阅读说明：本技术 一种含硼形状记忆合金及其制备方法 (Boron-containing shape memory alloy and preparation method thereof ) 是由 黎小辉 甘春雷 周楠 郑开宏 于 2021-04-23 设计创作，主要内容包括：本发明公开了一种含硼形状记忆合金及其制备方法,该含硼形状记忆合金由Ni、Ti、Zr以及B制备得到,且含硼形状记忆合金的化学式为Ni-(51-y)Ti-(49-x)Zr-(x)B-(y)；其中,x＝1.0～5.0,y＝1.0～3.0,且x、y分别为Zr、B在合金中所占的摩尔百分比。该含硼形状记忆合金通过添加硼元素形成具有纳米尺度的TiB-(2)粒子,作为异质形核核心细化基体组织来提高合金的强度并改善其塑性,从而使得该合金具有高强韧、高弹性以及可恢复性能好的优点,能满足形状记忆合金对高热稳定性以及优异塑性的使用要求。该含硼形状记忆合金的制备方法整体工艺简单,容易控制,容易实现连续性生产,且生产成本低。(The invention discloses a boron-containing shape memory alloy and a preparation method thereof, wherein the boron-containing shape memory alloy is prepared from Ni, Ti, Zr and B, and the chemical formula of the boron-containing shape memory alloy is Ni 51‑y Ti 49‑x Zr x B y (ii) a Wherein x is 1.0-5.0, y is 1.0-3.0, and x and y are mol percentages of Zr and B in the alloy. The boron-containing shape memory alloy forms the TiB with the nanometer scale by adding boron element 2 Particles of asThe matrix structure is thinned for heterogeneous nucleation cores to improve the strength and plasticity of the alloy, so that the alloy has the advantages of high toughness, high elasticity and good restorability, and can meet the use requirements of the shape memory alloy on high thermal stability and excellent plasticity. The preparation method of the boron-containing shape memory alloy has the advantages of simple overall process, easy control, easy realization of continuous production and low production cost.)

1. A boron-containing shape memory alloy, comprising:

the boron-containing shape memory alloy is prepared from Ni, Ti, Zr and B, and the chemical formula of the boron-containing shape memory alloy is Ni_51-yTi_49-xZr_xB_y(ii) a Wherein x is 1.0-5.0, y is 1.0-3.0, and x and y are mole percentages of the Zr and B in the alloy.

2. The boron-containing shape memory alloy of claim 1, wherein:

according to the atomic percentage content, the content of Ni is 48.0at percent to 50.0at percent, the content of Ti is 44.0at percent to 48.0at percent, the content of Zr is 1.0at percent to 5.0at percent, and the content of B is 1.0at percent to 3.0at percent.

3. The boron-containing shape memory alloy of claim 1, wherein:

the purities of the Ni, the Ti, the Zr and the B are all more than 99.9 wt%; and the boron-containing shape memory alloy is in a nano-phase reinforced multi-element solid solution structure.

4. A method of making the boron-containing shape memory alloy of any one of claims 1 to 3, comprising the steps of:

pushing the cleaned Ni raw material, Ti raw material, Zr raw material and B raw material into a smelting chamber through a feeding system respectively to obtain molten metal;

after being irradiated and melted by electron beams, a part of molten metal is dripped into a water-cooled copper bed to form a skull, the surface of the skull is melted under the continuous irradiation of the electron beams to form a skull melting bath, and the remaining part of molten metal flows through the skull melting bath and then passes through a crystallizer to obtain an ingot;

placing the cast ingot in a vacuum furnace for homogenization heat treatment, and cooling along with the furnace;

and carrying out hot rotary swaging processing on the homogenized cast ingot, and carrying out solid solution treatment and artificial aging heat treatment to obtain the boron-containing shape memory alloy.

