Preparation method of TiB2 enhanced AlCoCrFeNi high-entropy alloy

Abstract

The invention belongs to the technical field of metal materials and powder metallurgy, and discloses a preparation method of a TiB2 enhanced AlCoCrFeNi high-entropy alloy, which comprises the following steps: S1, weighing raw materials: weighing Al, Co, Cr, Fe and Ni metal powder according to an equal atomic ratio, and weighing TiB2 powder which accounts for 5-20% of the total mass of the Al, Co, Cr, Fe and Ni metal powder; s2, mechanical alloying machining is conducted, specifically, Al, Co, Cr, Fe and Ni metal powder and TiB2 powder are mixed and then subjected to high-energy ball milling machining, and composite powder is obtained; s3, molding processing: drying and sieving the composite powder in the S2, and loading the composite powder into a mold for cold press molding to obtain a green body; and S4, atmosphere protection sintering is conducted, specifically, the green body is placed in sintering equipment under inert atmosphere protection to be sintered, and the TiB2 reinforced AlCoCrFeNi high-entropy alloy is obtained. According to the preparation method, high-dispersion distribution of TiB2 particles in alloy powder is achieved through high-energy ball milling, and a bulk material which is uniform in structure and high in density is obtained in cooperation with a sintering process.

Description

Technical Field

[0001] This invention belongs to the field of metal materials and powder metallurgy technology, specifically relating to a method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy. Background Technology

[0002] High-entropy alloys break away from the traditional single-element-based design framework of alloys, typically consisting of five or more elements in equiatomic or near-equiatomic ratios. Their high mixing entropy effect helps form stable solid solution phases and exhibits a variety of excellent comprehensive properties, often referred to as the "cocktail effect," such as high strength, high hardness, good wear resistance, corrosion resistance, and high-temperature stability.

[0003] Among the many high-entropy alloy systems, AlCoCrFeNi high-entropy alloy has been widely studied because it forms a body-centered cubic solid solution with high strength in the as-cast state. However, the plasticity of this alloy system still needs to be improved. In order to further improve its strength, hardness and wear resistance while maintaining a certain plasticity, introducing a ceramic reinforcing phase with high hardness and high thermal stability has become an effective material modification scheme.

[0004] Currently, the main methods for introducing ceramic reinforcing phases into alloy matrices include the additive method and powder metallurgy. The additive method is simple, directly mixing pre-made reinforcing phase particles with matrix powder. However, the interfacial bonding between the reinforcing phase and the metal matrix is ​​weak, and the reinforcing phase particles are prone to agglomeration during pretreatment and subsequent processes. This is because the distribution of the reinforcing phase and the metal matrix is ​​uneven, affecting the final performance of the material. Powder metallurgy, especially atmosphere-protected sintering technology, can effectively reduce the component segregation caused by casting. Furthermore, sintering in a protective atmosphere can prevent the oxidation of reactive elements (such as Al, Cr, and Ti) at high temperatures, which helps ensure the purity of the material. Nevertheless, when preparing ceramic particle-reinforced high-entropy alloy composites using powder metallurgy, a key technical challenge remains: how to achieve a uniform distribution of the reinforcing phase in the AlCoCrFeNi matrix by controlling the powder metallurgy process parameters, and ultimately obtain a composite material with high density, good cross-sectional bonding, and significantly improved comprehensive mechanical properties.

[0005] There is a lack of a mature, stable, and efficient preparation process in the current technology that can systematically solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to solve the problems in the background art and provide a method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy. This method adopts a combination of ball milling and atmosphere-protected sintering, which can achieve a highly dispersed distribution of the TiB2 reinforcing phase in the metal matrix, and prepare a high-entropy alloy composite material with uniform structure, strong interfacial bonding and excellent comprehensive mechanical properties.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy includes the following steps: S1 Raw Material Weighing: Weigh Al, Co, Cr, Fe, and Ni metal powders according to equiatomic ratios, and weigh TiB2 powder. The mass of TiB2 powder is 5% to 20% of the total mass of Al, Co, Cr, Fe, and Ni metal powders. S2 mechanical alloying: Al, Co, Cr, Fe, Ni metal powders are mixed with TiB2 powder, and then ball-milled under inert gas to obtain composite powder; S3 molding process: After drying and sieving the composite powder in S2, it is put into a mold and cold-pressed to obtain a green body; S4 atmosphere-protected sintering: The green blank is placed in a sintering equipment under an inert atmosphere for sintering to obtain a TiB2-reinforced AlCoCrFeNi high-entropy alloy.

