Preparation method of porous NiTi alloy based on selective dissolution and product
阅读说明：本技术 一种基于选择性溶解的多孔NiTi合金的制备方法及产品 (Preparation method of porous NiTi alloy based on selective dissolution and product ) 是由 郭威 邵雨曼 郑伟杰 赵觅 吴树森 吕书林 于 2020-07-13 设计创作，主要内容包括：本发明属于多孔合金制备领域,并具体公开了一种基于选择性溶解的多孔NiTi合金的制备方法及产品,其通过在Ni-Ti二元合金中添加Gd元素,利用Gd元素能够与Ni元素反应而不与Ti元素反应的特点,使得合金中只生成Ni-Ti和Ni-Gd相,然后利用酸溶液选择性腐蚀去除Ni-Gd相以获得孔隙均匀且可控的多孔NiTi合金。本发明可制备孔隙尺寸小且分布均匀的多孔NiTi合金,具有操作过程简便、成本较低的优点。(The invention belongs to the field of porous alloy preparation, and particularly discloses a preparation method and a product of a porous NiTi alloy based on selective dissolution. The method can prepare the porous NiTi alloy with small pore size and uniform distribution, and has the advantages of simple and convenient operation process and lower cost.)
1. A preparation method of a porous NiTi alloy based on selective dissolution is characterized in that Gd element is added into a Ni-Ti binary alloy, only Ni-Ti and Ni-Gd phases are generated in the alloy by utilizing the characteristic that the Gd element reacts with the Ni element but does not react with the Ti element, and then the Ni-Gd phases are selectively corroded and removed by utilizing an acid solution to obtain the porous NiTi alloy with uniform and controllable pores.
2. The method of preparing a selectively soluble based porous NiTi alloy according to claim 1, comprising the steps of:
s1, preparing a Ni-Ti-Gd alloy raw material to ensure that the alloy components meet Ni in terms of atomic fraction48-2xTi44-6xGd8(1+x)Wherein x is 0-2;
s2, carrying out vacuum arc melting on the alloy raw materials to prepare and obtain a Ni-Ti-Gd pre-alloy, and carrying out vacuum induction melting on the Ni-Ti-Gd pre-alloy to prepare and obtain a Ni-Ti-Gd alloy;
s3, the prepared Ni-Ti-Gd alloy is immersed in a pre-prepared acid solution, so that the Ni-Gd phase in the alloy is dissolved, and the porous NiTi alloy with uniform and controllable pores is prepared.
3. The method for preparing the selectively dissolution based porous NiTi alloy of claim 2, wherein the vacuum arc melting is specifically: and putting the prepared alloy raw materials into a vacuum arc melting furnace, vacuumizing, introducing protective gas, then starting arc melting, and cooling after melting to obtain the Ni-Ti-Gd prealloy.
4. The method of claim 3, wherein the alloy feedstock is melted multiple times during the arc melting, each time after the alloy feedstock is completely melted.
5. The method of preparing a selectively soluble based porous NiTi alloy according to any of claims 2-4, wherein the vacuum induction melting is a spray casting melting or a tilt casting melting.
6. The method for preparing the selectively soluble based porous NiTi alloy according to claim 5, wherein the spray casting smelting is specifically as follows: cutting the prepared Ni-Ti-Gd pre-alloy into blocks and placing the blocks into a crucible with a small hole at the bottom, vacuumizing and introducing protective gas, then carrying out induction heating on the Ni-Ti-Gd pre-alloy blocks, and applying inert gas flow with preset pressure to the melt after the Ni-Ti-Gd pre-alloy blocks are completely melted so as to spray the melt into a die below the crucible for cooling to obtain Ni-Ti-Gd alloy; preferably, the preset pressure is 0.02MPa to 0.08 MPa.
