CN115011858B - High-strength high-plasticity CoCrNiAlTi multi-principal-element alloy and preparation method thereof - Google Patents

Abstract

A high-strength and high-plasticity CoCrNiAlTi multi-principal element alloy and its preparation method, the alloy composition is Cr14-25%, Ni 25-35%, Al 4-6%, Ti 4-6%, Mo 0-1% by atomic percentage , the balance is Co; the method is: (1) prepare raw materials, melt and cast to make ingots; (2) homogenize treatment; (3) solution heat treatment; (4) cold deformation, deformation amount is 70-90%; (5) Aging heat treatment to obtain high strength and high plasticity CoCrNiAlTi multi-principal alloy. In the present invention, the composition of the CoCrNi-based medium entropy alloy is precisely designed to obtain low stacking fault energy and strong precipitation ability, and through special cold mechanical deformation and aging process, the precipitation kinetics of recrystallization and strengthening phase are regulated to obtain A unique heterostructure with a coarser distribution of strengthening phases within a crystalline matrix with a distinct structural gradient.

Description

High-strength and high-plasticity CoCrNiAlTi multi-principal element alloy and preparation method thereof

technical field

The invention belongs to the technical field of preparation of high-performance alloy materials, and in particular relates to a high-strength and high-plasticity CoCrNiAlTi multi-principal alloy and a preparation method thereof.

Background technique

The corrosion-resistant alloy CoCrNi has good comprehensive mechanical properties, and the alloy has excellent resistance to stress corrosion cracking under stress conditions, so that the alloy can obtain good service performance in harsh service environments. This performance is especially suitable for aerospace fasteners, space shuttle structures, chemical processing, medical, cryogenic equipment, marine equipment, oil and gas, food processing, springs, non-magnetic components, instrument parts and other fields. This type of alloy has a face-centered cubic crystal structure, and for a coarse crystal structure with a micron scale, the yield strength at room temperature is low (~400MPa). And some parts carrying critical loads require alloys with higher yield strength and better plasticity. In order to meet the needs of different environments, different mechanical properties can be obtained through the composition design of the alloy and the adjustment of the preparation process. From the perspective of microstructure control, the strong plasticity of the alloy can be greatly improved by means of grain refinement; however, when the yield strength reaches above 1GPa, due to the inversion relationship between strength and plasticity, the plastic deformation ability of the material decreases significantly, thereby reducing the strength of the material. The processability and safety of use; the reason is that when the grain is refined to a certain degree (ultrafine grain scale: submicron or nanoscale), the ability to store mobile dislocations in the grain drops sharply, making strain hardening during the deformation process The rate is also reduced, leading to premature "necking" phenomenon. Even if high-density stacking faults are formed during the deformation process by reducing the stacking fault energy, it is difficult to form twins in ultrafine grains, which cannot provide a high enough strain hardening rate, so that the alloy can obtain sufficient plasticity; that is, in In nanocrystalline and ultrafine-grained structures, even if the stacking fault energy is low, the effect of twinning toughening or phase transformation toughening cannot be achieved in this alloy system.

In order to improve the strength of the alloy, in addition to the means of fine grain strengthening, precipitation strengthening is also an effective method. Adding elements such as Al and Ti to the CoCrNi-based alloy with a face-centered cubic lattice structure can form strengthening particles coherent with the matrix to achieve precipitation strengthening. The strengthening effect mainly comes from the orderly strengthening of precipitated particles. However, to obtain a higher yield strength of the alloy, a higher volume fraction of precipitated particles is required, so that the distance between the precipitated particles is smaller, which seriously hinders the nucleation of stacking faults and twins during deformation; similarly, through this method, the toughness It is also difficult to overcome the inversion relationship of "strength-plasticity" by means of twinning toughening or phase transformation toughening. As a result, the plastic deformation capacity of the alloy is insufficient, often at high stress levels up to 1 GPa at the yield strength.