[0008] The process control agent in step S2 is ethanol. The amount of ethanol added is 5-10% of the total mass of the powder. This range can effectively suppress cold welding and excessive agglomeration during the ball milling process and optimize the powder refinement result.

[0009] The parameters for high-energy ball milling in step S2 are: ball-to-material ratio of 8:1 to 12:1, ball milling speed of 300 to 600 rpm, and ball milling time of 30 to 60 h.

[0010] Furthermore, the preferred parameters for high-energy ball milling are: a ball-to-powder ratio of 10:1, a ball milling speed of 400 rpm, a ball milling time of 48 h, and ethanol accounting for 5% of the total powder mass as the process control agent. Under these preferred parameters, high-quality composite powder with fine particle size, concentrated distribution, good crystallization, and an FCC+BCC multiphase structure can be obtained.

[0011] In step S3, the pressure for cold pressing is 50~80MPa.

[0012] In step S4, the inert gas is argon or nitrogen with a purity of not less than 99.999%.

[0013] In step S4, the sintering process is a two-step sintering method: first, degassing is performed by holding the temperature at 300~500℃ for 0.5~2h, and then the temperature is increased to 1100~1300℃ at a rate of 5~15℃ / min and held for 1~4h. This two-step method is beneficial for fully removing adsorbed gases and impurities, and promotes atomic diffusion, thereby achieving high-density sintering.

[0014] The beneficial effects of the method for preparing TiB2-reinforced AlCoCrFeNi high-entropy alloy provided by this invention are: (1) High dispersion of TiB2 particles in alloy powder was achieved by high-energy ball milling. Combined with optimized sintering process, a bulk material with uniform structure and high density was obtained, and the reinforcing phase was firmly bonded to the matrix. (2) The introduction of TiB2 refines the grains and produces a variety of strengthening mechanisms such as solid solution strengthening and dispersion strengthening, which greatly improves the hardness of the alloy compared with the unreinforced alloy. (3) Ball milling and sintering under inert gas protection effectively avoids the oxidation of active elements such as Al, Cr, and Ti, ensuring the purity and final performance of the alloy; (4) The equipment cost is low, the process is stable and controllable, and it is easy to achieve large-scale production. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The SEM and EDS surface scans of the metal powder surface morphology provided in the embodiments of the present invention are shown.

[0017] Figure 2 This is a laser particle size distribution diagram of alloy powder provided in an embodiment of the present invention.

[0018] Figure 3 The XRD pattern of the alloy powder provided in the embodiment of the present invention.

[0019] Figure 4 SEM and EDS surface scans of the TiB2-reinforced AlCoCrFeNi high-entropy alloy prepared in Example 1 of this invention.

[0020] Figure 5 The density and hardness of the alloy at different temperatures are provided for embodiments of the present invention.

[0021] Figure 6This is a comparison image of the alloy powder before and after ball milling, provided in an embodiment of the present invention.

[0022] Figure 7 The images show a comparison of the alloys prepared in Example 1 and Comparative Example 1 of this invention.

[0023] Figure 8 A comparison chart of dry sliding friction coefficients provided for embodiments of the present invention.

[0024] Figure 9 Comparison chart of oil sliding friction coefficients provided in embodiments of the present invention

[0025] Figure 10 Impedance electrochemical comparison diagram provided for embodiments of the present invention.

[0026] Figure 11 An electrochemical Tafel comparison diagram provided for an embodiment of the present invention. Detailed Implementation

[0027] Example 1

[0028] like Figures 1-6 As shown, the preparation method of TiB2-reinforced AlCoCrFeNi high-entropy alloy provided in this embodiment includes the following steps: S1 Raw Material Weighing: Weigh Al, Co, Cr, Fe, and Ni metal powders according to equiatomic ratios to ensure they meet the requirements; and weigh TiB2 powder, the mass of which is 10% of the total mass of Al, Co, Cr, Fe, and Ni metal powders.