7. The method for preparing the selectively soluble based porous NiTi alloy of claim 5, wherein the tilt casting smelting is specifically: cutting the prepared Ni-Ti-Gd prealloy into blocks and putting the blocks into a crucible, then vacuumizing and introducing protective gas, then carrying out induction heating on the Ni-Ti-Gd prealloy blocks, inclining the crucible after the Ni-Ti-Gd prealloy blocks are completely melted, and pouring the melt into a mold to be cooled to obtain the Ni-Ti-Gd alloy.
8. The method for preparing a selectively soluble based porous NiTi alloy according to any one of claims 2 to 7, wherein the vacuum degree is 3 x 10 in vacuum arc melting and vacuum induction melting-3～5×10-3Pa, the protective gas is inert gas with the purity of 99.999 percent, the atmosphere pressure of the protective gas is-0.05 MPa, and the smelting temperature is 1600-1800 ℃.
9. The method for preparing a selectively dissolution based porous NiTi alloy according to any of claims 2 to 8, wherein the concentration of the acid solution is 2mol/L to 2.5mol/L, preferably 2.15 mol/L.
10. A porous NiTi alloy with uniform and controlled porosity, produced by the method of any of claims 1-9.
Technical Field
The invention belongs to the field of porous alloy preparation, and particularly relates to a preparation method of a porous NiTi alloy based on selective dissolution and a product.
Background
The NiTi alloy with the nearly equal atomic ratio has unique shape memory effect, superelasticity, excellent fracture toughness, corrosion resistance, biocompatibility, damping performance and the like, so that the NiTi alloy has wide application prospects in the aspects of biomedicine, buildings, bridges, high-speed trains and the like. However, the NiTi alloy has high density, and is difficult to meet the use requirements of lightweight structural members in the fields of aerospace, automobile manufacturing and the like. Due to the introduction of a pore structure, the density of the porous NiTi alloy is reduced, and the lightweight of the alloy is facilitated. And the high damping performance of the porous NiTi alloy enables the porous NiTi alloy to be expected to be used as a damping device and effectively converts external vibration energy into heat for dissipation, so that the energy absorption effect is achieved, and the damage of mechanical damage such as external noise, vibration, impact and the like to a structural member is reduced. In addition, the pore structure in the porous NiTi alloy is beneficial to blood flow and bone cell adsorption growth in bone repair, and meanwhile, the porous NiTi alloy has good biocompatibility and elasticity modulus close to that of human bones, so that the porous NiTi alloy plays an important role in the biomedical fields of bone repair, bone replacement and the like.
Because the NiTi alloy has a high melting point (1350 ℃), the main preparation method of the porous NiTi alloy at present is a powder metallurgy method, and the method comprises self-propagating high-temperature synthesis, spark plasma sintering, hot isostatic pressing, conventional sintering, microwave sintering and the like. For example, patent CN1418974A discloses a porous NiTi alloy forming method combining metal injection forming and self-propagating high-temperature synthesis, the pore size of the porous NiTi alloy prepared by the method is about 10-400 μm; the patent CN102534284A discloses a method for preparing a medical porous NiTi shape memory alloy by microwave sintering, the method is simple and convenient, and is suitable for industrial production, and the pore size of the prepared porous NiTi alloy is 30-600 mu m; patent CN108637255A discloses a self-propagating high-temperature synthesis method for preparing a porous NiTi alloy by using a steel sheath, the pore size of the porous NiTi alloy obtained by the method is more uniform than that of the porous NiTi alloy obtained by the conventional self-propagating high-temperature synthesis method, and the pore size of the prepared porous NiTi alloy is more than 100 mu m.
However, the existing preparation method of the porous NiTi alloy still has the following defects: the prepared porous NiTi alloy has large pore size of dozens of microns or even hundreds of microns, and the uniformity of the pore size is limited, so that the porous NiTi alloy with small-size pores and uniformly distributed pores cannot be prepared. Therefore, further research is needed in the art to obtain a method for preparing a porous NiTi alloy with small pore size and uniform distribution.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a preparation method of a porous NiTi alloy based on selective dissolution and a product thereof, which firstly utilize the characteristics of Gd element to generate Ni-Ti and Ni-Gd phases in the alloy, and then utilize the difference of corrosivity of each phase in an acid solution to selectively dissolve other composition phases except the Ni-Ti phase, thereby preparing the porous NiTi alloy with uniform and controllable pores.
