Patent Description:
Therefore, one of the targets pursued in the die casting field is to develop a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy and study its preparation and die-casting process, so as to satisfy the actual operating requirements improved day by day on a high quality high-performance aluminum alloy die casting. <CIT> discloses a non-heat treatment self-reinforcing aluminium-silicon alloy preparation technology, which comprises the following steps: adding pure magnesium ingot, intermediate alloys AL-Si, AL-Mn, AL-Cu, and AL-Ti in a fusing aluminium liquid at temperature of <NUM>-<NUM> DEG C, after fusing, insulating for <NUM> minutes at <NUM> DEG C; heating the temperature of an alloy liquid to <NUM> DEG C, adding mixing rare earth, removing the scummings on the surface after fusing the mixing rare earth, stirring for <NUM>-<NUM> minutes and increasing the temperature of the alloy liquid to <NUM>-<NUM> DEG C, insulating and standing for <NUM> minutes; finally cooling the alloy liquid to <NUM> DEG C for refining, refining for <NUM> minutes, removing the slag, degassing, and finally completing the casting production. The mixing rare earth and an element Mn are used for refining Si and Cu in an aluminium alloy material according to strict mol fraction ratio.

The objective of the present invention is to, under the background of the prior art, provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy and a preparation method therefor. In the premise of guaranteeing good casting performance of the alloy, a non-heat-treatable casting features excellent comprehensive mechanical properties so as to satisfy the performance requirement on the body structural member, particularly a large thin-walled body structural member.

To achieve the objective, it is found in a long-term aluminum die casting alloy study that the Si content in the die-casting aluminum-silicon alloy significantly affects the casting performance, the strength and the plasticity of the alloy. Under normal circumstances, with the increase of the Si content, the strength of the alloy is increased, the flowability thereof is increased, and the plasticity thereof is reduced. Although the element Sr can play a role of modification refinement on eutectic Si in the alloy, the plasticity thereof still shows a reducing trend along with increase of the Si content. Therefore, <NUM>% of plasticity is hardly achieved. The present invention mainly aims to solve the problem that the plasticity of the Al-Si alloy is reduced under a die-casting condition in a case where the Si content is increased. With increase of the Si content in the alloy, the content of the eutectic Si in structures is increased, and the size and shape of the eutectic Si are also changed therewith, which becomes a key factor that affects the plasticity of the alloy. To overcome reduction of the plasticity of the material due to increase of the Si content in the alloy, the present invention creatively introduces the element V to refine an eutectic Si phase, so as to obtain a fine eutectic Si structure. In addition, it is found by a plenty of experimental verifications in early stage that rare earth elements such as La, Er and Ce can be compounded with element V to further refine the eutectic Si structures in the alloy, so that the size and shape of the eutectic Si change. Due to compound addition of V+RE, fine eutectic Si particles are generated in an as-cast structure, thereby guaranteeing that a die-casting aluminum alloy material with great Si content still has high plasticity. On the one hand, by adding the high content of Si, the alloy features excellent strength and flowability. On the other hand, due to compound addition of V+RE, the eutectic Si is retained in a fine and dispersed state, so that the plasticity of the alloy is improved. Furthermore, in the premise of guaranteeing excellent casting performance, the present invention can greatly improve the mechanical performance of the die-casting aluminum-silicon alloy and obtain comprehensive mechanical properties of high strength and high toughness taking strength and shaping into consideration.

Accordingly, the objective of the present invention is realized by the following technical solution:
The present invention provides a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight: <NUM>-<NUM>% of Si, <NUM>-<NUM>% of Mg, <NUM>-<NUM>% of Mn, <NUM>-<NUM>% of Cu, <NUM>-<NUM>% of Ti, <NUM>-<NUM>% of Sr, <NUM>-<NUM>% of V, <NUM>-<NUM>% of RE, less than <NUM>% of Fe, less than or equal to <NUM>% of other impurities, and a balance of Al.

The RE is one or more of elements La, Ce and Er.

The present invention further relates to a method for preparing a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following steps:.

As an embodiment of the present invention, preferably, a pre-heating temperature in S1 is <NUM>-<NUM>.

As an embodiment of the present invention, preferably, a preliminary heating temperature in S2 is <NUM>-<NUM>.

As an embodiment of the present invention, preferably, a cooling temperature in S2 is <NUM>-<NUM>.

As an embodiment of the present invention, preferably, a secondary heating temperature in S2 is <NUM>-<NUM>.

