Semi-solid preparation method of porous Ni-Cu alloy

Abstract

This invention relates to the field of porous metal preparation, and more particularly to a semi-solid preparation method for porous Ni-Cu alloys. The preparation method provided by this invention includes mixing nickel powder, copper powder, and ammonium bicarbonate to obtain a mixed powder; the mass ratio of nickel powder to copper powder is 5:1 to 1:2; the mixed powder is then sequentially pressed and subjected to electromagnetic levitation induction semi-solid heating to obtain a porous Ni-Cu alloy. This invention utilizes the rapid heating effect of electromagnetic levitation to keep the sample within the temperature range of the Ni-Cu two-phase region, allowing the melting of the precursor and the decomposition of ammonium bicarbonate to occur simultaneously. Simultaneously, it ensures sufficient liquid phase in the sample for bubble growth, while the decomposition of ammonium bicarbonate provides the impetus for bubble growth. Furthermore, the unmelted Ni present during the preparation process inhibits the aggregation and merging of pores. Therefore, the preparation method enables effective control of the pore morphology and distribution in the porous Ni-Cu alloy.

Description

Technical Field

[0001] This invention relates to the field of porous metal preparation, and more particularly to a semi-solid preparation method for porous Ni-Cu alloys. Background Technology

[0002] Porous metals are a new type of metallic material with a large number of pores dispersed throughout the metal material. Compared with traditional metallic materials, porous metals have advantages such as high specific strength, large specific surface area, and energy absorption and vibration reduction. Porous metals have the dual properties of structural and functional materials. Therefore, in recent years, porous metals have been widely used and have achieved rapid development. Their application fields include automotive machinery, aerospace industry, biomedicine, filtration and separation, catalysts, mufflers, battery electrodes, and heat exchange. Powder metallurgy is currently the most widely used method for preparing porous metals. The traditional powder sintering method for preparing porous metals usually includes the following steps: (1) using metal powder as raw material and mixing it evenly with a pore-forming agent; (2) cold pressing the resulting mixed powder to obtain a precursor; (3) sintering the obtained precursor at high temperature for a long time in a vacuum environment to finally prepare the porous metal. Powder sintering has the advantages of simple process flow and controllable porosity. However, during its preparation, the sample remains solid, and the formation and growth of the sintering neck depends on molecular diffusion. This method requires a long sintering time and makes it difficult to effectively control the pore characteristics. Summary of the Invention

[0003] The purpose of this invention is to provide a semi-solid preparation method for porous Ni-Cu alloys, which can effectively control the pore morphology and distribution in the porous Ni-Cu alloys.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a semi-solid preparation method for porous Ni-Cu alloys, comprising the following steps:

[0006] Nickel powder, copper powder and ammonium bicarbonate are mixed to obtain a mixed powder; the mass ratio of nickel powder to copper powder is 5:1 to 1:2.

[0007] The mixed powder is sequentially pressed and shaped, and then subjected to electromagnetic levitation induction semi-solid heating to obtain the porous Ni-Cu alloy.

[0008] Preferably, the nickel powder and copper powder have independent particle sizes of 50 to 400 mesh.

[0009] Preferably, the mass percentage of ammonium bicarbonate in the mixed powder is 3-7%.

[0010] Preferably, the mixing method is ball milling;

[0011] The ball milling speed is 100-350 r / min, and the time is 20-60 min.

[0012] Preferably, the molding pressure for the compression molding is 1-5 MPa, and the holding time is 1-5 min.

[0013] Preferably, the precursor obtained after compression molding is cylindrical;

[0014] The cylindrical shape has a diameter of 4–8 mm and a height of 4–10 mm.

[0015] Preferably, the heating temperature of the electromagnetic levitation induction semi-solid heating is 1200-1450℃, and the heating time is 1-4 min.

[0016] Preferably, the device used for the electromagnetic levitation induction semi-solid heating is an electromagnetic levitation melting device;

[0017] The electromagnetic levitation melting device includes a high-frequency induction heating coil, which includes an upper coil and a lower coil with a spacing of 10-20 mm.

[0018] Both the upper and lower coils are hollow copper conduits with a diameter of 3 to 8 mm, and are wound in reverse series.

[0019] Preferably, the input current of the electromagnetic levitation melting device is 13-17A, the input power is 5-15kW, and the frequency is 100-500kHz.

