Two-phase high-entropy alloy and preparation method thereof

文档序号：695993 发布日期：2021-05-04 浏览：54次中文

阅读说明：本技术 一种双相高熵合金及其制备方法 (Two-phase high-entropy alloy and preparation method thereof ) 是由彭英博张伟刘咏于 2020-12-29 设计创作，主要内容包括：本申请提供一种双相高熵合金,包括呈FCC相的第一合金成分和呈BCC相的第二合金成分,所述第一合金成分为FeCoCrNi,所述第二合金成分为FeCoCrNiAl。该双相高熵合金含有合适比例的FCC结构和BCC结构,其综合力学性能优异,具有较高的硬度、强度,以及良好的塑性、韧性。除此之外,本发明还提供一种双相高熵合金的制备方法,该方法生产周期短,可直接成型复杂形状的零件,且成型零件精度高、致密度高、具有优异的综合力学性能。(The application provides a biphase high-entropy alloy, including being the first alloy composition of FCC looks and being the second alloy composition of BCC looks, first alloy composition is FeCoCrNi, the second alloy composition is FeCoCrNiAl. The biphase high-entropy alloy contains an FCC structure and a BCC structure in a proper proportion, has excellent comprehensive mechanical property, higher hardness and strength, and good plasticity and toughness. In addition, the invention also provides a preparation method of the biphase high-entropy alloy, the method has short production period, can directly form parts with complex shapes, and the formed parts have high precision, high density and excellent comprehensive mechanical properties.)

1. A two-phase high-entropy alloy comprising a first alloy component in the FCC phase and a second alloy component in the BCC phase,

the first alloy component is FeCoCrNi,

the second alloy component is FeCoCrNiAl.

2. A dual-phase high entropy alloy according to claim 1, wherein the atomic molar ratio of Fe, Co, Cr, Ni in the first alloy composition is 1: 1: 1: 1;

in the second alloy component, the atomic mole ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

3. a dual-phase high entropy alloy according to claim 1 or 2, wherein the weight ratio of the first alloy component to the second alloy component is 1: (1-2.7).

4. A dual-phase high entropy alloy according to claim 1 or 2, characterized in that the atomic percentage of Al element in the dual-phase high entropy alloy is between 11% and 15%.

5. A method of producing a dual phase high entropy alloy according to any of claims 1 to 4, characterized by comprising the steps of:

preparing a first prealloyed powder based on the elemental composition of the first alloy constituent;

preparing a second prealloyed powder based on the elemental composition of the second alloy constituent;

uniformly mixing the first pre-alloyed powder and the second pre-alloyed powder to obtain mixed powder;

putting the mixed powder into a powder feeding cylinder of SLM equipment, vacuumizing, and introducing inert gas for protection;

establishing a three-dimensional model of a part, slicing and layering the three-dimensional model to obtain data of each section, and importing the data into SLM equipment;

setting technological parameters of a forming process in SLM equipment, wherein the laser power is 250-350W, the scanning speed is 700-1000mm/s, the scanning interval is 0.05-0.09mm, and the powder spreading thickness is 0.03-0.07 mm;

and opening the printing to obtain a molded part.

6. A method for the preparation of a biphasic high entropy alloy according to claim 5, wherein the laydown thickness is 0.05 mm.

7. A method of preparation of a dual phase high entropy alloy according to claim 5, wherein the particle size of the first pre-alloyed powder is in the range of 15-53 μm,

the second pre-alloyed powder has a particle size in the range of 15-53 μm.

8. A method for the preparation of a biphasic high entropy alloy according to claim 5, wherein the process of preparing the mixed powder comprises the steps of:

weighing the first alloy powder and the second alloy powder according to the proportion,

and (3) putting the first alloy powder and the second alloy powder into a mixer for mixing, wherein the mixing time is 4 h.

9. A method for the preparation of a dual phase high entropy alloy of claim 8, wherein the process for the preparation of the mixed powder comprises the steps of:

weighing the first alloy powder and the second alloy powder according to the proportion,

putting the first alloy powder and the second alloy powder into the mixer for mixing for 4h,

and after the mixing is finished, drying the mixed powder at 80 ℃ for 12h for later use.

