Eutectic medium-entropy alloy synergistically strengthened by multiple carbides

Abstract

The chemical general formula of the eutectic medium-entropy alloy is CrFeTiCx, in the formula, x is larger than or equal to 0.2 and smaller than or equal to 0.4, the solidification phase of the eutectic medium-entropy alloy comprises a BCC phase and MC, M7C3 and M23C6 type carbide phases, and the microscopic structure of the eutectic medium-entropy alloy is a lamellar eutectic structure composed of the BCC phase and the carbide phases. According to the eutectic medium-entropy alloy, the low-cost CrFeTi serves as the basis, the C element is introduced, a eutectic structure is formed, the cost is low, carbide has the effect of coordinating and enhancing the mechanical property, the medium-entropy alloy is endowed with excellent comprehensive mechanical property, the medium-entropy alloy has high breaking strength and Vickers hardness at the room temperature, and the alloy has the good mechanical property. Wide application prospects are realized in the high-temperature wear-resistant field.

Description

Technical Field

[0001] The present invention belongs to the technical field of medium-entropy alloys, and in particular relates to a eutectic medium-entropy alloy synergistically strengthened by multiple carbides. Background Art

[0002] Medium-entropy alloys (MEAs) exhibit significant potential for application in engineering due to their comprehensive properties, including high strength, high hardness, high wear resistance, excellent corrosion resistance, and good high-temperature stability. However, single-phase MEAs with a predominantly solid solution structure suffer from poor fluidity and casting properties. Metallurgical defects such as segregation, porosity, and shrinkage cavities are easily generated during solidification, seriously affecting the quality of the ingot. Furthermore, MEAs with a single-phase BCC structure exhibit excellent strength but insufficient toughness, while MEAs with a single-phase FCC structure exhibit good toughness but relatively low strength. This suggests that rationally designing the alloy composition to promote the formation of a eutectic structure can effectively address the strength-toughness trade-off in single-phase alloys, thereby achieving excellent overall mechanical properties.

[0003] Carbides have excellent properties such as high strength, high hardness, high modulus and high wear resistance. Adding an appropriate amount of C element to the alloy can improve the strength of the alloy through interstitial solid solution and precipitation strengthening. For example, Wei et al. reported a Nb2MoWC 0.96 The alloy is designed through the eutectic of BCC niobium solid solution and NbC, and the specific compressive strength reaches 77.2MPa·cm at 1673K. 3 / g, while retaining 37.5% of the plasticity, which is significantly better than traditional niobium alloys; Tian et al. reported a eutectic refractory high entropy alloy TiNbTaWC 0.7 When the carbon content is equal to 0.7, a complete eutectic is achieved, and at a high temperature of 1200 ° C, it exhibits excellent strength and plasticity, with yield strength and ultimate tensile strength of 625 MPa and 860 MPa respectively, and a fracture strain of about 30%, and a fracture strain of 15.6% at room temperature. However, the existing Nb2MoWC 0.96 、TiNbTaWC 0.7 All contain rare metals (such as Ta, W or Nb), especially TiNbTaWC 0.7 , and contains rare and precious metals Ta, W and Nb, which leads to high preparation costs of such alloys, seriously affecting their practical applications in the engineering field. Summary of the Invention

[0004] The present invention aims to provide a eutectic medium entropy alloy synergistically strengthened by multiple carbides, which is not only low in cost but also has excellent comprehensive mechanical properties.

[0005] The present invention is achieved through the following technical solutions:

[0006] A eutectic medium entropy alloy synergistically strengthened by multiple carbides, characterized in that the general chemical formula is CrFeTiC x , where 0.2≤x≤0.4.

[0007] Furthermore, the solidified phase includes BCC phase as well as MC, M7C3 and M 23 C6 type carbide phase.

[0008] Furthermore, the MC is a primary TiC phase, and the BCC phase, M7C3 and M 23 C6 forms a lamellar eutectic structure.

[0009] Further, it is prepared by the following method:

[0010] Step 1: placing metal elements Cr, Fe and Ti into anhydrous ethanol, ultrasonically cleaning and drying to obtain pretreated metal elements Cr, Fe and Ti;

[0011] Step 2: According to the chemical formula CrFeTiC x , respectively weighing the pretreated metal elements Cr, Fe and Ti and the iron-carbon particles, wherein: 0.2≤x≤0.4, and the carbon content in the iron-carbon particles is 10wt%;

[0012] Step 3: placing the metal elements Cr, Fe, and Ti and the iron-carbon particles weighed in step 2 in a water-cooled crucible in a vacuum non-consumable arc melting furnace in ascending order of melting point, repeatedly evacuating the vacuum non-consumable arc melting furnace and filling it with argon until the desired vacuum level is reached, and then starting vacuum arc melting. After the raw materials are completely melted, an alloy ingot is formed.

