Sc-containing heat-resistant high-strength magnesium alloy and preparation method thereof

Abstract

The invention provides an Sc-containing heat-resistant high-strength magnesium alloy and a preparation method thereof. The Sc-containing heat-resistant high-strength magnesium alloy is prepared from the following components in percentage by mass: 9%-10.5% of Gd, 2.0%-3.5% of Y, 1.0%-2.0% of Zn, 1%-1.5% of Sc, 0.5%-1% of Mn, 0.2%-0.6% of Ce, 0.3%-0.5% of Zr and the balance of Mg and impurity elements. According to the heat-resistant high-strength magnesium alloy containing Sc, the service temperature range of the high-strength magnesium alloy is greatly widened, the room temperature strength is greatly improved to 510 MPa, and meanwhile the creep rate of 300 DEG C or above is reduced by 1-2 orders of magnitude.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy materials, and in particular to a heat-resistant high-strength magnesium alloy containing Sc and a preparation method thereof. Background Art

[0002] As the lightest commercial metal structural material, magnesium alloy has been widely used in aviation, aerospace, automobile, and 3C (computer, communication, consumer electronics) fields due to its high specific strength and specific stiffness, as well as excellent damping performance, anti-magnetic, shielding and heat dissipation characteristics. Taking the application of magnesium alloy in automobiles and motorcycle rail trains as an example, this material not only significantly reduces the overall weight, improves the dynamic performance of the vehicle, reduces energy consumption, but also effectively controls vibration and noise. However, the current application of magnesium has not fully tapped its potential advantages. The main reason is that most magnesium structural parts are manufactured using die-casting technology, which limits the types and types of products: the application range is narrow, of which 80% of die-cast parts are used in the automotive industry, and 90% are limited to small-volume structural parts at room temperature, while heat-resistant and high-strength magnesium alloy materials are still scarce.

[0003] Among rare earth elements, scandium (Sc) has a significant advantage due to its high melting point (1514°C). Every 1% (molar fraction) of scandium added can increase the melting point of magnesium alloy by about 5°C, which is very beneficial for the development of heat-resistant magnesium alloys. At the same time, the density of scandium is only 3.0g / cm 3 , which is lower than other rare earth elements, thus maintaining the lightweight advantage of magnesium alloys while enhancing high temperature performance. In addition, due to the high melting point and low diffusion coefficient of scandium, it can also improve the creep resistance of the alloy at high temperatures. However, there are relatively few studies on magnesium rare earth alloys containing hafnium, and there are no public reports on their actual applications. Magnesium alloy grades containing scandium have not yet been introduced in the latest national standards. Summary of the invention

[0004] In view of the defects in the prior art, the object of the present invention is to provide a heat-resistant and high-strength magnesium alloy containing Sc; in addition, the present invention also provides a preparation method of the heat-resistant and high-strength magnesium alloy containing Sc.

[0005] The first aspect of the present invention provides a heat-resistant and high-strength magnesium alloy containing Sc, which is composed of the following components in percentage by mass: Gd: 9% to 10.5%, Y: 2.0% to 3.5%, Zn: 1.0% to 2.0%, Sc: 1% to 1.5%, Mn: 0.5% to 1%, Ce: 0.2% to 0.6%, Zr: 0.3% to 0.5%, and the remainder is Mg and impurity elements.

[0006] In the present invention, firstly, the maximum solid solubility of Sc in Mg is 25.9wt%. In addition to forming a Mn2Sc phase with high thermal stability with Mn, Sc mainly exists in the Mg matrix in the form of solid solution. It is known from previous reports that the Mn2Sc phase is often granular, but in the present invention, the addition of trace Ce, in addition to forming Mg12Ce with the same high thermal stability, also changes the morphology of Mn2Sc from granular to a disc elongated along (0001) Mg. The disc-shaped Mn2Sc and lath-shaped Mg12Ce distributed along (0001) Mg can hinder non-basal slip, thereby significantly improving high-temperature creep resistance. Secondly, a large number of stacking faults are observed in Sc-containing alloys, which is related to the solid solution of Sc in the Mg matrix. High-density stacking faults can strongly hinder dislocation slip, thereby improving room temperature strength. In addition, micro-nano-sized Mn2Sc and Mg12Ce can pin the migration of recrystallized grain boundaries during forging, inhibiting the growth of recrystallized grains. Grain refinement also significantly improves the room temperature strength.

