A 6-series aluminum alloy with high strength and high deformability and its preparation method

Abstract

The present invention relates to a high-strength and high-deformability 6-series aluminum alloy and a preparation method thereof. The alloy comprises, by mass, the following components: Mg: 0.70-1.20%; Si: 0.65-1.10%; Cu: ≤0.30%; Mn: ≤1.00%; Cr: ≤0.30%; Zr: ≤0.20%; Fe: ≤0.35%; and other unavoidable impurity elements, the remainder being Al. By strictly limiting the component contents and providing a corresponding production process, the resulting product exhibits excellent strength and deformation resistance and can be applied to various automotive components, particularly functional structural parts such as front beams, longitudinal beams, bumpers, and battery compartments.

Description

Technical Field

[0001] The present invention belongs to the field of aluminum alloys, and in particular relates to a 6-series aluminum alloy with high strength and high deformability and a preparation method thereof. Background Art

[0002] 6-series aluminum profiles are increasingly used in vehicle bodies. Besides their obvious lightweighting advantages, their excellent recyclability, extrudability, and heat treatability make them an essential component of vehicle body materials, particularly structural components. Currently, the demand for lightweighting vehicles is becoming increasingly urgent, and the requirements are also becoming increasingly stringent. One trend in lightweighting is the demand for higher material strength, which reduces the effective load area of ​​parts while maintaining a safe load, thereby achieving weight reduction.

[0003] Currently, most 6-series aluminum profiles only maintain good resistance to deformation cracking at low strength levels. Improving this resistance at high strength levels is of paramount importance. Currently, there are few reports on 6-series aluminum alloys with high resistance to deformation cracking at yield strengths greater than 320 MPa. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-strength and high-deformation-ability 6-series aluminum alloy and a preparation method thereof. By strictly limiting the component content and providing a corresponding production process, the obtained product has excellent strength and deformation resistance and can be applied to various parts of the automobile, especially functional structural parts, such as front beams, longitudinal beams, anti-collision bars, battery boxes and other parts.

[0005] The present invention provides a 6 series aluminum alloy with high strength and high deformability, which is composed of the following components by mass percentage:

[0006] Mg: 0.70-1.20%;

[0007] Si: 0.65-1.10%;

[0008] Cu: ≤0.30%;

[0009] Mn: ≤1.00%;

[0010] Cr: ≤0.30%;

[0011] Zr: ≤0.20%;

[0012] Fe: ≤0.35%;

[0013] Other unavoidable impurity elements, the rest is Al;

[0014] Among them, the Mg / Si ratio is 0.72-1.43;

[0015] -0.2≤Mn-2Cr-5Zr≤+0.2;

[0016] 0.65≤Mn+2Cr+5Zr≤1.8.

[0017] The individual content of the unavoidable impurity elements is ≤0.05%, and the total content is ≤0.15%.

[0018] The present invention provides a method for preparing a first high-strength and high-deformability 6-series aluminum alloy, comprising the following steps:

[0019] The prepared aluminum alloy raw materials are added into the melting furnace, and the melt is subjected to online refining, online degassing and online filtration, and then the liquid aluminum alloy is cast into aluminum alloy casting rods; then it is homogenized at 550-590℃ for 5-10h, and cooled by strong wind or water mist; the homogenized casting rods are preheated to 500℃±30℃, extruded, and quenched at a temperature ≥500℃, and cooled by water mist or water cooling; profiles are produced according to the parameters of 200-210℃ / 2-8h to obtain high-strength and high-deformability 6 series aluminum alloy.

[0020] The present invention also provides a method for preparing a second high-strength and high-deformability 6-series aluminum alloy, comprising the following steps:

[0021] The prepared aluminum alloy raw materials are added into a melting furnace, and the melt is subjected to online refining, online degassing, and online filtration, and then the liquid aluminum alloy is cast into aluminum alloy casting rods; then, the casting rods are homogenized at 400-500℃ for 4-8h and at 550-590℃ for 5-10h, and cooled by strong wind or water mist; the homogenized casting rods are preheated to 500℃±30℃, extruded, and quenched at a temperature ≥500℃, and cooled by water mist or water cooling; profiles are produced according to the parameters of 200-210℃ / 2-8h to obtain 6 series aluminum alloy with high strength and high deformability.

[0022] The present invention also provides an application of a high-strength and high-deformation-ability 6-series aluminum alloy in automobile parts.

[0023] The principles of the present invention are as follows:

[0024] Mg, Si:

[0025] In the present invention, the aging state of the 6-series alloy is a transitional state between overaging and peak aging. Its primary aging-precipitation-strengthening phases are a composite coexistence of β' and β" phases. The Mg / Si mass ratio in the β' phase is 1.43, and the Mg / Si mass ratio in the β" phase is 0.72. Considering that excess Mg and Si (which do not form strengthening precipitates) not only contribute very little to strength improvement but also increase the difficulty of alloy production, the Mg / Si ratio in the alloy is designed to be within the range of 0.72-1.43. When the Mg / Si ratio is less than 0.72, Si is in excess, and when the Mg / Si ratio is greater than 1.43, Mg is in excess.

