阅读说明：本技术 新型耐热高强Mg-Al-Ca-Gd镁合金及其制备方法 (Novel heat-resistant high-strength Mg-Al-Ca-Gd magnesium alloy and preparation method thereof ) 是由 于文波 马超胜 黄振莺 李世波 周洋 于 2019-10-30 设计创作，主要内容包括：本发明涉及一种新型耐热高强Mg-Al-Ca-Gd镁合金及其制备方法。本发明的合金化学成分质量百分比为：铝：5.4-6.3,锰：0.5-0.9,钙：3.9-4.0,钆：0.3-0.7,其余为镁和不可避免的杂质；同时,该镁合金还含有添加元素锌和锑质量百分比：锌；0-0.1,锑：0-0.09。制备方法：坩埚底部涂上氮化硼,加入纯镁锭,然后加入所需铝锭,在CO<Sub>2</Sub>和SF<Sub>6</Sub>混合气体保护下加热熔化；将预热的镁-钆中间合金加入熔体中；将预热的加入铝-锰或镁-锰中间合金加入熔体中,均匀搅拌,进行除铁和硅杂质；加入元素钙或镁-钙中间合金到熔体中,温度保持在800℃以下,均匀搅拌；静止处理,待温度降至720℃以下,将熔体直接进行浇注可获得铸锭；或者先浇注成铸锭,然后将铸锭在270-470℃挤压成型材或厚板,再轧制成薄板。(The invention relates to a novel heat-resistant high-strength Mg-Al-Ca-Gd magnesium alloy and a preparation method thereof. The alloy comprises the following chemical components in percentage by mass: aluminum: 5.4-6.3, manganese: 0.5-0.9, calcium: 3.9-4.0, gadolinium: 0.3 to 0.7, and the balance of magnesium and inevitable impurities; meanwhile, the magnesium alloy also contains the following additive elements in percentage by mass: zinc; 0-0.1, antimony: 0-0.09. The preparation method comprises the following steps: coating boron nitride on the bottom of the crucible, adding pure magnesium ingot, adding needed aluminum ingot, and adding CO 2 And SF 6 Heating and melting under the protection of mixed gas; adding the preheated magnesium-gadolinium intermediate alloy into the melt; adding the preheated added aluminum-manganese or magnesium-manganese intermediate alloy into the melt, uniformly stirring, and removing iron and silicon impurities; adding element calcium or magnesium-calcium intermediate alloy into the melt, keeping the temperature below 800 ℃, and uniformly stirring; standing, cooling to below 720 deg.C, and directly pouring the melt to obtain castingAn ingot; or casting into an ingot, extruding the ingot at the temperature of 470 ℃ at 270 ℃ to form a profile or a thick plate, and rolling into a thin plate.)

1. The heat-resistant high-plasticity magnesium alloy is characterized by comprising the following chemical components in percentage by mass: aluminum: 5.4-6.3, manganese: 0.5-0.9, calcium: 3.9-4.0, gadolinium: 0.3-0.7, which is associated with magnesium and unavoidable impurities; meanwhile, the magnesium alloy also contains additive elements of zinc and antimony.

2. The heat-resistant high-strength magnesium alloy according to claim 1, wherein the chemical components comprise, by mass: aluminum: 5.4-6.3, manganese: 0.5-0.9, calcium: 3.9-4.0, gadolinium: 0.3-0.7.

3. A method for preparing the heat-resistant high-plasticity magnesium alloy according to claim 1, which comprises the following steps: (1) mixing the materials according to the components of the magnesium alloy, wherein the materials comprise pure magnesium, pure aluminum, aluminum-manganese or magnesium-manganese intermediate alloy, aluminum-gadolinium or magnesium-gadolinium intermediate alloy, pure calcium or magnesium-calcium intermediate alloy and pure antimony, and the adopted intermediate alloy is a commercial standard intermediate alloy; (2) coating boron nitride on the bottom of the crucible, adding pure magnesium ingot, adding the required aluminum ingot on the magnesium ingot, and reacting with CO₂And SF₆Heating and melting under the protection of mixed gas; (3) adding the preheated magnesium-gadolinium intermediate alloy into the melt; (4) adding the preheated added aluminum-manganese or magnesium-manganese intermediate alloy into the melt, uniformly stirring, and removing iron and silicon impurities; (5) adding element calcium or magnesium-calcium intermediate alloy into the melt, keeping the temperature below 800 ℃, and uniformly stirring; (6) standing, and directly pouring the melt to obtain an ingot when the temperature is reduced to below 720 ℃; or casting into an ingot, extruding the ingot at the temperature of 470 ℃ at 270 ℃ to form a profile or a thick plate, and rolling into a thin plate.

