Al-ag controllable loading function gradient composite material and preparation method thereof

Abstract

The application discloses an Al-Ag controllable loading function gradient composite material and a preparation method thereof. The gradient composite material has 10-15 layers, and the wave impedance distribution index is 2-3. The content of Al decreases from 100% to 0 in the gradient from the first layer to the last layer, and the content of Ag increases from 0 to 100% in the gradient. The preparation method comprises the following steps: taking the powder of the last layer to be pressed into shape, then taking the composite powder of the second last layer to be pressed on the surface of the last layer, and the like, so that a pre-pressing sample is obtained, and the whole is pressed and sintered. The single-layer component of the material is designed, the wave impedance (density) of the single-layer composite material powder changes in an exponential law according to the design curve of the gradient material, the macroscopic surface flatness of the obtained composite material is good, the densification degree, the strength and the peak stress are high, and the composite material is a gradient material with continuous or quasi-continuous impedance (density); the preparation process is simple, the operability is high, and the application prospect is good.

Description

Technical Field

[0001] This invention belongs to the technical field of functionally graded materials, specifically relating to an Al-Ag controllable loading functionally graded composite material and its preparation method. Background Technology

[0002] With the increasing demand for improved reliability and safety of key materials in national defense, aerospace, and high-end manufacturing, there is a pressing need for dynamic property data of graded materials under service loads (different stresses and strain rates). The main method for obtaining such dynamic property data is multi-stage lightweight gas gun loading technology. The core of this loading technology is controllable loading of functionally graded materials. Therefore, the study of controllable loading of functionally graded materials has become a research focus.

[0003] Currently, the main research systems for controllable loading functional graded materials are Al-Cu and Ag-W. However, in the Al-Cu system, intermetallic compounds are formed during sintering. These intermetallic compounds are brittle, while the raw materials Al and Cu are tough. The different material properties cause fluctuations in the loading rate waveform. In the Ag-W system, the two materials have a large difference in thermal expansion coefficients, which leads to stress generation. Stress release can cause cracks to form, resulting in defects inside the material. Ultimately, the loading rate waveform decreases and has poor smoothness.

[0004] Therefore, there is an urgent need for a controllable loading functional gradient material with continuously or quasi-continuously varying wave impedance (density). Summary of the Invention

[0005] The purpose of this invention is to provide an Al-Ag controllable loading functional gradient composite material and its preparation method. The gradient composite material has good macroscopic surface smoothness, high degree of densification, high strength and peak stress, and is a gradient material with continuous or quasi-continuous impedance (density).

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A controllable-load functionally graded composite material of Al-Ag is provided, wherein the functionally graded composite material has 10-15 layers, the first layer being pure Al and the last layer being pure Ag; wherein:

[0008] The Al content decreases from 100% to 0 from the first layer to the last layer, while the Ag content increases from 0 to 100%.

[0009] The wave impedance distribution index of the gradient composite material is 2-3.

[0010] According to the above scheme, from the first layer to the last layer, the difference in Al content between adjacent layers first increases gradually from 0.14-0.17% to 20-21%, and then decreases gradually to 5-6%.

[0011] According to the above scheme, the total thickness of the gradient composite material is 2-3 mm.

[0012] According to the above scheme, in the gradient composite material, the thickness of the single layer of the middle layer is 100-200μm, and the thickness of the first layer and the last layer is increased by 200-300μm respectively based on the thickness of the single layer of the middle layer.

[0013] A method for preparing the above-mentioned Al-Ag controllably loaded functionally graded composite material is provided, comprising the following steps:

[0014] 1) Weigh out the powder according to the ratio of Al powder to Ag powder in each layer and mix them evenly;

[0015] 2) First, take the last layer of powder and press it into shape. After pressing, take the second to last layer of composite powder and press it on the surface of the last layer. Repeat this process until the first layer of powder is pressed to obtain a pre-pressed sample.

[0016] 3) The pre-pressed sample obtained in step 2) is pressed as a whole, and then sintered at 90-100 MPa and 570-580℃ to obtain Al-Ag controllable loading functional gradient composite material.

[0017] According to the above scheme, in step 2), since Al powder will stick to the upper pressing head during the pressing process, a layer of graphite paper or weighing paper needs to be placed between the upper pressing head and the powder to avoid powder loss.

