High-strength (CoCrNi) 94Al3Ti3 medium-entropy alloy and preparation method thereof

Abstract

The invention discloses a high-strength (CoCrNi) 94Al3Ti3 medium-entropy alloy and a preparation method thereof, and the high-strength (CoCrNi) 94Al3Ti3 medium-entropy alloy is prepared by combining powder plasma arc additive manufacturing with a single-step cold rolling annealing process and introducing various lattice defects and fine heterogeneous structures. According to the technical scheme, the high-strength (CoCrNi) 94Al3Ti3 medium-entropy alloy is prepared, the preparation efficiency is high, the quality is good, and the cost is low. The method has good economic benefits and wide application prospects.

Description

Technical Field

[0001] The invention relates to metal materials, and proposes a plasma arc additive manufacturing combined with a single-step cold rolling annealing process, and prepares a medium-entropy alloy by introducing a variety of lattice defects and fine inhomogeneous structures, specifically a high-strength (CoCrNi) 94 Al3Ti3 medium-entropy alloy and preparation method thereof. Background Art

[0002] CoCrNi-based medium-entropy alloys have been studied the most due to their stable FCC phase and excellent mechanical properties. However, the low yield strength of single-phase CoCrNi medium-entropy alloys at room temperature limits their application in engineering. The strength of CoCrNi-based medium-entropy alloys can be effectively enhanced by introducing multiple strengthening mechanisms. However, this can only be achieved through complex manufacturing routes, including melting, casting, homogenization, rolling, recrystallization or partial recrystallization, which is a challenge for its application.

[0003] One way to shorten the complex manufacturing route is to find an ideal starting material that can improve the efficiency of recrystallization. Additive manufacturing (AM) has been used to manufacture high-performance and complex structural materials at high cooling rates. Compared with alloys prepared by other preparation methods (casting), the alloys prepared by AM have uniform microstructures and fewer defects. In addition, the alloys prepared by AM have a unique microstructure (dislocation network structure and orientation structure). These characteristics make the alloys prepared by AM potentially an ideal starting material for shortening the thermomechanical processing (cold rolling and annealing) route. The alloys do not require pretreatment (hot rolling or homogenization) before thermomechanical treatment because their microstructure is uniform and has few defects. In addition, the unique microstructure can greatly affect the accumulation of deformation energy in the material and improve the recrystallization rate. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a high strength (CoCrNi) 94 Al3Ti3 medium entropy alloy and preparation method thereof, prepared by using plasma arc additive manufacturing technology (CoCrNi) 94 Al3Ti3 medium entropy alloy block, and the prepared high entropy alloy block is cold rolled by 50%, and then the rolled high entropy alloy is heat treated at 800℃ for 1 hour. By introducing various lattice defects and fine inhomogeneous structures in the above manner, a high strength (CoCrNi) 94 Preparation method of Al3Ti3 medium entropy alloy.

[0005] To achieve the above object, the present invention provides the following technical solution: a high strength (CoCrNi) 94The Al3Ti3 medium entropy alloy is prepared by mixing the alloy in the atomic percentages of Co: 31.3%, Cr: 31.3%, Ni: 31.3%, Al: 3%, and Ti: 3%.

[0006] Furthermore, the purity of the Co, Cr, Ni, Al and Ti original metal single substance powders is higher than 99.5%, and the particle size of each material is between 150 and 250 meshes.

[0007] A high strength (CoCrNi) 94 The preparation method of Al3Ti3 medium entropy alloy specifically comprises the following preparation steps:

[0008] (1) Convert the atomic percentages of Co: 31.3%, Cr: 31.3%, Ni: 31.3%, Al: 3%, and Ti: 3% with a purity higher than 99.5% and a particle size between 150 and 250 meshes into the corresponding mass ratios of the metal powders, and obtain the corresponding mass of the metal powders by weighing;

[0009] (2) After the weighed metal powders are briefly mixed in a vacuum glove box, they are placed in a ball milling jar of a high-energy ball mill together with alumina grinding balls. The mass ratio of alumina grinding balls to metal mixed powders is 1:2. The ball mill is set to a cyclic operation mode. The ball mill is set to run forward for 5 minutes, stop for 5 minutes, and reverse for 5 minutes. The total operation time is set to 6 hours.