As an embodiment of the present invention, preferably, the refinement in S2 specifically includes: introducing a nitrogen with a refining agent powder into the third resulting alloy melt by using a rotary blowing device for an injection refining to obtain a first refined melt, performing a deslagging treatment and a degassing treatment on the first refined melt to obtain a second refined melt, then leaving the second refined melt still for <NUM>-<NUM>, and completing a slagging-off treatment on the second refined melt to obtain the fourth resulting alloy melt.

As an embodiment of the present invention, preferably, process parameters for the rotary blowing device are as follows: a degassing revolution is <NUM>-<NUM> r/min; a degassing time is <NUM>-<NUM>, a pressure of a gas source during the degassing treatment is <NUM>±<NUM> MPa, and a gas flow is <NUM>-<NUM> sccm.

As an embodiment of the present invention, preferably, the refining agent powder includes one of magnesium chloride and calcium chloride.

Compared with the prior art, the present invention has the following beneficial effects:.

By reading and referring to detailed description made by the following drawings to non-restrictive embodiments, other features, purposes and advantages of the present invention will become more obvious.

<FIG> shows observation schematic diagrams of SEM structures of castings in examples and comparative examples, wherein a represents the observation schematic diagram of the SEM structure of the casting A1, b represents the observation schematic diagram of the SEM structure of the casting A2, c represents the observation schematic diagram of the SEM structure of the casting A3, d represents the observation schematic diagram of the SEM structure of the casting A4, e represents the observation schematic diagram of the SEM structure of the casting A5, f represents the observation schematic diagram of the SEM structure of the casting A6, g represents the observation schematic diagram of the SEM structure of the casting A7, h represents the observation schematic diagram of the SEM structure of the casting A8, i represents the observation schematic diagram of the SEM structure of the casting A9, j represents the observation schematic diagram of the SEM structure of the casting A10, k represents the observation schematic diagram of the SEM structure of the casting A11 and l represents the observation schematic diagram of the SEM structure of the casting A12.

A high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy and a preparation method therefor provided by the present invention are further described below in combination with examples, so that those skilled in the art can easily understand advantages and features of the present invention, which is not used to limit the application scope of the present invention.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight: <NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of V, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

Preparation and die-casting processes for the high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy of the embodiment include the following steps:.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight: <NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of Er, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight:<NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti,<NUM>% of Cu, <NUM>% of V, <NUM>% of Er, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight:<NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of V, <NUM>% of Er, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight:<NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of V, <NUM>% of La, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight:<NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of V, <NUM>% of Ce, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities the balance of Al.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight: <NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of V, <NUM>% of La, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities the balance of Al.

The comparative example of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight: <NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti,<NUM>% of Cu, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

Preparation and die-casting processes for the high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy of the comparative example include the following steps:.

The comparative example of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight: <NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti, <NUM>% of Cu, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

The embodiment of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight:<NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti,<NUM>% of Cu, <NUM>% of V, <NUM>% of La, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

The comparative example of the present invention provide a high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, including the following components in percentage by weight:<NUM>% of Si, <NUM>% of Mg, <NUM>% of Mn, <NUM>% of Ti,<NUM>% of Cu, <NUM>% of V, <NUM>% of La, <NUM>% of Sr, <NUM>% of Fe, <NUM>% of other impurities and the balance of Al.