[0018] According to the above scheme, in step 2), the pressing process is: pressing at 10MPa-20MPa for 1-2 minutes.

[0019] According to the above scheme, in step 3), the pressing process is: pressure 10-20MPa, time 20-30min.

[0020] According to the above scheme, in step 3), the sintering holding time is 2 to 3 hours.

[0021] According to the above scheme, in step 3), the sintering process is as follows: first, raise the temperature to 280–320℃ and hold for 25–40 minutes; then, increase the pressure to 90–100 MPa; finally, continue to raise the temperature to 570–580℃ and hold for 2–3 hours. The powder shows initial signs of sintering at 280–320℃, and the powder contact area is relatively large. Increasing the pressure at this point is beneficial for the tight bonding between layers.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention provides an Al-Ag controllable loading functional gradient composite material. By selecting Ag and Al for composite and combining them with gradient design, the resulting gradient composite material has good surface smoothness, high strength, high peak stress, and is a gradient material with continuous or quasi-continuous impedance (density).

[0024] 2. This invention provides a method for preparing Al-Ag controllable loading functionally graded composite materials. First, the last layer with the highest density is pressed to prevent excessive diffusion from the high-density layer to the low-density layer when pressing the next layer, ensuring the material's regularity. During sintering, appropriate temperature and pressure are selected to ensure good bonding of the gradient composite material, guarantee the material's shape, and prevent melting and precipitation due to excessive temperature exceeding the liquidus line, which would compromise the overall integrity of the material. Under high temperature and pressure, the powder particles rearrange, resulting in a tighter bond. The different ratios of Al and Ag powder in the middle layer lead to the appearance of a small amount of liquid phase, further strengthening the bond of the Al-Ag controllable loading functionally graded material. The preparation process is simple, highly operable, and has promising prospects for industrial application. Attached Figure Description

[0025] Figure 1 These are wave impedance, sound velocity, and density distribution diagrams obtained from the wave impedance parameters designed in Examples 1-4, where... Figure 1 'a' represents the wave impedance distribution with thickness. Figure 1 b represents the sound velocity distribution with thickness. Figure 1 c represents the density distribution with thickness.

[0026] Figure 2 This refers to the sintering process used in hot pressing sintering in Embodiments 1 and 4 of the present invention, wherein... Figure 2 a is 570℃-100MPa in Example 1. Figure 2 b is 580℃-90MPa in Example 4.

[0027] Figure 3 This is a three-dimensional profile of the Al-Ag controllably loaded functionally graded material prepared in Example 4 of this invention, wherein... Figure 3 a is the Al plane. Figure 3 b is the Ag side.

[0028] Figure 4 This is a microstructure diagram of the Al-Ag controllably loaded functionally graded material prepared in Example 4 of this invention, wherein... Figure 4 a is a microstructure diagram of the functionally graded material. Figure 4 b is the energy spectrum of Al and Ag in the functionally graded material.

[0029] Figure 5 The loading speed waveform is obtained from the dynamic loading experiment of a two-stage light gas gun using the Al-Ag controllable loading functional gradient material prepared in Example 4 of this invention. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments and accompanying drawings, but is not limited to the contents described below.

[0031] Example 1:

[0032] First, the parameters of the Al-Ag controllably loaded functionally graded material were designed: the wave impedance distribution index is 3, the first and last layers are 0.4 mm thick, the remaining layers are 0.2 mm thick, the number of layers is 10, and the total thickness is 2.4 mm; the first layer is pure Al, and the last layer is pure Ag; where:

[0033] The Al content decreases from 100% to 0 from the first layer to the last layer, while the Ag content increases from 0 to 100%.

[0034] The Al content from the first layer to the last layer is 100%, 99.842%, 97.657%, 90.314%, 76.348%, 57.316%, 37.012%, 19.06%, 5.2266%, and 0%, respectively, with Ag representing the corresponding balance.