[0029] S2 Mechanical Alloying Processing: The Al, Co, Cr, Fe, and Ni metal powders from step S1, along with TiB2 powder, are loaded into a ball mill jar. Stainless steel alloy balls are added, and inert gas is introduced for ball milling. The ball-to-powder ratio is 10:1. Then, 5% or 10% of the total powder mass of ethanol is added as a process control agent. The milling speed is selected as 300 rpm, 400 rpm, 500 rpm, or 600 rpm, and the milling time is selected as 36 h, 48 h, or 60 h. Finally, a composite powder is obtained. Comparison before and after milling is shown. Figure 6 As shown, the scanning electron microscope (SEM) results of the ball-milled composite powder are as follows: Figure 1 As shown, the obtained metal powder mainly consists of fine particles and the resulting micro-aggregates, with clearly distinguishable particle morphologies. Energy dispersive spectroscopy (EDS) analysis of the metal powder further indicates that Al, Co, Cr, Fe, and Ni are all spatially uniformly distributed in the powder, with no obvious elemental segregation.

[0030] This excellent compositional uniformity helps suppress compositional segregation during subsequent sintering, while the microstructure of fine particles filling the gaps between large particles increases the contact area between particles, thereby promoting the densification process. Although the performance of the final sintered body is still constrained by specific sintering process parameters, judging from the initial state of the powder, it possesses good alloy sintering potential and is expected to provide a high-quality raw material basis for preparing dense high-entropy alloy products.

[0031] Through this process, Figure 2 The laser particle size distribution of high-entropy alloy powders prepared at different ball milling speeds under conditions of 5% and 10% process control agent is shown, where (a) represents 5% control agent and (b) represents 10% control agent. The results show that increasing the ball milling speed significantly promotes powder refinement, specifically manifested as a systematic leftward shift in the particle size distribution curve, with the main peak shifting from the 30-50µm range to the 10-20µm range, reflecting the intensifying effect of higher mechanical energy input on the particle crushing process. A distinct bimodal distribution is observed in the lower speed range of 300 rpm, with a significant secondary peak in the 30-40µm range in addition to the main peak at 10-20µm, indicating the presence of insufficiently refined coarse particle groups. Bimodal distribution also appears in the higher speed ranges of 500 rpm and 600 rpm, indicating that some powder agglomeration occurs due to excessive mechanical energy, demonstrating that the process control agent content significantly affects powder refinement behavior. Under 5% control agent conditions, the particle size distribution at 400 rpm exhibits a well-converged single-peak morphology, concentrated in the 10-20 µm range, indicating that this parameter combination effectively suppresses cold welding and agglomeration, achieving uniform refinement. In contrast, under 10% control agent conditions, although a single-peak distribution is also observed at 400 rpm, the proportion of small-sized particles and the concentration of particle distribution are both inferior to those under 5% control agent conditions.

[0032] Figure 3The X-ray diffraction (XRD) patterns of AlCoCrFeNi high-entropy alloys prepared from alloy powders under conditions of 5% and 10% process control agent are shown to analyze the changes in phase composition and crystal structure with ball milling speed. (a) represents the 5% control agent, and (b) represents the 10% control agent. As the ball milling speed increases from 300 rpm to 600 rpm, the diffraction peaks of both FCC and BCC phases under both control agent conditions show a trend of gradually sharpening and increasing intensity, indicating that increasing mechanical energy input helps promote grain refinement and crystal structure ordering, thereby improving the degree of phase crystallization perfection. At lower speeds of 300 rpm and 400 rpm, the material forms a composite phase structure of FCC and BCC; while at higher speeds of 500 rpm and 600 rpm, the phase composition gradually shifts to be dominated by the BCC phase. From a performance regulation perspective, a single BCC phase usually has poor plasticity, while the FCC+BCC composite phase helps to achieve a good synergy between strength and plasticity. Comparing the effects of different control agent contents, it can be seen that at the same rotation speed, the diffraction peak of the 5% control agent sample is sharper and the intensity is slightly higher than that of the 10% condition. This indicates that appropriately increasing the control agent content helps to further improve the crystallinity and structural uniformity of the alloy. The reason may be that the control agent effectively inhibits powder cold welding and agglomeration, allowing mechanical energy to act more fully on the powder refining and structural ordering process.