5. The method of making a boron-containing shape memory alloy of claim 4, wherein:

the vacuum degree of the smelting chamber is less than or equal to 1 multiplied by 10^-2Pa, and argon with the purity of 99.99 wt% needs to be filled in the smelting chamber when the smelting operation is carried out.

6. The method of making a boron-containing shape memory alloy of claim 4, wherein:

the annealing temperature of the homogenization heat treatment step is 1200-1500 ℃, the heat preservation time of the annealing of the homogenization heat treatment step is 12-48 h, and the vacuum degree of the heat treatment furnace is 1 multiplied by 10^-2Pa。

7. The method of making a boron-containing shape memory alloy of claim 4, wherein:

the voltage of the electron beam is 20kV to 30kV, and the current of the electron beam is 1A to 5A.

8. The method of making a boron-containing shape memory alloy of claim 4, wherein:

before the hot rotary swaging processing step, the method also comprises the step of preserving the heat of the cast ingot for 2 to 4 hours at the temperature of between 800 and 900 ℃.

9. The method of making a boron-containing shape memory alloy of claim 4, wherein:

preserving the heat of the alloy after the hot rotary swaging processing step at 800-920 ℃ for 4-8 h for carrying out the solution treatment step, wherein the cooling condition is water cooling; and preserving the heat of the alloy subjected to the solution treatment at 500-550 ℃ for 1-4 h to perform the artificial aging treatment step.

10. The method of making a boron-containing shape memory alloy of claim 4, wherein:

the cleaning step specifically comprises respectively removing surface oxide films of the Ni raw material, the Ti raw material, the Zr raw material and the B raw material, and then respectively carrying out ultrasonic cleaning pretreatment.

Technical Field

The invention relates to the technical field of shape memory alloys, in particular to a boron-containing shape memory alloy and a preparation method thereof.

Background

Shape memory alloys are unique materials that can be deformed and return to a predetermined shape after being unloaded or heated. To date, there are three main types of shape memory alloys with practical application: Ni-Ti based, Fe based and Cu based memory alloy, wherein the Ni-Ti based memory alloy has the characteristics of good shape memory property, strong anti-fatigue property, high strength, excellent biocompatibility and the like, and is suitable for application in most fields. While Fe-based and Cu-based memory alloys are low in cost, poor stability and thermo-mechanical properties limit development and application. Even the most mature NiTi shape memory alloy at present has low tensile strength and martensite phase transition temperature, and can not meet the requirements of some key driving devices such as aerospace, nuclear power engineering, airplane morphing wings, space robots and the like on the service performance of materials.

The martensite phase transition temperature can be improved by adding elements such as Pd, Pt, Au and the like to replace Ni or adding elements such as Zr, Hf and the like to replace Ti in the NiTi binary alloy. Alloying elements Cu, Nb, Fe and the like are added, so that the phase transition temperature of the alloy is greatly reduced, and the M phase transition and the R phase transition are separated. The NiTi binary alloy matrix has low strength, and the martensite phase transformation critical shear stress is not obviously higher than the plastic slip critical stress, so that the alloy is easy to slip in the deformation process to cause the deterioration of the memory performance. For example, the addition of Hf in a binary NiTi alloy causes severe lattice distortion, resulting in poor room temperature plastic deformability. At present, the single maximum cold deformation of the NiTiHf alloy is less than 20%, and the process forming of subsequent parts is severely restricted.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a method for forming a nano coherent phase TiB by compositely adding Zr and B₂And the matrix strength of the NiTi alloy is improved by refining grains, so that the boron-containing shape memory alloy has high toughness.

The embodiment of the invention is realized by the following steps:

in a first aspect, the present invention provides a boron-containing shape memory alloy prepared from Ni, Ti, Zr and B, wherein the chemical formula of the boron-containing shape memory alloy is Ni_51-yTi_49-xZr_xB_y(ii) a Wherein x is 1.0-5.0, y is 1.0-3.0, and x and y are mol percentages of Zr and B in the alloy.

