阅读说明：本技术 基于三向约束变形的高体积分数SiC纳米线增强铝基复合材料致密化装置及方法 (High-volume-fraction SiC nanowire reinforced aluminum matrix composite densification device and method based on three-dimensional constrained deformation ) 是由 周畅 武高辉 肖云臻 杨文澍 周勇孝 吴翌铭 于 2019-11-27 设计创作，主要内容包括：基于三向约束变形的高体积分数SiC纳米线增强铝基复合材料致密化装置及方法,涉及一种SiC纳米线/Al复合材料致密化装置及方法。目的是解决高SiC<Sub>nw</Sub>含量的SiC纳米线增强铝基复合材料热挤压后易开裂和高温挤压后存在不良反应的问题。装置由模具、模具底板、上压头、下压头和约束体构成。约束体具有圆柱形空腔。方法：组装装置并将铝基复合材料置于圆柱形空腔内,预热后施加压力。本发明方法及模具进行致密化处理时复合材料处于三向压应力下,致密化的同时避免铝基复合材料的开裂。铝基复合材料强度、致密度和延伸率提高。本发明适用于铝基复合材料的致密化。(A device and a method for densifying a high-volume-fraction SiC nanowire reinforced aluminum matrix composite based on three-dimensional constrained deformation relate to a device and a method for densifying a SiC nanowire/Al composite. Aims to solve the problem of high SiC nw The SiC nanowire reinforced aluminum matrix composite material with the content is easy to crack after hot extrusion and has adverse reaction after high-temperature extrusion. The device consists of a die, a die bottom plate, an upper pressure head, a lower pressure head and a restraint body. The constraining body has a cylindrical cavity. The method comprises the following steps: assembling the device, placing the aluminum matrix composite material in the cylindrical cavity, and applying pressure after preheating. The method and the die of the invention are used for densification treatment of the composite material in three directionsUnder the action of force, densification is carried out while cracking of the aluminum matrix composite material is avoided. The aluminum matrix composite material has high strength, compactness and elongation. The invention is suitable for densification of the aluminum matrix composite material.)

1. A high volume fraction SiC nanowire reinforcing aluminum matrix composite densification device based on three-dimensional restraint deformation, its characterized in that: the device consists of a die (1), a die bottom plate (2), an upper pressure head (3), a lower pressure head (4) and a restraint body;

the die (1) is a cylinder, the die (1) is arranged on the upper surface of the die bottom plate (2), and the upper pressing head (3), the restraint body and the lower pressing head (4) are stacked inside the die (1) from top to bottom; the upper pressure head (3) and the lower pressure head (4) are cylinders, a first cylindrical boss is arranged on the lower end face of the upper pressure head (3), and a second boss which is the same as the first boss in shape and size is arranged on the upper end face of the lower pressure head (4);

the restraining body is a cylinder, the outer circumferential surface of the restraining body is in clearance fit with the inner circumferential surface of the die (1), the restraining body is composed of two identical semi-restraining bodies (5), a circular blind hole is formed in the center of each semi-restraining body (5), and openings of the circular blind holes of the two semi-restraining bodies (5) are oppositely arranged to form a cylindrical cavity.

2. The high volume fraction SiC nanowire-reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation of claim 1, characterized in that: the bottom thickness of the circular blind hole in the semi-restraint body (5) is 2-5 mm.

3. The high volume fraction SiC nanowire-reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation of claim 1, characterized in that: the die (1) is connected with the die base plate (2) through a bolt, the die base plate (2) is provided with a through hole, a threaded hole is formed in the inner lower end face of the side wall of the die (1), and the bolt penetrates through the through hole of the die base plate (2) and is screwed into the threaded hole in the side wall of the die (1).

4. The high volume fraction SiC nanowire-reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation of claim 1, characterized in that: the outer circumferential surface of the upper pressure head (3) is in clearance fit with the inner circumferential surface of the die (1), and the outer circumferential surface of the lower pressure head (4) is in clearance fit with the inner circumferential surface of the die (1).

5. The high volume fraction SiC nanowire-reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation of claim 1, characterized in that: the length-diameter ratio of a cylindrical cavity arranged in the center of the restraint body is (0.5-0.1): 1. the ratio of the diameter of the cylindrical cavity arranged in the center of the restraint body to the diameter of the first boss in the upper pressure head (3) is (1.5-1.1): 1, and the ratio of the inner diameter of the die (1) to the diameter of the first boss is (1.6-1.2): 1.

6. The high volume fraction SiC nanowire-reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation of claim 1, characterized in that: the die is made of stainless steel, heat-resistant alloy steel, high-temperature alloy or graphite.

