CN114561581B - Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing and preparation method thereof - Google Patents

Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing and preparation method thereof Download PDF

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CN114561581B
CN114561581B CN202210152210.7A CN202210152210A CN114561581B CN 114561581 B CN114561581 B CN 114561581B CN 202210152210 A CN202210152210 A CN 202210152210A CN 114561581 B CN114561581 B CN 114561581B
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shape memory
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CN114561581A (en
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陈岁元
贾无名
王悦
周林
汪芦婷
崔彤
梁京
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Northeastern University China
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Abstract

The invention belongs to the technical field of laser additive manufacturing functional materials, and particularly relates to a Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing and a preparation method thereof. The alloy material comprises the following chemical components in atomic percentage: ni:40 to 43%, co:8 to 10%, mn:28 to 32%, al:19 to 21%, Y:0.1 to 0.3 percent. The characteristic indexes of the Ni-Co-Mn-Al-Y alloy powder prepared by adopting the vacuum induction melting gas atomization technology meet the laser additive manufacturing requirement, and the Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared from the alloy powder through direct laser deposition has reversible martensite phase change characteristics and good mechanical properties, and the alloy powder and the preparation method have important application prospects in the field of laser additive manufacturing of magnetic shape memory alloys.

Description

Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing and preparation method thereof
Technical Field
The invention belongs to the technical field of laser additive manufacturing functional materials, and particularly relates to a Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing and a preparation method thereof.
Background
The magnetic shape memory alloy has unique magnetic performance, so that the magnetic shape memory alloy can be used as a sensor and a driver of a temperature field and a magnetic field, and the magnetic thermal performance and the elastic thermal performance under the drive of an external field also make the magnetic shape memory alloy become a novel environment-friendly refrigeration material. Therefore, the magnetic shape memory alloy has wide application prospect. Currently, the most studied magnetic shape memory alloys are mainly Ni-Mn based heusler alloys, including Ni-Mn-Ga, ni-Mn-In, ni-Mn-Sn, ni-Mn-Al series. Wherein, the Ni-Co-Mn-Al alloy has the advantages of low price and environmental protection.
However, the remarkable magnetic field induced strain properties of magnetic shape memory alloys have only been reported for single crystals, specially produced polycrystalline directionally solidified castings (1%) and foam alloys (up to 8.7%). However, these machining methods are not only time consuming, but also difficult to machine complex structural parts because of the brittleness of the alloy. In the prior art, a great deal of research and success has been made in preparing materials that are difficult to process by using laser additive manufacturing (including direct laser deposition and selective laser melting), such as nickel-based superalloys, high-entropy alloys, and the like. The Direct Laser Deposition (DLD) is characterized in that a material is deposited layer by layer through a laser heat source, the DLD has the characteristics of high cooling rate, remelting and reheating the previous layer and the like, and the DLD has favorable conditions for preparing a magnetic shape memory alloy part with a special shape and a phase change function. However, since the alloy manufacturing process by laser additive is a non-equilibrium metallurgical process, there are often problems of phase transformation and crack defects caused by thermal stress, and the problem that the memory alloy of the present magnetic state is difficult to process due to its brittleness, which restricts the development of the technology for manufacturing the magnetic shape memory alloy by laser additive.
At present, the research field of laser additive manufacturing magnetic shape memory alloy is in the beginning stage at home and abroad, and a basic theory and technology which are suitable for a special high-performance well-formed magnetic shape memory alloy powder raw material for laser additive manufacturing and an alloy material with excellent forming performance and obdurability matching are still lacked, so that the magnetic shape memory alloy powder with good powder characteristics is researched and prepared, the internal relations of alloy components, a laser forming process, tissue performance obdurability matching and the like are clarified, and a material-process-tissue-performance integrated original technology with independent intellectual property rights is obtained, and has important scientific significance and practical application value for promoting research and industrial application of laser additive manufacturing high-performance magnetic shape memory alloy.
Disclosure of Invention
In view of the problems in the prior art, the present application aims to provide a Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing and a preparation method thereof. According to the invention, the Y element is added into the Ni-Co-Mn-Al magnetic shape memory alloy to form a new alloy element composition and component proportion, so that the effects of refining grains by the rare earth Y element, purifying a molten pool, promoting tissue change, eliminating crack sensitivity and the like are fully exerted, and the formability and mechanical property of the alloy prepared by laser are improved. The invention provides a novel method for preparing alloy powder and a direct laser deposition alloy sample by VIGA, clarifies the influence rule of laser process parameters and post-heat treatment on the tissue phase change and the performance of a formed alloy sample, and provides a basic theory and a technology for regulating and controlling the tissue to improve the performance of the alloy sample. The prepared alloy sample not only has reversible martensite phase transformation characteristics, but also has good formability and mechanical properties.
In order to achieve the above object, the present invention is achieved by the following means.
The invention provides Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing, which comprises the following chemical components in atomic percentage: ni:40 to 43%, co:8 to 10%, mn:28 to 32%, al:19 to 21%, Y:0.1 to 0.3 percent, and the percentage is 100 percent.
In the technical scheme, the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder is spherical, the sphericity is more than 97 percent, the hollow sphere rate is not more than 3 percent, the oxygen content of the powder is less than 0.05 percent, the particle size distribution is 1-150 mu m, and the apparent density is 4.10-4.25 g/cm 3 The fluidity is 26.2-27.4 s/50g.
In the technical scheme, the fluidity of the alloy powder with the grain diameter of 1-52 mu m is 64.51s/50g, and the fluidity of the alloy powder with the grain diameter of 53-150 mu m is 19.72s/50g.
In the above solution, the alloy powder consists of austenite, martensite and γ phases.