[0010] (3) The high-energy ball mill that has been running for 6 hours is turned off, the uniformly mixed metal powder in the ball mill is taken out, and the uniformly mixed alloy powder is immediately placed in a vacuum drying oven for 2 hours, and then the mixed powder is placed in a dry and sealed container for subsequent use;

[0011] (4) Grinding the substrate for deposition with an angle grinder to remove the oxide layer, oxides and impurities on the surface of the substrate, and then repeatedly cleaning with alcohol and acetone to further remove stains and surface impurities on the substrate;

[0012] (5) placing the mixed powder prepared after drying in step (3) into a powder feeding tank of an additive manufacturing device, opening a protective gas cylinder and a plasma arc additive manufacturing device, setting a suitable deposition path and deposition parameters on the plasma arc additive manufacturing device, and operating the device to perform layer-by-layer deposition on a substrate;

[0013] (6) During the deposition process, the material is kept in a formed state. After each layer of deposition is completed, an angle grinder is used to remove the oxide layer from the formed surface, and then the next layer is deposited until the required height is reached to obtain a medium-entropy alloy block.

[0014] Preferably, the plasma additive manufacturing equipment deposits (CoCrNi)94 The parameters set in the Al3Ti3 medium entropy alloy are as follows: deposition current is 100A; powder feeding speed is 25r / min; ion gas flow rate is 2.5~3L / min; shielding gas flow rate is 12L / min, powder feeder flow rate is 2.5~3L / min, and plasma welding gun operating speed is 395mm / min. The ion gas, shielding gas, and powder feeding gas used in the entire deposition process are all inert gas argon.

[0015] Preferably, after the metal element powder is placed in the ball mill, sufficient argon is kept in the ball mill as a protective gas during the mixing process within 6 hours of grinding and mixing to prevent the mixed powder from oxidative deterioration during the ball milling mixing process.

[0016] Preferably, the formed (CoCrNi) 94 The Al3Ti3 medium entropy alloy block is polished with sandpaper, and then the polished medium entropy alloy block is cold rolled, and the rolling direction is the deposition direction. Finally, the cold rolled (CoCrNi) 94 The Al3Ti3 medium entropy alloy bulk is further annealed.

[0017] Preferably, the cold rolling process adopts multiple rolling passes, and the cold rolling equipment is used for (CoCrNi) 94 The amount of pressure applied to the Al3Ti3 medium entropy alloy block each time is about 0.1 mm, and the high entropy alloy block is measured each time after single-pass rolling. The rolling is completed when the cold rolling deformation reaches 50%, and the annealing temperature after rolling is 800°C.

[0018] In summary, the present invention has the following beneficial effects:

[0019] The present invention prepares (CoCrNi) by mixing metal powders of Co: 31.3%, Cr: 31.3%, Ni: 31.3%, Al: 3%, and Ti: 3% by ball milling and vacuum drying. 94 Al3Ti3 medium entropy alloy powder, and prepared by powder plasma arc and other additive manufacturing processes (CoCrNi) 94 Al3Ti3 medium entropy alloy block. (CoCrNi) of the present invention 94 Al3Ti3 medium entropy alloy, using plasma arc additive manufacturing combined with a single-step cold rolling annealing process, by introducing a variety of lattice defects and fine inhomogeneous structure, obtained a high-strength (CoCrNi) 94 Al3Ti3 medium-entropy alloy, this preparation method has the advantages of simplicity and high efficiency, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is the phase analysis diagram of the directly deposited sample and the sample after thermomechanical treatment.

[0021] Figure 2 It is the IPF diagram and grain size distribution diagram of the sample after thermomechanical treatment.

[0022] Figure 3 This is a Vickers hardness test chart of untreated alloy and treated alloy.

