperature, holding the heat for 30 to 50 min till the A356 alloy raw material is completely smolten, deslagging and stirring for 30 s, charging an Ar gas, N 2  or other inert gases for 3 to 30 min for degassing, holding the heat for 5 to 15 min and then deslagging; adding the Zr-Cu-Al-Pd-Nb amorphous ribbon prepared in Step 1 according to 0.2 to 0.6% of the alloy raw material in terms of weight percentage, and holding the heat for 5 to 120 min at 750 to 800° C. ; and charging an Ar gas, N 2  or other inert gases for 3 to 30 min in a heat holding process for degassing, deslagging and stirring for 3 to 5 min after the heat holding is completed, and taking out a crucible to expose in the air. 
         [0033]    Step 3, gravity casting, to be specific, deslagging when the temperature of molten aluminum is 700 to 750° C., pouring the molten aluminum into a cast iron mold preheated to 200° C., and performing air cooling naturally to form an aluminum alloy rod; 
         [0034]    Step 4, thermal treatment, to be specific, performing thermal treatment on the aluminum alloy rod in the cast iron mold, which comprises: 
         [0035]    solid solution treatment, to be specific, holding the heat for the aluminum alloy rod for 2 to 6 hours in a thermal treatment furnace at 535±5° C., after heat holding, transferring the aluminum alloy rod into hot water at 70 to 90° C. within 20 seconds for quenching treatment, and taking out the rod after maintaining the rod in the hot water for 2 to 5 min; 
         [0036]    aging treatment, to be specific, after the quenching treatment is completed, transferring the rod into the thermal treatment furnace at the temperature of 130 to 160° C., holding the heat for 3 to 12 hours, and performing air cooling. 
         [0037]    In one aspect of the present invention, an application of the A356 aluminum alloy, prepared according to the forgoing technological method for modification treatment of the A356 aluminum alloy with the Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy as described, to the manufacturing of automobile wheels is provided. 
         [0038]    In one aspect of the present invention, a technological method for modification treatment of an A356 aluminum alloy with a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is provided, which comprises the following steps: preparing a Zr-Cu-Al-Pd-Nb amorphous ribbon by using a single-roll melt spinner; with an A356 aluminum alloy as an alloy raw material and the Zr-Cu-Al-Pd-Nb amorphous ribbon as an intermediate alloy, adding the intermediate alloy according to 0.2 to 0.6% of the alloy raw material in terms of weight percentage, placing the aluminum alloy into the resistance furnace for smelting at the smelting temperature of 750 to 800° C., and holding the heat for 5 to 120 min after the intermediate alloy is added; and performing gravity casting and thermal treatment. Compared with the A356 aluminum alloy to which the intermediate alloy is not added, the A356 aluminum alloy to which the Zr-Cu-Al-Pd-Nb amorphous ribbon is added as the intermediate alloy is refined in crystal grains, more even in the dispersion of an eutectic silicon structure and has the mechanical property improved to a certain extent. 
         [0039]    With adoption of the Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy as a modifier for the A356 aluminum alloy, the refiner provided by the present invention can favorably refine crystal grains as well as improve the mechanical property of the aluminum alloy to a certain extent (as shown in  FIG. 3 ). Moreover, the intermediate alloy improves the strength and plasticity of the alloy, and the refined A356 aluminum alloy is very suitable for the manufacturing of automobile wheels. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0040]    In the following, embodiments of the present invention are illustrated in detail in combination with the drawings, wherein 
           [0041]      FIG. 1A  is a diagram of an as cast metallographic structure of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiment 1 of the present invention. 
           [0042]      FIG. 1B  is a diagram of an as cast metallographic structure of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiment 2 of the present invention. 
           [0043]      FIG. 1C  is a diagram of an as cast metallographic structure of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiment 3 of the present invention. 
           [0044]      FIG. 1D  is a diagram of an as cast metallographic structure of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiment 4 of the present invention. 