Technical Field

The invention relates to the technical field of metal materials, in particular to a two-phase high-entropy alloy and a preparation method thereof.

Background

High-entropy Alloys (HEAs) have superior properties, such as a combination of properties including High strength, High hardness, High temperature creep resistance, High temperature oxidation resistance, corrosion resistance, and electromagnetism, which are incomparable with conventional single-principal-element Alloys. The crystal structure of solid solution in the high-entropy alloy is a main factor for controlling the strength, hardness and toughness of the high-entropy alloy, and researches show that: the HEAS of the Face Centered Cubic (FCC) structure has lower strength and hardness but better toughness, while the HEAS of the Body Centered Cubic (BCC) structure has higher strength and hardness but poorer toughness.

Therefore, how to provide a two-phase high-entropy alloy with high strength, high plasticity and excellent comprehensive mechanical properties is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

In order to solve the technical problems, the invention provides a two-phase high-entropy alloy which contains an FCC structure and a BCC structure in a proper proportion, has excellent comprehensive mechanical properties, and has higher hardness, strength, and good plasticity and toughness. In addition, the invention also provides a preparation method of the biphase high-entropy alloy, the method has short production period, can directly form parts with complex shapes, and the formed parts have high precision, high density and excellent comprehensive mechanical properties.

High-entropy Alloys (HEAs) differ from traditional alloy design concepts in that HEAs are not based on one or two elements as principal elements, but instead contain at least four major elements in equal or nearly equal atomic percentages (at.%), tend to form single or simple solid solution phases due to their High mixed entropy effect, and HEAs have a "cocktail" effect in terms of composition-structure-properties. The "cocktail" effect of HEAs refers to a complex effect that results from the fundamental nature of elements and their interactions that make HEAs tissue-properties appear. Due to the designability of the HEAS composition-structure-property, the required microstructure and mechanical properties can be obtained by changing the content of alloying elements.

The invention provides a two-phase high-entropy alloy which comprises a first alloy component in an FCC phase and a second alloy component in a BCC phase, wherein the first alloy component is FeCoCrNi, and the second alloy component is FeCoCrNiAl.

According to the invention, the two-phase high-entropy alloy has FCC and BCC two-phase structures simultaneously by mixing the two-component alloy, and has the high-strength and high-hardness properties of the BCC structure and the good plasticity of the FCC structure.

Furthermore, the proportion of each alloy element in the biphase high-entropy alloy is optimally designed, so that the biphase high-entropy alloy has uniform structure, stable structure, better strength, hardness, wear resistance, good plasticity and other comprehensive mechanical properties.

Preferably, in the first alloy component, an atomic molar ratio of Fe, Co, Cr, and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mole ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

furthermore, the proportion of the FCC-BCC biphase in the biphase high-entropy alloy can be adjusted by regulating and controlling the proportion of the first alloy component and the second alloy component, so that the biphase high-entropy alloy can obtain good balance between high-strength high-hardness property and plasticity, and has excellent comprehensive mechanical property.

Preferably, the weight ratio of the first alloy component to the second alloy component is 1: (1-2.7).

Alloying elements have obvious influence on the organization structure and the performance of the high-entropy alloy, and the main research is more light-weight element Al. In the CuCoNiCrAlxFe high-entropy alloy system, the phase structure of the alloy shows regular change from FCC to BCC along with the increase of Al content, and the microhardness of the alloy shows an increasing 'cocktail' effect. In the CoCrCuFeNi alloy, with the increase of Al element, the phase structure of the alloy undergoes FCC → FCC + BCC → BCC transformation, the hardness of the alloy is increased from 133HV to 655HV, but the plasticity is obviously reduced (the fracture strain is reduced to < 3%), and the hardness is improved due to the solid solution strengthening effect of Al atoms on one hand and the transformation of the toughness FCC phase into a BCC phase with higher strength and hardness on the other hand.