In order to achieve the above object, according to one aspect of the present invention, a method for preparing a porous NiTi alloy based on selective dissolution is provided, in which Gd is added to a Ni-Ti binary alloy, only Ni-Ti and Ni-Gd phases are generated in the alloy by using the characteristic that Gd reacts with Ni but not Ti, and then Ni-Gd phases are selectively removed by using an acid solution to obtain a porous NiTi alloy with uniform and controllable pores.
The method selectively dissolves other composition phases except the NiTi phase by utilizing the difference of corrosivity of the composition phases in the prealloy in an acid solution to prepare the porous NiTi alloy with uniform pores, and can regulate and control the pore structure of the porous NiTi alloy through a preparation process, namely, the composition phase proportion and the content of a dissolved phase are changed through the design of Ni-Ti-Gd ternary alloy components, the final porosity is then regulated and controlled, the composition phase and the size of the dissolved phase can be regulated and controlled through the cooling speed of the alloy, and the size of the final pores is then regulated and controlled.
As a further preferred, the preparation method of the selectively dissolved porous NiTi-based alloy comprises the following steps:
s1, preparing a Ni-Ti-Gd alloy raw material to ensure that the alloy components meet Ni in terms of atomic fraction48-2xTi44-6xGd8(1+x)Wherein x is 0-2;
s2, carrying out vacuum arc melting on the alloy raw materials to prepare and obtain a Ni-Ti-Gd pre-alloy, and carrying out vacuum induction melting on the Ni-Ti-Gd pre-alloy to prepare and obtain a Ni-Ti-Gd alloy;
s3, the prepared Ni-Ti-Gd alloy is immersed in a pre-prepared acid solution, so that the Ni-Gd phase in the alloy is dissolved, and the porous NiTi alloy with uniform and controllable pores is prepared.
More preferably, the vacuum arc melting is specifically: and putting the prepared alloy raw materials into a vacuum arc melting furnace, vacuumizing, introducing protective gas, then starting arc melting, and cooling after melting to obtain the Ni-Ti-Gd prealloy.
Further preferably, the alloy raw material is melted a plurality of times in the arc melting, and each melting is maintained for a certain period of time after the alloy raw material is completely melted.
Further preferably, the vacuum induction melting is a spray casting melting or a tilt casting melting.
As a further preferred option, the injection casting smelting is specifically: cutting the prepared Ni-Ti-Gd pre-alloy into blocks and placing the blocks into a crucible with a small hole at the bottom, vacuumizing and introducing protective gas, then carrying out induction heating on the Ni-Ti-Gd pre-alloy blocks, and applying inert gas flow with preset pressure to the melt after the Ni-Ti-Gd pre-alloy blocks are completely melted so as to spray the melt into a die below the crucible for cooling to obtain Ni-Ti-Gd alloy; preferably, the preset pressure is 0.02MPa to 0.08 MPa.
As a further preferred option, the tilt casting smelting is specifically: cutting the prepared Ni-Ti-Gd prealloy into blocks and putting the blocks into a crucible, then vacuumizing and introducing protective gas, then carrying out induction heating on the Ni-Ti-Gd prealloy blocks, inclining the crucible after the Ni-Ti-Gd prealloy blocks are completely melted, and pouring the melt into a mold to be cooled to obtain the Ni-Ti-Gd alloy.
More preferably, the degree of vacuum in the vacuum arc melting and vacuum induction melting is
More preferably, the concentration of the acid solution is 2mol/L to 2.5mol/L, and preferably 2.15 mol/L.
According to another aspect of the present invention, there is provided a porous NiTi alloy with uniform and controllable pores, which is prepared by the method.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. the method combines the characteristic that Gd element reacts with Ni element but not Ti element, adopts a selective dissolution method to prepare the porous NiTi alloy, does not need the operation step of atomizing the block raw material in the powder metallurgy method, and has the advantages of simple and convenient operation process and lower cost compared with the existing preparation method.