Technical Field

The invention relates to a novel heat-resistant high-strength Mg-Al-Ca-Gd magnesium alloy and a preparation method thereof

Background

Magnesium alloy is the lightest metal structure material in the world, and has important application value and wide development prospect in the competitive field of light weight and low emission of the automobile industry [ Joost W J, script Materialia,2017,128: 107: 112 ]. However, the magnesium alloy has low absolute strength, especially poor high-temperature performance, and limits the application of the magnesium alloy in the aspects of engine and transmission mechanism parts, but the magnesium alloy plays a role in playing a role in lifting light weight for the whole automobile^[4]. At present, in the field of heat-resistant magnesium alloys for automobiles, developed countries such as europe and the united states are in the leading level in the world. Against the domestic view, under the condition that developed countries strictly control the export of the technology and protect the patent in China, the application of the heat-resistant magnesium alloy in the automobile industry in China has a large gap with the application in China. The application of the heat-resistant magnesium alloy in high-temperature structural members is an important development trend, and therefore, the heat-resistant magnesium alloy is one of key research objects in key special items of key basic material technology improvement and industrialization in national research and development plans in China. Therefore, the development of high-performance heat-resistant magnesium alloy and the research on the creep rupture mechanism thereof have extremely strong application prospects and urgent needs [ Wenlihua, light alloy processing technology,2016, 44(9):7-11 ].

Development of a novel heat-resistant magnesium alloy through alloying is an important development direction. The Mg-Al series magnesium alloy has good casting performance and low price. The magnesium alloy developed by adding rare earth elements, such as AE series magnesium alloy such as Mg-Al-RE, has high creep strength and good comprehensive performance, and can be used for automobile power system parts^[8]. However, the AE-based magnesium alloy is suitable only for production by die casting with a relatively high cooling rate because a relatively low cooling rate results in coarse Al₂RE compounds are formed, thereby reducing the mechanical properties of magnesium alloys [ Zhang J, Zhang M, Materials Science and Engineering A2010,527: 2527-. On the other hand, since rare earth metals are relatively expensive, the use of AE-based magnesium alloys is greatly limited in the fields of automobile industry and power system [ Pan F, Journal of Materials Science andtechnology,2016,32(12):1211-1221 ]. Therefore, it is sought to develop a novel heat-resistant magnesium alloy by adding alkaline earth elements (Ca, Sr, Ba) to other elements to reduce the cost. Wherein, Ca has low price, low melting point and density approximate to that of Mg (about 1.55 g/cm)³) As magnesium alloy additive elements, there is an increasing interest [ Amberger D, Acta Materialia,2012,60(5): 2277-. The addition of Ca element in conventional magnesium alloy can not only raise the oxidizing combustion temperature of magnesium alloy, but also refine the casting structure and raise the normal temperature mechanical property and high temperature creep resistance of magnesium alloy. Elamai et Al investigated the effect of Ca/Al changes on the choice and properties of phases in Mg-Al-Ca alloys, and the results showed that (Mg/Al) in Mg-Al-Ca alloys when Ca/Al is between 0.6 and 0.9₂The Ca phase mainly comprises C36 and C14, and the C15 is less, so that the Ca phase has a very effective barrier effect on grain boundary sliding in the high-temperature creep process, and the heat resistance of the magnesium alloy can be obviously improved; on the other hand, (Mg/Al)₂Ca is in the form of coarse mesh or plate, which severely reduces strength and toughness, and has more insufficient properties compared with rare earth-containing heat-resistant magnesium alloy [ Elamami H A, Journal of Alloys and Compounds,2018,764: 216-.

From the above, the high temperature stable phase (Mg/Al)₂Ca can effectively pin the grain boundary sliding, is beneficial to improving the creep property of the heat-resistant magnesium alloy, and on the other hand, the coarse plates are distributed in a sheet shape or a net shape (Mg/Al)₂Ca phase, which divides the matrix, severely limits strength and toughness and inhibits coarse plate-like (Mg/Al)₂The generation of Ca phase to promote uniform and fine (Mg/Al)₂The Ca phase is dispersed in the solidification structure, which becomes the key point for developing the heat-resistant Mg-Al-Ca alloy with high creep resistance and low cost. With coarse plates in sheet or web form (Mg/Al)₂Ca phase, which divides the matrix, severely limits strength and toughness and inhibits coarse plate-like (Mg/Al)₂The generation of Ca phase to promote uniform and fine (Mg/Al)₂The Ca phase is dispersed in the solidification structure, which becomes the key point for developing the heat-resistant Mg-Al-Ca alloy with high creep resistance and low cost.