           [0045]      FIG. 1E  is a diagram of an as cast metallographic structure of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiment 5 of the present invention. 
           [0046]      FIG. 2A  is a diagram of a metallographic structure of an A356 aluminum alloy, in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added, at a thermal treatment state in Embodiment 1 of the present invention. 
           [0047]      FIG. 2B  is a diagram of a metallographic structure of an A356 aluminum alloy, in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added, at a thermal treatment state in Embodiment 2 of the present invention. 
           [0048]      FIG. 2C  is a diagram of a metallographic structure of an A356 aluminum alloy, in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added, at a thermal treatment state in Embodiment 3 of the present invention. 
           [0049]      FIG. 2D  is a diagram of a metallographic structure of an A356 aluminum alloy, in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added, at a thermal treatment state in Embodiment 4 of the present invention. 
           [0050]      FIG. 2E  is a diagram of a metallographic structure of an A356 aluminum alloy, in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added, at a thermal treatment state in Embodiment 5 of the present invention. 
           [0051]      FIG. 3A  is a diagram of tensile strength of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiments 1 to 5 of the present invention. 
           [0052]      FIG. 3B  is a diagram of yield strength of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiments 1 to 5 of the present invention. 
           [0053]      FIG. 3C  is a diagram of percentage of elongation of an A356 aluminum alloy in which a Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy is added in Embodiments 1 to 5 of the present invention. 
           [0054]      FIG. 4A  is a DSC diagram of a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon added in the present invention. 
           [0055]      FIG. 4B  is an XRD diagram of a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon added in the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0056]    In the following, the present invention is described in detail through embodiments, and the embodiments are provided for the convenience of understanding instead of limiting the present invention. 
         [0057]    The present invention provides performing modification treatment on an A356 aluminum alloy with a Zr-Cu-Al-Pd-Nb amorphous ribbon as an intermediate alloy, which improves the strength and plasticity of the alloy, and the treated A356 aluminum alloy can be applied to the manufacturing of automobile wheels. 
         [0058]    Embodiment 1: Technological method for modification treatment of A356 aluminum alloy with Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, comprising the following steps: 
         [0059]    Step 1, preparing a Zr-Cu-Al-Pd-Nb amorphous ribbon by using a single-roll melt spinner, to be specific, preparing a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy according to 50% of Zr, 35% of Cu, 7% of Al, 5% of Pd and 3% of Nb in terms of atomic percentage, wherein a process comprises the following substeps: mixing pure metals of Zr, Cu, Al, Pd and Nb according to a certain propertion, pre-vacuumizing a vacuum electric arc furnace to be below 10 −3  Pa, charging an argon gas (under a partial pressure of 0.02 to 0.05 MPa) for smelting, and repeatedly smelting 5 times to prepare a master alloy with even components; and breaking the master alloy into small lumps, placing the small lumps into a quartz tube, pre-vacuumizing a single-roll melt spinner to be below 10 −3  Pa, charging the argon gas (under a partial pressure of 0.05 to 0.1 MPa) to melt the master alloy in the quartz tube through induction heating, with the temperature of molten alloy of 900 to 1000° C., regulating the rotation speed of a copper roll to be 3000 to 4000 r/min, and spraying the molten alloy out to the surface of the copper roll by using the argon gas, thereby preparing an amorphous alloy ribbon.  FIG. 4  shows DSC and XRD diagrams of the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon, indicating that the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  intermediate alloy of the present invention is an amorphous alloy. 