On the other hand, the invention provides a preparation method of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder, which comprises the steps of preparing an alloy ingot by vacuum induction melting, and preparing the alloy ingot by a crucible vacuum induction melting gas atomization method (VIGA), wherein the final melting temperature is 1620-1635 ℃, the vacuum degree is below 10Pa, and the atomization gas pressure is 9-12.5 MPa.
In another aspect of the invention, a preparation method for manufacturing a Ni-Co-Mn-Al-Y magnetic shape memory alloy material by laser additive manufacturing is provided, which is characterized by comprising the following steps:
1) Sieving the alloy powder to obtain powder with the particle size of 53-150 mu m for later use;
2) Drying the 53-150 mu m powder obtained in the step 1) in an oven at the temperature of 80-120 ℃ for 3h, and putting the powder into a powder feeder;
3) The experiment is carried out in a vacuum box in an argon atmosphere, the oxygen content is controlled to be below 100ppm by cleaning gas in a bin, a 2KW optical fiber laser is adopted, a coaxial powder feeding system is matched for direct laser deposition forming, the shape and the printing path of a printing body are set by self-contained programming software, the printing path is in layer-by-layer parallel reciprocating scanning, the scanning direction between layers rotates by 90 degrees, the printed shape path is converted and programmed into a G code, and a magnetic shape memory alloy sample with few defects and good mechanical property is prepared on a substrate.
In the above technical solution, the method further includes: separating the magnetic shape memory alloy sample obtained in the step 3) from the substrate by using a wire cutting machine, sealing the sample in a vacuum quartz tube, putting the quartz tube into a heat treatment furnace for carrying out homogenization heat treatment, cooling the furnace to room temperature after the heat preservation is finished, and taking out the quartz tube, thereby finally obtaining the polycrystalline magnetic shape memory alloy sample with uniform tissue.
In the above technical solution, the direct laser deposition process parameters in step 3) are as follows: the laser power is 1100-1300W, the scanning speed is 4-5 mm/s, the powder feeding amount is 1.70-1.85 g/min, the protective gas flow is 400-800 l/h, the lap joint rate is 30-50%, and the Z-axis lifting amount is 0.4-0.8 mm.
In the above technical solution, the preparation method further comprises: sealing the magnetic shape memory alloy material obtained in the step 3) in a vacuum quartz tube, putting the vacuum quartz tube into a heat treatment furnace for carrying out homogenization heat treatment, and cooling the furnace to room temperature after heat preservation and taking out the furnace.
In the above technical scheme, the homogenizing heat treatment process comprises: the heat preservation temperature is 1000 ℃, and the heat preservation time is 24 hours.
The invention also provides a Ni-Co-Mn-Al-Y magnetic shape memory alloy material prepared by the preparation method, the compressive strength of the Ni-Co-Mn-Al-Y magnetic shape memory alloy obtained by direct laser deposition reaches 2128-2321 MPa, and the maximum compressive strain reaches 28.1-30.6%; the Ni-Co-Mn-Al-Y magnetic shape memory alloy after heat treatment has reversible martensite phase transformation characteristic, and the entropy change reaches 15.0 to 20.5 J.kg -1 ·K -1 The compression strength is 1169-1241 MPa, and the maximum compression strain is 14.0% -16.1%.
The invention has the beneficial effects that:
(1) The characteristic indexes of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared by the method meet the characteristic requirements of laser additive manufacturing technology on the alloy powder, and the VIGA preparation process technology has the application prospect of industrially preparing the magnetic shape memory alloy powder.
(2) The Ni-Co-Mn-Al-Y magnetic shape memory alloy prepared by the direct laser deposition method has the effects of removing slag in a laser melting pool, refining crystal grains, regulating and controlling tissues and the like due to the design of the rare earth Y and the adjustment of the component proportion, so that a formed alloy sample has good formability, the problem that the alloy is easy to crack and deform in laser additive manufacturing is effectively solved, and beneficial guidance is provided for forming tough matched alloy parts.
(3) The alloy sample prepared by the invention has better magnetic shape memory function and good mechanical property, and lays an important theoretical and technical foundation for manufacturing high-performance, high-toughness and matched magnetic shape memory alloy materials by laser additive manufacturing.
Drawings
FIG. 1 is an ingot XRD of a Ni-Co-Mn-Al-Y master alloy used in examples of the present invention;
FIG. 2 shows the surface microscopic morphology of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in example 1 of the present invention, (a) 100 times, (b) 500 times, (c) 2000 times, and (d) 5000 times;
FIG. 3 is a scanning photograph of the surface element distribution (a) of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 1 of the present invention, (b) Ni element distribution, (c) Co element distribution, (d) Mn element distribution, (e) Al element distribution, and (f) Y element distribution;
FIG. 4 is a cross-sectional view of the grain boundary and the intragranular element of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in example 1 of the present invention, (a) a scanning photograph, (b) Ni element distribution, (c) Co element distribution, (d) Mn element distribution, (e) Al element distribution, and (f) Y element distribution;
FIG. 5 is a metallographic photograph showing the cross section of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder according to example 1 of the present invention, (a) low magnification, and (b) high magnification;
FIG. 6 is a particle size distribution diagram of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in example 1 of the present invention;
FIG. 7 is an X-ray diffraction pattern of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 1 of the present invention;
FIG. 8 is a photomicrograph of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy made by laser additive manufacturing in accordance with example 1 of the present invention;
FIG. 9 is a scanning microstructure of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample produced by laser additive manufacturing according to example 1 of the present invention (a) after direct laser deposition and (b) after heat treatment;
FIG. 10 is an X-ray diffraction pattern of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by laser additive manufacturing according to example 1 of the present invention, (a) direct laser deposition, (b) after heat treatment;
FIG. 11 is a DSC curve of a sample of Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by laser additive manufacturing according to example 1 of the present invention, (a) direct laser deposition, (b) after heat treatment;
FIG. 12 is a compressive stress-strain curve of a sample of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy made in example 1 of the present invention;
FIG. 13 shows the surface micro-morphology of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in example 2 of the present invention, (a) 100 times, (b) 500 times, and (c) 5000 times;
FIG. 14 is a metallographic photograph showing a cross section of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 2 of the present invention, wherein (a) is low magnification and (b) is high magnification;
