阅读说明：本技术 一种粉末预烧结加压发泡制备泡沫铝材料的方法 (Method for preparing foamed aluminum material by powder pre-sintering pressurization foaming ) 是由 曹卓坤 冮峰郡 于洋 郑兴璋 王加奇 于 2021-03-05 设计创作，主要内容包括：一种粉末预烧结加压发泡制备泡沫铝材料的方法,按以下步骤进行：(1)将TiH-2通过振动筛筛分生成TiH-2粉；(2)加热至410～530℃保温,获得预热发泡剂粉；(3)将发泡剂粉、镁粉和硅粉加入到铝粉中,然后球磨混合至少8h；(4)混合粉料置于坩埚中,用加热炉升温至400～500℃保温预烧结；将预烧结物料填充至模具中冷压；(5)将发泡模具预热至700～720℃,放入预制体,然后置于然650～670℃的加热炉中；(6)加热炉密封通入氩气,至压力0.2～0.5MPa进行发泡,随炉冷却后取出脱模。本发明的方法有效的改善泡沫铝材料的泡孔结构、泡孔大小与泡孔均匀度,进而改善泡沫铝材料的品质。(A method for preparing foamed aluminum material by powder presintering and pressurizing foaming comprises the following steps: (1) mix TiH 2 Production of TiH by screening with vibrating screen 2 Pulverizing; (2) heating to 410-530 ℃ and preserving heat to obtain preheated foaming agent powder; (3) adding foaming agent powder, magnesium powder and silicon powder into the aluminum powder, and then performing ball milling and mixing for at least 8 hours; (4) placing the mixed powder in a crucible, heating the mixed powder to 400-500 ℃ by using a heating furnace, and carrying out heat preservation and pre-sintering; filling the pre-sintered material into a die for cold pressing; (5) preheating a foaming mold to 700-720 ℃, putting the foaming mold into a prefabricated body, and then putting the prefabricated body into a heating furnace at 650-670 ℃; (6) and introducing argon gas into the heating furnace in a sealed manner until the pressure is 0.2-0.5 MPa, foaming, cooling along with the furnace, taking out and demolding. The method effectively improves the cell structure, the cell size and the cell uniformity of the foamed aluminum material, thereby improving the quality of the foamed aluminum material.)

1. The method for preparing the foamed aluminum material by powder pre-sintering and pressurizing foaming is characterized by comprising the following steps of:

(1) mix TiH₂Separating out a part with the particle size of 72-74 mu m as TiH by a vibrating screen screening mode₂Pulverizing;

(2) mix TiH₂Heating the powder to 410-530 ℃ by using a heating furnace, then preserving heat for 40-50 min, and cooling to normal temperature along with the furnace to obtain preheated foaming agent powder;

(3) adding foaming agent powder, magnesium powder and silicon powder into aluminum powder, and then performing ball milling and mixing for at least 8 hours to prepare mixed powder; wherein the foaming agent powder accounts for 0.8-1.4% of the mass of the aluminum powder, the magnesium powder accounts for 0.6-1% of the mass of the aluminum powder, and the silicon powder accounts for 10-11.6% of the mass of the aluminum powder; the granularity of the aluminum powder is 400-500 meshes, the granularity of the magnesium powder is 500-600 meshes, and the particle size of the silicon powder is 18-20 mu m;

(4) placing the mixed powder into a crucible, placing the crucible into a heating furnace, heating to 400-500 ℃, then preserving heat for 40-50 min for presintering, directly filling the obtained presintering material into a mold at 400-500 ℃, cold pressing under the pressure of 400-450 MPa for 10-20 min, and then demolding to obtain a preform;

(5) preheating a foaming mold to 700-720 ℃, and placing the prefabricated body in the preheated foaming mold; then placing the foaming mold with the prefabricated body into a heating furnace heated to 650-670 ℃;

(6) and sealing the heating furnace, introducing argon into the heating furnace through an air inlet of the heating furnace until the pressure in the heating furnace is 0.2-0.5 MPa, foaming for 8-12 min under the condition, cooling to normal temperature along with the furnace, taking out the foaming mold, and demolding to obtain the foamed aluminum material.