[0033] Therefore, the optimal ball milling process is: under the conditions of ball milling for 48 hours and rotating at 400 rpm, 5% process control agent was used to successfully prepare AlCoCrFeNi+TiB2 high-entropy alloy powder with fine particle size, concentrated distribution, good crystallization and FCC+BCC multiphase structure.

[0034] S3 molding process: The composite powder in S2 is dried in a vacuum drying oven at 60℃, then sieved through a 200-mesh sieve to remove lumps. The sieved powder is vacuum-sealed and stored. Then, an appropriate amount of sieved alloy powder is weighed and loaded into a mold, and cold-pressed on a hydraulic press at a pressure of 60MPa to obtain a green blank with a certain strength.

[0035] S4 Atmosphere Protected Sintering: The green blank obtained in S3 is placed in a vacuum tube furnace for sintering. After evacuation, high-purity argon or nitrogen is introduced to positive pressure. The purity of argon and nitrogen is ≥99.999%. The replacement is repeated 2-3 times to ensure that the oxygen content is reduced to the minimum. Then, under the condition of continuous introduction of protective gas, sintering is carried out. During sintering, the temperature is first held at 400℃ for 1 hour to remove gas. Then, the temperature is raised to 1200℃ at the same rate and held for 2 hours. Subsequently, it is cooled to room temperature with the furnace to obtain TiB2 reinforced AlCoCrFeNi high-entropy alloy bulk. Ball milling and sintering are carried out under the protection of inert gas throughout the process, which effectively avoids the oxidation of active elements such as Al, Cr, and Ti, and ensures the purity and final performance of the alloy.

[0036] Figure 5 The density and hardness of the TiB2-reinforced AlCoCrFeNi high-entropy alloy bulk obtained in this embodiment at 1000℃, 1100℃, 1200℃ and 1300℃ are shown in the figure. It can be seen from the figure that the TiB2-reinforced AlCoCrFeNi high-entropy alloy bulk has extremely high stability under high temperature conditions.

[0037] Example 2

[0038] This embodiment is basically the same as Embodiment 1, except that the amount of TiB2 added is adjusted to 5%.

[0039] Example 3

[0040] This embodiment is basically the same as Embodiment 1, except that the amount of TiB2 added is adjusted to 15%.

[0041] Example 4

[0042] This embodiment is basically the same as Embodiment 1, except that the amount of TiB2 added is adjusted to 20%.

[0043] Examples 2-4 only adjusted the TiB2 addition amount to 5%, 15%, and 20%. The test results showed that within the TiB2 addition range of 5%-20%, the alloy hardness was significantly higher than that of Comparative Example 1. Among them, the alloy with the best overall performance in terms of hardness and density was achieved when the addition amount was 10%-15%.

[0044] Comparative Example 1

[0045] like Figures 1-11 As shown, this comparative example 1 is basically the same as example 1, but without the addition of TiB2 powder, only AlCoCrFeNi high-entropy alloy is prepared.

[0046] like Figure 7 As shown, the sintered alloy images of Comparative Example 1 and Example 1 are shown under the same parameter conditions. (a) is the sintered physical image of Comparative Example 1 and (b) is the sintered physical image of Example 1. It can be clearly seen that the introduction of TiB2 successfully refined the microstructure of AlCoCrFeNi high-entropy alloy, and the metal surface has a silvery-white luster and is smoother.

[0047] Vickers hardness tests were performed on alloys with and without TiB2, and the results are shown in Table 1.

[0048] Table 1: Vickers hardness test results for different alloys sample Test 1 Test 2 Test 3 average value AlCoCrFeNi 309.17HV 304.45HV 311.48HV 308.37HV <![CDATA[AlCoCrFeNiTiB2]]> 427.13HV 421.25HV 431.43HV 426.60HV As shown in Table 1, the three-dimensional average hardness of the AlCoCrFeNiTiB2 alloy is 426.60 HV, which is significantly higher than that of Q235B carbon steel (140~160 HV) and slightly higher than that of TC4 titanium alloy (350~400 HV). The higher hardness of AlCoCrFeNiTiB2 alloy compared to AlCoCrFeNi alloy is likely due to the high hardness of TiB2 itself, which refines the grains, leading to lattice distortion and thus higher hardness. Furthermore, XRD analysis of the alloy reveals that TiB2 enhances the σ phase, significantly improving the material's hardness.