FIG. 15 is a particle size distribution diagram of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 2 of the present invention;
FIG. 16 is an X-ray diffraction pattern of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 2 of the present invention;
FIG. 17 is a photomicrograph of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy made by laser additive manufacturing in accordance with example 2 of the present invention;
FIG. 18 is a scanning microstructure of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample fabricated by laser additive manufacturing according to example 2 of the present invention (a) direct laser deposition (b) after heat treatment;
FIG. 19 is an X-ray diffraction pattern of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by laser additive manufacturing according to example 2 of the present invention, (a) direct laser deposition, (b) after heat treatment;
FIG. 20 is a DSC curve of a sample of Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by laser additive manufacturing according to example 2 of the present invention, (a) direct laser deposition, (b) after heat treatment;
FIG. 21 is a compressive stress-strain curve of a sample of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy made in example 2 of the present invention;
FIG. 22 shows the surface micro-topography of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in example 3 of the present invention, which is (a) 100 times, (b) 500 times, (c) 2000 times, (d) 5000 times;
FIG. 23 is a metallographic photograph showing a cross section of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder according to example 3 of the present invention, wherein (a) is low magnification and (b) is high magnification;
FIG. 24 is a particle size distribution diagram of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 3 of the present invention;
FIG. 25 is an X-ray diffraction pattern of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in example 3 of the present invention;
FIG. 26 is a photomicrograph of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy made by laser additive manufacturing in accordance with example 3 of the present invention;
FIG. 27 is a scanning microstructure of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing in accordance with example 3 of the present invention after (a) direct laser deposition and (b) heat treatment;
FIG. 28 is a graph of the X-ray diffraction pattern of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy made by laser additive manufacturing according to example 3 of the present invention (a) after direct laser deposition and (b) after heat treatment;
FIG. 29 is a DSC curve of a sample of Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by laser additive manufacturing according to example 3 of the present invention, (a) direct laser deposition, (b) after heat treatment;
FIG. 30 is a graph of the compressive stress strain curves of the Ni-Co-Mn-Al-Y magnetic shape memory alloy samples made by laser additive manufacturing in accordance with example 3 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and the following detailed description, but the present invention is not limited to these embodiments.
The following examples used a printer for laser additive manufacturing and a performance detection apparatus:
preparing a Ni-Co-Mn-Al-Y magnetic shape memory alloy forming material by adopting an IPG YLR-2000 fiber laser which is matched with a coaxial powder feeding system and has the maximum power of 2kW, wherein the forming system is sealed in a vacuum glove box;
carrying out heat treatment on the formed sample by adopting a GR.TF60/16 vacuum tube furnace;
measuring chemical components and oxygen contents of Ni-Co-Mn-Al-Y magnetic shape memory alloy ingots, powder and forming materials by adopting an AGILENT-7700 inductively coupled plasma mass spectrometer and a TCH-600 nitrogen-oxygen-hydrogen analyzer;
measuring the apparent density and the fluidity of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder by using a HYL-102 Hall flow meter;
observing the hollow sphere rate of the powder and the metallographic structure of a formed sample by adopting an OLYMPUS-GX71 type inverted Optical Microscope (OM);
observing the surface appearance of the powder, the element EDS analysis and the microstructure of the formed sample by adopting a Shimadzu-SSX-550 Scanning Electron Microscope (SEM);
phase analysis of the powder and the molded sample was carried out by using a SmartLab-9000 model Japan X-ray diffractometer (XRD);
testing the heat flow change of a formed sample in the process of heating and cooling by adopting a TA-Q100 type differential scanning calorimetry analyzer;
carrying out compression performance test on the printed and formed sample by adopting an INSTRON-5969 electronic universal material testing machine;
the Ni-Co-Mn-Al-Y magnetic shape memory alloy master alloy used in the following examples comprises the following chemical components in percentage by mass: 45.7 to 46.4%, co:9.0 to 9.1, mn:34.8 to 35.0%, al:9.8 to 9.9%, Y:0.20 to 0.30 percent, and the percentage is 100 percent. The alloy steel ingot is prepared by adopting a vacuum induction ultra-clean smelting technology (VIM) and can be prepared by adopting conventional process parameter setting, the oxygen content of the alloy steel ingot is controlled below 0.01 percent and is applicable to the invention, and FIG. 1 shows that the cast ingot XRD of the Ni-Co-Mn-Al-Y master alloy mainly comprises austenite and martensite.
The Ni-Co-Mn-Al-Y alloy powder for laser additive manufacturing comprises the following components in atomic percentage: ni:40 to 43%, co:8 to 10%, mn:28 to 32%, al:19 to 21%, Y:0.1 to 0.3 percent, and the percentage is 100 percent.
Example 1
A preparation method of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder and a laser additive preparation method thereof. The method comprises the following steps:
step 1, preparation of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder:
preparing an alloy ingot by vacuum induction melting, and then preparing the alloy ingot by using a crucible vacuum induction melting gas atomization method (VIGA), wherein the method comprises the steps of reducing the vacuum degree in a furnace to 9.4Pa, filling argon to 0.01MPa, and finally melting at 1625 ℃ and atomizing at 12.5MPa;
step 2, substrate material and powder pretreatment
Adopting a pure nickel substrate, firstly carrying out rust removal and decontamination on the surface of the substrate by using a grinding wheel to ensure that the surface is bright and clean, and blowing dry the substrate for later use after alcohol wiping;
drying Ni-Co-Mn-Al-Y magnetic shape memory alloy powder with the particle size of 53-150 mu m at 80 ℃ for 2h, and filling the powder into a powder feeder for later use;
step 3, laser additive manufacturing process
The method is carried out in a vacuum box in an argon atmosphere, the oxygen content is controlled to be below 10ppm, a 2kW optical fiber laser is adopted, a coaxial powder feeding system is matched for direct laser deposition forming, the shape and the printing path of a printing body are set by self-contained programming software, the printing path is in layer-by-layer parallel reciprocating scanning, the scanning direction between layers rotates by 90 degrees, a magnetic shape memory alloy sample with few defects and good mechanical property is prepared on a substrate, and the magnetic shape memory alloy sample is taken out from the vacuum box after being cooled to the room temperature, wherein the process parameters of laser material increase manufacturing are as follows: the laser power is 1100W, the scanning speed is 4mm/s, the powder feeding amount is 1.8g/min, the protective gas flow is 800l/h, the lap joint rate is 35 percent, and the Z-axis lifting amount is 0.4mm.