2. The method for preparing foamed aluminum material by powder pre-sintering and pressure foaming as claimed in claim 1, wherein the foamed aluminum material has an apparent density of 0.2-0.32 g/cm³。

3. The method for preparing the foamed aluminum material by powder pre-sintering and pressure foaming according to claim 1, wherein the foamed aluminum material has a porosity of 68-96%.

4. The method for preparing foamed aluminum material by powder presintering and pressure foaming as claimed in claim 1, wherein in step (6), the expansion rate of the foamed aluminum material is 266-390%.

5. The method for preparing foamed aluminum material by powder pre-sintering and pressure foaming according to claim 1, wherein in the step (5), the side wall of the foaming mold is cylindrical, the material is stainless steel, and the wall thickness is 2-3 mm; a plurality of air holes with the diameter of 1-2 mm are uniformly formed in the side wall.

Technical Field

The invention belongs to the technical field of porous metal materials, and particularly relates to a method for preparing a foamed aluminum material by powder pre-sintering and pressurizing foaming.

Background

The preparation method of the foamed aluminum mainly comprises a melt foaming method and a powder metallurgy method, and is recorded in the text of research progress on preparing the closed-cell foamed aluminum by the powder metallurgy foaming method, the melt foaming method is to directly add a thickening agent and a foaming agent into a metal melt, the foaming agent is decomposed by heat to generate gas to prepare the closed-cell foamed aluminum, and the product quality is easily influenced by environmental factors and is not easy to prepare a foamed aluminum part with a complex structure. The traditional powder metallurgy method for preparing the foamed aluminum material is to prepare a prefabricated body by hot pressing and then heat and foam in a resistance furnace, but the foamed aluminum prepared by the method has the disadvantages of uneven structure, low comprehensive performance, complex and unstable production process.

Disclosure of Invention

The invention aims to provide a method for preparing foamed aluminum material by powder pre-sintering and pressurizing foaming, which comprises the steps of pre-sintering a powder raw material, preparing a prefabricated body by cold pressing, and finally pressurizing and foaming to prepare the foamed aluminum material with uniform pore diameter and excellent performance.

The method of the invention is carried out according to the following steps:

1. mix TiH₂Separating out a part with the particle size of 72-74 mu m as TiH by a vibrating screen screening mode₂Pulverizing;

2. mix TiH₂Heating the powder to 410-530 ℃ by using a heating furnace, then preserving heat for 40-50 min, and cooling to normal temperature along with the furnace to obtain preheated foaming agent powder;

3. adding foaming agent powder, magnesium powder and silicon powder into aluminum powder, and then performing ball milling and mixing for at least 8 hours to prepare mixed powder; wherein the foaming agent powder accounts for 0.8-1.4% of the mass of the aluminum powder, the magnesium powder accounts for 0.6-1% of the mass of the aluminum powder, and the silicon powder accounts for 10-11.6% of the mass of the aluminum powder; the granularity of the aluminum powder is 400-500 meshes, the granularity of the magnesium powder is 500-600 meshes, and the particle size of the silicon powder is 18-20 mu m;

4. placing the mixed powder into a crucible, placing the crucible into a heating furnace, heating to 400-500 ℃, then preserving heat for 40-50 min for presintering, directly filling the obtained presintering material into a mold at 400-500 ℃, cold pressing under the pressure of 400-450 MPa for 10-20 min, and then demolding to obtain a preform;

5. preheating a foaming mold to 700-720 ℃, and placing the prefabricated body in the preheated foaming mold; then placing the foaming mold with the prefabricated body into a heating furnace heated to 650-670 ℃;

6. and sealing the heating furnace, introducing argon into the heating furnace through an air inlet of the heating furnace until the pressure in the heating furnace is 0.2-0.5 MPa, foaming for 8-12 min under the condition, cooling to normal temperature along with the furnace, taking out the foaming mold, and demolding to obtain the foamed aluminum material.