2. The invention can regulate the proportion of NiTi and NiGd phases by regulating the proportion of Ni, Ti and Gd elements, and further regulate the porosity of the porous NiTi alloy, and specifically, the Ni, Ti and Gd elements are designed to meet the requirement of Ni according to atomic fraction48- 2xTi44-6xGd8(1+x)Therefore, a structure only containing NiTi and NiGd phases is formed, the subsequent preparation of porous NiTi is facilitated, the porosity is regulated and controlled by adjusting the size of x, and the larger x is, the higher the content of the NiGd phase is, and the higher the porosity is.
3. The preparation method realizes the preparation of the Ni-Ti-Gd alloy by the way of vacuum arc melting prealloy first and then vacuum induction melting, thereby ensuring the melting uniformity, reducing the alloy oxidation and ensuring the alloy components through the arc melting, and realizing the spray casting or pouring of a sample through the induction melting to ensure the structure and the performance of the alloy.
4. According to the invention, through designing spray casting smelting and tilting casting smelting, Ni-Ti-Gd alloys with different sizes can be prepared, and the regulation of the cooling rate of the alloy can be realized through the regulation of the size of the Ni-Ti-Gd alloy, so that the regulation of the pore size of the Ni-Ti-Gd alloy is further realized.
5. The invention designs the airflow with proper pressure (0.02 MPa-0.08 MPa) so that the melt in the crucible can fully enter the copper mold before cooling and solidification, the copper mold is completely filled, and gas is prevented from being involved in the melt, thereby ensuring that no pore defect is generated in the solidified sample.
6. The invention can effectively protect the alloy from being oxidized by designing the vacuum degree, the purity of the protective gas, the atmosphere pressure of the protective gas and the melting temperature, and can effectively avoid the evaporation of the raw material alloy while ensuring the raw material alloy to be fully melted.
7. By designing the concentration of the acid solution, the NiGd phase can be corroded at a proper rate, and the complete porous NiTi alloy is obtained.
8. The invention can prepare the porous NiTi alloy with small, controllable and uniform pore size, the porosity of the alloy is 25-74%, the pore size is 0.27-4.86 μm, the compressive strength is 30-290 MPa, and the internal consumption peak value is 0.03-0.08.
Drawings
FIG. 1 is a flow chart of a method for preparing a selectively soluble porous NiTi alloy according to an embodiment of the present invention;
FIG. 2 is Ni48Ti44Gd8(at.%) a schematic representation of the microstructure of the porous NiTi alloy obtained after the pre-alloy has been corroded;
FIG. 3 is Ni48Ti44Gd8(at.%) obtaining a compressive mechanical property map of the porous NiTi alloy after the prealloy is corroded;
FIG. 4 is Ni48Ti44Gd8(at.%) the change curve of damping coefficient with temp. of porous NiTi alloy obtained after pre-alloy is corroded.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The principle of the invention is as follows: adding gadolinium element which can react with nickel element to form a compound on the basis of the Ni-Ti binary alloy, ensuring that only NiTi and Ni-Gd compounds are generated in the Ni-Ti-Gd pre-alloy because the gadolinium element and the titanium element are non-mixed elements and do not react, and then corroding by using acid solution to remove the Ni-Gd phase to obtain the porous NiTi alloy. As the Ni-Gd phase is generated in situ in the melt cooling process, the Ni-Gd phase and the NiTi phase are distributed uniformly and continuously, and the pore distribution of the obtained porous NiTi alloy is relatively uniform.