Separating the magnetic shape memory alloy part from the substrate by using a wire cutting machine, then placing the magnetic shape memory alloy part into a vacuum tube furnace, sealing the pipe orifice, pumping out gas in the furnace by using a vacuum pump, then injecting argon, repeating the steps for three times, setting the heating rate to be 3 ℃/min, heating to 1000 ℃, preserving the temperature for 24 hours, then cooling to room temperature at the rate of 2 ℃/min, and finally obtaining the polycrystalline magnetic shape memory alloy sample with uniform tissue.
The following analytical tests were performed on the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing and the direct laser deposition sample prepared in this example:
(1) Chemical composition and oxygen content analysis
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in the embodiment is measured according to the national standard GB/T14265-1993, and the chemical component content of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder according to the atom percentage is as follows: 40.9%, co:8.5%, mn:31.1%, al:19.3%, Y:0.2 percent.
(2) Sphericity and surface morphology
The surface and the microscopic morphology of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in this example were observed, as shown in FIG. 2. The powder of 1-150 μm has good sphericity, which exceeds 97%. The particle size distribution is uniform, the surface is smooth, the defects of the broken balls are few, and a small amount of satellite balls exist. The satellite balls are mainly formed by impacting powder particles with smaller particle sizes onto powder particles with larger particle sizes which are not solidified in the atomization process. The content of the satellite balls can be changed by adjusting the atomization air pressure, but cannot be completely avoided. Meanwhile, the degree of sphericity of the powder and the number of the satellite balls also influence the flowability and the apparent density of the powder, and further influence the powder delivery rate and the powder paving effect, so that the forming quality is influenced. From fig. 2 (d), it can be seen that two kinds of particulate matter exist on the surface of the powder, one is larger particles a having the same color as the matrix, and the other is smaller white particles B, and the EDS detection results are shown in table 1. Granule A has similar average composition to powder, and granule B has high content of Y, O element.
TABLE 1 Ni-Co-Mn-Al-Y magnetic shape memory alloy powder surface particles EDS results (at.%)
Figure BDA0003510953520000081
The element distribution of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in this example was observed, as shown in FIG. 3. It can be seen that the elements on the surface of the powder are uniformly distributed for the whole powder, and no obvious component segregation occurs. The powder was further enlarged and the difference in elemental content between the grain and the grain boundary on the surface of the powder was observed, as shown in fig. 4. The content of Al and Mn elements in the grain boundary of the powder is different from that in the crystal grain, the content of Al elements in the grain boundary is low, and the content of Mn elements is high. This is mainly due to the diffusion of elements during the solidification of the powder to form grains.
(3) Hollow sphere fraction analysis
FIG. 5 is a metallographic photograph showing the cross section of a Ni-Co-Mn-Al-Y magnetic shape memory alloy powder having a particle size of 1 to 150 μm. It can be seen from the figure that the hollow sphere rate of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder with the particle size range of 1-150 mu m is not more than 3 percent by adopting the crucible vacuum induction melting gas atomization method under the technological parameters of the atomization gas pressure of 12.5MPa at the melting temperature of 1625 ℃. The hollow sphere is formed by residual atomizing gas inside the powder, so that the influence on the porosity of a formed part is caused, and the hollow sphere rate of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared by the method meets the laser additive manufacturing requirement.
(4) Powder particle size distribution test
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in this example was examined for particle size distribution and cumulative mass distribution using a laser particle size analyzer, and the resulting particle size distribution was shown in FIG. 6. As can be seen from fig. 6, the particle size distribution of the powder is concentrated and the whole powder is normally distributed, which can meet the requirements of most laser additive manufacturing technologies. Wherein, the powder with the particle size of 53-150 mu m can be used for powder feeding type laser additive manufacturing, and the powder with the particle size of 0-53 mu m can be used for powder spreading type laser additive manufacturing.
(5) XRD phase analysis
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing obtained in this example was subjected to X-ray diffraction, and the X-ray diffraction pattern obtained is shown in FIG. 7. As can be seen from fig. 7, the phases of the powder are composed of austenite, martensite and γ -phase.
(6) Bulk density and flow test
The spherical Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing with the particle size of 1-150 mu m prepared in the embodiment is measured by adopting a HYL-102 type Hall flow meter according to the national standard GB/T1479.1-2011 and using a stainless steel funnel with the aperture of 2.5mm, the result of 5 times of measurement is shown in Table 2, and the average value obtained by 5 times of powder loose packing density is 4.145g/cm 3 。
TABLE 2 Ni-Co-Mn-Al-Y magnetic shape memory alloy powder apparent Density measurements
Figure BDA0003510953520000091
The spherical Ni-Co-Mn-Al-Y alloy powder for laser additive manufacturing, prepared in the present example, having particle size ranges of 1 to 150 μm, 1 to 52 μm, and 53 to 150 μm was respectively tested using a HYL-102 type Hall flow meter according to the national standard GB/T1482-2010 using a stainless steel funnel having a pore size of 2.5mm, and the results of the 5-time measurements are shown in Table 3. The flow of powder with a particle size in the range from 1 to 150 μm gives an average of 26.56s/50g in 5 measurements, the flow of powder with a particle size in the range from 1 to 52 μm gives an average of 64.51s/50g in 5 measurements and the flow of powder with a particle size in the range from 52 to 150 μm gives an average of 19.72s/50g in 5 measurements.