Mechanical properties of the castings A1-A12 prepared in the examples <NUM>-<NUM> and the comparative examples <NUM>-<NUM> are tested, and the test results are shown in Table <NUM>. It can be found by comparing the mechanical properties of the castings A1, A2, A3 and A9 that by independently adding the element V or the rare earth element Er, the strength and ductility of the alloy are obviously improved, the tensile strength is increased by <NUM> MPa to the maximum extent, and the improved amplitude of the ductility reaches <NUM>%. By adding the elements V and Er simultaneously, the plasticity of the alloy is more obviously improved, and the ductility of the casting is significantly increased from <NUM>% (A9) to <NUM>% (A3) with an increase amplitude of <NUM>%. The above rule can also be found by comparing the mechanical properties of the castings A4 and A10. By means of compound addition of the elements V and Er, the plasticity of the die-casting aluminum alloy with high Si content (<NUM> wt%) is significantly improved, so that the ductility is increased from <NUM> (the casting A10) to <NUM>% (the casting A4), and the characteristics of high strength and high toughness of the alloy are satisfied. It is found by comparing the mechanical properties of the castings A4, A5, A6 and A10 that by means of compound addition of V and rare earth elements Er, La and Ce, the plasticity and tensile strength of the die-casting aluminum alloy can be significantly improved. The tensile strength of the castings A4-A6 is about <NUM> MPa, the ductility is about <NUM>%, and compared with the casting A10, the tensile strength and the ductility are respectively increased by <NUM>% and <NUM>%. Thus, it is illustrated that the three RE rare earths included in the patent have significant effects to the alloy. It can be known by comparing the mechanical properties of the castings A5, A7, A8, A11 and A12 that within a range of composition of the alloy provided by the patent, by means of compound addition of V and rare earth elements, the yield strength of the die-casting aluminum alloy can be greater than <NUM> MPa, the tensile strength thereof can be greater than <NUM> MPa and the ductility thereof can be greater than <NUM>% (the castings A5, A7 and A8), reflecting excellent mechanical properties of the alloy within the range of composition of the alloy provided by the patent. When V in the alloy reaches <NUM> (the casting A11) or the rare earth elements reach <NUM> (the casting A12), which exceeds the range of the patent, the ductility and the tensile strength of the alloy are significantly reduced, and particularly, the ductility of the alloy is reduced to be less than <NUM>%, so that the high-strength and high-toughness die-casting aluminum alloy material cannot be obtained. In conclusion, in the range of composition of the alloy involved in the present invention, by adding the element V and RE elements (La, Er and Ce), the die-casting Al-Si alloy features high strength and high toughness in a non-heat treatment condition.

Microstructures of the castings A1-A12 respectively prepared in the above-mentioned examples <NUM>-<NUM> and comparative examples <NUM>-<NUM> are observed. The microstructures are shown in <FIG>. It is found by comparing structures in A1(a), A2(b), A3(c) and A9(i) that with introduction of V and the rare earth element Er, the eutectic Si structure is obviously refined. When the alloy does not contain V and Er, the eutectic Si in the structure of the casting is of a layered structure in <FIG>, with a particle size of about <NUM>. With introduction of the element V or Er, the eutectic Si structure is transformed from being lamellar to being granular, and the particle size is significantly decreased to <NUM>, as shown in <FIG>. By compound addition of V and Er, the size of the eutectic Si in the structure is further decreased, and the eutectic Si is a much smaller vermiform structure, as shown in <FIG>. Change of structural characteristics is closely related to change of mechanical properties. It is apparent that by introducing the elements V and Er, the eutectic Si structure can be significantly refined, and its shape is changed, so that the performance of the alloy changes significantly. It can be found by comparing structures of A4 and A10 that the compound action of the elements V and Er is also effective to the alloy structure with the high Si content. When the Si content is <NUM> wt. % and elements V and Er are not added into the alloy, the eutectic Si structure in the structure is in a thick broken line shape, and the maximum size of the fold line-shaped structure can reach up to <NUM> (as shown in <FIG>). With introduction of the elements V and Er in the alloy, the eutectic Si structure in the alloy is significantly refined to be vermiform (as shown in <FIG>), but there are block eutectic Si structures partially, which somewhat affects the plasticity of the alloy. Therefore, the plasticity of the alloy A3 is superior to that of the alloy A4. It is found by comparing the structures of the castings A4, A5, A6, A7, A8 and A10 that in the range of the alloy provided by the patent, by means of compound addition of the element V and the rare earth elements Er, La and Ce, the thick broken line-shaped structure in the die-casting aluminum alloy can disappear, so that the performance of the alloy is guaranteed. It can be known by comparing the structures of the castings A5, A11 and A12 that by adding excessive element V, second phases AIV can appear in the alloy structures, and by adding excessive rare earth elements, second phases AlLa can appear in the alloys. These second phases will reduce the plasticity of the alloys greatly. Generally, by introducing the compound action of the elements V and RE into the alloy provided by the patent, eutectic Si particles in the structures are finer and dispersive, and the shapes are greatly improved, so that the alloy has excellent mechanical properties due to the structural characteristic.

Claim 1:
A high-strength and high-toughness non-heat-treatable die-casting aluminum-silicon alloy, characterized by comprising the following components in percentage by weight: <NUM>-<NUM>% of Si, <NUM>-<NUM>% of Mg, <NUM>-<NUM>% of Mn, <NUM>-<NUM>% of Cu, <NUM>-<NUM>% of Ti, <NUM>-<NUM>% of Sr, <NUM>-<NUM>% of V, <NUM>-<NUM>% of RE, less than <NUM>% of Fe, less than or equal to <NUM>% of other impurities, and a balance of Al, wherein the RE is one or more of elements La, Ce, and Er.