[0020] This invention provides a semi-solid preparation method for a porous Ni-Cu alloy, comprising the following steps: mixing nickel powder, copper powder, and ammonium bicarbonate to obtain a mixed powder; the mass ratio of nickel powder to copper powder is 5:1 to 1:2; sequentially pressing the mixed powder into shape and then subjecting it to electromagnetic levitation induction semi-solid heating to obtain the porous Ni-Cu alloy. This invention utilizes the rapid heating effect of electromagnetic levitation, allowing the melting of the precursor and the decomposition of ammonium bicarbonate (NH4HCO3→NH3↑+H2O+CO2↑) to occur simultaneously. By controlling the experimental parameters of the electromagnetic levitation device, the sample is kept within the temperature range of the Ni-Cu two-phase region. This ensures sufficient liquid phase for bubble growth, while the decomposition of ammonium bicarbonate provides the impetus for bubble growth. Furthermore, the unmelted Ni present during the preparation process inhibits the aggregation and merging of pores.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] 1) The sample is in a semi-solid state during the preparation process. By controlling the flow of the liquid phase during the preparation process, the growth environment and movement state of the bubbles can be changed, thereby achieving effective control over the characteristics such as pore morphology, pore size and distribution.

[0023] 2) The unmelted Ni present during the preparation process inhibits the aggregation and merging of pores, making the pores uniformly distributed in the sample and with high pore size concentration, effectively avoiding the generation and propagation of fatigue cracks that may be caused by stress concentration.

[0024] 3) The preparation of porous metals by electromagnetic levitation induction semi-solid heating and melting has a heating rate much higher than that of traditional methods, which greatly shortens the experimental cycle. It has a great advantage, especially in the preparation of high melting point metals. The preparation method is simple and the technology is novel.

[0025] 4) During the preparation process, the sample is always in a containerless state, which avoids problems such as uneven pore distribution and irregular pore morphology caused by the collapse of the sample due to contact with the container wall under normal conditions.

[0026] 5) The electromagnetic stirring effect in the electromagnetic levitation induction semi-solid heating used in the preparation process ensures the uniform distribution of liquid phase components during the preparation process, which is beneficial to the preparation of high-performance porous metal materials. Attached Figure Description

[0027] Figure 1 This is a macroscopic morphology diagram of the porous Ni-Cu alloy described in Example 1;

[0028] Figure 2 This is a scanning electron microscope image of the porous Ni-Cu alloy described in Example 1;

[0029] Figure 3 The pore size distribution diagram is shown in Example 1 for the porous Ni-Cu alloy.

[0030] Figure 4 This is a scanning electron microscope image of the porous Ni-Cu alloy described in Example 2;

[0031] Figure 5 The image shows the macroscopic morphology of the porous Ni-Cu alloy described in Comparative Example 1.

[0032] Figure 6 This is a scanning electron microscope image of the porous Ni-Cu alloy described in Comparative Example 2. Detailed Implementation

[0033] This invention provides a semi-solid preparation method for porous Ni-Cu alloys, comprising the following steps:

[0034] Nickel powder, copper powder and ammonium bicarbonate are mixed to obtain a mixed powder; the mass ratio of nickel powder to copper powder is 5:1 to 1:2.

[0035] The mixed powder is sequentially pressed and shaped, and then subjected to electromagnetic levitation induction semi-solid heating to obtain the porous Ni-Cu alloy.

[0036] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0037] This invention mixes nickel powder, copper powder and ammonium bicarbonate to obtain a mixed powder.

[0038] In this invention, the particle size of the nickel powder and copper powder is preferably 50-400 mesh, and more preferably 100-300 mesh.

[0039] In this invention, the mass ratio of nickel powder to copper powder is 5:1 to 1:2, preferably 4:1 to 2:3, and more preferably 3.5:1 to 2:2.5.

[0040] In this invention, the mass percentage of ammonium bicarbonate in the mixed powder is preferably 3-7%, more preferably 3.5-5.5%.

[0041] In this invention, the mixing method is preferably ball milling; the ball milling speed is preferably 100-350 r / min, more preferably 100-200 r / min; the time is preferably 20-60 min, more preferably 35-45 min.

[0042] After obtaining the mixed powder, the present invention sequentially presses and heats the mixed powder with electromagnetic levitation induction to obtain the porous Ni-Cu alloy.

[0043] In this invention, the molding pressure for pressing is preferably 1-5 MPa, more preferably 1-2.5 MPa; the holding time is preferably 1-5 min, more preferably 1-3 min.

[0044] In this invention, the precursor obtained after compression molding is preferably cylindrical; the diameter of the cylindrical shape is preferably 4-8 mm, more preferably 5-6 mm; the height of the cylindrical shape is preferably 4-10 mm, more preferably 5-7 mm.

[0045] In this invention, the heating temperature of the electromagnetic levitation induction semi-solid heating is preferably 1200-1450℃, more preferably 1250-1400℃; the heating time is preferably 1-4 min, more preferably 1-3 min.