TABLE 3 Ni-Co-Mn-Al-Y magnetic shape memory alloy powder flowability measurements
Figure BDA0003510953520000092
(7) Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing and tissue morphology
FIG. 8 is a photomicrograph of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing, wherein the size of the deposition sample is 30mm multiplied by 15mm multiplied by 8mm, the forming quality is good, and no crack defect exists.
FIG. 9 is a scanning microstructure of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample made by laser additive manufacturing, wherein (a) is a pre-heat treatment morphology and (b) is a post-heat treatment morphology. Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy samples consisted primarily of martensite, austenite and gamma phases. The gamma phase is mainly distributed at grain boundaries, and a small amount of gamma phase exists in the crystal, the martensite phase is distributed around the gamma phase, and the untransformed austenite phase is mainly distributed in the crystal grains. At the same time, some subgrain boundaries were present in the sample. The heat treated sample is mainly in a martensite phase, a small amount of unconverted austenite phase is contained in partial grains, the area of gamma-phase grains is reduced, and the gamma-phase grains are transformed from irregular shapes into spherules. After heat treatment, the grains grow and the content of subgrain boundaries is reduced, while the subgrain boundaries are generally connected with the gamma phase.
(8) Phase analysis of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 10 is an X-ray diffraction pattern of a sample of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein (a) is before heat treatment and (b) is after heat treatment. Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy samples consisted primarily of martensite, austenite, and γ phases. Among them, the austenite phase peak is highest. After heat treatment, the samples consisted primarily of an austenite phase and a martensite phase, with the martensite phase having the highest peak. The gamma phase, due to its smaller volume, has no diffraction peak observed in XRD.
(9) Phase change performance of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 11 is a dsc curve of a sample of laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein (a) is before heat treatment and (b) is after heat treatment. The Ni-Co-Mn-Al-Y magnetic shape memory alloy sample manufactured by laser additive manufacturing has no martensite transformation characteristic peak between 0 and 150 ℃. And obvious endothermic exothermic peaks can be observed on the sample after heat treatment, which indicates that the normal and reverse martensitic transformation occurs. The martensite start and finish transition temperatures were 96.6 ℃ and 44 ℃, respectively, the austenite start and finish transition temperatures were 62.3 ℃ and 114.9 ℃, respectively, and the thermal hysteresis was 17.9 ℃. Entropy change in temperature-induced martensitic transformation can be used to evaluate the elasto-thermal performance potential, and the expression is that delta S = delta H/T 0 Wherein, delta H is latent heat of phase change and can be obtained by dsc curve integral, T 0 The peak temperature of the phase transition is also obtained by curve integration of dsc. Entropy change of the final calculated sample was 15.0 J.kg -1 ·K -1 。
(11) Room temperature compression curve of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 12 is a compressive stress-strain curve of a sample of laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein the solid line is before heat treatment and the dotted line is after heat treatment. The compressive strength of the Ni-Co-Mn-Al-Y magnetic shape memory alloy sample manufactured by laser additive manufacturing is 2128MPa, and the maximum compressive strain is 28.2%. The compressive strength of the sample after heat treatment was 1169MPa, and the maximum compressive strain was 14.7%. Therefore, the Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by the laser additive has good mechanical properties.
Example 2
A method for preparing Ni-Co-Mn-Al-Y magnetic shape memory alloy powder and a laser additive manufacturing method thereof. The method comprises the following steps:
step 1, preparation of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder:
preparing an alloy ingot by vacuum induction melting, and then preparing the alloy ingot by using a crucible vacuum induction melting gas atomization method (VIGA), wherein the method comprises the steps of reducing the vacuum degree in a furnace to 9.1Pa, filling argon to 0.01MPa, and finally melting at the temperature of 1635 ℃ and atomizing at the pressure of 11MPa;
step 2, substrate Material and powder Pre-treatment
Adopting a pure nickel substrate, firstly carrying out rust removal and decontamination on the surface of the substrate by using a grinding wheel to ensure that the surface is bright and clean, and blowing dry the substrate for later use after alcohol wiping;
drying Ni-Co-Mn-Al-Y magnetic shape memory alloy powder with the particle size of 53-150 mu m at 80 ℃ for 2h, and filling the powder into a powder feeder for later use;
step 3, laser additive manufacturing process
Go on in the vacuum chamber of argon gas atmosphere, adopt 2kW fiber laser, the coaxial powder feeding system of collocation carries out direct laser deposition and takes shape, the shape and the printing route of the printing body are set up to the programming software of taking certainly, the printing route is the parallel reciprocating scanning of successive layer, scanning direction is rotatory 90 between the layer, on the base plate, prepare the magnetic shape memory alloy sample that the defect is few, mechanical properties is good, take out from the vacuum chamber after cooling the magnetic shape memory alloy sample to the room temperature, wherein, the technological parameter of laser vibration material disk manufacturing is: the laser power is 1200W, the scanning speed is 4mm/s, the powder feeding amount is 1.8g/min, the protective gas flow is 800l/h, the lap joint rate is 35 percent, and the Z-axis lifting amount is 0.4mm.
And separating the magnetic shape memory alloy part from the substrate by using a wire cutting machine, putting the substrate into a vacuum tube furnace, and sealing the tube opening. And pumping out the gas in the furnace by using a vacuum pump, and then flushing argon, and repeating the steps for three times. Setting the heating rate to be 3 ℃/min, heating to 1000 ℃, preserving the heat for 24h, and then cooling to the room temperature at the rate of 2 ℃/min. Finally obtaining a polycrystalline magnetic shape memory alloy sample with uniform tissue.