[0023] Figure 4 This is a tensile properties test chart of untreated alloy and treated alloy. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0025] This embodiment provides a high strength (CoCrNi) 94 Al3Ti3 medium entropy alloy and preparation method thereof, comprising five metal powders of Co: 31.3%, Cr: 31.3%, Ni: 31.3%, Al: 3%, Ti: 3% by atomic percentage, the purity of the above metal alloy powders is higher than 99.5%, and the particle size of each material is between 150 and 250 meshes, and the preparation steps are as follows:

[0026] (1) Convert the atomic percentages of Co: 31.3%, Cr: 31.3%, Ni: 31.3%, Al: 3%, and Ti: 3% with a purity higher than 99.5% and a particle size between 150 and 250 meshes into the corresponding mass ratios of the metal powders, and obtain 300 g of the mixed metal powder by weighing;

[0027] (2) After the weighed metal powders are briefly mixed in a vacuum glove box, they are placed in a ball milling tank of a high-energy ball mill together with alumina grinding balls. The mass ratio of alumina grinding balls to metal mixed powders is 1:2. The ball mill is set to a cyclic operation mode. The ball mill is set to run forward for 5 minutes, stop for 5 minutes, and reverse for 5 minutes. The total operation time is set to 6 hours.

[0028] (3) The high-energy ball mill that has been running for 6 hours is turned off, the uniformly mixed metal powder in the ball mill is taken out, and the uniformly mixed alloy powder is immediately placed in a vacuum drying oven for 2 hours, and then the mixed powder is placed in a dry and sealed container for subsequent use;

[0029] (4) Grinding the substrate for deposition with an angle grinder to remove the oxide layer, oxides and impurities on the surface of the substrate, and then repeatedly cleaning with alcohol and acetone to further remove stains and surface impurities on the substrate;

[0030] (5) placing the mixed powder prepared after drying in step (3) into a powder feeding tank of an additive manufacturing device, opening a protective gas cylinder and a plasma arc additive manufacturing device, setting a suitable deposition path and deposition parameters on the plasma arc additive manufacturing device, and operating the device to perform layer-by-layer deposition on a substrate;

[0031] (6) During the deposition process, the material is kept in a formed state. After each layer of deposition is completed, an angle grinder is used to remove the oxide layer from the formed surface, and then the next layer is deposited until the required height is reached to obtain a medium-entropy alloy block.

[0032] Preferably, the plasma additive manufacturing equipment deposits (CoCrNi) 94 The parameters set in the Al3Ti3 medium entropy alloy are as follows: deposition current is 100A; powder feeding speed is 25r / min; ion gas flow rate is 2.5~3L / min; shielding gas flow rate is 12L / min; powder feeder flow rate is 2.5~3L / min; plasma welding gun operating speed is 395mm / min. The ion gas, shielding gas and powder feeding gas used in the entire deposition process are all inert gas argon.

[0033] Preferably, the formed (CoCrNi) 94 The Al3Ti3 medium entropy alloy block is polished with sandpaper, and then the polished medium entropy alloy block is cold rolled, and the rolling direction is the deposition direction. Finally, the cold rolled (CoCrNi) 94 The Al3Ti3 medium entropy alloy bulk is further heat treated.

[0034] Preferably, the cold rolling treatment adopts multi-pass rolling, and the rolling is completed when the cold rolling deformation reaches 50%. The annealing temperature after rolling is 800° C. and the annealing time is 1 hour.

[0035] The two (CoCrNi) prepared in the above examples 94 Al3Ti3 medium entropy alloy was analyzed by X-ray diffraction at 4°min -1 The scanning rate is scanned in the range of 20° to 100° of 2θ, such as Figure 1 As shown, both the directly deposited sample (As-printed) and the sample after thermomechanical treatment (RA-50+800℃) exhibit FCC phase structure.

[0036] like Figure 2 As shown in the IPF diagram and grain size distribution diagram of the sample after thermomechanical treatment (RA-50+800℃), the average grain size is 14.74μm, the grain size shows an obvious bimodal distribution, and has a heterogeneous structure.

[0037] like Figure 3 As shown, the untreated (CoCrNi) 94 Al3Ti3 medium entropy alloy and (CoCrNi) after 50% cold rolling and 800℃ annealing 94 The Vickers hardness test of Al3Ti3 medium entropy alloy was carried out. One point was taken every 1mm from top to bottom, and a total of 30 points were taken to calculate the average hardness. Untreated (CoCrNi) 94 The average hardness of Al3Ti3 medium entropy alloy is 255.6HV, after 50% cold rolling and 800℃ annealing (CoCrNi) 94 The average hardness of Al3Ti3 medium entropy alloy is as high as 466.7HV.