In an alternative embodiment, the Ni content is 48.0 at% to 50.0 at%, the Ti content is 44.0 at% to 48.0 at%, the Zr content is 1.0 at% to 5.0 at%, and the B content is 1.0 at% to 3.0 at%, in terms of atomic percentage content.

In an alternative embodiment, the purity of each of Ni, Ti, Zr, and B is greater than 99.9 wt%; and the boron-containing shape memory alloy is in a nano-phase reinforced multi-element solid solution structure.

In a second aspect, the present disclosure provides a method of making the boron-containing shape memory alloy of any one of the preceding embodiments, comprising the steps of:

pushing the cleaned Ni raw material, Ti raw material, Zr raw material and B raw material into a smelting chamber through a feeding system respectively to obtain molten metal;

after being irradiated and melted by electron beams, a part of molten metal is dripped into a water-cooled copper bed to form a skull, the surface of the skull is melted to form a skull melting bath under the continuous irradiation of the electron beams, and the remaining part of molten metal flows through the skull melting bath and then passes through a crystallizer to obtain an ingot;

placing the cast ingot in a vacuum furnace for homogenization heat treatment, and cooling along with the furnace;

and (3) performing hot rotary swaging processing on the homogenized cast ingot, and performing solid solution treatment and artificial aging heat treatment to obtain the boron-containing shape memory alloy.

In an alternative embodiment, the vacuum degree of the melting chamber is 1 × 10 or less^-2Pa, and argon with the purity of 99.99 wt% needs to be filled in the smelting chamber when the smelting operation is carried out.

In an alternative embodiment, the annealing temperature of the homogenization heat treatment step is 1200-1500 ℃, the heat preservation time of the annealing of the homogenization heat treatment step is 12-48 h, and the vacuum degree of the heat treatment furnace is 1 x 10^-2Pa。

In an alternative embodiment, the voltage of the electron beam is between 20kV and 30kV and the current of the electron beam is between 1A and 5A.

In an optional embodiment, before the step of hot rotary swaging, the method further comprises the step of preserving the temperature of the cast ingot at 800-900 ℃ for 2-4 h.

In an optional embodiment, the alloy after the hot rotary swaging processing step is subjected to solution treatment at 800-920 ℃ for 4-8 h, and the cooling condition is water cooling; and (3) preserving the heat of the alloy after the solution treatment step at 500-550 ℃ for 1-4 h for artificial aging treatment.

In an alternative embodiment, the cleaning step specifically includes removing the surface oxide films of the Ni raw material, the Ti raw material, the Zr raw material, and the B raw material, respectively, and then performing ultrasonic cleaning pretreatment.

Embodiments of the invention have at least the following advantages or benefits:

embodiments of the present invention provide a boron-containing shape memory alloy prepared from Ni, Ti, Zr, and B, and having a chemical formula of Ni_51-yTi_49-xZr_xB_y(ii) a Wherein x is 1.0-5.0, y is 1.0-3.0, and x and y are mol percentages of Zr and B in the alloy. The boron-containing shape memory alloy forms the TiB with the nanometer scale by adding boron element₂The particles are used as heterogeneous nucleation cores to refine the matrix structure to improve the strength and plasticity of the alloy, so that the alloy has high toughness and elasticityAnd the shape memory alloy has the advantage of good restorability, and can meet the use requirements of the shape memory alloy on high thermal stability and excellent plasticity.

The embodiment of the invention also provides a preparation method of the boron-containing shape memory alloy, which is characterized in that high-temperature refractory metal smelting is carried out by heat generated by electron beam bombardment, the molten metal above a skull is enabled to obtain sufficient liquid state maintaining time and superheat degree while the raw material is melted, various impurity elements or inclusions in the raw material are promoted to be effectively removed, and the shape memory alloy with uniform components and high purity is obtained. On the other hand, after hot rotary swaging processing and homogenizing annealing heat treatment, the method is favorable for obtaining single-phase solid solution, promoting the obtaining of a fine equiaxed crystal structure and further improving the comprehensive performance of the shape memory alloy; meanwhile, the preparation method has the advantages of simple overall process, easy control, easy realization of continuous production and low production cost.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a transmission electron micrograph of a boron-containing shape memory alloy prepared according to example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The features and properties of the present invention are described in further detail below with reference to examples.