[0013] Step 4: Turn the ingot over, remelt it, repeat several times, and finally cool it to room temperature with the furnace to obtain a eutectic medium-entropy alloy synergistically strengthened by multiple carbides.

[0014] Furthermore, the purity of the metal elements Cr and Ti in step 1 is 99.95%, and the purity of the iron-carbon particles and the metal element Fe is 99.9%.

[0015] Furthermore, the ultrasonic cleaning time in step 1 is 15 to 20 minutes.

[0016] Furthermore, the process of repeatedly evacuating the vacuum non-consumable arc melting furnace and filling it with argon in step 3 is as follows: first, the vacuum degree in the vacuum non-consumable arc melting furnace is evacuated to 3×10 -3 ~6×10 -3 Pa, and then fill it with argon until the internal pressure is 0.05Pa, and repeat this three times.

[0017] Furthermore, in step 3, another water-cooled crucible in the vacuum non-consumable arc melting furnace is placed with elemental Ti for removing residual oxygen.

[0018] Furthermore, the vacuum arc melting in step 3 is carried out under electromagnetic stirring.

[0019] Furthermore, the re-smelting in step 4 is performed 5 times, and the time for each re-smelting is 4 to 5 minutes.

[0020] The present invention has the following beneficial technical effects:

[0021] 1) The carbide eutectic medium entropy alloy CrFeTiC provided by the present invention x (0.2≤x≤0.4) Based on low-cost CrFeTi, the C element is introduced to form a eutectic structure, which not only has low cost, but also the carbide has the effect of coordinating and enhancing the mechanical properties, giving the medium-entropy alloy excellent comprehensive mechanical properties.

[0022] 2) The three types of carbides MC, M7C3 and M in the medium entropy alloy of the present invention 23 C6 is essentially a hard ceramic phase with extremely high hardness. It effectively "embeds" into the relatively soft BCC matrix through the eutectic structure and synergistically improves the overall hardness of the medium-entropy alloy, that is, improves the strength through second-phase strengthening and load-bearing effects. In addition, MC and M7C3 are not easily dissolved or coarsened at high temperatures, can effectively pin dislocations and grain boundaries, and hinder creep deformation, thereby improving the high-temperature strength and high-temperature hardness of the medium-entropy alloy. Therefore, the medium-entropy alloy of the present invention has good comprehensive mechanical properties.

[0023] 3) The eutectic medium entropy alloy CrFeTiC proposed by the present invention x (0.2≤x≤0.4) At room temperature, it has good fracture strength and high hardness, and the preparation method is simple. It can be cast into large-sized and complex-shaped workpieces, which broadens its practical application in different engineering fields. It can be widely used in aerospace, industrial manufacturing, mechanical processing, cutting and forming, energy and chemical industries.

[0024] 4) The present invention can produce large-sized and complex-shaped workpieces through casting. In addition, an alloy coating can be prepared on its surface through laser cladding technology to further improve the wear-resistant life of the material. It is very suitable for large-scale production of workpieces in the field of high-temperature wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 XRD patterns of the eutectic medium entropy alloys prepared in Examples 1 to 3 of the present invention;

[0026] Figure 2The low-magnification and high-magnification SEM structures of the eutectic medium-entropy alloys prepared in Examples 1 to 3 of the present invention are shown;

[0027] Figure 3 Room temperature compressive stress-strain curves of the eutectic medium entropy alloys prepared in Examples 1 to 3 of the present invention;

[0028] Figure 4 This is a hardness bar graph of the eutectic medium entropy alloys prepared in Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0030] The iron-carbon particles of the present invention are produced by Beijing Yanbang Material Technology Co., Ltd., are named iron-carbon 10wt% particles, have a purity of 99.9%, a specification of 3 to 15 mm, and are produced on 2024121.

[0031] The metal elements Cr and Ti of the present invention are Cr sheets and Ti bars with a purity of 99.95% respectively, and the metal element Fe has a purity of 99.9% and a specification of 3 to 15 mm.