[0046] In this invention, the device used for the electromagnetic levitation induction semi-solid heating is preferably an electromagnetic levitation melting device; the electromagnetic levitation melting device preferably includes a high-frequency induction heating coil, the high-frequency induction heating coil preferably includes an upper coil and a lower coil with a spacing of 10-20 mm, and the spacing between the upper coil and the lower coil is more preferably 13-16 mm; both the upper coil and the lower coil are preferably hollow copper conduits with a diameter of 3-8 mm, and are wound in reverse series.

[0047] In this invention, the input current of the electromagnetic levitation melting device is preferably 13-17A, more preferably 14-16A; the input power is preferably 5-15kW, more preferably 8-12kW; and the frequency is preferably 100-600kHz, more preferably 200-350kHz.

[0048] In this invention, during the electromagnetic levitation induction semi-solid heating process, the hollow copper conduit is preferably cooled. The cooling method is preferably to introduce cooling water into the hollow copper conduit to cool the coil. The pressure of the cooling water is preferably 0.3-0.7 MPa, more preferably 0.4-0.6 MPa, and the flow rate is preferably 3-7 L / min, more preferably 4-6 L / min.

[0049] In this invention, the electromagnetic levitation induction semi-solid heating process preferably involves continuously introducing an inert gas to provide a protective atmosphere and achieve temperature control; the inert gas in this invention is preferably helium.

[0050] The following detailed description of the semi-solid preparation method of porous Ni-Cu alloy provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1

[0052] 4.75g of nickel powder (200 mesh), 4.75g of copper powder (200 mesh), and 0.5g of ammonium bicarbonate were poured into a ball mill jar, and the ball mill jar was fixed on a planetary ball mill. The mixture was ball milled at 150 r / min for 40 min to obtain a mixed powder.

[0053] 0.95g of the mixed powder was pressed into shape at a pressure of 1.5MPa and a holding time of 1min to obtain a cylindrical precursor (6mm in diameter and 6mm in height).

[0054] The cylindrical precursor was placed in an electromagnetic levitation melting device, and helium was continuously introduced to maintain an inert atmosphere. The temperature was controlled, and the current of the electromagnetic levitation device was adjusted to 15A, the input power to 10kV, and the frequency to 280kHz to stabilize the sample. The sample was kept at approximately 1300℃ by blowing air and heated for 1 minute. During the heating process, cooling water was circulated through a hollow copper conduit to cool the coil. The pressure of the cooling water was 0.5MPa and the flow rate was 5L / min, thus obtaining the porous Ni-Cu alloy.

[0055] The porous Ni-Cu alloy was cut axially, then mounted and polished before metallographic observation. Figure 1 This is a macroscopic morphology diagram of the porous Ni-Cu alloy. Figure 2 This is a scanning electron microscope image of the porous Ni-Cu alloy. Figure 3 The diagram shows the pore size distribution of the porous Ni-Cu alloy. Figures 1-3 It can be seen that the porous Ni-Cu alloy has spherical pores that are evenly distributed, with a pore size concentration of 20-100 μm of more than 80%. This is because the Cu content is relatively high, which can generate enough liquid phase during sample preparation to support the growth of bubbles generated by the decomposition of ammonium bicarbonate. Furthermore, the presence of a small amount of unmelted Ni makes it difficult for the bubbles to aggregate and merge.

[0056] Example 2

[0057] 7.125g of nickel powder (200 mesh), 2.375g of copper powder (200 mesh), and 0.5g of ammonium bicarbonate were poured into a ball mill jar, and the ball mill jar was fixed on a planetary ball mill. The mixture was ball milled at 150 r / min for 40 min to obtain a mixed powder.

[0058] 0.95g of the mixed powder was pressed into shape at a pressure of 1.5MPa and a holding time of 1min to obtain a cylindrical precursor (6mm in diameter and 6mm in height).

[0059] The cylindrical precursor was placed in an electromagnetic levitation melting device, and helium was continuously introduced to maintain an inert atmosphere. The temperature was controlled, and the current of the electromagnetic levitation device was adjusted to 15.5A, the input power to 10kV, and the frequency to 280kHz to stabilize the sample. The sample was kept at approximately 1350℃ by blowing air and heated for 1 minute. During the heating process, cooling water was circulated through a hollow copper conduit to cool the coil. The pressure of the cooling water was 0.5MPa and the flow rate was 5L / min, thus obtaining the porous Ni-Cu alloy.

[0060] The porous Ni-Cu alloy prepared in this example was cut, mounted, and polished according to the method in Example 1. The polished sample was observed under a scanning electron microscope, and its porosity characteristics are as follows. Figure 4 As shown in the figure, the porous Ni-Cu alloy prepared in this example has a uniform pore distribution, but the pore morphology is significantly different from that of Example 1. Due to the reduced flow of the liquid phase, the bubbles encounter the obstruction of unmelted Ni during growth, resulting in a significantly different pore morphology compared to the porous Ni-Cu alloy described in Example 1, although the pores can maintain a uniform distribution. This indicates that the pore characteristics can be controlled by regulating the flow of the liquid phase during the preparation process.