Examples of the inventionA boron-containing shape memory alloy is provided, which is prepared from Ni, Ti, Zr and B, and has a chemical formula of Ni_51-yTi_49-xZr_xB_y(ii) a Wherein x is 1.0-5.0, y is 1.0-3.0, and x and y are mol percentages of Zr and B in the alloy.

In detail, the boron-containing shape memory alloy forms TiB with nanometer scale by adding boron element₂The particles, as heterogeneous nucleation cores, refine the matrix structure to improve the strength of the alloy and improve its plasticity. Meanwhile, x is limited within 1.0-5.0, and y is limited within 1.0-3.0, so that on one hand, the formation of the TiB with the nanoscale can be ensured₂The particles and the matrix structure are refined, on the other hand, the excessive consumption of titanium element can be avoided, the boron-containing shape memory alloy can be obtained, the alloy has the advantages of high toughness, high elasticity and good restorability, and the use requirements of the shape memory alloy on high thermal stability and excellent plasticity can be met.

Optionally, in terms of atomic percentage, the content of Ni is 48.0 at% to 50.0 at%, the content of Ti is 44.0 at% to 48.0 at%, the content of Zr is 1.0 at% to 5.0 at%, and the content of B is 1.0 at% to 3.0 at%. Similar to the principle of limiting x and y, controlling the contents of the components within the above ranges ensures formation of TiB having a nano-scale₂The particles refine the matrix structure, on the other hand, can avoid consuming excessive titanium element, and ensure that the shape memory alloy containing boron can be obtained.

In the examples of the present invention, the purities of Ni, Ti, Zr, and B were all greater than 99.9 wt% to reduce the contamination of impurities and ensure the purity of the alloy. Meanwhile, the boron-containing shape memory alloy is in a nano-phase reinforced multi-element solid solution structure, so that the alloy has the advantages of high toughness, high elasticity and good restorability, and the use requirements of the shape memory alloy on high thermal stability and excellent plasticity can be met.

Embodiments of the present invention also provide a method of making the boron-containing shape memory alloy of any one of the preceding embodiments, comprising the steps of:

s1: and pushing the cleaned Ni raw material, Ti raw material, Zr raw material and B raw material into a smelting chamber through a feeding system respectively to obtain molten metal.

Specifically, the cleaning step includes removing the surface oxide films of the Ni material, the Ti material, the Zr material, and the B material, respectively, and then performing ultrasonic cleaning pretreatment. The boron-containing shape memory alloy with high toughness, high elasticity and good restorability can be formed by cleaning and removing the oxidation film to effectively remove surface impurities.

Meanwhile, in the embodiment of the invention, the vacuum degree of the smelting chamber is less than or equal to 1 multiplied by 10^-2Pa, and argon with the purity of 99.99 wt% needs to be filled in the smelting chamber when the smelting operation is carried out. The vacuum degree is controlled to be less than the range, and argon is filled as protective gas, so that the purity of the alloy preparation process can be ensured, the oxidation is avoided, and the boron-containing shape memory alloy with high toughness, high elasticity and good restorability can be conveniently prepared.

S2: and (2) dropping a part of molten metal into a water-cooled copper bed to form a skull through electron beam irradiation melting, melting the surface of the skull to form a skull melting bath under the continuous irradiation of the electron beams, and allowing the rest part of molten metal to flow through the skull melting bath and then pass through a crystallizer to obtain an ingot.