The foamed aluminum material has an apparent density of 0.2 to 0.32g/cm³。

The foamed aluminum material has a porosity of 68-96%.

In the step 6, the expansion rate of the foamed aluminum material is 266-390%.

In the step 5, the side wall of the foaming mold is cylindrical, the material is stainless steel, and the wall thickness is 2-3 mm; a plurality of air holes with the diameter of 1-2 mm are uniformly formed in the side wall.

In the above step 2, TiH is added₂The purpose of powder heating and heat preservation is to enable a titanium dioxide oxidation layer to be generated on the surface of the titanium hydride, so that the effect of delaying hydrogen release is achieved, and the temperature of the gas released by the titanium hydride during foaming in the step 4 is more matched with the melting temperature of the preform.

In the step 3, the pre-sintered material is directly filled into the die at 400-500 ℃, so that the metallurgical bonding is enhanced, and the compactness of the pressed preform is better.

In the step 5, the foaming mold is preheated to 700-720 ℃, and the prefabricated part is placed in the preheated foaming mold; then placing the foaming mold with the prefabricated body into a heating furnace heated to 650-670 ℃; the aim is that when the prefabricated body is arranged in a foaming mould, the melting point of the prefabricated body is reduced to below 600 ℃ due to the fact that silicon is contained in the prefabricated body, the prefabricated body is heated fully at a high mould temperature and is melted quickly, the prefabricated body is transferred into a heating furnace with a low temperature, hydrogen is not released too fast by titanium hydride at the low temperature, the melting temperature of the prefabricated body is enabled to be matched with the peak time of hydrogen release better, and the foaming effect is enabled to be better.

The invention has the beneficial effects that: the pre-sintering of the mixed material can improve the bonding degree of metal bonds among aluminum particles, the particles can be coated on the surface of titanium hydride through the sintered material, the primary metallurgical bonding among powder is realized, higher density is obtained, and aluminum ash on the surface generates an aluminum oxide layer, so that the loss of hydrogen before metal melting in the subsequent expansion process is slowed down, the phenomenon that micro-cracking holes exist in a pressed blank caused by cold pressing is avoided, and the phenomenon that the pressed blank is cracked and cannot be foamed during foaming is avoided; because the small titanium hydride particles are aggregated due to mixing, the presintering is to connect the oxide layers among the titanium hydride particles, so that the oxide layer is thickened, and the release of hydrogen is further delayed; the presintered material is pressed at high temperature, so that metallurgical bonding can be enhanced, and the foamed aluminum preform can obtain higher density, thereby slowing down the release of oxygen before metal melting in the subsequent expansion process and reducing the loss of hydrogen; in the foaming process, the argon is introduced to cause the increase of air pressure (the argon has low activity at high temperature, can reduce the activity of gas in a heating furnace and is relatively safe under the high-temperature operation condition), so that the decomposition delay of the foaming agent can be ensured, the temperature of a prefabricated body during melting is better matched, the bubble merging phenomenon of the foamed aluminum is weakened, the size of the bubble hole of the foamed aluminum depends on the foaming pressure, and the foaming height is not influenced; along with the increase of the air pressure, the foam aluminum material foaming process can be stabilized, the cell structure, the cell size, the cell uniformity and the like of the foam aluminum material are effectively improved, the uniformity, the consistency and the stability of the foam aluminum gas cells can be greatly improved, the quality of the foam aluminum material is further improved, and products with different porosities and different properties can be selectively prepared by adjusting the conditions such as the pressure and the like; after a foaming mold is preheated at a high temperature, the prefabricated body is placed, the melting point of the prefabricated body is about 590 ℃ because the prefabricated body contains silicon, the prefabricated body can be quickly melted at a higher mold temperature, and hydrogen can not be quickly released by titanium hydride in a heating furnace with a lower temperature, so that the titanium hydride can better fit with the peak time of hydrogen release, and the foaming effect is better; when the foaming mould adopted the stainless steel thin wall material, can make heat-conduction more abundant, make in the mould temperature more agree with furnace actual temperature, realize good foaming effect, when the mould outer wall was equipped with the gas pocket, can guarantee not only at foam aluminium upper portion atress when the pressurization foaming, foam aluminium also has the pressure effect all around, and the pressurization effect is exerted on foam aluminium wholly, realizes better foaming effect.