         [0060]    Step 2, smelting and refining, to be specific, with the A356 aluminum alloy as an alloy raw material and the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy prepared in Step 1 as the intermediate alloy, smelting in a resistance furnace at the smelting temperature of 790° C., adding the A356 aluminum alloy at the smelting temperature, holding the heat for 35 min till the A356 alloy raw material is completely smolten, deslagging and stirring for 30 seconds, charging an Ar gas for 3 minutes for degassing, holding the heat for 5 min and then deslagging; adding the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy accounting for 0.2 wt % of the A356 alloy, and holding the heat for 5 min at 790° C.; and charging the Ar gas for 5 min in the heat holding process for degassing, deslagging and stirring for 3 to 5 min after the heat holding is completed, and taking out a crucible to expose in the air. 
         [0061]    Step 3, gravity casting, to be specific, deslagging when the temperature of molten aluminum is 750° C., pouring the molten aluminum into a cast iron mold preheated to 200° C., and performing air cooling naturally to form a rod; 
         [0062]    Step 4, performing T6 thermal treatment on the rod in the cast iron mold (i.e. performing aging treatment after solid solution treatment), wherein the solid solution treatment is to hold the heat for the rod in a thermal treatment furnace at 540° C. for 2 hours, and then perform quenching treatment in hot water at 80° C.; and the aging treatment is to transfer the rod into the thermal treatment furnace at the temperature of 150° C. after the quenching treatment is completed, holding the heat for 12 hours, and performing air cooling. 
         [0063]    Step 5, thermal treatment, to be specific, performing thermal treatment on the aluminum alloy rod in the cast iron mold, which comprises the following substeps: 
         [0064]    solid solution treatment, to be specific, holding the heat for the aluminum alloy rod for 2 hours in a thermal treatment furnace at 540° C., after heat holding, transferring the aluminum alloy rod into hot water at 80° C. within 20 seconds for quenching treatment, and taking out the rod after maintaining the rod in the hot water for 2 to 5 minutes; and 
         [0065]    aging treatment, to be specific, after the quenching treatment is completed, transferring the rod into the thermal treatment furnace at the temperature of 150° C., holding the heat for 12 hours, and performing air cooling. 
         [0066]    With an Olympus metallographic microscope GX51, metallographic detection is performed on a test sample obtained from Step 3, as shown in  FIG. 1 ( a ) , and a test sample obtained from Step 4, as shown in  FIG. 2( a ) ; and with a WDW-20 universal mechanics testing machine, a tensile mechanical property test is performed on the test samples obtained from Step 4 at the tension rate of 0.1 mm/min, as shown in  FIG. 3 ( a ), ( b ) and ( c ) . 
         [0067]    Embodiment 2: Technological method for modification treatment of A356 aluminum alloy with Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, comprising the following steps: 
         [0068]    Step 1, preparing a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy, which is the same as that in Embodiment 1; 
         [0069]    Step 2, smelting and refining, which is different from Step 2 in Embodiment 1 only in that the heat holding time at 790° C. is changed from 5 min to 10 min after the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy is added; 
         [0070]    Step 3, gravity casting, which is the same as that in Embodiment 1; and 
         [0071]    Step 4, performing T6 thermal treatment on the rod in a cast iron mold, which is the same as that in Embodiment 1. 
         [0072]    Metallographic detection is performed on a test sample obtained from Step 3, as shown in  FIG. 1 ( b ) , and a test sample obtained from Step 4, as shown in  FIG. 2( b ) ; and a tensile mechanical property test is performed on the test samples obtained from Step 4, as shown in  FIG. 3 ( a ), ( b ) and ( c ) . 
         [0073]    Embodiment 3: Technological method for modification treatment of A356 aluminum alloy with Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, comprising the following steps: 
         [0074]    Step 1, preparing a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy, which is the same as that in Embodiment 1; 
         [0075]    Step 2, smelting and refining, which is different from Step 2 in Embodiment 1 only in that the heat holding time at 790° C. is changed from 5 min to 30 min after the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy is added; 
         [0076]    Step 3, gravity casting, which is the same as that in Embodiment 1; and 
         [0077]    Step 4, performing T6 thermal treatment on the rod in a cast iron mold, which is the same as that in Embodiment 1. 