[0032] Example 1

[0033] Step 1: placing metal elements Cr, Ti, and Fe in anhydrous ethanol, ultrasonically cleaning them for 15 minutes, and then drying them with a hair dryer to obtain pretreated metal elements Cr, Fe, and Ti;

[0034] Step 2: According to the chemical formula CrFeTiC 0.2 , weigh the pretreated metal elements Cr, Fe, Ti and iron-carbon particles;

[0035] Step 3: placing the metal elements Cr, Fe, and Ti and the iron-carbon particles weighed in step 2 in a water-cooled crucible in a vacuum non-consumable arc melting furnace in ascending order of melting point, and placing elemental Ti in another water-cooled crucible to remove residual oxygen in the melting furnace;

[0036] Step 4: First, draw the vacuum degree in the vacuum non-consumable arc melting furnace to 3×10 -3 Pa, then fill with argon until the internal pressure is 0.05Pa, and repeat step 4 three times;

[0037] Step 5: Under electromagnetic stirring, vacuum arc melting is started, and the raw materials are completely melted to form an alloy ingot;

[0038] Step 6: Turn the alloy ingot over, re-smelt for 4 minutes, repeat 5 times, and cool to room temperature with the furnace to obtain CrFeTiC0.2 Eutectic medium-entropy alloy.

[0039] Example 2

[0040] Step 1: placing metal elements Cr, Ti, and Fe in anhydrous ethanol, ultrasonically cleaning for 20 minutes, and then drying with a hair dryer to obtain pretreated metal elements Cr, Fe, and Ti;

[0041] Step 2: According to the chemical formula CrFeTiC 0.3 , weigh the pretreated metal elements Cr, Fe, Ti and iron-carbon particles;

[0042] Step 3: placing the metal elements Cr, Fe, and Ti and the iron-carbon particles weighed in step 2 in a water-cooled crucible in a vacuum non-consumable arc melting furnace in ascending order of melting point, and placing elemental Ti in another water-cooled crucible to remove residual oxygen in the melting furnace;

[0043] Step 4: First, draw the vacuum degree in the vacuum non-consumable arc melting furnace to 4.5×10 -3 Pa, then fill with argon until the internal pressure is 0.05Pa, and repeat step 4 three times;

[0044] Step 5: Under electromagnetic stirring, vacuum arc melting is started, and the raw materials are completely melted to form an alloy ingot;

[0045] Step 6: Turn the alloy ingot over, re-smelt for 5 minutes, repeat 5 times, and cool to room temperature with the furnace to obtain CrFeTiC 0.3 Eutectic medium-entropy alloy.

[0046] Example 3

[0047] Step 1: placing metal elements Cr, Ti, and Fe in anhydrous ethanol, ultrasonically cleaning them for 18 minutes, and then drying them with a hair dryer to obtain pretreated metal elements Cr, Fe, and Ti;

[0048] Step 2: According to the chemical formula CrFeTiC 0.4 , weigh the pretreated metal elements Cr, Fe, Ti and iron-carbon particles;

[0049] Step 3: placing the metal elements Cr, Fe, and Ti and the iron-carbon particles weighed in step 2 in a water-cooled crucible in a vacuum non-consumable arc melting furnace in ascending order of melting point, and placing elemental Ti in another water-cooled crucible to remove residual oxygen in the melting furnace;

[0050] Step 4: First, draw the vacuum degree in the vacuum non-consumable arc melting furnace to 6×10 -3Pa, then fill with argon until the internal pressure is 0.05Pa, and repeat step 4 three times;

[0051] Step 5: Under electromagnetic stirring, vacuum arc melting is started, and the raw materials are completely melted to form an alloy ingot;

[0052] Step 6: Turn the alloy ingot over and re-smelt for 4 minutes, repeat 4 times, and cool to room temperature with the furnace to obtain CrFeTiC 0.4 Eutectic medium-entropy alloy.

[0053] See also Figure 1 It can be seen that the characteristic peaks of the eutectic medium entropy alloys prepared in Examples 1 to 3 correspond to BCC, TiC, M7C3 and M 23 C6 carbide, indicating that Examples 1 to 3 successfully prepared eutectic medium-entropy alloys composed of BCC and various carbides.