[0035] The wave impedance at each location is calculated using the formula: Z(d)=Z0+a·d P Where Z0 is the initial layer impedance value, a is a coefficient, d is the flyback thickness, and P is the wave impedance distribution index. Then, the density of each layer is calculated using Z = ρ·c. The calculated results are as follows: from the first layer to the last layer, the densities are: 2.712, 2.7152, 2.7599, 2.9218, 3.2888, 3.9678, 5.0885, 6.7825, 9.1225, and 10.49 g / cm³. 3 .

[0036] The powder is then pre-pressed. First, the last layer of powder is pressed. 2.0597g ​​of powder is weighed and placed in a mold for bidirectional pressing at a pressure of 10MPa for 2 minutes. Then, the ninth layer of composite powder, weighing 0.8956g, is weighed and pressed onto the surface of the final pressed layer under the same conditions. This process is repeated, with composite powders weighed sequentially from the eighth to the first layer, weighing 0.6659g, 0.4996g, 0.3895g, 0.3229g, 0.2868g, 0.2709g, 0.2665g, and 0.5325g respectively, and pressed to obtain the pre-pressed sample. The entire pre-formed sample is then subjected to a pressure of 20MPa for 20–30 minutes to ensure bonding between the powder particles.

[0037] The pre-formed sample is sintered by placing it into a sintering mold. A release agent is sprayed onto the contact area between the sample and the mold to facilitate demolding after sintering. The mold is then placed in a hot press furnace for sintering, with the vacuum level inside the furnace evacuated to 100 kJ / m³. -3 ~10 -2 The sintering temperature was set to 570℃ and the pressure to 100MPa. First, the temperature was raised to 300℃, then paused for 30 minutes. During this time, the pressure program was activated, raising the pressure to 100MPa. The temperature was then raised again to 570℃ and held for 2 hours. The sintering process was as follows: Figure 2 As shown in Figure a, the heating rate is automatically set by the hot press furnace and is not considered. After the holding period ends and the temperature cools down, the sample is taken out, which is the Al-Ag controllable loading functional gradient material.

[0038] Example 2:

[0039] First, the parameters of the Al-Ag controllable loading functionally graded material were designed: the wave impedance distribution index was 3, the first and last layers were 0.4 mm, the remaining layers were 0.2 mm, the number of layers was 10, and the total thickness was 2.4 mm. The Al and Ag content and the density of each layer from the first layer to the last layer were designed as in Example 1.

[0040] The powder was then pre-pressed. First, the last layer of powder was pressed. 2.0597g ​​of powder was weighed and placed in a mold for bidirectional pressing at 10MPa for 2 minutes. Then, 0.8956g of the ninth layer of composite powder was weighed and pressed onto the surface of the final pressed layer under the same conditions. This process was repeated, with composite powders weighed sequentially from the eighth to the first layer, at masses of 0.6659g, 0.4996g, 0.3895g, 0.3229g, 0.2868g, 0.2709g, 0.2665g, and 0.5325g respectively, and pressed to obtain the pre-pressed sample. The entire pre-formed sample was then subjected to a pressure of 20MPa for 20–30 minutes to ensure bonding between the powder particles.

[0041] The pre-formed sample is sintered by placing it into a sintering mold. A release agent is sprayed onto the contact area between the sample and the mold to facilitate demolding after sintering. The mold is then placed in a hot press furnace for sintering, with the vacuum level inside the furnace evacuated to 100 kJ / m³. -3 ~10 -2 Pa, the sintering temperature is set to 580℃ and the pressure to 100MPa. First, the temperature is raised to 300℃ and paused for 30 minutes. At this time, the pressure is raised to 100MPa and then the temperature is raised to 580℃. The temperature is held for 2 hours. The heating rate is automatically set by the hot press furnace and is not taken into account. After the holding time is completed and the temperature is cooled down, the sample is taken out, which is the Al-Ag controllable loading functional gradient material.

[0042] Example 3:

[0043] First, the parameters of the Al-Ag controllable loading functionally graded material were designed: the wave impedance distribution index was 3, the thickness of the first and last layers was 0.4 mm, the thickness of the remaining layers was 0.2 mm, the number of layers was 10, and the total thickness was 2.4 mm. The Al and Ag content design from the first layer to the last layer and the density of each layer were the same as in Example 1.