         [0078]    Metallographic detection is performed on a test sample obtained from Step  3 , as shown in  FIG. 1 ( c ) , and a test sample obtained from Step 4, as shown in  FIG. 2( c ) ; and a tensile mechanical property test is performed on the test samples obtained from Step 4, as shown in  FIG. 3 ( a ), ( b ) and ( c ) . 
         [0079]    Embodiment 4: Technological method for modification treatment of A356 aluminum alloy with Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, comprising the following steps: 
         [0080]    Step 1, preparing a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy, which is the same as that in Embodiment 1; 
         [0081]    Step 2, smelting and refining, which is different from Step 2 in Embodiment 1 only in that the heat holding time at 790° C. is changed from 5 min to 45 min after the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy is added; 
         [0082]    Step 3, gravity casting, which is the same as that in Embodiment 1; and 
         [0083]    Step 4, performing T6 thermal treatment on the rod in a cast iron mold, which is the same as that in Embodiment 1. 
         [0084]    Metallographic detection is performed on a test sample obtained from Step 3, as shown in  FIG. 1 ( d ) , and a test sample obtained from Step 4, as shown in  FIG. 2( d ) ; and a tensile mechanical property test is performed on the test samples obtained from Step 4, as shown in  FIG. 3 ( a ), ( b ) and ( c ) . 
         [0085]    Embodiment 5: Technological method for modification treatment of A356 aluminum alloy with Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, comprising the following steps: 
         [0086]    Step 1, preparing a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy, which is the same as that in Embodiment 1; 
         [0087]    Step 2, smelting and refining, which is different from Step 2 in Embodiment 1 only in that the heat holding time at 790° C. is changed from 10 min to 60 min after the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy is added; 
         [0088]    Step 3, gravity casting, which is the same as that in Embodiment 1; and 
         [0089]    Step 4, performing T6 thermal treatment on the rod in a cast iron mold, which is the same as that in Embodiment 1. 
         [0090]    Metallographic detection is performed on a test sample obtained from Step 3, as shown in  FIG. 1 ( e ) , and a test sample obtained from Step 4, as shown in  FIG. 2( e ) ; and a tensile mechanical property test is performed on the test samples obtained from Step 4, as shown in  FIG. 3 ( a ), ( b ) and ( c ) . 
         [0091]    Embodiment 6: Technological method for modification treatment of A356 aluminum alloy with Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, comprising the following steps: 
         [0092]    Step 1, preparing a Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy, which is the same as that in Embodiment 1; 
         [0093]    Step 2, smelting and refining, which is different from Step 2 in Embodiment 1 only in that the weight of the Zr 50 Cu 35 Al 7 Pd 5 Nb 3  amorphous ribbon intermediate alloy added is changed from 0.2 wt % to 0.6 wt % of the A356 aluminum alloy; 
         [0094]    Step 3, gravity casting, which is the same as that in Embodiment 1; and 
         [0095]    Step 4, performing T6 thermal treatment on the rod in a cast iron mold, which is the same as that in Embodiment 1. 
         [0096]    From Embodiments 1 to 6 and  FIGS. 1, 2 and 3 , it can be seen that with the addition of the Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, the α-Al phase is refined to a certain extent, and the mechanical properties of the modified A356 are improved to a certain extent. Based on comparison between  FIG. 1  and  FIG. 2 , it can be seen that an eutectic silicon phase in an eutectic structure changes from shapes of strip and clustered sphere to a shape of approximate spheres dispersed in an a-Al matrix after thermal treatment. Based on comparison among ( a ), ( b ), ( c ), ( d ) and ( e ) in  FIG. 1 , it can be seen that a dendritic crystal structure in (c), i.e. Embodiment 3, is the coarsest, with primary dendritic crystals and secondary dendritic crystals higher than other structures;  FIG. 3  shows that both tensile strength and yield strength of ( c ) are very low, but the percentage of elongation of the material is improved, indicating that the growth of the dendritic crystals reduces the tensile strength and yield strength of the material but increases the plasticity of the material. The general requirements of the automobile wheels for the mechanical properties of the A356 aluminum alloy are as follows: the tensile strength being Rm&gt;220 MPa, the yield strength being Rp0.2&gt;180 MPa, and the percentage of elongation being As&gt;7%. Embodiments 1, 2 and 4 meet these requirements, and the mechanical properties of the alloy subjected to 5 min heat holding in Embodiment 1 are the best. As the heat holding time increases, the mechanical properties undergo a phenomenon of decrease and increase in order. However, the plasticity of the material presents the opposite tendency, that is, as the heat holding time increases, the plasticity increases and decreases in order, which is in conformity with the general law that the tensile strength increases and the plasticity decreases. 