In detail, the high-elasticity shape memory alloy can be subjected to high-temperature refractory metal smelting through heat generated by high-energy electron beam bombardment, so that the molten metal above a solidified shell can obtain sufficient liquid state maintaining time and superheat degree while the raw material is melted, various impurity elements or inclusions in the raw material are promoted to be separated from a matrix, the impurity elements or the inclusions are effectively removed, and the shape memory alloy with uniform components and high purity can be further obtained.

Meanwhile, in the embodiment of the present invention, the voltage of the electron beam is 20kV to 30kV, and the current of the electron beam is 1A to 5A. The voltage and current are controlled within this range to produce a shape memory alloy containing boron uniformly.

S3: and placing the cast ingot in a vacuum furnace for homogenization heat treatment, and cooling along with the furnace.

S4: and (3) performing hot rotary swaging processing on the homogenized cast ingot, and performing solid solution treatment and artificial aging heat treatment to obtain the boron-containing shape memory alloy.

In detail, after hot rotary swaging and homogenizing annealing heat treatment, the method is favorable for obtaining single-phase solid solution, promoting to obtain a fine equiaxed crystal structure and further improving the comprehensive performance of the shape memory alloy.

Wherein the annealing temperature of the homogenization heat treatment step is 1200-1500 ℃, the heat preservation time of the annealing of the homogenization heat treatment step is 12-48 h, and the vacuum degree of the heat treatment furnace is 1 multiplied by 10^-2Pa. The homogenizing annealing temperature and the heat preservation time are determined by alloy components, better diffusion in the treatment process can be ensured, the uniformity of tissues is ensured, and aggregation is avoided being formed locally, so that the boron-containing memory alloy prepared by the method has the advantages of high toughness, high elasticity and good restorability, and the use requirements of the shape memory alloy on high thermal stability and excellent plasticity can be met.

In the embodiment of the present invention, before the step of performing the hot-swaging process, the method further includes maintaining the temperature of the ingot at 800 to 900 ℃ for 2 to 4 hours. Meanwhile, the alloy after the hot rotary swaging processing step is subjected to solution treatment at the temperature of 800-920 ℃ for 4-8 h, and the cooling condition is water cooling; and (3) preserving the heat of the alloy after the solution treatment step at 500-550 ℃ for 1-4 h for artificial aging treatment. The temperature and the heat preservation time are determined according to the alloy components, so that a single-phase solid solution can be obtained in the preparation process, and a fine equiaxed crystal structure can be obtained, thereby improving the comprehensive performance of the shape memory alloy.

In addition, the boron-containing shape memory alloy can be prepared through the steps and the flow, so that the preparation method has the advantages of simple overall process, easiness in control, easiness in realization of continuous production and low production cost.

The preparation of the boron-containing shape memory alloy described above is described in detail by the following specific examples:

example 1

This example provides a boron-containing shape memory alloy prepared by the following steps:

s1: weighing the following raw materials in percentage by atom: 50.0 at% Ni, 48.0 at% Ti, 1.0 at% Zr, and 1.0 at% B;

s2: respectively removing surface oxide films of the Ni raw material, the Ti raw material, the Zr raw material and the B raw material, and then respectively carrying out ultrasonic cleaning pretreatment;

s3: the cleaned Ni raw material, Ti raw material, Zr raw material and B raw material are respectively pushed into a smelting chamber through a feeding system, and the vacuum degree in the smelting chamber is maintained at 1 x 10^-2Pa, filling argon with the purity of 99.99 wt%, and obtaining molten metal liquid under the irradiation of electron beams with the voltage of 25kV and the current of 3A;

s4: continuously irradiating and melting a part of molten metal by electron beams, then dripping the molten metal into a water-cooled copper bed to form a skull, and melting the surface of the skull under the continuous irradiation of the electron beams to form a skull melting bath;

s5: after the other part of the molten metal flows through the skull melting bath, obtaining an ingot with the diameter of 60mm through a crystallizer;

s6: placing the cast ingot in a vacuum furnace for homogenizing heat treatment for 24h at 1200 ℃, wherein the vacuum degree of the heat treatment furnace is 1 multiplied by 10^-2Pa, cooling along with the furnace;

s7: preheating the cast ingot for 3h at 850 ℃, carrying out hot rotary swaging processing, then carrying out solid solution treatment for 6h at 880 ℃, and then carrying out artificial aging treatment at 500 ℃/2h to obtain Ni with the chemical formula₅₀Ti₄₈Shape memory alloy of ZrB.