[0026] Mn, Cr, Zr

[0027] The added elements Mn, Cr, and Zr exist in the form of submicron-sized dispersed phase particles in aluminum alloys. These dispersed phase particles have the effect of hindering recrystallization, and Zr has the highest ability to hinder recrystallization, followed by Cr, and Mn has the weakest. Since Mn and Al are in a eutectic relationship in their binary alloys, a Mn-poor area will appear in the central area of ​​the grain during solidification and casting, which will cause uneven distribution of Mn, resulting in deformation and structural unevenness in subsequent processing and deformation, and further resulting in weak deformation ability of the produced products. In order to compensate for this, Cr and Zr elements are added. Since Cr, Zr and Al are in a peritectic relationship in their binary alloys, Cr and Zr elements are mainly enriched in the central area of ​​the grain during solidification and casting, which can make up for the problems of insufficient number of dispersed particles and decreased ability to hinder recrystallization caused by Mn deficiency, thereby ensuring a relatively uniform distribution of dispersed particles and ability to hinder recrystallization over the entire grain.

[0028] According to the constraint relationship of Mn, Cr and Zr in the present invention, the addition amount is designed to ensure that the dispersed phase particles in the entire grain are evenly distributed. Figure 1 . Figure 1 In a, only Mn element is added, and there is an obvious dispersed phase-poor area in the core area of ​​the grain. Figure 1 In b, Mn, Cr, and Zr elements are added in combination, and the distribution of dispersed phase particles in the entire grain range becomes relatively uniform.

[0029] -0.2≤Mn-2Cr-5Zr≤+0.2: When Mn-2Cr-5Zr<-0.2, the dispersed particles in the center of the grain are significantly more than those in the surrounding area of ​​the grain center; when Mn-2Cr-5Zr>0.2, the dispersed particles in the center of the grain are significantly less than those in the surrounding area of ​​the grain center.

[0030] 0.65≤Mn+2Cr+5Zr≤1.8: When Mn+2Cr+5Zr<0.65, the number of dispersed particles in the grains is insufficient, and the grain growth cannot be controlled, resulting in a relatively coarse microstructure, which is not conducive to improving the crack resistance during deformation; when Mn+2Cr+5Zr>1.8, it will cause alloy processing difficulties, which will bring difficulties to actual production.

[0031] Beneficial effects

[0032] By strictly limiting the content of ingredients and providing corresponding production processes, the present invention obtains a product with excellent strength and deformation resistance, and can be applied to various parts of automobiles, especially functional structural parts such as front beams, longitudinal beams, anti-collision bars, battery boxes and other parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 a and b are the distribution of dispersed phase particles in the grains. DETAILED DESCRIPTION

[0034] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0035] The preparation methods of alloys 1-8 are the same and include the following steps:

[0036] The prepared aluminum alloy raw material is added into the melting furnace, and the melt is subjected to online refining, online degassing and online filtration, and then the liquid aluminum alloy is cast into aluminum alloy casting rods; then it is homogenized at 550℃ for 5 hours and cooled by strong wind or water mist; the homogenized casting rods are preheated to 500℃±30℃ and extruded, with a quenching temperature of ≥500℃ and cooled by water mist or water cooling; profiles are produced according to the parameters of 200-210℃ / 2-8h to obtain 6 series aluminum alloy.

[0037] The properties of alloys 1-8 are shown in Table 1.

[0038] Table 1 Chemical composition and properties of alloys 1-8

[0039]

[0040]

Claims

1. A 6-series aluminum alloy with high strength and high deformability, characterized by: By mass percentage, it is composed of the following ingredients: Mg: 0.89%; Si: 0.81%; Cu: 0.16%; Mn: 0.70%; Cr：0.10％； Zr：0.10％； Fe: 0.14%; Other unavoidable impurity elements, the rest is Al; The preparation method of the 6 series aluminum alloy comprises the following steps: The prepared aluminum alloy raw material is added into the melting furnace, and the melt is subjected to online refining, online degassing and online filtration, and then the liquid aluminum alloy is cast into aluminum alloy casting rods; then it is homogenized at 550℃ for 5 hours and cooled by strong wind or water mist; the homogenized casting rods are preheated to 500℃±30℃ and extruded, with a quenching temperature of ≥500℃ and cooled by water mist or water cooling; profiles are produced according to the parameters of 200-210℃ / 2-8h to obtain 6 series aluminum alloy.

2. The 6 series aluminum alloy according to claim 1, characterized in that: The individual content of the unavoidable impurity elements is ≤0.05%, and the total content is ≤0.15%.

3. A method for preparing the high-strength and high-deformability 6-series aluminum alloy according to claim 1, comprising the following steps: The prepared aluminum alloy raw material is added into the melting furnace, and the melt is subjected to online refining, online degassing and online filtration, and then the liquid aluminum alloy is cast into aluminum alloy casting rods; then it is homogenized at 550℃ for 5 hours and cooled by strong wind or water mist; the homogenized casting rods are preheated to 500℃±30℃ and extruded, with a quenching temperature of ≥500℃ and cooled by water mist or water cooling; profiles are produced according to the parameters of 200-210℃ / 2-8h to obtain 6 series aluminum alloy.

4. Use of the high-strength and high-deformability 6 series aluminum alloy according to claim 1 in automobile parts.

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