Drawings

FIG. 1 is a photographic image showing the appearance of a foamed aluminum material of comparative example 1 of the present invention;

FIG. 2 is a photographic view showing the external appearance of the foamed aluminum material of example 1 of the present invention;

FIG. 3 is a photograph showing the appearance of the foamed aluminum material of example 2 of the present invention;

FIG. 4 is a photographic view showing the appearance of the foamed aluminum material of example 3 of the present invention;

FIG. 5 is a photographic view showing the external appearance of the foamed aluminum material of example 4 of the present invention;

FIG. 6 is a photographic image showing the appearance of the foamed aluminum material of comparative example 2 of the present invention;

FIG. 7 is a graph showing the pore size distribution of the foamed aluminum material of example 1 of the present invention;

FIG. 8 is a graph showing the pore size distribution of the foamed aluminum material of example 2 of the present invention;

FIG. 9 is a graph showing the pore size distribution of the foamed aluminum material of example 3 of the present invention;

FIG. 10 is a graph showing the pore size distribution of the aluminum foam material of example 4 of the present invention;

FIG. 11 is a stress-strain curve of the foamed aluminum material of example 1 of the present invention;

FIG. 12 is a stress-strain curve of the foamed aluminum material of example 2 of the present invention;

FIG. 13 is a stress-strain curve of the foamed aluminum material of example 3 of the present invention;

FIG. 14 is a stress-strain diagram of the foamed aluminum material of example 4 of the present invention.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to the following examples.

The purity of the aluminum powder adopted in the embodiment of the invention is more than or equal to 99.5%.

The purity of the silicon powder adopted in the embodiment of the invention is more than or equal to 99.5%.

The purity of the magnesium powder adopted in the embodiment of the invention is more than or equal to 99.5%.

When the presintering material is filled into the die in the embodiment of the invention, the die is coated with high-temperature-resistant lubricating oil on the inner wall in advance, and then the presintering material is put into the die through a funnel.

In the embodiment of the invention, a press is adopted for cold pressing.

In the embodiment of the invention, when cold pressing is carried out, the pressing speed is adjusted to be 1mm/min, when the pressure reaches a set value, the pressing speed is 0, and pressure maintaining is started; and closing the press machine after the pressure maintaining is finished, and taking out the die for demolding.

In the embodiment of the invention, before the foaming mold is preheated, the release agent is sprayed on the inner wall of the foaming mold in advance.

When foaming is carried out in the embodiment of the invention, the heating furnace is provided with the quartz observation window, and the height of the material in the die is observed by the laser range finder.

In the examples of the present invention, when the preform diameter is 50mm, the inner diameter of the foaming mold is 55 mm.

In the embodiment of the invention, the height of the prefabricated body is H1, and the height of the foamed aluminum material after foaming is H2, (H2-H1)/H1 = expansion rate.

In the embodiment of the invention, the side wall of the foaming mold is cylindrical, the material is stainless steel, and the wall thickness is 2-3 mm; a plurality of air holes with the diameter of 1-2 mm are uniformly formed in the side wall.

In the embodiment of the invention, step 2 is to mix TiH₂The purpose of powder heating and heat preservation is to enable a titanium dioxide oxidation layer to be generated on the surface of the titanium hydride, so that the effect of delaying hydrogen release is achieved, and the temperature of the gas released by the titanium hydride during foaming in the step 4 is more matched with the melting temperature of the preform.