Specifically, prealloyed Ni-Ti-Gd containing a NiTi phase is prepared firstly, and then the prealloyed is corroded in an acid solution for a period of time to obtain the porous NiTi alloy, wherein the content and the size of the NiTi phase in the prealloyed determine the final pore size. More specifically, the prealloy Ni-Ti-Gd is smelted in a vacuum state, the prealloy is cut into small blocks and then is subjected to spray casting or tilting casting to obtain the Ni-Ti-Gd alloy, the alloy is placed into a prepared acid solution and is taken out after being soaked for a certain time, and the porous NiTi alloy is obtained. The porous NiTi alloy prepared by the method has uniform pore distribution and adjustable porosity and pore size, and is beneficial to the design and application of the porous NiTi alloy.
The method utilizes the difference of corrosivity of composition phases in the prealloy in an acid solution to selectively dissolve other composition phases except the NiTi phase to prepare the porous NiTi alloy with uniform pores, and can regulate and control the pore structure through a preparation process, namely the proportion of the composition phases to the dissolved phase is changed through the design of the component proportion of the Ni-Ti-Gd ternary alloy, and then the final porosity is regulated and controlled. The invention can effectively prepare the porous NiTi with small pore size (several microns) and uniform distribution, can prepare the porous NiTi alloy with different pore structures, and is expected to meet various application requirements such as damping devices, biomedicine and the like.
Specifically, as shown in fig. 1, the preparation method of the porous NiTi alloy based on selective dissolution provided in the embodiment of the present invention is a method for preparing and controlling a pore structure of the porous NiTi alloy by using a selective dissolution process, and includes the following steps:
s1, batching:
mixing raw materials of a nickel block, a titanium block and a gadolinium block according to a certain proportion, wherein the target alloy comprises Ni in terms of atomic fraction 48-2xTi44-6xGd8(1+x)The pre-alloy can form a structure only containing NiTi and NiGd under the proportion, the atomic ratio of Ni to Ti is proper, the shape memory effect of the pre-alloy is facilitated, the larger X is, the smaller the proportion of NiTi in the pre-alloy is, and the higher the porosity of porous NiTi is; the purity of the nickel block, the titanium block and the gadolinium block is over 99.9 percent;
preparing S2Ni-Ti-Gd prealloy and Ni-Ti-Gd alloy:
s21 arc melting:
the method comprises the following steps of performing vacuum arc melting on prepared alloy raw materials to prepare and obtain a Ni-Ti-Gd prealloy, specifically, putting the prepared alloy raw materials into a vacuum arc melting furnace, vacuumizing, introducing protective gas, then performing arc melting on the alloy raw materials, cooling after the melting is finished to obtain the Ni-Ti-Gd prealloy, wherein the arc melting temperature is high, the alloy raw materials can be fully melted through the arc melting, and the uniformity of prealloy components is facilitated;
s22 induction melting:
carrying out vacuum induction smelting on the prepared Ni-Ti-Gd prealloy to prepare and obtain a Ni-Ti-Gd alloy, wherein the vacuum induction smelting is spray casting smelting or tilting casting smelting, specifically, a corresponding smelting process is selected according to the size of the prepared Ni-Ti-Gd alloy, and the Ni-Ti-Gd alloy with small size (the average diameter (volume divided by the surface area)) is subjected to spray casting smelting, and the tilting casting is difficult to fill due to the small size; while the Ni-Ti-Gd alloy with large size (mean average diameter is more than 7mm) is smelted by tilting casting because the Ni-Ti-Gd alloy with large size is easy to be subjected to air entrainment by spray casting.
Specifically, the spray casting smelting comprises the following steps: cutting the prepared Ni-Ti-Gd pre-alloy into small blocks, cleaning the small blocks, putting the small blocks into a crucible (such as a quartz tube crucible) with a small hole (the aperture is generally 1-2 mm) formed in advance at the bottom, vacuumizing the crucible, introducing protective gas, then carrying out induction heating on the Ni-Ti-Gd pre-alloy block until the Ni-Ti-Gd pre-alloy block is completely melted, applying inert gas flow with preset pressure on the melt to spray the melt into a mold (such as a copper mold) below the crucible, and opening the mold after cooling to room temperature to obtain the Ni-Ti-Gd alloy. The tilting casting smelting specifically comprises the following steps: cutting the prepared Ni-Ti-Gd prealloy into small blocks, cleaning the small blocks, putting the small blocks into a crucible (such as a boron nitride crucible), vacuumizing the crucible, introducing protective gas, then carrying out induction heating on the Ni-Ti-Gd prealloy until the Ni-Ti-Gd prealloy blocks are completely melted, inclining the crucible so as to pour the melt into a mold (such as a copper mold), and opening the mold after cooling to room temperature to obtain the Ni-Ti-Gd alloy. Specifically, the preset pressure of the inert gas flow is 0.02 MPa-0.08 MPa, so that the melt in the crucible can fully enter the copper mold before cooling and solidification, the copper mold is completely filled, gas is prevented from being involved in the melt, and the defect of air holes cannot be generated in the solidified sample.