The following analytical tests were performed on the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing and the direct laser deposition sample prepared in this example:
(1) Chemical composition and oxygen content analysis
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in the embodiment is measured according to the national standard GB/T14265-1993, and the chemical component content of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder according to the atom percentage is as follows: 42.6%, co:8.4%, mn:29.4%, al:19.4%, Y:0.2 percent.
(2) Sphericity and surface morphology
The surface and the microscopic morphology of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder produced in this example were observed, as shown in FIG. 13. When the final smelting temperature reaches 1635 ℃, the powder prepared by atomization under the atomization pressure of 11MPa has good sphericity which exceeds 97%. The particle size distribution is uniform, the broken ball has less defects, but a small amount of satellite balls exist.
(3) Hollow sphere fraction analysis
FIG. 14 is a metallographic photograph showing the cross section of a Ni-Co-Mn-Al-Y magnetic shape memory alloy powder having a particle size of 1 to 150 μm. It can be seen from the figure that by adopting the crucible vacuum induction melting gas atomization method, the hollow sphere rate of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder with the particle size range of 1-150 mu m is not more than 3% under the technological parameter of the atomization gas pressure of 11MPa at the melting temperature of 1635 ℃.
(4) Powder particle size distribution test
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in this example was examined by a laser particle size analyzer for particle size distribution and cumulative mass distribution, and the resulting particle size distribution is shown in FIG. 15. As can be seen from fig. 15, the particle size distribution of the powder is concentrated and the whole is normally distributed, which can satisfy the requirements of most laser additive manufacturing technologies on the particle size of the alloy steel powder.
(5) XRD phase analysis
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing obtained in this example was subjected to X-ray diffraction, and the X-ray diffraction pattern obtained is shown in FIG. 16. As can be seen from fig. 4, the phases of the powder are composed of austenite, martensite and γ -phase.
(6) Bulk density and flow test
The spherical Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing with the particle size of 1-150 mu m prepared in the embodiment is measured by adopting a HYL-102 type Hall flow meter according to the national standard GB/T1479.1-2011 and using a stainless steel funnel with the aperture of 2.5mm, the result of 5 times of measurement is shown in Table 4, the 5 times of average value obtained by powder loose density is 4.219g/cm 3 。
TABLE 4 measurement of apparent Density of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder
Figure BDA0003510953520000121
The results of 5 measurements of the spherical Ni-Co-Mn-Al-Y alloy powder for laser additive manufacturing with a particle size of 1 to 150 μm prepared in this example using a HYL-102 type Hall flow meter and a stainless steel funnel with a pore size of 2.5mm according to the national standard GB/T1482-2010 are shown in Table 5, and the average of the 5 measurements of the powder flowability is 27.32s/50g.
TABLE 5 flowability measurement of Ni-Co-Mn-Al-Y magnetic shape memory alloy powders (1 to 150 μm)
Figure BDA0003510953520000122
(7) Preparation of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample and metallographic structure by laser additive manufacturing
FIG. 17 is a photomicrograph of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing, wherein the size of the deposition sample is 30mm multiplied by 15mm multiplied by 8mm, the forming quality is good, and no crack defect exists.
FIG. 18 is a scanning microstructure of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample made by laser additive manufacturing, wherein (a) is a pre-heat treatment morphology and (b) is a post-heat treatment morphology. Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy samples consisted primarily of martensite, austenite and gamma phases. The gamma phase is mainly distributed at grain boundaries, and a small amount of gamma phase exists in the crystal, the martensite phase is distributed around the gamma phase, and the untransformed austenite phase is mainly distributed in the crystal grains. At the same time, some subgrain boundaries were present in the sample. The heat treated sample is mainly martensite phase, the area of gamma phase crystal grains is reduced, the gamma phase crystal grains are distributed in crystal boundaries and crystal grains, and the irregular shape is converted into a globular shape. After heat treatment, the crystal grains grow and the content of the subgrain boundary is reduced.
(8) Phase analysis of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 19 is an X-ray diffraction pattern of a sample of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein (a) is before heat treatment and (b) is after heat treatment. Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy samples consisted primarily of martensite, austenite, and γ phases. Among them, the martensite phase corresponds to the austenite phase peak. After heat treatment, the sample consisted mainly of the martensite phase. Since the γ phase and the austenite phase are relatively small, no diffraction peak is observed in XRD.
(9) Phase change performance of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 20 is a dsc curve of a sample of laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein (a) is before heat treatment and (b) is after heat treatment. The Ni-Co-Mn-Al-Y magnetic shape memory alloy sample manufactured by laser additive manufacturing has no martensite transformation characteristic peak between 0 and 150 ℃. And obvious endothermic exothermic peaks can be observed on the sample after heat treatment, which indicates that the normal and reverse martensitic transformation occurs. The entropy change of the curve is 20.5 J.kg through the integral calculation of the curve dsc -1 ·K -1 。
(10) Room temperature compression curve of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 21 is a compressive stress-strain curve of a sample of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein the solid line is before heat treatment and the dotted line is after heat treatment. The compressive strength of the Ni-Co-Mn-Al-Y magnetic shape memory alloy sample manufactured by laser additive manufacturing is 2321MPa, and the maximum compressive strain is 30.2%. The compressive strength of the sample after heat treatment was 1241MPa, the maximum compressive strain was 16.1%. Therefore, the Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by the laser additive has good mechanical properties.
Example 3
A method for preparing Ni-Co-Mn-Al-Y magnetic shape memory alloy powder and laser additive manufacturing thereof comprises the following steps:
step 1, preparation of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder:
the alloy ingot is prepared by vacuum induction melting, and then is prepared by a crucible vacuum induction melting gas atomization method (VIGA), wherein the method comprises the steps of reducing the vacuum degree in a furnace to 9.3Pa, filling argon to 0.01MPa, and finally melting at 1620 ℃ and atomizing at 9.3MPa.