7. The method for densifying the composite material by using the high-volume-fraction SiC nanowire-reinforced aluminum-based composite material densification device based on three-way constrained deformation as claimed in claim 1, wherein: the method comprises the following steps:

one, assembly

Taking an aluminum-based composite material which has the same shape and size as a cylindrical cavity in the center of the restraint body, placing the aluminum-based composite material in the cylindrical cavity, and then assembling the die (1), the die bottom plate (2), the upper pressure head (3), the lower pressure head (4) and the restraint body to form a prefabricated member;

the aluminum matrix composite material is prepared from a matrix and SiC nanowires;

the material of the restraint body is the same as that of the matrix in the aluminum matrix composite material;

secondly, preheating

Heating the prefabricated member to be 30-50 ℃ below the melting point of a matrix in the aluminum matrix composite material, and preserving heat for 0.5-3 h;

thirdly, densification treatment

And applying pressure to the upper pressure head (3) to perform densification treatment, thus completing the densification treatment.

8. The method of claim 7 for composite densification using a high volume fraction SiC nanowire reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation, wherein: step one, the base material in the aluminum-based composite material is aluminum or aluminum alloy; the aluminum alloy is aluminum-silicon alloy, aluminum-copper alloy, aluminum-magnesium alloy, aluminum-silicon-copper alloy, aluminum-copper-magnesium alloy, aluminum-zinc-magnesium-copper alloy, aluminum-silicon-copper-magnesium, aluminum-silicon-magnesium alloy, aluminum-lithium alloy or aluminum-beryllium alloy.

9. The method of claim 7 for composite densification using a high volume fraction SiC nanowire reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation, wherein: in the aluminum matrix composite material in the first step, the volume content of the SiC nanowires is 40-60%, the average diameter of the SiC nanowires is 50-500 nm, and the length-diameter ratio is 100-300.

10. The method of claim 7 for composite densification using a high volume fraction SiC nanowire reinforced aluminum matrix composite densification apparatus based on three-way constrained deformation, wherein: in the third step, when the upper pressing head (3) applies pressure to carry out densification treatment, the moving speed of the upper pressing head (3) relative to the lower pressing head (4) is 5-50 mm/min, and the displacement of the upper pressing head (3) relative to the lower pressing head (4) is 20-50% of the height of the restraint body.

Technical Field

The invention relates to a SiC nanowire/Al composite material densification device and method.

Background

In recent years, metal matrix composites with nanoreinforcements as the reinforcing phase exhibit very excellent properties, and have become the focus of research. Generally, when one of the three dimensions of the reinforcement is smaller than 100nm, the reinforcement can be called a nano reinforcement, and can be divided into a zero-dimensional (nanoparticle), a one-dimensional (nanowire) and a two-dimensional (nanosheet) reinforcement according to the size characteristics. Aluminum matrix composites have been an important research direction in the research of metal matrix composites, and among them, the research of aluminum matrix composites using SiC particles as reinforcement is the most intensive, because SiC has excellent mechanical properties at room temperature and high temperature and has a good interface bonding state with aluminum matrix. SiC_nwThe (silicon carbide nano-wire) as a one-dimensional nano reinforcement shows more outstanding strengthening efficiency in the aluminum matrix composite material than the traditional SiC particle, along with the SiC_nwThe preparation process is mature day by day, the preparation cost is reduced gradually, and people begin to use SiC more and more_nwPreparation of SiC instead of conventional SiC particles_nwa/Al composite material. Jindakosol et al prepared SiC by hot pressing sintering_nwSiC in an amount of 5-15 vol%_nwThe friction and wear performance of the/Al composite material is researched, and SiC is found_nwThe addition of (A) significantly reduces the friction coefficient and wear rate of the composite material. Wenshu Yang and Ronghua Dong et al prepared SiC with a volume fraction of 10-30% by pressure infiltration_nwAl composite material, the obtained composite material has no bad interface reaction, SiC_nwThe composite material is directionally arranged and shows excellent mechanical properties.

Currently, SiC_nwThe preparation method of the/Al composite material is comparedThe method mainly comprises a solid method and a liquid method, but the method has the problem of low density, and micro cavities in the composite material with low density can often become the source of crack initiation, so that the composite material is broken in advance, and the plasticity of the composite material is greatly reduced.

By hot extrusion of SiC_nwThe density of the composite material can be improved by treating the/Al composite material. But because of SiC_nwLimitation of the deformability of the Al composite, the hot-extrusion method being suitable only for SiC_nwThe composite material with the volume fraction below 40 percent cannot be applied to high SiC with the volume fraction of 40 to 60 percent_nwAluminum matrix composite material. High SiC with a volume fraction of 40-60%_nwThe aluminum matrix composite material with the content is particularly easy to crack during extrusion, and even if the temperature is increased to cause the aluminum matrix to approach the liquidus line, the cracking cannot be avoided. And the problems of coarse crystal grains, adverse reaction at an interface and the like exist at a higher extrusion temperature, and the inherent defect of uneven deformation also exists in extrusion. Therefore, how to achieve high volume fraction (40-60 vol.%) SiC_nwDensification of the/Al composite to fully develop SiC_nwThe difficulty of strengthening the effect.