To sum up, the above-mentioned alloy systems mainly rely on fine-grain strengthening and precipitation strengthening to achieve strengthening and toughening, and there is a significant "toughness-strength" trade-off effect. Therefore, under the premise of maintaining a certain plasticity, the ability to increase the strength, especially the yield strength, is limited; how to make this series of alloys have good plastic deformation ability while obtaining high strength (GPa level) is the realization of this alloy system. The problem of preparing components that carry critical loads is also the key to breaking the "toughness-strength" property inversion of this series of alloys.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention proposes a high-strength and high-plasticity CoCrNiAlTi multi-principal alloy and its preparation method, by adding AlTi(Mo) on the basis of CoCrNi, setting the composition ratio to form a high yield strength, with sufficient The use of multi-principal alloys with elongation > 30%.

The present invention proposes a high-strength and high-plasticity CoCrNiAlTi multi-principal alloy, the composition of which is Cr 14-25%, Ni 25-35%, Al 4-6%, Ti 4-6%, Mo 0-1% by atomic percentage , and the balance is Co.

The preferred composition of the above-mentioned high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 17-22%, Ni 28-30%, Al 4.5-5.5%, Ti 4.5-5.5%, Mo 0-0.5%, and the balance For Co.

The yield strength of the above-mentioned high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is 1.17-1.3 GPa.

The elongation of the above-mentioned high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is 27-32%.

The preparation method of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy of the present invention comprises the steps:

(1) Prepare raw materials according to the above-mentioned atomic percentages, then melt and cast them to make ingots;

(2) Homogenize the ingot to make a homogenized casting;

(3) The homogenized casting is subjected to solution heat treatment to obtain a solid solution casting with FCC single phase;

(4) Cold deforming the solid solution casting, the deformation amount is 70-90%, and made into a cold deformed part;

(5) Perform aging heat treatment on cold deformed parts to obtain high strength and high plasticity CoCrNiAlTi multi-principal element alloy.

In the above step (2), the homogenization treatment is to keep the ingot at 1000-1200° C. for 12-24 hours, and water quench to room temperature after the heat preservation is completed.

In the above step (3), the solution heat treatment is to keep the homogenized casting at 1150-1200° C. for 2-8 hours, and water quench to room temperature after the heat preservation is completed.

In the above step (4), the cold deformation is cold rolling, or swaging and/or drawing at room temperature.

In the above step (5), the aging heat treatment is to keep the cold deformed part at 750-850° C. for 50-200 hours.

In the present invention, the composition of the CoCrNi-based medium entropy alloy is precisely designed to obtain low stacking fault energy and strong precipitation ability, and through special cold mechanical deformation (more than 70% large deformation) and aging process (medium temperature range is relatively Long holding time), control the recrystallization and the precipitation kinetics of the strengthening phase, and obtain a unique heterogeneous structure of the strengthening phase with a clear structure gradient and a coarse distribution of the strengthening phase in the crystalline matrix, thus under the premise that the back stress can effectively increase the yield strength , during the deformation process, an additional strain hardening effect (derived from stacking faults and nano-twins) is generated through local inhomogeneous deformation, so as to achieve comprehensive strengthening and toughening during the deformation process, resulting in back stress toughening and precipitation toughening The mutual coupling behavior endows the alloy with ultra-high comprehensive performance indicators of strength and plasticity. In addition, the low alloying of Mo in the present invention can produce a very strong solid solution strengthening effect, which contributes to the improvement of yield strength.

The alloy prepared by the present invention is a series of corrosion-resistant alloys. Through the reasonable design of the composition of Co-Cr-Ni-Al-Ti(Mo) and the preparation process, the inhomogeneous structure of the distribution of coarse precipitated particles inside the matrix grain structure can be obtained, so that The alloy obtains excellent comprehensive mechanical properties; the alloy profile can be processed into various forms of products, and is used in the production of fasteners used in aerospace, marine, oil and gas, food processing, springs, non-magnetic components, instrument components, etc. It has a wide range of applications; the use of Co, Ni, Cr, Al, Ti and a small amount of Mo makes the alloy price moderate, the material preparation process is relatively simple, and the industrialization investment is low.