According to the invention, by optimally designing the atomic percent of the Al element in the two-phase high-entropy alloy, the two-phase high-entropy alloy can have an FCC phase and a BCC phase in a proper proportion, and further has good strong plasticity comprehensive mechanical property.

Preferably, the atomic percentage of the Al element in the dual-phase high-entropy alloy is 11-15%.

Although the biphase structure has outstanding advantages in synchronously improving the strong plasticity of the HEAs, the preparation method mainly comprises vacuum arc melting, powder metallurgy and the like at present. In the casting technology such as vacuum arc melting or vacuum induction melting, the alloy element Al for promoting phase change is added in a block form, and is melted together with other pure metal elements or intermediate alloy and is formed in a liquid state, so that the defects of segregation, shrinkage cavity, shrinkage porosity and the like of the Al element or other alloy components (dendritic crystal) influencing the mechanical property are easily generated in the solidification process. Although the powder metallurgy technology can adopt prealloyed powder of two-phase HEAs, the principle is powder solid state sintering, so that the compactness is difficult to further improve, post-treatment processes such as hot isostatic pressing and the like are needed, the production period is long, and the performance of a formed part is poor.

In order to solve the technical problems, the invention also provides a preparation method of the biphase high-entropy alloy, which comprises the following steps:

preparing a first prealloyed powder based on the elemental composition of the first alloy constituent;

preparing a second prealloyed powder based on the elemental composition of the second alloy constituent;

uniformly mixing the first pre-alloyed powder and the second pre-alloyed powder to obtain mixed powder;

putting the mixed powder into a powder feeding cylinder of SLM equipment, vacuumizing, and introducing inert gas for protection;

establishing a three-dimensional model of a part, slicing and layering the three-dimensional model to obtain data of each section, and importing the data into SLM equipment;

the SLM is a complex processing and manufacturing technology, and has numerous related process parameters, which have different degrees of influence on the powder melting-solidifying process, the shape and performance of a formed part, and the like in the selective laser processing process, and a small change of the process parameters may cause a great difference in density, and if the parameter selection is not reasonable, defects such as cracks and holes may be caused, which leads to density reduction, and directly influences the mechanical properties of printed parts, so that SLM process parameter optimization is required.

Setting technological parameters of a forming process in SLM equipment, wherein the laser power is 250-350W, the scanning speed is 700-1000mm/s, the scanning interval is 0.05-0.09mm, and the powder spreading thickness is 0.03-0.07 mm; and (3) obtaining a printed product with the density of more than 99% by optimizing the SLM process parameters.

And opening the printing to obtain a molded part.

The special point-by-point, line-by-line, face-by-face and domain-by-domain forming method for additive manufacturing technology provides a new opportunity for manufacturing technology from traditional macroscopic appearance manufacturing to macro microstructure integrated manufacturing, the Selective Laser Melting (SLM) technology is an important component of the additive manufacturing technology, and is an advanced manufacturing technology which gives consideration to the integrated requirements of precise forming and high-performance formability.

The invention provides a method for preparing a two-phase high-entropy alloy by adopting laser selective melting, which adopts the raw materials of FeCoCrNi alloy powder of FCC phase and FeCoCrNiAl alloy powder of BCC phase, and because the two pre-alloy powders are alloyed, the two pre-alloy powders are simply and mechanically mixed according to a specific proportion to ensure that the pre-alloy powders are uniform, and then the laser selective melting and powder laying printing can be carried out, and the method has no component segregation of Al or other elements and has no casting defect. On the other hand, as the powder material in the SLM completes the melting-solidifying process, the density (more than 99%) of the biphase high-entropy alloy obtained by the SLM method is obviously higher than that of the powder metallurgy method through the optimization of process parameters. In addition, the SLM material increase manufacturing method is suitable for forming parts with complex shapes, and is beneficial to popularization and application of the biphase high-entropy alloy.

Preferably, the powder spreading thickness is 0.05 mm.

Since the median particle size of the selected high-entropy alloy powder suitable for SLM is about 35.1 μm, the printing quality is affected by too high or too low powder spreading thickness.