[0044] The powder is then pre-pressed. First, the last layer of powder is pressed. 2.0597g ​​of powder is weighed and placed in a mold for bidirectional pressing at a pressure of 10MPa for 2 minutes. Then, the ninth layer of composite powder, weighing 0.8956g, is weighed and pressed onto the surface of the final pressed layer under the same conditions. This process is repeated, with composite powders weighed sequentially from the eighth to the first layer, weighing 0.6659g, 0.4996g, 0.3895g, 0.3229g, 0.2868g, 0.2709g, 0.2665g, and 0.5325g respectively, and pressed to obtain the pre-pressed sample. The entire pre-formed sample is then subjected to a pressure of 20MPa for 20–30 minutes to ensure bonding between the powder particles.

[0045] The pre-formed sample is sintered by placing it into a sintering mold. A release agent is sprayed onto the contact area between the sample and the mold to facilitate demolding after sintering. The mold is then placed in a hot press furnace for sintering, with the vacuum level inside the furnace evacuated to 100 kJ / m³. -3 ~10 -2 Pa, set the sintering temperature to 570℃ and the pressure to 90MPa. First, raise the temperature to 300℃, pause for 30 minutes, then raise the pressure to 90MPa, and then continue to raise the temperature to 570℃, hold for 2 hours. The heating rate is automatically set by the hot press furnace and is not considered. After the holding period, wait for the temperature to cool down and then take out the sample, which is the Al-Ag controllable loading functional gradient material.

[0046] Example 4:

[0047] First, the parameters of the Al-Ag controllable loading functionally graded material were designed: the wave impedance distribution index was 3, the thickness of the first and last layers was 0.4 mm, the thickness of the remaining layers was 0.2 mm, the number of layers was 10, and the total thickness was 2.4 mm. The Al and Ag content design from the first layer to the last layer and the density of each layer were the same as in Example 1.

[0048] The powder is then pre-pressed. First, the last layer of powder is pressed. 2.0597g ​​of powder is weighed and placed into the mold for bidirectional pressing at a pressure of 10MPa for 2 minutes. Then, the ninth layer of composite powder, weighing 0.8956g, is weighed and pressed onto the surface of the final pressed layer under the same conditions. This process is repeated, with the composite powders from the eighth to the first layer weighed in sequence, with masses of 0.6659g, 0.4996g, 0.3895g, 0.3229g, 0.2868g, 0.2709g, 0.2665g, and 0.5325g respectively, and pressed to obtain the pre-pressed sample. The entire pre-formed sample is then subjected to a pressure of 20MPa for 10–20 minutes to ensure the bonding between the powder particles.

[0049] The pre-formed sample is sintered by placing it into a sintering mold. A release agent is sprayed onto the contact area between the sample and the mold to facilitate demolding after sintering. The mold is then placed in a hot press furnace for sintering, with the vacuum level inside the furnace evacuated to 100 kJ / m³. -3 ~10 -2 Pa, set the sintering temperature to 580℃ and the pressure to 90MPa. First, raise the temperature to 300℃, pause for 30 minutes, then raise the pressure to 90MPa, and then continue raising the temperature to 580℃, holding for 2 hours. The sintering process is as follows. Figure 2 As shown in b, the heating rate is automatically set by the hot press furnace and is not considered. After the holding period is over and the temperature has cooled down, the sample is taken out, which is the Al-Ag controllable loading functional gradient material.

[0050] Depend on Figure 3 It can be seen that the Al-Ag controllable loading functionally graded material prepared in Example 4 has good surface flatness, with a planar difference of less than 15 μm.

[0051] Depend on Figure 4 It can be seen that the Al-Ag controllable loading functional gradient material prepared in Example 4 has a high degree of parallelism between its internal layers, and the element distribution is uniform. The Ag element density decreases layer by layer from the upper layer to the lower layer, while the Al element density increases layer by layer.