In the embodiment of the invention, the pre-sintered material is directly filled into the die at 400-500 ℃, so that the metallurgical bonding is enhanced, and the compactness of the pressed preform is better.

In the embodiment of the invention, a foaming mold is preheated to 700-720 ℃, and a prefabricated body is placed in the preheated foaming mold; then placing the foaming mold with the prefabricated body into a heating furnace heated to 650-670 ℃; the aim is that when the prefabricated body is arranged in a foaming mould, the melting point of the prefabricated body is reduced to below 600 ℃ due to the fact that silicon is contained in the prefabricated body, the prefabricated body is heated fully at a high mould temperature and is melted quickly, the prefabricated body is transferred into a heating furnace with a low temperature, hydrogen is not released too fast by titanium hydride at the low temperature, the melting temperature of the prefabricated body is enabled to be matched with the peak time of hydrogen release better, and the foaming effect is enabled to be better.

Example 1

Mix TiH₂Separating out a part with the particle size of 72-74 mu m as TiH by a vibrating screen screening mode₂Pulverizing;

mix TiH₂Heating the powder to 410 ℃ by using a heating furnace, then preserving heat for 50min, and cooling to normal temperature along with the furnace to obtain preheated foaming agent powder;

adding foaming agent powder, magnesium powder and silicon powder into aluminum powder, and then carrying out ball milling and mixing for 8 hours to prepare mixed powder; wherein the foaming agent powder accounts for 0.8 percent of the mass of the aluminum powder, the magnesium powder accounts for 0.6 percent of the mass of the aluminum powder, and the silicon powder accounts for 10 percent of the mass of the aluminum powder; the particle size of the magnesium powder is 500-600 meshes, the particle size of the silicon powder is 18-20 mu m, and the particle size of the aluminum powder is 400-500 meshes;

placing the mixed powder into a crucible, placing the crucible into a heating furnace, heating to 400 ℃, then preserving heat for 50min for presintering, directly filling the obtained presintering material into a mold at 400 ℃, cold-pressing under the pressure of 450MPa, keeping the pressure for 10min, and then demolding to obtain a preform;

preheating a foaming mold to 720 ℃, and placing the prefabricated body in the preheated foaming mold; then placing the foaming mould with the prefabricated body into a heating furnace which is heated to 670 ℃;

sealing the heating furnace, introducing argon gas into the heating furnace through an air inlet of the heating furnace until the pressure in the heating furnace is 0.2MPa, foaming for 12min, cooling to normal temperature along with the furnace, taking out the foaming mold, and demolding to obtain the foamed aluminum material with the apparent density of 0.201g/cm³Porosity 79.3%, and expansion of foamed aluminum material 389.6%;

the foamed aluminum material is wire-cut into cylinders of phi 30 x 30mm, the appearance is shown in fig. 2, the pore size distribution curve is shown in fig. 7, and the stress-strain curve is shown in fig. 11.

Example 2

The method is the same as example 1, except that:

(1) mix TiH₂Heating the powder to 530 ℃ by using a heating furnace, and then preserving heat for 40 min;

(2) ball milling and mixing for 9 h; the foaming agent powder accounts for 1 percent of the mass of the aluminum powder, the magnesium powder accounts for 0.8 percent of the mass of the aluminum powder, and the silicon powder accounts for 10.5 percent of the mass of the aluminum powder;

(3) preserving heat for 40min at 500 ℃ for pre-sintering;

(4) directly filling the pre-sintered material into a mold at 500 ℃, and carrying out cold pressing under the pressure of 400MPa for 20 min;

(5) preheating a foaming mold to 700 ℃, and putting the foaming mold with the preform into a heating furnace heated to 650 ℃;

(6) introducing argon until the pressure in the heating furnace is 0.3MPa, and foaming for 11 min; foamed aluminum material having an apparent density of 0.226g/cm³The porosity is 77.4 percent, and the expansion rate of the foamed aluminum material is 385.4 percent;

the foamed aluminum material is wire-cut into cylinders of phi 30 x 30mm, the appearance is shown in fig. 3, the pore size distribution curve is shown in fig. 8, and the stress-strain curve is shown in fig. 12.