Preferably, the first pre-alloyed powder has a particle size in the range of 15-53 μm and the second pre-alloyed powder has a particle size in the range of 15-53 μm.

Preferably, the preparation process of the mixed powder comprises the following steps:

weighing the first alloy powder and the second alloy powder according to the proportion,

and (3) putting the first alloy powder and the second alloy powder into a mixer for mixing, wherein the mixing time is 4 h.

Preferably, the preparation process of the mixed powder comprises the following steps:

weighing the first alloy powder and the second alloy powder according to the proportion,

putting the first alloy powder and the second alloy powder into the mixer for mixing for 4h,

and after the mixing is finished, drying the mixed powder at 80 ℃ for 12h for later use.

Preferably, the inert gas is argon,

Compared with the prior art, the preparation method of the biphase high-entropy alloy provided by the invention has the following beneficial effects:

1. the powder mixing ratio of the first pre-alloyed powder and the second pre-alloyed powder can be regulated and controlled, and further the ratio of FCC-BCC biphase in the formed biphase high-entropy alloy can be regulated and controlled.

2. The density of the formed part is more than 99%.

3. The yield strength and the elongation of the formed part can be freely regulated and controlled within the range of 200-1600 MPa and 1-50% respectively;

when the powder mixing ratio of the first pre-alloyed powder to the second pre-alloyed powder is 1:1.66, the obtained two-phase high-entropy alloy has the optimal comprehensive mechanical property, the yield strength is 1310MPa, and the elongation is 4.5%.

4. The formed part has high forming precision (+ -0.1 mm) and the surface roughness of the formed part is less than 4.2 Ra.

5. The preparation method provided by the invention has the advantages of short flow, low energy consumption and low cost, and does not need subsequent diffusion annealing or hot isostatic pressing post-treatment process.

Drawings

FIG. 1 is a stress-strain plot of a molded part prepared in example 5;

FIG. 2 is the microstructure of the dual-phase high-entropy alloy prepared in example 5.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the present application will be clearly and completely described below with reference to specific embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Example 1

A two-phase high-entropy alloy comprises a first alloy component in an FCC phase and a second alloy component in a BCC phase, wherein the first alloy component is FeCoCrNi, and the second alloy component is FeCoCrNiAl.

In the first alloy component, the atomic mol ratio of Fe, Co, Cr and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mol ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

the weight ratio of the first alloy component to the second alloy component is 1:1.

the dual-phase high-entropy alloy provided in example 1 had a strength of 826MPa, a hardness of 400HV, and a toughness of 23%.

Example 2

In the first alloy component, the atomic mol ratio of Fe, Co, Cr and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mol ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

the weight ratio of the first alloy component to the second alloy component is 1: 2.7.

the dual-phase high-entropy alloy provided by the embodiment 2 has the strength of 1510MPa, the hardness of 863HV and the toughness of 2.1%.

Example 3

In the first alloy component, the atomic mol ratio of Fe, Co, Cr and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mol ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

the weight ratio of the first alloy component to the second alloy component is 1: 1.85.

the dual-phase high-entropy alloy provided in example 3 has a strength of 1416MPa, a hardness of 712HV and a toughness of 3%.

Example 4

In the first alloy component, the atomic mol ratio of Fe, Co, Cr and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mol ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

the weight ratio of the first alloy component to the second alloy component is 1: 1.66.

the preparation method of the two-phase high-entropy alloy comprises the following steps:

preparing a first prealloyed powder based on the elemental composition of the first alloy constituent;

preparing a second prealloyed powder based on the elemental composition of the second alloy constituent;

weighing first alloy powder and second alloy powder according to a proportion, putting the first alloy powder and the second alloy powder into a mixer for mixing for 4 hours, and drying the mixed powder at 80 ℃ for 12 hours for later use after the mixing is finished;

putting the mixed powder into a powder feeding cylinder of SLM equipment, vacuumizing, and introducing inert gas for protection;

establishing a three-dimensional model of a part, slicing and layering the three-dimensional model to obtain data of each section, and importing the data into SLM equipment;

setting technological parameters of a forming process in SLM equipment, wherein the laser power is 250W, the scanning speed is 700mm/s, the scanning interval is 0.05mm, and the powder spreading thickness is 0.03 mm;

and opening the printing to obtain a molded part.

