Method and apparatus for preparing aluminum matrix composite with high strength, high toughness, and high neutron absorption

Abstract

The present invention relates to an aluminum matrix composite (AMC), and particularly to a method and apparatus for preparing an AMC with a high strength, a high toughness, and a high neutron absorption. The present invention combines a high-neutron-absorption and highly stable micro-B.sub.4C extrinsic reinforcement with an in-situ nano-reinforcement containing elements B, Cd, and Hf and having high neutron capture ability, achieves efficient absorption of neutrons by using the large cross-sectional area of the micro-reinforcement, achieves effective capture of rays penetrating gaps of the micro-reinforcement by means of the highly dispersed in-situ nano-reinforcement, and significantly improves the toughness of the composite material by means of the high-dispersion toughening effect of the nano-reinforcement, obtaining a particle-reinforced aluminum matrix composite (PAMC) having high toughness and high neutron absorption.

Claims

1. A method for preparing an aluminum matrix composite (AMC), wherein through a siphon channel in a center of a melt surface generated by a radial magnetic field, a micro-B.sub.4C extrinsic ceramic reinforcement and an intermediate alloy or compound with one or more selected from the group consisting of B, Cd, Hf, Ti, and Zr are introduced into a melt, and a temperature and a pressure caused by cavitation and acoustic streaming generated through an ultrasonic field below a liquid surface of the siphon channel help to achieve infiltration and dispersion of the micro-B.sub.4C extrinsic ceramic reinforcement and promote generation of an in-situ nano-reinforcement from the intermediate alloy or compound with one or more selected from the group consisting of B, Cd, Hf, Ti, and Zr and uniform dispersion of the in-situ nano-reinforcement, such that the aluminum matrix composite reinforced by a cross-scale hybrid of the micro-B.sub.4C extrinsic ceramic reinforcement and the in-situ nano-reinforcement is prepared, wherein a micro-B.sub.4C powder of the micro-B.sub.4C extrinsic ceramic reinforcement comprises B.sub.4C microparticles with a B.sub.4C content of 98.8 wt % or more and an average particle size of 10 μm to 300 μm, and a volume fraction of the B.sub.4C microparticles in the AMC is 5 vol % to 30 vol %, and wherein the in-situ nano-reinforcement with one or more selected from the group consisting of B, Cd, Hf, Ti, and Zr comprises one or more selected from the group consisting of ZrB.sub.2, TiB.sub.2, CdB, and HfB.sub.2 that are generated by introducing different intermediate alloys or reactants in the melt for an in-situ reaction, the in-situ nano-reinforcement comprises in-situ nano-reinforcement particles with a particle size of 2 nm to 100 nm; and a volume fraction of the in-situ nano-reinforcement particles in the AMC is 0.2 vol % to 25 vol %, the method specifically comprises the following steps: step 1: melting a matrix aluminum alloy in a crucible of an integrated composite preparation apparatus at 850° C. to 950° C. to obtain a melt; step 2: turning on a radial magnetic field device and an ultrasonic device of the integrated composite preparation apparatus, and adding the intermediate alloy or compound with one or more selected from the group consisting of B, Cd, Hf, Ti, and Zr mixed in a predetermined ratio through a feed pipe to conduct a reaction for 20 min to 30 min, to generate the in-situ nano-reinforcement; and step 3: cooling the melt to 780° C. to 800° C., adding the B.sub.4C microparticles through the feed pipe, and applying the radial magnetic field and the ultrasonic field to promote infiltration and dispersion of the B.sub.4C microparticles in the composite melt; and stirring for 10 min to 30 min, cooling to 720° C. to 750° C., followed by casting.

2. The method according to claim 1, wherein the matrix aluminum alloy is heated by an electromagnetic induction heating device, and the radial magnetic field device and the ultrasonic device are used to promote synthesis of the in-situ nano-reinforcement particles and the infiltration and dispersion of the B.sub.4C microparticles.

3. The method according to claim 1, wherein the siphon channel in the center of the melt surface generated by the radial magnetic field is generated due to flow inside the melt caused by the radial magnetic field; and the radial magnetic field has a power of 80 kW to 160 kW and a current of 10 A to 100 A, and the siphon channel has a depth of 5 cm to 15 cm.

4. The method according to claim 1, wherein the ultrasonic field is generated by the ultrasonic device at a bottom of the integrated composite preparation apparatus, with an ultrasonic power of 5 kW to 20 kW; and an amplitude transformer has a length of 10 cm, and there is a distance of 8 cm to 15 cm between a top of the amplitude transformer and a bottom of the siphon channel, and the amplitude transformer is made of a niobium alloy.

5. The method according to claim 1, wherein the matrix aluminum alloy in the step 1 is selected from the group consisting of 2xxx, 5xxx, 6xxx, and 7xxx series aluminum matrices according to different uses of thermal conduction, electric conduction, high strength, low expansion, and wear resistance; and in the step 2, a feed speed of the feed pipe is controlled at 5 g/min to 50 g/min by a mechanical device.