[0007] In one embodiment of the present invention, the composition is composed of the following components in mass percentage: Gd: 9% to 10.5%, Y: 2.0% to 3.5%, Zn: 1.0% to 2.0%, Sc: 1% to 1.5%, Mn: 0.5% to 1%, Ce: 0.2% to 0.6%, Zr: 0.3% to 0.5%, and the remainder is Mg and impurity elements.

[0008] The second aspect of the present invention provides a method for preparing the above-mentioned heat-resistant high-strength magnesium alloy containing Sc, comprising the following steps:

[0009] S1. Alloy casting: weighing a formula amount of pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy as raw materials, and casting them into alloy ingots after melting;

[0010] S2, solution treatment: the alloy ingot obtained in S1 is placed in a heat treatment furnace for homogenization, heated to 480°C, kept at this temperature for 24 hours, and processed into forging plates;

[0011] S3. Forging: preheat the magnesium alloy ingot after homogenization treatment to 475℃-490℃, preheat the upper and lower anvils to 400℃, and perform upsetting and drawing multi-directional forging on the ingot. The downsetting pass is 40-50% and the downdrawing pass is 20-25%. The downdrawing speed is controlled at 200-400mm / min. The above three upsetting and drawing treatments are performed. The aging treatment must be completed after forging. The forging plate is kept at 200℃ for 48h and taken out for air cooling.

[0012] S4. Aging treatment: Place the forged plate in a resistance furnace at 210℃ and keep it warm for 30-45h.

[0013] In one embodiment of the present invention, step S1 specifically includes the following steps:

[0014] S11, first preheating pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy at 150-180° C. for 20-30 minutes, and drying, and preheating the refining agent and the mold at 150-200° C. for 30-60 minutes;

[0015] S12, pure Mg, Mg-Sc master alloy and Mg-Mn master alloy are melted under the protection of CO2 and SF6 mixed gas, and when the liquid temperature is 700-720°C after melting, other preheated raw materials are added to the melt, and then stirred until the alloy elements are completely dissolved in the melt, the melt is heated to 730-750°C, a refining agent is added for refining, and the temperature is kept at 730-750°C for 20-30 minutes and then cooled to 700-730°C;

[0016] S13. After skimming off the slag, casting is performed into a preheated mold under the protection of a mixed gas of CO2 and SF6, and immediately water quenching is performed to obtain an alloy ingot.

[0017] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0018] 1. The heat-resistant high-strength magnesium alloy containing Sc provided by the present invention greatly broadens the service temperature range of the high-strength magnesium alloy, and while significantly improving the room temperature strength to 510 MPa, it also reduces the creep rate above 300°C by 1-2 orders of magnitude.

[0019] 2. The preparation method of the heat-resistant high-strength magnesium alloy containing Sc provided by the present invention adopts conventional deformation and heat treatment processes and is easy to realize industrial production. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0021] Example 1

[0022] The present embodiment provides a heat-resistant and high-strength magnesium alloy containing Sc, which is composed of the following components in percentage by mass: Gd: 10%, Y: 3.0%, Zn: 1.5%, Sc: 1.2%, Mn: 0.8%, Ce: 0.4%, Zr: 0.4%, and the remainder is Mg and unavoidable impurities.

[0023] The preparation method of the Sc-containing heat-resistant high-strength magnesium alloy is as follows:

[0024] S1. Alloy casting:

[0025] S11, first preheating pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy at 150-180° C. for 20-30 minutes, and drying, and preheating the refining agent and the mold at 150-200° C. for 30-60 minutes;

[0026] S12, pure Mg, Mg-Sc master alloy and Mg-Mn master alloy are melted under the protection of CO2 and SF6 mixed gas, and when the liquid temperature is 700-720°C after melting, other preheated raw materials are added to the melt, and then stirred until the alloy elements are completely dissolved in the melt, the melt is heated to 730-750°C, a refining agent is added for refining, and the temperature is kept at 730-750°C for 20-30 minutes and then cooled to 700-730°C;

[0027] S13, after skimming off the scum, casting into a preheated mold under the protection of a mixed gas of CO2 and SF6, and immediately quenching with water to obtain an alloy ingot;

[0028] S2, solution treatment: the alloy ingot obtained in S1 is placed in a heat treatment furnace for homogenization, heated to 480°C, kept at this temperature for 24 hours, and processed into forging plates;

[0029] S3. Forging: preheat the magnesium alloy ingot after homogenization treatment to 475°C-490°C, preheat the upper and lower anvils to 400°C, and perform upsetting and drawing multi-directional forging on the ingot. The downsetting pass is 40-50% and the downsetting pass is 20-25%. The down-pressing speed is controlled at 200-400mm / min, and the above three upsetting and drawing treatments are performed.