[0054] Figure 2 (a) Figure 2 (b) and Figure 2 (c) shows the low-magnification SEM microstructures of the eutectic medium-entropy alloys prepared in Examples 1 to 3, respectively. Figure 2 (d) Figure 2 (e) and Figure 2 (f) shows the high-magnification SEM microstructures of the eutectic medium-entropy alloys prepared in Examples 1 to 3, respectively. Figure 2 (a)~ Figure 2 (f) It can be seen that the eutectic medium entropy alloy CrFeTiC prepared in Examples 1 to 3 x The microstructure of (0.2≤x≤0.4) is composed of primary TiC phase and lamellar eutectic structure BCC / M7C3 / M 23 C6 composition, that is, its solidification phase includes BCC phase and MC, M7C3 and M 23 C6 type carbide phase.

[0055] See also Figure 3 It can be seen that the eutectic medium entropy alloys prepared in Examples 1 to 3 have a fracture strength of more than 1800 MPa at room temperature and have a high fracture strain, especially the CrFeTiC prepared in Example 2. 0.3 , the fracture strength at room temperature reached 2193MPa.

[0056] See also Figure 4 It can be seen that the eutectic medium entropy alloys prepared in Examples 1 to 3 have a Vickers hardness of not less than 862 N / mm at room temperature. 2 , and the Vickers hardness increases with the increase of carbon content, among which the CrFeTiC prepared in Example 3 0.4 The Vickers hardness at room temperature reaches 887N / mm2 .

[0057] In order to more clearly demonstrate the mechanical properties of the eutectic medium entropy alloys prepared in Examples 1 to 3, their fracture strength and fracture strain are listed in Table 1;

[0058] Table 1 Eutectic medium entropy alloy CrFeTiC x Room temperature mechanical properties of (0.2≤x≤0.4)

[0059]

[0060] It can be clearly seen from Table 1 that the eutectic medium entropy alloys prepared in Examples 1 to 3 not only have high tensile strength, but also exhibit good plasticity and wear resistance, and the Vickers hardness and fracture strain increase with increasing carbon content.

Claims

1. A eutectic medium-entropy alloy synergistically strengthened by multiple carbides, characterized in that: The general chemical formula is CrFeTiC x , where 0.2≤x≤0.

4.

2. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 1, characterized in that: Including BCC phase as well as MC, M7C3 and M 23 C6 type carbide phase.

3. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 2, characterized in that: The MC is the primary TiC phase, the BCC phase, M7C3 and M 23 C6 forms a lamellar eutectic structure.

4. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to any one of claims 1 to 3, characterized in that: Prepared by the following method: Step 1: placing metal elements Cr, Fe and Ti into anhydrous ethanol, ultrasonically cleaning and drying to obtain pretreated metal elements Cr, Fe and Ti; Step 2: According to the chemical formula CrFeTiC x , respectively weighing the pretreated metal elements Cr, Fe and Ti and the iron-carbon particles, wherein: 0.2≤x≤0.4, and the carbon content in the iron-carbon particles is 10wt%; Step 3: placing the metal elements Cr, Fe, and Ti and the iron-carbon particles weighed in step 2 in a water-cooled crucible in a vacuum non-consumable arc melting furnace in ascending order of melting point, repeatedly evacuating the vacuum non-consumable arc melting furnace and filling it with argon until the desired vacuum level is reached, and then starting vacuum arc melting. After the raw materials are completely melted, an alloy ingot is formed. Step 4: Turn the ingot over, remelt it, repeat several times, and finally cool it to room temperature with the furnace to obtain a eutectic medium-entropy alloy synergistically strengthened by multiple carbides.

5. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 4, characterized in that: The purity of the metal elements Cr and Ti in step 1 is 99.95%, and the purity of the iron-carbon particles and the metal element Fe is 99.9%.

6. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 4, characterized in that: The ultrasonic cleaning time in step 1 is 15 to 20 minutes.

7. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 4, characterized in that: The process of repeatedly evacuating the vacuum non-consumable arc melting furnace and filling it with argon in step 3 is as follows: first, the vacuum degree in the vacuum non-consumable arc melting furnace is evacuated to 3×10 -3 ~6×10 -3 Pa, and then fill it with argon until the internal pressure is 0.05Pa, and repeat this three times.

8. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 4, characterized in that: In the step 3, another water-cooled crucible in the vacuum non-consumable arc melting furnace is placed with elemental Ti for removing residual oxygen.

9. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 4, characterized in that: The vacuum arc melting in step 3 is carried out under electromagnetic stirring.

10. The eutectic medium entropy alloy synergistically strengthened by multiple carbides according to claim 4, characterized in that: The re-smelting in step 4 is performed 5 times, and the time for each re-smelting is 4 to 5 minutes.

Images