As shown in FIG. 1, the shape memory alloy prepared in this example is a nano-phase reinforced multi-element solid solution structure.

Example 2

This example provides a boron-containing shape memory alloy prepared by the following steps:

s1: weighing the following raw materials in percentage by atom: 50.0 at% Ni, 46.0 at% Ti, 3.0 at% Zr, and 1.0 at% B;

s2: respectively removing surface oxide films of the Ni raw material, the Ti raw material, the Zr raw material and the B raw material, and then respectively carrying out ultrasonic cleaning pretreatment;

s3: the cleaned Ni raw material, Ti raw material, Zr raw material and B raw material are respectively pushed into a smelting chamber through a feeding system, and the vacuum degree in the smelting chamber is maintained at 1 x 10^-2Pa, filling argon with the purity of 99.99 wt%, and obtaining molten metal liquid under the irradiation of electron beams with the voltage of 25kV and the current of 3A;

s4: continuously irradiating and melting a part of the molten metal by electron beams, then dripping the molten metal into a water-cooled copper bed to form a skull, and melting the surface of the skull under the continuous irradiation of the electron beams to form a skull melting bath;

s5: enabling the other part of the residual molten metal liquid to flow through the skull melting bath and then pass through a crystallizer to obtain an ingot with the diameter of 60 mm;

s6: placing the cast ingot in a vacuum furnace for carrying out homogenization heat treatment for 48 hours at the temperature of 1500 ℃, wherein the vacuum degree of the heat treatment furnace is 1 multiplied by 10^-2Pa, cooling along with the furnace;

s7: preheating the cast ingot at 900 ℃ for 4h, carrying out hot rotary swaging processing, then carrying out solid solution treatment at 900 ℃ for 8h, and then carrying out artificial aging treatment at 520 ℃/4h to obtain Ni with the chemical formula₅₀Ti₄₆Zr₃B is a shape memory alloy.

Example 3

This example provides a boron-containing shape memory alloy prepared by the following steps:

s1: weighing the following raw materials in percentage by atom: 48.0 at% Ni, 44.0 at% Ti, 5.0 at% Zr, and 3.0 at% B;

s2: respectively removing surface oxide films of the Ni raw material, the Ti raw material, the Zr raw material and the B raw material, and then respectively carrying out ultrasonic cleaning pretreatment;

s3: respectively pushing the cleaned Ni raw material, Ti raw material, Zr raw material and B raw material into a smelting chamber through a feeding system, and waiting for the Ni raw material, the Ti raw material, the Zr raw material and the B raw material in the smelting chamberThe degree of hollowness is maintained at 1 x 10^-2Pa, filling argon with the purity of 99.99 wt%, and obtaining molten metal liquid under the irradiation of electron beams with the voltage of 30kV and the current of 5A;

s4: continuously irradiating and melting a part of the molten metal by electron beams, then dripping the molten metal into a water-cooled copper bed to form a skull, and melting the surface of the skull under the continuous irradiation of the electron beams to form a skull melting bath;

s5: enabling the other part of the residual molten metal liquid to flow through the skull melting bath and then pass through a crystallizer to obtain an ingot with the diameter of 60 mm;

s6: placing the cast ingot in a vacuum furnace, carrying out homogenization heat treatment for 24 hours at the temperature of 1200 ℃, wherein the vacuum degree of the heat treatment furnace is 1 x 10 < -2 > Pa, and cooling along with the furnace;

s7: preheating the cast ingot at 900 ℃ for 4h, performing hot rotary swaging processing, then performing solid solution treatment at 900 ℃ for 8h, and then performing artificial aging treatment at 500 ℃/4h to obtain Ni with a chemical formula₄₈Ti₄₄Zr₅B₃The shape memory alloy of (1).