         [0097]    The preparation method of the present invention has the following advantages: 
         [0098]    (1) with adoption of a novel amorphous intermediate alloy, the ribbon is shown as an amorphous alloy in DSC and XRD in  FIG. 4  and the use of the amorphous alloy allows a more even metallographic structure of a final product; 
         [0099]    (2) the intermediate alloy added in a ribbon form dissolves quickly in molten aluminum and can be distributed in an even dispersion way after proper mechanical stirring; 
         [0100]    (3) the A356 aluminum alloy treated with the Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy have even and fine crystal grains, with alloy elements distributing in an aluminum matrix in an even dispersion way, which is beneficial to the improvement of the mechanical properties of the A356 aluminum alloy; 
         [0101]    (4) with addition of the Zr-Cu-Al-Pd-Nb amorphous ribbon intermediate alloy, the as-cast structure subjected to 30 min heat holding has the most and coarsest dendritic crystals; and 
         [0102]    (5) the mechanical properties of the alloy subjected to 5 min heat holding in Embodiment 1 are the best. As the heat holding time increases, the mechanical properties undergo a phenomenon of decrease and increase in order. However, the plasticity of the material presents the opposite tendency, that is, as the heat holding time increases, the plasticity increases and decreases in order, which is in conformity with the general law that the tensile strength increases and the plasticity decreases. 
         [0103]    At the same time, the inventors also prepare and test the Zr-Cu-Al-Pd-Nb amorphous alloy comprising the following components: 
         [0104]    (A) 40 parts of Zr, 45 parts of Cu, 1 part of Al, 10 parts of Pd and 1 part of Nb; 
         [0105]    (B) 60 parts of Zr, 25 parts of Cu, 15 parts of Al, 1 part of Pd and 10 parts of Nb; 
         [0106]    (C) 52 parts of Zr, 29 parts of Cu, 7 parts of Al, 7 parts of Pd and 3 part of Nb; and 
         [0107]    (D) 57 parts of Zr, 41 parts of Cu, 12 parts of Al, 5 parts of Pd and 1 part of Nb. 
         [0108]    Results show that for the amorphous alloys in the groups above under the conditions of Embodiment 1, 
         [0109]    (1) the tensile strengths Rm of all the aluminum alloys produced by treatment are higher than 230 MPa, with the highest Rm value (283 MPa) of the amorphous alloy from Group (B); 
         [0110]    (2) the yield strengths Rp0.2 of all the aluminum alloys produced by treatment are higher than 180 MPa, with the highest Rp value (220.1 MPa) from Group (D); and 
         [0111]    (3) the percentages of elongation As of all the aluminum alloys produced by treatment are higher than 7.0%, with the highest As value (10.625%) from Group (A). 
         [0112]    Although the present invention is illustrated through the embodiments as described above in combination with the drawings of the description, the embodiments above are intended only to illustrate the experiments of the present invention in a better way, instead of limiting the scope of implementation of the present invention. Equivalent variations and relevant modifications made according to the present invention or without departing from the experimental spirit of the present invention are within the protection scope of the invention.