Disclosure of Invention

The invention aims to solve the problem of high SiC_nwThe problem that the SiC nanowire reinforced aluminum matrix composite with high content is easy to crack after being hot extruded is solved, and a device and a method for densifying the high-volume-fraction SiC nanowire reinforced aluminum matrix composite based on three-dimensional constrained deformation are provided.

The high volume fraction SiC nanowire reinforced aluminum matrix composite densification device based on three-dimensional constrained deformation is composed of a mold, a mold bottom plate, an upper pressure head, a lower pressure head and a constraint body;

the die is a cylinder, the die is arranged on the upper surface of the die bottom plate, and the upper pressing head, the lower pressing head and the restraint body are stacked inside the die from top to bottom; the upper pressure head and the lower pressure head are cylinders, a first cylindrical boss is arranged on the lower end face of the upper pressure head, and a second boss which is the same as the first boss in shape and size is arranged on the upper end face of the lower pressure head;

the restraining body is a cylinder, the outer circumferential surface of the restraining body is in clearance fit with the inner circumferential surface of the die, the restraining body is composed of two identical semi-restraining bodies, a circular blind hole is formed in the center of each semi-restraining body, and openings of the circular blind holes of the two semi-restraining bodies are oppositely arranged to form a cylindrical cavity.

The method for performing composite material densification by using the high-volume-fraction SiC nanowire reinforced aluminum matrix composite material densification device based on three-dimensional constrained deformation comprises the following steps of:

one, assembly

Taking an aluminum-based composite material with the same shape and size as a cylindrical cavity in the center of the restraint body, placing the aluminum-based composite material in the cylindrical cavity, and then assembling the die, the die bottom plate, the upper pressure head, the lower pressure head and the restraint body to form a prefabricated member;

the material of the restraint body is the same as that of the matrix in the aluminum matrix composite material;

secondly, preheating

Heating the prefabricated member to be 30-50 ℃ below the melting point of a matrix in the aluminum matrix composite material, and preserving heat for 0.5-3 h;

thirdly, densification treatment

And applying pressure to the upper pressure head to perform densification treatment, thus completing the densification treatment.

The invention has the advantages that:

1. by adopting the method and the die of the invention to treat high volume fraction SiC_nwWhen the Al composite material is subjected to densification treatment, the aluminum composite material is in a three-dimensional compressive stress state, and the three-dimensional compressive stress refers to the axial downward compressive stress applied by an upper pressure head and the circumferential compressive stress applied by the side wall of the mold, the softness coefficient α of the aluminum composite material under the three-dimensional compressive stress can reach about 4, which is greater than that of other deformation treatment modes, the deformation capability is extremely high, and the aluminum composite material can be prevented from cracking while the aluminum composite material is densified.

2. After the densification treatment is carried out on the aluminum-based composite material by adopting the method and the die, the elongation of the aluminum-based composite material is improved by 100-200%; the compactness of the aluminum-based composite material is improved to 97-99% from lower than 90%; the yield strength of the aluminum-based composite material is improved from less than 300MPa to 450MPa, and the improvement is nearly 50%. Meanwhile, the aluminum matrix composite extends and paves around under the extrusion of the upper pressure head and the lower pressure head, so that the nanowires extend and pave along with the extrusion, and are distributed in a plane in two dimensions, thereby better playing the reinforcing effect of the nanowires and improving the strength of the aluminum matrix composite.

3. The densification method provided by the invention has simple principle, easy operation and certain universality, and can also be used for other reinforcements and matrixes or aluminum-based composite materials with low and medium volume fractions. The device and the restraint body are simple, the materials are conventional, the processing difficulty is almost avoided, and the cost is low.

Drawings

FIG. 1 is a schematic diagram of the densification apparatus of example 1;

FIG. 2 is a schematic structural view of a densification apparatus according to example 1, prior to densification after assembly, in which a is an aluminum matrix composite material prior to densification;

FIG. 3 is a schematic view of the densification apparatus of example 1 after densification, wherein a is an aluminum-based composite material after densification;

FIG. 4 is a photograph of the microstructure of the aluminum-based composite material before densification in example 1;

FIG. 5 is a photograph of the microstructure of the aluminum-based composite material after the densification treatment in example 1.

The specific implementation mode is as follows:

the technical scheme of the invention is not limited to the specific embodiments listed below, and any reasonable combination of the specific embodiments is included.