Step 2, substrate Material and powder Pre-treatment
Adopting a pure nickel substrate, firstly carrying out rust removal and decontamination on the surface of the substrate by using a grinding wheel to ensure that the surface is bright and clean, and then wiping the surface with alcohol and then blowing the cleaned surface to dry for later use;
drying Ni-Co-Mn-Al-Y magnetic shape memory alloy powder with the particle size of 53-150 mu m at 80 ℃ for 2h, and filling the powder into a powder feeder for later use;
step 3, laser additive manufacturing process
Go on in the vacuum chamber of argon gas atmosphere, adopt 2kW fiber laser, the coaxial powder feeding system of collocation carries out direct laser deposition and takes shape, the shape and the printing route of the printing body are set up to the programming software of taking certainly, the printing route is the parallel reciprocating scanning of successive layer, scanning direction is rotatory 90 between the layer, on the base plate, prepare the magnetic shape memory alloy sample that the defect is few, mechanical properties is good, take out from the vacuum chamber after cooling the magnetic shape memory alloy sample to the room temperature, wherein, the technological parameter of laser vibration material disk manufacturing is: the laser power is 1300W, the scanning speed is 4mm/s, the powder feeding amount is 1.8g/min, the protective gas flow is 800l/h, the lap joint rate is 35 percent, and the Z-axis lifting amount is 0.4mm.
Separating the magnetic shape memory alloy part from the substrate by using a wire cutting machine, then placing the magnetic shape memory alloy part into a vacuum tube furnace, sealing a pipe orifice, pumping out gas in the furnace by using a vacuum pump, then filling argon, repeating the steps for three times, setting the heating rate to be 3 ℃/min, heating to 1000 ℃, keeping the temperature for 24 hours, and then cooling to room temperature at the rate of 2 ℃/min. Finally obtaining a polycrystalline magnetic shape memory alloy sample with uniform tissue.
The following analytical tests were performed on the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing and the direct laser deposition sample prepared in this example:
(1) Chemical composition and oxygen content analysis
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in the embodiment is measured according to the national standard GB/T14265-1993, and the chemical component content of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder according to the atom percentage is as follows: 40.8%, co:9.2%, mn:28.8%, al:21.1%, Y:0.1 percent.
(2) Sphericity and surface morphology
The surface and the microscopic morphology of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder prepared in this example were observed as shown in FIG. 22. When the final smelting temperature reaches 1635 ℃, the powder prepared by atomization under the atomization pressure of 11MPa has good sphericity which exceeds 97%. The particle size distribution is uniform, the broken ball has less defects, but a small amount of satellite balls exist.
(3) Hollow sphere fraction analysis
FIG. 23 is a metallographic photograph showing the cross section of a Ni-Co-Mn-Al-Y magnetic shape memory alloy powder having a particle size of 1 to 150 μm. It can be seen from the figure that the hollow sphere rate of the Ni-Co-Mn-Al-Y magnetic shape memory alloy powder with the particle size range of 1-150 mu m is not more than 3% under the technological parameter of the atomizing air pressure of 11MPa by adopting the crucible vacuum induction melting gas atomization method at the melting temperature of 1635 ℃.
(4) Powder particle size distribution test
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder obtained in this example was examined for particle size distribution and cumulative mass distribution using a laser particle size analyzer, and the resulting particle size distribution was shown in FIG. 24. As can be seen from fig. 24, the particle size distribution of the powder is concentrated and the whole is normally distributed, which can satisfy the requirements of most laser additive manufacturing technologies on the particle size of the alloy steel powder. The particle size of the powder produced in this example was relatively large compared to examples 1 and 2, primarily due to the low atomization gas pressure used in this example.
(5) XRD phase analysis
The Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing obtained in this example was subjected to X-ray diffraction, and the X-ray diffraction pattern obtained is shown in FIG. 25. As can be seen from fig. 25, the phases of the powder are composed of austenite, martensite, and γ -phase.
(6) Bulk density and flow test
The spherical Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing with the particle size of 1-150 mu m prepared in the embodiment is measured by adopting a HYL-102 type Hall flow meter according to the national standard GB/T1479.1-2011 and using a stainless steel funnel with the aperture of 2.5mm, the result of 5 times of measurement is shown in Table 6, the 5 times of average value obtained by powder loose density is 4.188g/cm 3 。
TABLE 6 Ni-Co-Mn-Al-Y magnetic shape memory alloy powder apparent Density measurements
Figure BDA0003510953520000151
The results of 5 measurements of the spherical Ni-Co-Mn-Al-Y alloy powder for laser additive manufacturing with a particle size of 1 to 150 μm prepared in this example using a HYL-102 type Hall flow meter according to the national standard GB/T1482-2010 using a stainless steel funnel with a pore diameter of 2.5mm are shown in Table 7, and the average of the 5 measurements of the powder flowability is 26.44s/50g.
TABLE 7 Ni-Co-Mn-Al-Y magnetic shape memory alloy powders (1-150 μm) flowability measurements
Figure BDA0003510953520000152
(7) Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy sample and metallographic structure
FIG. 26 is a photomicrograph of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing, wherein the size of the deposition sample is 30mm multiplied by 15mm multiplied by 8mm, the forming quality is good, and no crack defect exists.
FIG. 27 is a scanning microstructure of a Ni-Co-Mn-Al-Y magnetic shape memory alloy sample made by laser additive manufacturing, wherein (a) is a pre-heat treatment profile and (b) is a post-heat treatment profile. Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy samples consisted primarily of martensite, austenite and gamma phases. The gamma phase is mainly distributed at the grain boundary and exists in a small amount in the crystal, the martensite phase is distributed around the gamma phase, and the unconverted austenite phase is mainly distributed in the crystal grain. At the same time, some subgrain boundaries were present in the sample. The heat-treated sample is mainly in a martensite phase, a small amount of unconverted austenite phase is contained in part of grains, the area of gamma-phase grains is reduced, and the gamma-phase grains are converted into spherules from irregular shapes. After heat treatment, the grains grow and the subgrain boundaries decrease, while the subgrain boundaries generally connect with the gamma phase.
