阅读说明：本技术 一种低密度低成本Fe-Mn-Al-C中熵合金的制备方法 (Preparation method of low-density low-cost Fe-Mn-Al-C intermediate entropy alloy ) 是由 惠希东 百瑞 刘旭莉 吉铮 于 2020-06-11 设计创作，主要内容包括：本发明公开一种低密度低成本Fe-Mn-Al-C中熵合金的制备方法,属于金属材料及制备领域。其合金化学成分按原子百分比为：Fe33.0～38.0％,Mn33.0～38.0％,Al21.0～25.0％,C4.0～7.0％。该合金的制备工艺为将冶金原料Fe、Mn、Al、C去氧化皮,采用超声波或酸洗方法进行清洗；用非自耗真空电弧炉或感应炉熔炼合金,通过真空吸铸或浇铸方法,获得中熵合金板状或棒状材料。该中熵合金具有低密度的同时,材料还具有高强度和高塑性,并且合金元素成本低,可用于交通、机械和能源等工业领域。(The invention discloses a preparation method of a low-density and low-cost Fe-Mn-Al-C entropy alloy, belonging to the field of metal materials and preparation. The alloy comprises the following chemical components in atomic percentage: 33.0-38.0% of Fe33.0%, 33.0-38.0% of Mn33.0%, 21.0-25.0% of Al0% and 4.0-7.0% of C. The preparation process of the alloy comprises the steps of removing oxide skin from metallurgical raw materials of Fe, Mn, Al and C, and cleaning by an ultrasonic wave or acid pickling method; the alloy is smelted by a non-consumable vacuum arc furnace or an induction furnace, and the medium-entropy alloy plate-shaped or rod-shaped material is obtained by a vacuum suction casting or casting method. The medium-entropy alloy has low density, high strength and high plasticity, and low cost of alloy elements, and can be used in the industrial fields of traffic, machinery, energy and the like.)

1. A preparation method of a low-density low-cost Fe-Mn-Al-C intermediate entropy alloy is characterized in that the alloy comprises the following chemical components in atomic percentage: 33.0-38.0% of Fe33.0%, 33.0-38.0% of Mn33.0%, 21.0-25.0% of Al0%, and 4.0-7.0% of C;

the preparation method comprises the following steps:

1) removing surface oxide skin of raw material metal from metallurgical raw materials of Fe, Mn, Al and C with the purity of more than 99.9% by mechanical polishing or acid pickling for alloy preparation;

2) the mixture ratio is accurately weighed by converting the molar ratio into the mass ratio, the Mn raw material is additionally added by 5 percent by mass to compensate the smelting loss, and then the raw material is cleaned by absolute ethyl alcohol ultrasonic oscillation;

3) smelting the alloy, and carrying out suction casting or casting on the molten alloy melt into a mold to obtain a medium-entropy alloy plate-shaped or rod-shaped material;

4) homogenizing and solution-treating the plate-shaped or rod-shaped sample of the medium-entropy alloy.

2. The method for preparing low-density and low-cost Fe-Mn-Al-C entropy alloy as claimed in claim 1, wherein the chemical composition of the alloy in atomic percentage is preferably in the range of: 35.0-37.0% of FeC, 34.5-36.5% of MnC, 22.0-24.0% of AlC and 4.0-4.5% of C.

3. The method of claim 1, wherein the melting is vacuum arc non-consumable melting with a vacuum value of less than 5 × 10^-2Introducing argon to the pressure in the furnace to reach 0.05 MPa; the smelting current is 100-250A, the electric arc holding time is 1-3 min, and the overturning and repeated smelting is carried out for more than 4 times so as to ensure that the components of the alloy ingot are uniform.

4. The method for preparing a low-density and low-cost Fe-Mn-Al-C entropy alloy as claimed in claim 1, wherein the melting is induction melting, the induction heating frequency is medium frequency or high frequency, the melting environment is atmospheric air, and the melting temperature is 1450 ℃ to 1550 ℃.

5. The method for preparing the low-density and low-cost Fe-Mn-Al-C entropy alloy as recited in claim 1, wherein the homogenization heat treatment process comprises: the heat preservation temperature is 1000-1200 ℃, and the heat preservation time is 1-4 h.

6. The method for preparing the low-density and low-cost Fe-Mn-Al-C entropy alloy as claimed in claim 1, wherein the solution heat treatment process comprises the following steps: heating at 1000-1150 deg.c for 0.5-4 hr, and water quenching at normal temperature.

Technical Field

The invention relates to a preparation method of a low-density, low-cost and high-performance medium-entropy alloy, belonging to the field of metal materials and preparation thereof.