Furthermore, the shape and size of the Ni-Ti-Gd alloy can be determined according to the needs, such as rod shape, block shape, plate shape and the like, a corresponding mold is prepared after the shape and size of the Ni-Ti-Gd alloy are determined, then a corresponding smelting process is selected according to the average diameter of the Ni-Ti-Gd alloy for smelting, and the smelted alloy solution is poured into the corresponding mold to obtain the required Ni-Ti-Gd alloy.
Furthermore, the smaller the average diameter of the Ni-Ti-Gd alloy is, the faster the alloy cooling speed is during casting, the finer the alloy structure is, and the smaller the pore size of the finally obtained Ni-Ti-Gd alloy is, so that the cooling speed of the alloy can be regulated and controlled by designing the size of the Ni-Ti-Gd alloy, and the larger the pore size is further regulated and controlledIs small. Wherein, the spray casting is suitable for preparing small-size Ni-Ti-Gd alloy, and the tilting casting is suitable for preparing large-size Ni-Ti-Gd alloy. Specifically, the cooling rate T and the die diameter (i.e., the average diameter of the alloy) R are related as follows: T1000/R2The dimension d of the NiTi phase and the cooling rate T are related as follows: BT and d ═ BT-nWhere B and n are constants (in the present invention, B is 11.6 and n is 0.2), the larger the cooling rate, the smaller the pores.
Specifically, during arc melting, the alloy raw materials are melted for more than 4 times, each melting is carried out for 3 minutes after the alloy is completely melted, then the arc is closed, the alloy is turned over after being cooled, and then the alloy is melted, and the alloy is melted for more than 4 times.
Further, in the case of arc melting and induction melting, the degree of vacuum is
S3 selective phase etching:
and immersing the prepared Ni-Ti-Gd alloy into a pre-prepared acid solution to selectively dissolve the Ni-Gd phase in the alloy into the acid solution, thereby preparing the porous NiTi alloy. Specifically, the alloy is preferably taken out after being soaked for more than 12 hours, and the porous NiTi alloy is obtained after being cleaned and dried.
Furthermore, the concentration of the acid solution is 2-2.5 mol/L, preferably 2.15mol/L, and the design can ensure that the corrosion rate of the pre-alloy is proper, so that the problems that the corrosion rate is slow, the reaction time is long, the reaction is incomplete, or the corrosion rate is high, and the NiGd phase is rapidly separated from the pre-alloy to cause the damage of the pores of the porous NiTi are solved. The acid solution is preferably nitric acid solution, specifically 65% HNO3And water in a volume ratio of 2: 1, obtaining 2.15mol/L acid solution.
For the porous NiTi alloy with a certain porosity, the more uniform the pore distribution and the finer the pore size, the higher the damping performance and the mechanical strength, and the application on a damping device is facilitated; the porous NiTi alloy with uniform pore distribution and larger pores is more beneficial to the application in biomedicine aspects such as bone tissue repair and the like. In the invention, spray casting smelting is adopted when smelting the porous NiTi alloy, so that the porous NiTi alloy with uniform pore distribution and fine pore size can be prepared, and the porous NiTi alloy with uniform pore distribution and larger pores can be prepared when tilt casting is adopted.
The following are examples of the present invention:
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