(8) Phase analysis of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 28 is an X-ray diffraction pattern of a sample of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy. Wherein (a) is before heat treatment and (b) is after heat treatment. Laser additive manufacturing Ni-Co-Mn-Al-Y magnetic shape memory alloy samples consisted primarily of martensite, austenite, and γ phases. After heat treatment, the samples consisted primarily of an austenite phase and a martensite phase. The gamma phase, due to its smaller volume, has no diffraction peak observed in XRD.
(9) Phase change performance of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 29 is a dsc curve of a laser additive manufactured Ni-Co-Mn-Al-Y magnetic shape memory alloy sample. Wherein (a) is before heat treatment and (b) is after heat treatment. The Ni-Co-Mn-Al-Y magnetic shape memory alloy sample manufactured by laser additive manufacturing has no martensite transformation characteristic peak between 0 and 150 ℃. While it is hotThe treated sample can observe obvious endothermic exothermic peak, which indicates that the normal and reverse martensite phase transformation occurs. The entropy change of the material is 18.9 J.kg through the curve integral calculation of dsc -1 ·K -1 。
(11) Room temperature compression curve of Ni-Co-Mn-Al-Y magnetic shape memory alloy sample prepared by laser additive manufacturing
FIG. 30 is a compressive stress strain curve of a sample of a Ni-Co-Mn-Al-Y magnetic shape memory alloy laser additive manufactured. Wherein the solid line is before heat treatment and the dotted line is after heat treatment. The compressive strength of the Ni-Co-Mn-Al-Y magnetic shape memory alloy sample manufactured by laser additive manufacturing is 2316MPa, and the maximum compressive strain is 30.6 percent. The compressive strength of the sample after heat treatment was 1184MPa, and the maximum compressive strain was 14.0%. Therefore, the Ni-Co-Mn-Al-Y magnetic shape memory alloy manufactured by the laser additive has good mechanical properties.

Claims (6)

1. A preparation method of Ni-Co-Mn-Al-Y magnetic shape memory alloy powder for laser additive manufacturing is characterized in that the alloy powder comprises the following chemical components in atomic percentage: ni:40 to 43%, co:8 to 10%, mn:28 to 32%, al:19 to 21%, Y:0.1 to 0.3 percent;
the alloy ingot is prepared by vacuum induction melting, and then is prepared by a crucible vacuum induction melting gas atomization method, wherein the final melting temperature is 1620-1635 ℃, the vacuum degree is below 10Pa, and the atomization pressure is 9-12.5 MPa.
2. The method according to claim 1, wherein the alloy powder is spherical, the sphericity is more than 97%, the hollow sphere ratio is not more than 3%, the oxygen content of the powder is less than 0.05%, the particle size distribution is 1 to 150 μm, and the bulk density is 4.10 to 4.25g/cm 3 The fluidity is 26.2 to 27.4s/50g.
3. The production method according to claim 2, wherein, of the alloy powders, the powder having a particle size distribution of 1 to 52 μm has a flowability of 64.51s/50g; the flowability of the powder with a particle size distribution of 53-150 μm was 19.72s/50g.
4. The alloy powder of claim 1 wherein said alloy powder constituents are comprised of austenite, martensite, and gamma-phases.
5. A preparation method of a Ni-Co-Mn-Al-Y magnetic shape memory alloy material for laser additive manufacturing is characterized by comprising the following steps:
1) Screening the alloy powder prepared by the preparation method of any one of claims 1 to 4, and selecting the powder with the particle size of 53-150 μm for later use;
2) Drying the alloy powder obtained in the step 1) in an oven at 80-120 ℃ for 0.5-3 h for later use;
3) Adopting 2KW optical fiber laser forming equipment to directly carry out laser deposition on an alloy sample, controlling the oxygen content in a forming vacuum box to be below 100ppm, setting the shape and the printing path of a printing body by using self-contained programming software, wherein the printing path is parallel reciprocating scanning layer by layer, the scanning direction between layers rotates by 90 degrees to obtain a Ni-Co-Mn-Al-Y magnetic shape memory alloy material, sealing the magnetic shape memory alloy material obtained in the step 3) in a vacuum quartz tube, putting the vacuum quartz tube into a heat treatment furnace for homogenization heat treatment, and cooling the furnace to room temperature after heat preservation and taking out the alloy material;
in the step 3), the parameters of the direct laser deposition process are as follows: the laser power is 1100-1300W, the scanning speed is 3-5 mm/s, the powder feeding amount is 1.70-1.85 g/min, the lap joint rate is 30-50%, the Z-axis lifting amount is 0.3-0.5 mm, and the argon protective gas flow is 400-800 l/h; the homogenizing heat treatment process comprises the following steps: the heat preservation temperature is 1000 ℃, and the heat preservation time is 24 hours.
6. The Ni-Co-Mn-Al-Y magnetic shape memory alloy material prepared by the preparation method of claim 5, which is characterized in that the compressive strength of the Ni-Co-Mn-Al-Y magnetic shape memory alloy obtained by direct laser deposition reaches 2128-2321 MPa, and the maximum compressive strain reaches 28.1-30.6%; the Ni-Co-Mn-Al-Y magnetic shape memory alloy after heat treatment has reversible martensite phase transformation characteristic, and the entropy change reaches 15.0 to 20.5 J.kg -1 ·K -1 The compression strength is 1169-1241 MPa, and the maximum compression strain is 14.0-16.1%.
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