[0049] like Figure 4 As shown, the alloy surface was characterized by scanning electron microscopy (SEM). At the 50 μm scale, a uniform and dense microstructure was observed, with no obvious defects such as pores or cracks, only uniformly distributed fabrication texture. At the 500 nm scale, the matrix remained highly dense, with uniform grain size, clear grain boundaries, and no agglomeration or phase separation of second-phase particles was observed. This multi-scale morphological characteristic indicates that the addition of TiB2 effectively promoted the densification process of the alloy while maintaining structural uniformity. EDS surface scanning analysis showed that the main elements, including Al, Co, Cr, Fe, Ni, and Ti, were highly uniformly distributed within the observed area, without local segregation or depletion. This elemental distribution characteristic corroborates the dense morphology observed by SEM, verifying the "high mixing entropy" effect of the high-entropy alloy. Particularly noteworthy is the uniform distribution of Ti, confirming the good dispersion of TiB2 in the alloy matrix, which forms the structural basis for its reinforcing effect.

[0050] like Figure 8 , Figure 9 As shown, the sliding friction coefficients of the existing carbon steel, Example 1 and Example 2 materials were compared under dry sliding friction and oil sliding friction, respectively. The comparison shows that the friction coefficient of the TiB2 reinforced AlCoCrFeNi high-entropy alloy block is lower.

[0051] like Figure 10 , Figure 11 As shown, the high-entropy alloy with added TiB2 and the high-entropy alloy without added TiB2 have a stronger impedance effect in impedance electrochemistry and are more stable in electrochemical Tafel.

[0052] The process of this invention is stable and has a low cost: Compared with rapid sintering technologies such as spark plasma sintering, the protective atmosphere sintering used in this invention is a more mature powder metallurgy process with lower equipment costs, which is easy to achieve large-scale production and has better industrial application prospects.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications and substitutions based on the technical solutions and inventive concepts provided by the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy, characterized in that, Includes the following steps: S1 Raw Material Weighing: Weigh Al, Co, Cr, Fe, and Ni metal powders according to equiatomic ratios, and weigh TiB2 powder. The mass of TiB2 powder is 5% to 20% of the total mass of Al, Co, Cr, Fe, and Ni metal powders. S2 mechanical alloying: Al, Co, Cr, Fe, Ni metal powders are mixed with TiB2 powder, and then ball-milled under inert gas to obtain composite powder; S3 molding process: After drying and sieving the composite powder in S2, it is put into a mold and cold-pressed to obtain a green body; S4 atmosphere-protected sintering: The green blank is placed in a sintering equipment under an inert atmosphere for sintering to obtain a TiB2-reinforced AlCoCrFeNi high-entropy alloy.

2. The method for preparing TiB2-reinforced AlCoCrFeNi high-entropy alloy according to claim 1, characterized in that: The process control agent in step S2 is ethanol, and the amount of ethanol added is 5-10% of the total mass of the powder.

3. The method for preparing TiB2-reinforced AlCoCrFeNi high-entropy alloy according to claim 1 or 2, characterized in that: The parameters for high-energy ball milling in step S2 are: ball-to-material ratio of 8:1 to 12:1, ball milling speed of 300 to 600 rpm, and ball milling time of 30 to 60 h.

4. The method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy according to claim 1, characterized in that: In step S3, the pressure for cold pressing is 50~80MPa.

5. The method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy according to claim 1, characterized in that: In step S4, the inert gas is argon or nitrogen with a purity of not less than 99.999%.

6. The method for preparing a TiB2-reinforced AlCoCrFeNi high-entropy alloy according to claim 1, characterized in that: In step S4, the sintering process is a two-step sintering method: first, degassing is performed by holding the temperature at 300~500℃ for 0.5~2h, and then the temperature is increased to 1100~1300℃ at a rate of 5~15℃ / min and held for 1~4h.

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