[0061] Comparative Example 1

[0062] 2.375g of nickel powder (200 mesh), 7.125g of copper powder (200 mesh), and 0.5g of ammonium bicarbonate were poured into a ball mill jar, and the ball mill jar was fixed on a planetary ball mill. The mixture was ball milled at 150 r / min for 40 min to obtain a mixed powder.

[0063] 0.95g of the mixed powder was pressed into shape at a pressure of 1.5MPa and a holding time of 1min to obtain a cylindrical precursor (6mm in diameter and 6mm in height).

[0064] The cylindrical precursor was placed in an electromagnetic levitation melting device, and helium was continuously introduced to maintain an inert atmosphere. The temperature was controlled, and the current of the electromagnetic levitation device was adjusted to 15A, the input power to 10kV, and the frequency to 280kHz to stabilize the sample. The sample was kept at approximately 1300℃ by blowing air and heated for 1 minute. During the heating process, cooling water was circulated through a hollow copper conduit to cool the coil. The pressure of the cooling water was 0.5MPa and the flow rate was 5L / min, thus obtaining the porous Ni-Cu alloy.

[0065] The porous Ni-Cu alloy prepared in this example was cut, mounted, and polished according to the method in Example 1. The polished sample was observed under a scanning electron microscope, and its porosity characteristics are as follows. Figure 5 As shown. By Figure 5 It can be seen that the pores of the porous Ni-Cu alloy exhibit obvious merging and uneven distribution. This is because the sample is completely melted during the preparation process, resulting in unrestricted movement of bubbles in the melt, which leads to the aggregation and merging of a large number of bubbles.

[0066] Comparative Example 2

[0067] 4.75g of nickel powder (200 mesh), 4.75g of copper powder (200 mesh), and 0.5g of ammonium bicarbonate were poured into a ball mill jar, and the ball mill jar was fixed on a planetary ball mill. The mixture was ball milled at 150 r / min for 40 min to obtain a mixed powder.

[0068] 0.95g of the mixed powder was pressed into shape at a pressure of 1.5MPa and a holding time of 1min to obtain a cylindrical precursor (6mm in diameter and 6mm in height).

[0069] The cylindrical precursor was placed in a box furnace for vacuum atmosphere sintering. The heating rate of the box furnace was set to 10℃ / min. The temperature was raised to 1300℃, held for 5 min, and then cooled in air to obtain a porous Ni-Cu alloy.

[0070] The porous Ni-Cu alloy was cut along the direction of gravity, then mounted and polished, followed by metallographic observation. Figure 6 The image shown is a scanning electron microscope image of the porous Ni-Cu alloy. Figure 6 It can be seen that the porous Ni-Cu alloy has irregular pore shapes and very low porosity.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A semi-solid preparation method for a porous Ni-Cu alloy, characterized in that, The steps are as follows: Nickel powder, copper powder, and ammonium bicarbonate are mixed to obtain a mixed powder; the mass ratio of nickel powder to copper powder is 5:1 to 1:

2. The mixed powder was sequentially pressed into shape and subjected to electromagnetic levitation induction semi-solid heating to obtain the porous Ni-Cu alloy; The electromagnetic levitation induction semi-solid heating has a heating temperature of 1200~1450℃ and a heating time of 1~4min; The electromagnetic levitation induction semi-solid heating device is an electromagnetic levitation melting device. The electromagnetic levitation melting device has an input current of 13~17A, an input power of 5~15kW, and a frequency of 100~500kHz.

2. The semi-solid preparation method according to claim 1, characterized in that, The nickel powder and copper powder have independent particle sizes of 50-400 mesh.

3. The semi-solid preparation method according to claim 2, characterized in that, The mass percentage of ammonium bicarbonate in the mixed powder is 3-7%.

4. The semi-solid preparation method according to claim 1, characterized in that, The mixing method is ball milling; The ball milling speed is 100~350 r / min, and the time is 20~60 min.

5. The semi-solid preparation method according to claim 1, characterized in that, The molding pressure for the compression molding is 1~5MPa, and the holding time is 1~5min.

6. The semi-solid preparation method according to claim 1 or 5, characterized in that, The precursor obtained after compression molding is cylindrical; The cylindrical shape has a diameter of 4-8 mm and a height of 4-10 mm.

7. The semi-solid preparation method according to claim 1, characterized in that, The electromagnetic levitation melting device includes a high-frequency induction heating coil, which includes an upper coil and a lower coil with a spacing of 10~20mm. Both the upper and lower coils are hollow copper conduits with a diameter of 3-8 mm, and are wound in reverse series.

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