[0030] S4. Aging treatment needs to be completed after forging. The forged plate should be kept at 210℃ for 40h and then taken out for air cooling.

[0031] Example 2

[0032] The present embodiment provides a heat-resistant and high-strength magnesium alloy containing Sc, which is composed of the following components in percentage by mass: Gd: 10.5%, Y: 3.5%, Zn: 2.0%, Sc: 1.5%, Mn: 1.0%, Ce: 0.6%, Zr: 0.5%, and the remainder is Mg and unavoidable impurities.

[0033] The preparation method of the Sc-containing heat-resistant high-strength magnesium alloy is as follows:

[0034] S1. Alloy casting:

[0035] S11, first preheating pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy at 150-180° C. for 20-30 minutes, and drying, and preheating the refining agent and the mold at 150-200° C. for 30-60 minutes;

[0036] S12, pure Mg, Mg-Sc master alloy and Mg-Mn master alloy are melted under the protection of CO2 and SF6 mixed gas, and when the liquid temperature is 700-720°C after melting, other preheated raw materials are added to the melt, and then stirred until the alloy elements are completely dissolved in the melt, the melt is heated to 730-750°C, a refining agent is added for refining, and the temperature is kept at 730-750°C for 20-30 minutes and then cooled to 700-730°C;

[0037] S13, after skimming off the scum, casting into a preheated mold under the protection of a mixed gas of CO2 and SF6, and immediately quenching with water to obtain an alloy ingot;

[0038] S2, solution treatment: the alloy ingot obtained in S1 is placed in a heat treatment furnace for homogenization, heated to 480°C, kept at this temperature for 24 hours, and processed into forging plates;

[0039] S3. Forging: preheat the magnesium alloy ingot after homogenization treatment to 475°C-490°C, preheat the upper and lower anvils to 400°C, and perform upsetting and drawing multi-directional forging on the ingot. The downsetting pass is 40-50% and the downsetting pass is 20-25%. The down-pressing speed is controlled at 200-400mm / min, and the above three upsetting and drawing treatments are performed.

[0040] S4. Aging treatment needs to be completed after forging. The forged plate should be kept at 210℃ for 40h and then taken out for air cooling.

[0041] Example 3

[0042] The present embodiment provides a heat-resistant and high-strength magnesium alloy containing Sc, which is composed of the following components in percentage by mass: Gd: 9%, Y: 2.0%, Zn: 1.0%, Sc: 1.0%, Mn: 0.5%, Ce: 0.2%, Zr: 0.3%, and the remainder is Mg and unavoidable impurities.

[0043] The preparation method of the Sc-containing heat-resistant high-strength magnesium alloy is as follows:

[0044] S1. Alloy casting:

[0045] S11, first preheating pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy at 150-180° C. for 20-30 minutes, and drying, and preheating the refining agent and the mold at 150-200° C. for 30-60 minutes;

[0046] S12, pure Mg, Mg-Sc master alloy and Mg-Mn master alloy are melted under the protection of CO2 and SF6 mixed gas, and when the liquid temperature is 700-720°C after melting, other preheated raw materials are added to the melt, and then stirred until the alloy elements are completely dissolved in the melt, the melt is heated to 730-750°C, a refining agent is added for refining, and the temperature is kept at 730-750°C for 20-30 minutes and then cooled to 700-730°C;

[0047] S13, after skimming off the scum, casting into a preheated mold under the protection of a mixed gas of CO2 and SF6, and immediately quenching with water to obtain an alloy ingot;

[0048] S2, solution treatment: the alloy ingot obtained in S1 is placed in a heat treatment furnace for homogenization, heated to 480°C, kept at this temperature for 24 hours, and processed into forging plates;

[0049] S3. Forging: preheat the magnesium alloy ingot after homogenization treatment to 475°C-490°C, preheat the upper and lower anvils to 400°C, and perform upsetting and drawing multi-directional forging on the ingot. The downsetting pass is 40-50% and the downsetting pass is 20-25%. The down-pressing speed is controlled at 200-400mm / min, and the above three upsetting and drawing treatments are performed.

[0050] S4. Aging treatment needs to be completed after forging. The forged plate should be kept at 210℃ for 40h and then taken out for air cooling.