The dual-phase high-entropy alloy part prepared in the example 4 has the forming precision of 99.1% of density, 1014MPa of yield strength, 3.5% of elongation and more than 6.0Ra of surface roughness of a formed part of 100 +/-0.5 mm.

Example 5

In the first alloy component, the atomic mol ratio of Fe, Co, Cr and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mol ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

the weight ratio of the first alloy component to the second alloy component is 1: 1.66.

the preparation method of the two-phase high-entropy alloy comprises the following steps:

preparing a first prealloyed powder based on the elemental composition of the first alloy constituent;

preparing a second prealloyed powder based on the elemental composition of the second alloy constituent;

weighing first alloy powder and second alloy powder according to a proportion, and putting the first alloy powder and the second alloy powder into a mixer for mixing for 4 hours to obtain mixed powder;

putting the mixed powder into a powder feeding cylinder of SLM equipment, vacuumizing to 0.01Pa, and then flowing argon for protection;

establishing a three-dimensional model of a part, slicing and layering the three-dimensional model to obtain data of each section, and importing the data into SLM equipment;

setting technological parameters of a forming process in SLM equipment, wherein the laser power is 350W, the scanning speed is 1000mm/s, the scanning interval is 0.09mm, and the powder spreading thickness is 0.06 mm;

and opening the printing to obtain a molded part.

The formed part prepared in example 5 has a higher forming precision of 100 +/-0.1 mm, a compactness of 99.6%, a yield strength of 1310MPa, an elongation of 4.5%, and a surface roughness of a formed part of less than 4.2 Ra.

Example 6

In the first alloy component, the atomic mol ratio of Fe, Co, Cr and Ni is 1: 1: 1: 1; in the second alloy component, the atomic mol ratio of Fe, Co, Cr, Ni and Al is 1: 1: 1: 1:1.

the weight ratio of the first alloy component to the second alloy component is 1: 1.66.

the preparation method of the two-phase high-entropy alloy comprises the following steps:

preparing a first prealloyed powder based on the elemental composition of the first alloy constituent;

preparing a second prealloyed powder based on the elemental composition of the second alloy constituent;

uniformly mixing the first pre-alloyed powder and the second pre-alloyed powder in proportion to obtain mixed powder;

putting the mixed powder into a powder feeding cylinder of SLM equipment, vacuumizing, and introducing inert gas for protection;

establishing a three-dimensional model of a part, slicing and layering the three-dimensional model to obtain data of each section, and importing the data into SLM equipment;

setting technological parameters of a forming process in SLM equipment, wherein the laser power is 300W, the scanning speed is 850mm/s, the scanning interval is 0.07mm, and the powder spreading thickness is 0.05 mm;

and opening the printing to obtain a molded part.

The formed part prepared in example 6 had a high forming accuracy of 100 ± 0.3mm, a compactness of 99.0%, a yield strength of 1290MPa, an elongation of 4.0%, and a surface roughness of 5.0 Ra.

Comparative example 1

The FeCoCrNi high-entropy alloy with a single-phase FCC structure has the atomic mole ratio of Fe, Co, Cr and Ni of 1: 1: 1:1, setting technological parameters of a forming process in SLM equipment, wherein the laser power is 350W, the scanning speed is 1000mm/s, the scanning interval is 0.09mm, and the powder spreading thickness is 0.06 mm; the formed piece has yield strength of 428MPa and elongation of 49.5 percent.

Comparative example 2

The FeCoCrNiAl high-entropy alloy with the single-phase BCC structure has the atomic mole ratio of Fe, Co, Cr, Ni and Al of 1: 1: 1: 1:1, setting technological parameters of a forming process in SLM equipment, wherein the laser power is 350W, the scanning speed is 1000mm/s, the scanning interval is 0.09mm, and the powder spreading thickness is 0.06 mm;

the yield strength of a formed piece is 1600MPa, and the elongation is 1.0%.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

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