Description of drawings

Fig. 1 is the high-strength high-plasticity CoCrNiAlTi multi-principal element alloy electron micrograph of the embodiment of the present invention 1;

Fig. 2 is a stress-strain diagram of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy of Example 1 of the present invention.

Detailed ways

In the embodiment of the present invention, after the aging heat treatment is completed, it is cooled to room temperature with the furnace.

In the embodiment of the present invention, the raw materials are metal chromium, metal nickel, metal cobalt, metal aluminum, metal titanium and metal molybdenum.

The high-strength and high-plasticity CoCrNiAlTi multi-principal alloys in the embodiments of the present invention are plates or rods.

Example 1

The composition of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 19.9%, Ni 29.85%, Al 4.975%, Ti 4.975%, Mo 0.5%, Co 39.8% by atomic percentage;

The method is:

(1) Prepare raw materials according to the above-mentioned atomic percentages, then melt and cast them to make ingots;

(2) The ingot is subjected to homogenization treatment to make a homogenized casting; the homogenization treatment is to heat the ingot at 1200 ° C for 12 hours, and quench to room temperature after the heat preservation is completed;

(3) The homogenized casting is subjected to solution heat treatment to obtain a solid solution casting with FCC single phase; the solution heat treatment is to heat the homogenized casting at 1200 ° C for 2 hours, and quench to room temperature after the heat preservation is completed;

(4) Carry out cold deformation to solid solution casting, deformation amount is 80%, make cold deformation; Cold deformation is cold rolling;

(5) Perform aging heat treatment on the cold deformed parts to obtain a high-strength and high-plasticity CoCrNiAlTi multi-principal alloy; the aging heat treatment is to keep the cold deformed parts at 800 ° C for 100 hours;

The microstructure is shown in Figure 1. It can be seen from the figure that in the microstructure of the alloy, there are both nano-scale recrystallized matrix grain structures and micron-scale unrecrystallized structures, forming a strong heterostructure structure;

A tensile test was performed on the obtained alloy sample at a tensile rate of 10 ^-3 s ^-1 , and the results are shown in Figure 2 , at room temperature, the tensile plasticity (elongation) was 30%, and the yield strength was 1200MPa.

Example 2

The composition of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 15%, Ni 30%, Al 6%, Ti 6%, Co 43% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1000°C, time 20h;

(2) Solution heat treatment temperature 1200°C, time 3h;

(3) The deformation amount of cold deformation is 75%;

(4) Aging heat treatment temperature 800°C, time 110h;

(5) The elongation rate is 29%, and the yield strength is 1190MPa.

Example 3

The composition of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 19.8%, Ni 29.7%, Al 4.95%, Ti 4.95%, Mo 1%, Co 39.6% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1100°C, time 24h;

(2) Solution heat treatment temperature 1200°C, time 4h;

(3) The amount of deformation of cold deformation is 75%; cold deformation is swaging at room temperature;

(4) Aging heat treatment temperature 850°C, time 100h;

(5) The elongation rate is 31%, and the yield strength is 1230MPa.

Example 4

The composition of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 14.925%, Ni29.85%, Al 5.97%, Ti 5.97%, Mo 0.5%, Co 42.57% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1200°C, time 13h;

(2) Solution heat treatment temperature 1150°C, time 8h;

(3) The amount of deformation of cold deformation is 80%; cold deformation is swaging at room temperature;

(4) Aging heat treatment temperature 750°C, time 200h;

(5) The elongation rate is 28%, and the yield strength is 1300MPa.