Comparative example 1

Comparative example 1 provides a high elastic shape memory alloy, which is prepared by the following steps:

s1: weighing the following raw materials in percentage by atom: 51.0 at% Ni, 47.0 at% Ti, 1.0 at% Hf, and 1.0 at% Fe;

s2: respectively removing surface oxide films of a Ni raw material, a Ti raw material, an Hf raw material and an Fe raw material, and respectively carrying out ultrasonic cleaning pretreatment;

s3: the cleaned Ni raw material, Ti raw material, Hf raw material and Fe raw material are respectively pushed into a smelting chamber through a feeding system, and the vacuum degree in the smelting chamber is maintained at 1 x 10^-2Pa, filling argon with the purity of 99.99 wt%, and obtaining molten metal liquid under the irradiation of electron beams with the voltage of 30kV and the current of 5A;

s4: continuously irradiating and melting a part of the molten metal by electron beams, then dripping the molten metal into a water-cooled copper bed to form a skull, and melting the surface of the skull under the continuous irradiation of the electron beams to form a skull melting bath;

s5: enabling the other part of the residual molten metal liquid to flow through the skull melting bath and then pass through a crystallizer to obtain an ingot with the diameter of 60 mm;

s6: preheating the cast ingot at 850 ℃ for 4h, performing hot rotary swaging processing, then performing solid solution treatment at 920 ℃ for 6h, and then performing artificial aging treatment at 500 ℃/4h to obtain Ni with the chemical formula₅₁Ti₄₇HfFe shape memory alloy.

Comparative example 2

Comparative example 2 provides a high elastic shape memory alloy, which is prepared by the following steps:

s1: weighing the following raw materials in percentage by atom: 50.0 at% Ni, 48.0 at% Ti, 1.0 at% Nb, and 1.0 at% Cu;

s2: respectively removing oxide films on the surfaces of the Ni raw material, the Ti raw material, the Nb raw material and the Cu raw material, and then respectively carrying out ultrasonic cleaning pretreatment;

s3: pushing the cleaned Ni raw material, Ti raw material, Nb raw material and Cu raw material into a smelting chamber through a feeding system respectively, keeping the vacuum degree in the smelting chamber at 1 x 10 < -2 > Pa, filling argon with the purity of 99.99 wt%, and obtaining molten metal under the irradiation of an electron beam with the voltage of 30kV and the current of 5A;

s4: continuously irradiating and melting a part of the molten metal by electron beams, then dripping the molten metal into a water-cooled copper bed to form a skull, and melting the surface of the skull under the continuous irradiation of the electron beams to form a skull melting bath;

s5: enabling the other part of molten metal to flow through the skull melting bath, and then passing through a crystallizer to obtain an ingot with the diameter of 60 mm;

s6: preheating the cast ingot at 850 ℃ for 4h, performing hot rotary swaging processing, then performing solid solution treatment at 920 ℃ for 6h, and then performing artificial aging treatment at 500 ℃/4h to obtain Ni with the chemical formula₅₀Ti₄₈NbCu shape memory alloys.