The invention content is as follows:

the invention is based onHeterogeneous nucleation and modification mechanism, and control (Mg/Al) by regulating calcium and gadolinium content₂The Ca phase nucleation and growth process successfully develops the novel heat-resistant high-strength Mg-Al-Ca-Gd magnesium alloy which is suitable for casting and deformation working conditions.

The technical scheme of the invention is as follows:

melting a magnesium ingot and aluminum required to be added together, adding a magnesium-gadolinium intermediate alloy to introduce gadolinium, stirring, adding aluminum-manganese or magnesium-manganese intermediate alloy to introduce manganese, removing iron and silicon impurities, adding calcium required to be added or magnesium-calcium intermediate alloy to introduce calcium, refining, standing, keeping the temperature, and directly casting the melt into an ingot; or cast into ingots, and then extruded and rolled into sheets.

The alloy of the invention comprises the following components:

the heat-resistant high-plasticity magnesium alloy is characterized by comprising the following chemical components in percentage by mass: aluminum: 5.4-6.3, manganese: 0.5-0.9, calcium: 3.9-4.0, gadolinium: 0.3-0.7, which is associated with magnesium and unavoidable impurities; meanwhile, the magnesium alloy also contains additive elements of zinc and antimony.

The heat-resistant high-strength magnesium alloy according to claim 1, wherein the chemical components comprise, by mass: aluminum: 5.4-6.3, manganese: 0.5-0.9, calcium: 3.9-4.0, gadolinium: 0.3-0.7.

The heat-resistant high-strength magnesium alloy according to claim 1, wherein the mass percentages of the added elements are as follows: 0-0.1 of zinc, antimony: 0-0.09.

A method for preparing the heat-resistant high-plasticity magnesium alloy according to claim 1, which comprises the following steps:

step 1, mixing materials according to the components of the magnesium alloy, wherein the materials comprise pure magnesium, pure aluminum, aluminum-manganese or magnesium-manganese intermediate alloy, aluminum-gadolinium or magnesium-gadolinium intermediate alloy, pure calcium or magnesium-calcium intermediate alloy and pure antimony, and the adopted intermediate alloy is a commercial standard intermediate alloy;

step 2, coating boron nitride on the bottom of the crucible, adding a pure magnesium ingot, then adding a required aluminum ingot on the magnesium ingot, and subjecting the magnesium ingot to CO₂And SF₆Under the protection of mixed gas, addHot melting;

step 3, adding the preheated magnesium-gadolinium intermediate alloy into the melt;

step 4, adding the preheated added aluminum-manganese or magnesium-manganese intermediate alloy into the melt, uniformly stirring, and removing iron and silicon impurities;

step 5, adding element calcium or magnesium-calcium intermediate alloy into the melt, keeping the temperature below 800 ℃, and uniformly stirring;

step 6, standing, and directly pouring the melt to obtain an ingot when the temperature is reduced to below 720 ℃; or casting into an ingot, extruding the ingot at the temperature of 470 ℃ at 270 ℃ to form a profile or a thick plate, and rolling into a thin plate.

Compared with the prior art, the invention has the following characteristics:

1. the alloy of the invention is suitable for casting working conditions and deformation working conditions, such as rolling, extrusion and the like;

2. the magnesium alloy of the invention has the advantages of high cast tensile strength, high extensibility and high rolling deformation rate;

3. the alloy does not contain toxic lead elements and brittle silicon elements;

4. the alloy of the invention is added with gadolinium to form new Al₈Mn₄Gd phase, Al in alloy₂The Ca phase is refined, which is beneficial to improving the performance of the alloy;

5. the preparation method of the patent is characterized in that: firstly, melting magnesium ingot and aluminum ingot simultaneously, then adding required element gadolinium, stirring, adding manganese element, and finally adding calcium element.

Description of the drawings:

FIG. 1: mg-2.5Al₂Ca-0.1Al₈Mn₄Scanning electron microscope image of Gd proportioning alloy as cast

FIG. 2: mg-2.5Al₂Ca-0.1Al₈Mn₄Scanning electron microscope image of Gd proportioning alloy after 80% rolling amount

FIG. 3: alloy cast XRD scanning line spectrum with different element ratios.

Detailed Description