Example 5

The composition of high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 14.85%, Ni 29.7%, Al 5.94%, Ti 5.94%, Mo 1%, Co 42.57% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1200°C, time 14h;

(2) Solution heat treatment temperature 1200°C, time 4h;

(3) The deformation amount of cold deformation is 80%; cold deformation is drawing;

(4) Aging heat treatment temperature 850°C, time 200h;

(5) The elongation rate is 28%, and the yield strength is 1290MPa.

Example 6

The composition of high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 13.875%, Ni 27.75%, Al 5.55%, Ti 5.55%, Mo 0.75%, Co 39.775% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1200°C, time 24h;

(2) Solution heat treatment temperature 1200°C, time 4h;

(3) The amount of deformation of cold deformation is 80%; cold deformation is swaging and drawing at room temperature;

(4) Aging heat treatment temperature 700°C, time 150h;

(5) The elongation rate is 31%, and the yield strength is 1210MPa.

Example 7

The composition of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 19.8%, Ni 29.7%, Al 4.95%, Ti 4.95%, Mo 1%, Co 39.6% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1200°C, time 18h;

(2) Solution heat treatment temperature 1200°C, time 4h;

(3) The amount of deformation of cold deformation is 80%; cold deformation is swaging at room temperature;

(4) Aging heat treatment temperature 850°C, time 50h;

(5) The elongation rate is 30%, and the yield strength is 1200MPa.

Example 8

The composition of the high-strength and high-plasticity CoCrNiAlTi multi-principal alloy is Cr 20%, Ni 30%, Al 5%, Ti 5%, Co 40% by atomic percentage;

Method is with embodiment 1, and difference is:

(1) Homogenization treatment temperature 1200°C, time 24h;

(2) Solution heat treatment temperature 1200°C, time 4h;

(3) The amount of deformation of cold deformation is 80%; cold deformation is swaging at room temperature;

(4) Aging heat treatment temperature 750°C, time 100h;

(5) The elongation rate is 32%, and the yield strength is 1170MPa.

Claims (5)

1. a preparation method of high-strength high-plasticity CoCrNiAlTi multi-principal alloy, is characterized in that, its preparation method comprises the steps: (1) Prepare raw materials according to atomic percentage, then melt and cast them to make ingots; (2) Homogenize the ingot to make a homogenized casting; (3) The homogenized casting is subjected to solution heat treatment to obtain a solid solution casting with FCC single phase; (4) Cold deformation of solid solution castings, the deformation amount is 70-90%, and made into cold deformation parts; (5) Perform aging heat treatment on the cold deformed parts, and keep it at 750-850°C for 50-200 h to obtain high-strength and high-plasticity CoCrNiAlTi multi-principal alloy; The alloy composition is Cr 14-25% by atomic percentage, Ni 25-35%, Al 4-6%, Ti 4-6%, Mo 0-1%, and the balance is Co; The yield strength of the alloy is 1.17-1.3 GPa; The elongation of the alloy is 27-32%. 2. The preparation method of high-strength and high-plasticity CoCrNiAlTi multi-principal alloy according to claim 1, characterized in that the preferred components are Cr 17-22% by atomic percentage, Ni 28-30%, Al 4.5-5.5%, Ti 4.5 to 5.5%, Mo 0 to 0.5%, the balance being Co. 3. The preparation method of high-strength and high-plasticity CoCrNiAlTi multi-principal alloy according to claim 1, characterized in that in step (2), the homogenization treatment is to heat the ingot at 1000-1200 °C for 12-24 hours, and the heat preservation is completed Then water quenched to room temperature. 4. The method for preparing high-strength and high-plasticity CoCrNiAlTi multi-principal alloy according to claim 1, characterized in that in step (3), the solution heat treatment is to heat the homogenized casting at 1150-1200°C for 2-8 h, After the heat preservation was completed, the water was quenched to room temperature. 5. The method for preparing high-strength and high-plasticity CoCrNiAlTi multi-principal alloy according to claim 1, characterized in that in step (4), the cold deformation is cold rolling, or swaging and/or drawing at room temperature.

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