Comparative example 3

Comparative example 2 provides a high elastic shape memory alloy, which is prepared by the following steps:

s1: weighing the following raw materials in percentage by atom: 50.0 at% Ni, 48.0 at% Ti, 1.0 at% Fe and 1.0 at% V;

s2: respectively removing surface oxide films of a Ni raw material, a Ti raw material, a Fe raw material and a V raw material, and respectively carrying out ultrasonic cleaning pretreatment;

s3: pushing the cleaned Ni raw material, Ti raw material, Fe raw material and V raw material into a smelting chamber through a feeding system respectively, keeping the vacuum degree in the smelting chamber at 1 x 10 < -2 > Pa, filling argon with the purity of 99.99 wt%, and obtaining molten metal under the irradiation of an electron beam with the voltage of 30kV and the current of 5A;

s4: continuously irradiating and melting a part of the molten metal by electron beams, then dripping the molten metal into a water-cooled copper bed to form a skull, and melting the surface of the skull under the continuous irradiation of the electron beams to form a skull melting bath;

s5: enabling the rest part of molten metal liquid to flow through the skull melting bath, and then enabling the molten metal liquid to pass through a crystallizer to obtain an ingot with the diameter of 60 mm;

s6: preheating the cast ingot at 880 ℃ for 4h, performing hot rotary swaging, performing solid solution treatment at 900 ℃ for 4h, and performing artificial aging treatment at 520 ℃/4h to obtain Ni₅₀Ti₄₈A shape memory alloy of FeV.

It should be noted that the flow and parameters of the preparation method provided by the embodiment of the present invention adopted in each of comparative example 1, comparative example 2 and comparative example 3 do not mean that the flow and parameters of the preparation method disclosed in the embodiment of the present invention belong to the prior art, and the comparative example is different from the embodiment only in the difference of alloy components.

The shape memory alloys prepared in examples 1 to 3 and comparative examples 1 to 3 were subjected to a mechanical properties test apparatus and referred to in GB/T228.1-2010 metallic material tensile test part one: the specific results of the tensile strength, recoverable deformation and elongation of the shape memory alloy tested by the room temperature test method are shown in Table 1.

Table 1:

as can be seen from the data analysis in Table 1, the tensile strength, recoverable deformation and elongation of the shape memory alloys prepared in examples 1-3 are significantly better than those of the shape memory alloys prepared in comparative examples 1-3, which shows that the shape memory alloys of the present invention can obtain shape memory alloys with excellent comprehensive properties under the synergistic effect of the components and the component content ratios thereof. The shape memory alloys prepared in examples 1 to 3 and the shape memory alloys prepared in comparative examples 1 to 3 were measured using a micro vickers hardness tester, and the hardness of the shape memory alloys prepared in examples 1 to 3 was more than 421HV, but the shape memory alloys prepared in comparative examples 1 to 3 were significantly different from the shape memory alloys prepared in examples.

In summary, the boron-containing shape memory alloy provided by the embodiment of the invention uses Ni, Ti, Zr and B as preparation raw materials to obtain Ni with a chemical formula_51-yTi_49-xZr_xB_yThe shape memory alloy of (1), which forms TiB having a nano-scale by adding boron element₂The particles are used as heterogeneous nucleation cores to refine the matrix structure so as to improve the strength of the alloy and simultaneously improve the plasticity of the alloy, so that the alloy has the advantages of high toughness, high elasticity and good restorability, and can meet the use requirements of the shape memory alloy on high thermal stability and excellent plasticity. In addition, in the embodiment of the invention, the high-elasticity shape memory alloy is subjected to high-temperature refractory metal smelting by heat generated by high-energy electron beam bombardment, so that the molten metal above the solidified shell obtains sufficient liquid state maintaining time and superheat degree while the raw material is melted, various impurity elements or inclusions in the raw material are effectively removed, and the shape memory alloy with uniform components and high purity is obtained. Meanwhile, after the homogenization annealing heat treatment, the isothermal hot rotary swaging processing is beneficial to obtaining single-phase solid solution, promoting the obtaining of a fine equiaxed crystal structure and further improving the comprehensive performance of the shape memory alloy. In addition, the preparation method of the shape memory alloy has simple integral process, is easy to control and realize continuous production, and is rawThe production cost is low.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.