[0051] Comparative Example 1

[0052] This comparative example provides a Mg-Gd-based magnesium alloy, in which the weight percentages of the components are: Gd: 10%, Y: 3.5%, Zn: 1.5%, Mn: 0.8%, Ce: 0.4%, Zr: 0.4%, and the balance is Mg and unavoidable impurities.

[0053] The preparation method of the Mg-Gd based magnesium alloy in this comparative example is consistent with that in Example 1.

[0054] Comparative Example 2

[0055] This comparative example provides a magnesium alloy containing excess Sc, in which the weight percentages of the components in the magnesium alloy containing excess Sc are: Gd: 10%, Y: 3.5%, Zn: 1.5%, Sc: 2.5%, Mn: 0.8%, Ce: 0.4%, Zr: 0.4%, and the balance is Mg and unavoidable impurities.

[0056] The preparation method of the magnesium alloy containing excess Sc in this comparative example is consistent with that in Example 1.

[0057] Experimental example

[0058] In this experimental example, the properties of the magnesium alloys prepared in Examples 1-3 and Comparative Examples 1-2 were tested. The test results are shown in Table 1.

[0059] Table 1 Room temperature mechanical properties of examples and comparative examples

[0060]

[0061] The room temperature mechanical properties of the forged state after forging aging of the comparative example 1, comparative example 2 and embodiment 1 of the present invention are shown in Table 1. It can be seen from Table 1 that the mechanical properties of the alloys of comparative example 1, comparative example 2 and embodiment 1 of the present invention vary greatly, among which the alloy of embodiment 1 containing an appropriate amount of Sc has the best room temperature strength, high temperature strength and creep resistance.

[0062] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A heat-resistant high-strength magnesium alloy containing Sc, characterized in that: It is composed of the following components in percentage by mass: Gd: 9% to 10.5%, Y: 2.0% to 3.5%, Zn: 1.0% to 2.0%, Sc: 1% to 1.5%, Mn: 0.5% to 1%, Ce: 0.2% to 0.6%, Zr: 0.3% to 0.5%, and the remainder is Mg and impurity elements.

2. The heat-resistant high-strength magnesium alloy containing Sc according to claim 1, characterized in that: It is composed of the following components in percentage by mass: Gd: 9% to 10.5%, Y: 2.0% to 3.5%, Zn: 1.0% to 2.0%, Sc: 1% to 1.5%, Mn: 0.5% to 1%, Ce: 0.2% to 0.6%, Zr: 0.3% to 0.5%, and the remainder is Mg and impurity elements.

3. The method for preparing the heat-resistant high-strength magnesium alloy containing Sc according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Alloy casting: weighing a formula amount of pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy as raw materials, and casting them into alloy ingots after melting; S2, solution treatment: the alloy ingot obtained in S1 is placed in a heat treatment furnace for homogenization, heated to 480°C, kept at this temperature for 24 hours, and processed into forging plates; S3. Forging: preheat the magnesium alloy ingot after homogenization treatment to 475℃-490℃, preheat the upper and lower anvils to 400℃, and perform upsetting and drawing multi-directional forging on the ingot. The downsetting pass is 40-50% and the downdrawing pass is 20-25%. The downdrawing speed is controlled at 200-400mm / min. The above three upsetting and drawing treatments are performed. The aging treatment must be completed after forging. The forging plate is kept at 200℃ for 48h and taken out for air cooling. S4. Aging treatment: Place the forged plate in a resistance furnace at 210℃ and keep it warm for 30-45h.

4. The method for preparing a heat-resistant high-strength magnesium alloy containing Sc according to claim 3, characterized in that: Step S1 specifically includes the following steps: S11, first preheating pure Mg, pure Zn, Mg-Gd master alloy, Mg-Y master alloy, Mg-Sc master alloy, Mg-Mn master alloy, Mg-Ce master alloy and Mg-Zr master alloy at 150-180° C. for 20-30 minutes, and drying, and preheating the refining agent and the mold at 150-200° C. for 30-60 minutes; S12, pure Mg, Mg-Sc master alloy and Mg-Mn master alloy are melted under the protection of CO2 and SF6 mixed gas, and when the liquid temperature is 700-720°C after melting, other preheated raw materials are added to the melt, and then stirred until the alloy elements are completely dissolved in the melt, the melt is heated to 730-750°C, a refining agent is added for refining, and the temperature is kept at 730-750°C for 20-30 minutes and then cooled to 700-730°C; S13. After skimming off the slag, casting is performed into a preheated mold under the protection of a mixed gas of CO2 and SF6, and immediately water quenching is performed to obtain an alloy ingot.

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