Background

According to the mixing entropy zone of the alloy meltIn particular, the alloys can be classified as high entropy alloys (Δ S)_mix>1.6R, R is gas constant, the same below), medium entropy alloy (1.1R)<ΔS_mix<1.6R), low entropy alloy (Delta S)_mix<1.1R). The traditional metal materials such as steel, aluminum alloy, titanium alloy and the like are basically low-entropy alloys. The high-entropy alloy has various main elements, is widely researched due to the excellent performance of the high-entropy alloy, and various high-entropy alloy series are developed. For example, FeCoCrNiMn series high-entropy alloy has good mechanical property at low temperature, AlCoCrCuFeNi series high-entropy alloy can obtain higher strength and corrosion resistance, and NbMoTaW series high-entropy alloy has excellent high-temperature resistance.

Although high entropy alloys have gained widespread attention, the number of high entropy alloys that can be used for engineering applications is still small, particularly less high entropy alloys that can achieve high strength and plasticity matches. For example, FeCoCrNiMn-based high-entropy alloy has excellent tensile plasticity, but generally has a low tensile strength. Recently, medium entropy alloys are receiving increasing attention and research as a potential alloy. Compared with the high-entropy alloy, the medium-entropy alloy has the advantages that the principal element number is reduced, excellent performance can be obtained through proper regulation and control of components and processes, and industrial application is easier to realize. Currently, most researches are carried out on entropy alloys in a CoCrNi system and a FeCoNi system, nanocrystalline particles are separated out on an FCC solid solution matrix through component optimization and process adjustment, the number, the form and the distribution of a nano strengthening phase are changed, and the matching of strength and plasticity is realized. However, in the current medium-entropy alloy system, elements with high cost such as Co and Ni are contained, so that the cost of the alloy is high, and the large-scale popularization and application of the alloy are not facilitated. On the other hand, for engineering structural materials, the aim of pursuing light weight and high strength is constant, and the addition of high Co and Ni contents is not beneficial to the reduction of the alloy density. However, no report is found on the low-density Fe-Mn-Al-C medium entropy alloy which does not contain Co and Ni elements at present.

Disclosure of Invention

The invention aims to solve the problem of good matching of specific strength and plasticity of a medium-entropy alloy, and provides a medium-entropy Fe-Mn-Al-C alloy with low density, high specific strength, high plasticity and low cost and a preparation method thereof so as to be beneficial to popularization and application of the alloy and greatly reduce the cost of the alloy. The method designs the low-density and low-cost medium-entropy alloy components by adding a proper amount of alloy strong plasticizing elements. By formulating a reasonable hot working and solution aging heat treatment process system, on the premise of keeping better processing performance, higher strength and plasticity are kept. Therefore, the key technology for solving the problems is selection and dosage of alloy elements, optimization of a processing and preparation process and selection of a solution aging heat treatment process.

The invention is realized by the following technical scheme:

a preparation method of a low-density low-cost Fe-Mn-Al-C intermediate entropy alloy comprises the following alloy chemical components in atomic percentage: 33.0-38.0% of Fe33.0%, 33.0-38.0% of Mn33.0%, 21.0-25.0% of Al0% and 4.0-7.0% of C.

The preparation method comprises the following steps:

1) removing surface oxide skin of raw material metal from metallurgical raw materials Fe, Mn, Al and C with purity of over 99.9% by mechanical polishing or acid washing for alloy preparation;

2) the mixture ratio is accurately weighed by converting the molar ratio into the mass ratio, the Mn raw material is additionally added by 5 percent by mass to compensate the smelting loss, and then the raw material is cleaned by absolute ethyl alcohol ultrasonic oscillation;

3) smelting the alloy, and carrying out suction casting or casting on the molten alloy melt into a mold to obtain a medium-entropy alloy plate-shaped or rod-shaped material;

4) homogenizing and solution-treating the plate-shaped or rod-shaped sample of the medium-entropy alloy.

Further, the alloy chemical composition according to the atom percentage preferred range is: 35.0-37.0% of FeC, 34.5-36.5% of MnC, 22.0-24.0% of AlC and 4.0-4.5% of C.

Further, the smelting is vacuum non-consumable electrode arc furnace smelting, and the vacuum degree value is lower than 5 × 10^-2Introducing argon to the pressure in the furnace to reach 0.05 MPa; the smelting current is 100-250A, the electric arc holding time is 1-3 min, and the overturning and repeated smelting is carried out for more than 4 times so as to ensure that the components of the alloy ingot are uniform.

Further, the smelting is induction smelting, the induction heating frequency is medium frequency or high frequency, the smelting environment is atmosphere, and the melting temperature is 1450-1550 DEG C

Further, the homogenization heat treatment process comprises the following steps: the heat preservation temperature is 1000-1200 ℃, and the heat preservation time is 1-4 h;

further, the solution heat treatment process comprises the following steps: heating at 1000-1150 deg.c for 0.5-4 hr, and water quenching at normal temperature.