[0038] like Figure 4 As shown, the untreated (CoCrNi) prepared in the above embodiment 94 Al3Ti3 medium entropy alloy, 50% cold rolled and 800℃ annealed (CoCrNi) 94 The tensile properties of Al3Ti3 medium entropy alloy were tested, such as Figure 4 As shown, untreated (CoCrNi) 94 The Al3Ti3 medium entropy alloy has a high yield strength (413MPa) and fracture strength (748MPa). After 50% cold rolling and 800℃ annealing (CoCrNi) 94 The Al3Ti3 medium entropy alloy has higher tensile yield strength (1270MPa) and fracture strength (1430MPa).

[0039] Furthermore, the (CoCrNi) of the present invention 94 Al3Ti3 medium entropy alloy, using plasma arc additive manufacturing combined with a single-step cold rolling annealing process, by introducing a variety of lattice defects and fine inhomogeneous structure, obtained a high-strength (CoCrNi) 94 Al3Ti3 medium-entropy alloy, this preparation method has the advantages of simplicity and high efficiency, and has broad application prospects.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the design concept of the present invention should be included in the protection scope of the present invention.

Claims

1. A high strength (CoCrNi) 94 Al3Ti3 medium entropy alloy, characterized by: The alloy is prepared by using metal single substance powders of Co, Cr, Ni, Al and Ti in a proportioned manner through powder plasma additive manufacturing combined with a single-step cold rolling annealing process.

2. A high strength (CoCrNi) according to claim 1 94 Al3Ti3 medium entropy alloy, characterized by: The alloy element composition of the alloy is as follows in atomic percentage: Co: 31.3%, Cr: 31.3%, Ni: 31.3%, Al: 3%, Ti: 3%.

3. A high strength (CoCrNi) according to claim 1 94 Al3Ti3 medium entropy alloy, characterized by: The purity of the Co, Cr, Ni, Al and Ti metal single substance powders is higher than 99.5%, and the particle size of the metal single substance powder material is between 150 and 250 meshes.

4. A high strength (CoCrNi) according to claim 3 94 Al3Ti3 medium entropy alloy, characterized by: The alloy is converted into the corresponding mass ratio of each metal element powder according to the atomic ratio, and the corresponding actual mass of the metal element powder according to the mass ratio is obtained by weighing.

5. A method for preparing a high-strength (CoCrNi) as claimed in any one of claims 1 to 4 94 The preparation method of Al3Ti3 medium entropy alloy is characterized by: The steps include: 1) (CoCrNi) was prepared by plasma arc additive manufacturing 94 Bulk of Al3Ti3 medium entropy alloy. 2) A 60 mm × 10 mm × 4 mm sample was prepared by wire cutting, and the sample was subjected to 50% cold rolling. 3) After completion, the rolled sample was annealed at 800°C for 1 hour and then rapidly water quenched.

6. A high strength (CoCrNi) according to claim 5 94 The preparation method of Al3Ti3 medium entropy alloy is characterized by: In step 1, a suitable deposition path and deposition parameters are set on the plasma arc additive manufacturing device, and the device is operated to perform layer-by-layer deposition on the substrate.

7. A high strength (CoCrNi) according to claim 6 94 The preparation method of Al3Ti3 medium entropy alloy is characterized by: The plasma additive manufacturing equipment is used to deposit (CoCrNi) 94 The parameters set in the block of Al3Ti3 medium-entropy alloy are as follows: deposition current is 100A; powder feed plate speed is 25r / min; ion gas flow rate is 2.5~3L / min; shielding gas flow rate is 12L / min; powder feeder flow rate is 2.5~3L / min; plasma welding gun operating speed is 395mm / min, and the ion gas, shielding gas and powder feeding gas used in the entire deposition process are all argon.

8. A high strength (CoCrNi) according to claim 5 94 The preparation method of Al3Ti3 medium entropy alloy is characterized by: The cold rolling treatment in step 2 is: directly performing single-pass multiple cold rolling on the deposited sample, and completing the rolling when the cold rolling deformation reaches 50%.

9. A high strength (CoCrNi) according to claim 5 or 8 94 The preparation method of Al3Ti3 medium entropy alloy is characterized by: The rolling direction of the cold rolling process is the deposition direction.

10. A high strength (CoCrNi) according to claim 8 94 The preparation method of Al3Ti3 medium entropy alloy is characterized by: The cold rolling treatment is performed on (CoCrNi) 94 The downward pressure of the Al3Ti3 medium entropy alloy block is 0.1 mm.

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