Example 3

The method is the same as example 1, except that:

(1) mix TiH₂Heating the powder to 450 ℃ by using a heating furnace, and then preserving the heat for 45 min;

(2) ball milling and mixing for 10 h; the foaming agent powder accounts for 1.2 percent of the mass of the aluminum powder, the magnesium powder accounts for 0.9 percent of the mass of the aluminum powder, and the silicon powder accounts for 11 percent of the mass of the aluminum powder;

(3) preserving heat at 450 ℃ for 45min for pre-sintering;

(4) directly filling the pre-sintered material into a mould at 450 ℃, and carrying out cold pressing under the pressure of 430MPa for 15 min;

(5) preheating a foaming mold to 710 ℃, and putting the foaming mold with the prefabricated body into a heating furnace which is heated to 66 ℃;

(6) introducing argon until the pressure in the heating furnace is 0.4MPa, and foaming for 10 min; foamed aluminum materialHas an apparent density of 0.255g/cm³Porosity of 74.5%, and expansion rate of 333.3%;

the foamed aluminum material was wire-cut into cylinders of 30X 30mm in diameter, and the appearance was as shown in FIG. 4, the pore size distribution curve was as shown in FIG. 9, and the stress-strain curve was as shown in FIG. 13.

Example 4

The method is the same as example 1, except that:

(1) mix TiH₂Heating the powder to 470 ℃ by using a heating furnace, and then preserving the heat for 45 min;

(2) ball milling and mixing for 11 h; the foaming agent powder accounts for 1.4 percent of the mass of the aluminum powder, the magnesium powder accounts for 1 percent of the mass of the aluminum powder, and the silicon powder accounts for 11.6 percent of the mass of the aluminum powder;

(3) preserving heat at 450 ℃ for 45min for pre-sintering;

(4) directly filling the pre-sintered material into a mould at 450 ℃, and carrying out cold pressing under the pressure of 430MPa for 15 min;

(5) preheating a foaming mold to 710 ℃, and putting the foaming mold with the prefabricated body into a heating furnace which is heated to 66 ℃;

(6) introducing argon until the pressure in the heating furnace is 0.5MPa, and foaming for 8 min; foamed aluminum material having an apparent density of 0.32g/cm³The porosity is 68 percent, and the expansion rate of the foamed aluminum material is 266.7 percent;

the foamed aluminum material is wire-cut into cylinders of phi 30 x 30mm, the appearance is shown in fig. 5, the pore size distribution curve is shown in fig. 10, and the stress-strain curve is shown in fig. 14.

Comparative example 1

The method is the same as example 1, except that:

sealing the heating furnace, and introducing no argon gas, wherein the air pressure in the heating furnace is 0.1 MPa; foamed aluminum material has an apparent density of 0.047g/cm³The porosity is 96.3 percent, and the expansion rate of the foamed aluminum material is 372.5 percent;

cutting the foamed aluminum material wire into a cylinder, wherein the appearance is shown in figure 1; the cells coalesce more because they are not pressurized during foaming.

Comparative example 2

The method is the same as example 1, except that:

the mixed powder is directly cold-pressed without pre-sintering; the expansion rate of the foamed aluminum material is 210%;

cutting the foamed aluminum material wire into a cylinder, wherein the appearance is shown in figure 6; because the pre-sintering is not carried out, the foaming height is obviously shorter than the foaming height of the foamed aluminum of the preheated material, and the observation of the pore structure shows that the pore diameter is not uniform, the phenomenon of cell combination occurs, and the foaming quality is poor.