The alloy comprehensively considers the influence of the added elements on the density, the cost, the strength, the plasticity and the hot working performance of the alloy during component design, and the specific consideration factors are as follows:

mn: the Mn-Fe alloy is a main element forming a gamma phase in steel, a gamma phase region formed by Mn and Fe is increased along with the increase of Mn, and the solid solubility of Mn in the gamma phase can reach 31.5at percent at 400 ℃. From the perspective of reducing density, the 1 wt% Mn content in the alloy can reduce the density by 0.0085g/cm³Therefore, in order to make the alloy have good plasticity and low density, Mn in the alloy should be high enough, however, if the Mn content in the alloy is too high, α -Mn is easily formed in the structure at room temperature, and β -Mn phase is easily formed at high temperature, and the Mn content is Mn33.0-38.0% in consideration of the mechanical properties and density of the alloy.

Al in the binary phase diagram of Fe-Al, there is a broad Al composition range α -Fe solid solution region on the Fe side, while the face-centered cubic (gamma-Fe) -based solid solution region is closed, so Al promotes the formation of α -Fe₃Al and FeAl from the phase diagram of the Al-Mn binary system, Al has great solid solubility in β -Mn phase, or Al can promote the formation of β -Mn, the interaction of Al with Fe and Mn is comprehensively considered, the content of Al is not easy to be too high, however, Al is an element which is very effective in reducing the density, and the density of the alloy is reduced by 0.101g/cm for every 1 wt% of Al is added³The weight can be reduced by about 1.3%. Therefore, the mechanical property and the density are both considered, and the content of Al is 21.0-25.0%.

C: c is the most important strengthening element in steelC is an element enlarging α -Mn phase, so that a β -Mn phase region is closed, and simultaneously, the density of the alloy is reduced by 0.41g/cm for every 1wt percent of C added³The weight can be reduced by about 5.2%. Therefore, the mechanical property and the density are comprehensively considered, and the content of C is 4.0-7.0%.

The invention has the following beneficial effects:

1) the alloy can realize the matching of high strength and high plasticity. The addition of high Mn and C contents promotes the formation of austenite, so that the alloy takes an austenite phase as a matrix structure, and the alloy has excellent plasticity. Meanwhile, the addition of Al, Mn and C can also play a role in strengthening. Through a reasonable heat treatment process, a second phase can be further precipitated, so that the alloy is further strengthened.

2) The alloy has a low density. It is especially suitable for traffic, machinery and energy industry. Especially for equipment and devices requiring energy consumption such as automobiles, ships, gas turbines and the like, the use of the alloy will lead to weight reduction of the equipment, thereby further reducing energy consumption.

3) Compared with the existing high-entropy alloy and medium-entropy alloy, the alloy only contains Fe, Mn, Al and C elements with lower cost, so that the cost of the alloy is greatly reduced.

Drawings

FIG. 1 shows Fe as a component in example 5_36.4Mn_36.3Al_23.0C_4.3Scanning electron microscope organization after alloy heat treatment;

FIG. 2 shows Fe as a component in example 5_36.4Mn_36.3Al_23.0C_4.3X-ray diffraction curves of the alloy in an as-cast state and a heat treatment state;

FIG. 3 shows Fe as a component in example 5_36.4Mn_36.3Al_23.0C_4.3Room temperature mechanical property curve of the alloy.

Detailed Description

Table 1 shows the alloy compositions of the examples and part of the reference alloy compositions (atomic percent). It is apparent that the embodiments described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Preparing the alloy according to the components shown in alloy 1-9 in table 1, (1) removing surface oxide skin of raw material metal from metallurgical raw materials Fe, Mn, Al and C with the purity of more than 99.9% by mechanical polishing or acid washing, (2) converting the metallurgical raw materials into a mass ratio to accurately weigh and match, adding 5% of the mass of the Mn raw material to compensate smelting loss, and cleaning the raw material by absolute ethyl alcohol ultrasonic oscillation, (3) smelting the alloy by using a vacuum non-consumable arc furnace, wherein the vacuum degree is lower than 5 × 10^-3Introducing high-purity argon until the pressure in the furnace reaches 0.05 MPa; (4) the smelting current is 100-250A, the electric arc holding time is 1-3 min, and the alloy ingot is overturned and repeatedly smelted for more than 4 times so as to ensure that the components of the alloy ingot are uniform; (5) the master alloy ingot was suction-cast into a water-cooled copper mold using a vacuum suction casting apparatus to obtain a plate-like sample having a thickness of 10 mm.

Table 1 example alloy compositions