[0052] Depend on Figure 5 As can be seen, the Al-Ag controllably loaded functionally graded material prepared in Example 4 was used in a two-stage light gas gun experiment to obtain the target impact velocity waveform. Firstly, the target impact velocity waveform can reflect the density distribution to a certain extent, that is, it is consistent with... Figure 1The density distribution curves in the target material are correlated, and the accuracy of the velocity waveform can be judged by the density distribution curves. Secondly, the smooth velocity waveform reflects the absence of defects inside the gradient material. Combined with SEM image analysis, it can be seen that there are no obvious defects inside the material, indicating good density. Thirdly, the smooth velocity waveform also reflects the continuous or quasi-continuous changes of elements inside the material. This is because element diffusion occurs during sintering, and the Al and Ag elements inside the material exhibit continuous or quasi-continuous changes. Finally, in terms of application, since the velocity of the gradient material increases slowly during target loading, unlike the sudden increase to the peak velocity during impact loading, the entropy increase of the gradient material is small during loading, so the influence of temperature on the target material can be ignored. Since the first layer of the material is Al, which has a certain density, the impact velocity jumps instantaneously to around 240 m / s. Subsequently, due to the propagation of the shock wave from low impedance (low density) to high impedance (high density) within the flyer, the shock wave is reflected and acts on the target material, which is macroscopically manifested as a continuous increase in the impact velocity, eventually reaching a peak velocity of 300 m / s. The peak velocity is determined by the last layer material, namely Ag. This is a characteristic of controllable loading functionally graded materials.

[0053] Comparative Example 1

[0054] The specific process is the same as in Example 1, except that the sintering process is as follows: the temperature is 560℃ and the pressure is 100MPa. First, the temperature is raised to 300℃ and paused for 30 minutes. Then, the pressure is raised to 100MPa and the temperature is raised to 560℃ and held for 2 hours.

[0055] Table 1 shows the density and apparent porosity of the products obtained under different sintering regimes. The sintering temperature is 570-580℃. This temperature ensures good bonding of the gradient composite material, guarantees the molding shape of the material, and prevents melting and precipitation due to excessive temperature exceeding the liquidus line, which would damage the overall integrity of the material. Materials prepared at temperatures below this range have low densification. For example, at 560℃, the bonding between materials is merely interlocking between particles, resulting in incomplete sintering and the appearance of pores. If the temperature is too high, although the densification is high, the overall integrity of the material is damaged due to melting and precipitation. Therefore, a sintering temperature of 570-580℃ is chosen to achieve a tighter bond and lower porosity.

[0056] Table 1. Density and apparent porosity under different sintering regimes

[0057]

[0058] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An Al-Ag controllable loading functionally graded composite material, characterized in that, The gradient composite material consists of 10-15 layers, with a wave impedance distribution index of 2-3; wherein: From the first layer to the last layer, the Al content gradually decreases from 100% to 0, while the Ag content gradually increases from 0 to 100%. Counting sequentially from the first layer to the last layer, the difference in Al content between adjacent layers first gradually increases from 0.14~0.17% to 20~21%, and then gradually decreases to 5~6%. In the gradient composite material, the thickness of the single layer of the middle layer is 100-200μm, and the thickness of the first layer and the last layer is increased by 200-300μm respectively based on the thickness of the single layer of the middle layer.

2. The gradient composite material according to claim 1, characterized in that, The total thickness of the gradient composite material is 2~3mm.

3. A method for preparing the Al-Ag controllable loading functionally graded composite material according to any one of claims 1-2, characterized in that, Includes the following steps: 1) Weigh out the powder according to the ratio of Al powder to Ag powder in each layer and mix them evenly; 2) First, take the last layer of powder and press it into shape. After pressing, take the second to last layer of composite powder and press it on the surface of the last layer. Repeat this process until the first layer of powder is pressed to obtain a pre-pressed sample. 3) The pre-pressed sample obtained in step 2) is pressed as a whole, and then sintered at 90~100MPa and 570~580℃ to obtain Al-Ag controllable loading functional gradient composite material. The sintering process is as follows: first, raise the temperature to 280~320℃ and hold for 25~40 minutes, then increase the pressure to 90~100MPa, and finally continue to raise the temperature to 570~580℃ and hold for 2~3 hours.

4. The preparation method according to claim 3, characterized in that, In step 2), during the pressing process, a layer of graphite paper or weighing paper is placed between the upper press head and the powder to avoid powder loss.

5. The preparation method according to claim 3, characterized in that, In step 2), the pressing process is: pressing at 10-20MPa for 1-2 minutes.

6. The preparation method according to claim 3, characterized in that, In step 3), the pressing process is as follows: pressure 10~20MPa, time 20~30min.

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