6. The method according to claim 1, wherein the melting at 850° C. to 950° C. in the step 1 is adjusted according to a specific reaction system; the in-situ reaction is conducted for 20 min to 30 min to introduce the intermediate alloy or compound for forming the in-situ nano-reinforcement particles into the melt, and the in-situ reaction is accompanied by radial cyclic stirring, such that the in-situ nano-reinforcement is synthesized in-situ in the melt; the intermediate alloy or compound for forming the in-situ nano-reinforcement particles comprises one or more selected from the group consisting of Al—Zr, Al—Ti, Al—B, Al—Cd, Al—Hf, K.sub.2ZrF.sub.6, K.sub.2TiF.sub.6, KBF.sub.4, Na.sub.2B.sub.4O.sub.7, ZrO.sub.2, and B.sub.2O.sub.3; and the crucible is made of a heat-resistant die steel undergoing a surface passivation treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a structural schematic diagram of the integrated composite preparation apparatus that couples a radial magnetic field and an ultrasonic field according to the present invention, where 1 represents a feeder, 2 represents an air outlet, 3 represents an argon ventilation pipe, 4 represents an electromagnetic induction heating device, 5 represents a siphon channel, 6 represents a radial magnetic field device, 7 represents an ultrasonic device, 8 represents a melting furnace protective layer, and 9 represents a discharge port.

(2) FIG. 2 is a scanning electron microscopy (SEM) image of the (5 vol % B.sub.4C+1 vol % ZrB.sub.2)/Al composite prepared by the apparatus designed in the present invention.

DESCRIPTION OF THE EMBODIMENTS

(3) The present invention can be implemented according to the following examples, but is not limited to the following examples. These examples are used only to illustrate the present invention, but not to limit the scope of the present invention in any way. In the following examples, various processes and methods that are not described in detail are conventional methods known in the art.

Example 1

(4) K.sub.2ZrF.sub.6 and KBF.sub.4 were used as reactants and mixed in a chemical ratio enabling the production of 1 vol % ZrB.sub.2 nanoparticles, then ground, and dried at 200° C. for 2 h to obtain a mixed reactant powder. Pure aluminum was placed in a crucible and heated by an induction coil for melting, and after the temperature reached 870° C., the mixed reactant powder was added. A radial magnetic field device and an ultrasonic device were turned on with a radial magnetic field power of 120 kW, a current of 50 A, and an ultrasonic field power of 15 kW to conduct a reaction for 30 min. After a melt was cooled to 780° C. to 800° C., B.sub.4C particles with an average particle size of 20 μm were added at a speed of 20 g/min, and after a reaction was completed, a resulting melt was allowed to stand, then subjected to gas removal and slag removal, cooled to 720° C., and casted to finally obtain a (5 vol % B.sub.4C+1 vol % ZrB.sub.2)/Al composite. The composite had a tensile strength of 210 MPa, a yield strength of 120 MPa, and an elongation at break of 23.5%.

(5) FIG. 2 is an SEM image of the (5 vol % B.sub.4C+1 vol % ZrB.sub.2)/Al composite prepared by the apparatus designed in the present invention, and it can be seen from image that B.sub.4C particles enter the matrix and are uniformly dispersed.

Example 2

(6) Al—Hf and Al—B alloys were used as reactants, 6016 aluminum was used as a matrix, and a chemical composition enabling the production of 0.5 vol % HfB.sub.2 nanoparticles was adopted. 6016 aluminum was placed in a crucible and heated by an induction coil for melting, and after the temperature reached 870° C., the Al—Hf and Al—B alloys were added. A radial magnetic field device and an ultrasonic device were turned on with a radial magnetic field power of 110 kW, a current of 45 A, and an ultrasonic field power of 13 kW to conduct a reaction for 30 min. After a melt was cooled to 780° C. to 800° C., B.sub.4C particles with an average particle size of 15 μm were added at a speed of 20 g/min, and after a reaction was completed, a resulting melt was allowed to stand, then subjected to gas removal and slag removal, cooled to 720° C., and casted to finally obtain a (10 vol % B.sub.4C+0.5 vol % HfB.sub.2)/6016Al composite. The composite had a tensile strength of 380 MPa, a yield strength of 260 MPa, and an elongation at break of 16.5%.

Example 3

(7) Al—Ti and B.sub.2O.sub.3 alloys were used as reactants, 6082 aluminum was used as a matrix, and a chemical composition enabling the production of 0.3 vol % TiB.sub.2 nanoparticles was adopted. 6082 aluminum was placed in a crucible and heated by an induction coil for melting, and after the temperature reached 870° C., the Al—Ti and B.sub.2O.sub.3 alloys were added. A radial magnetic field device and an ultrasonic device were turned on with a radial magnetic field power of 110 kW, a current of 45 A, and an ultrasonic field power of 13 kW to conduct a reaction for 30 min. After a melt was cooled to 780° C. to 800° C., B.sub.4C particles with an average particle size of 10 μm were added at a speed of 20 g/min, and after a reaction was completed, a resulting melt was allowed to stand, then subjected to gas removal and slag removal, cooled to 720° C., and casted to finally obtain a (15 vol % B.sub.4C+0.3 vol % TiB.sub.2)/6082Al composite. The composite had a tensile strength of 396 MPa, a yield strength of 273 MPa, and an elongation at break of 12.3%.

Example 4

(8) Al—Cd and Al—B alloys were used as reactants, A356 aluminum was used as a matrix, and a chemical composition enabling the production of 0.5 vol % CdB nanoparticles was adopted. A356 aluminum was placed in a crucible and heated by an induction coil for melting, and after the temperature reached 870° C., the Al—Cd and Al—B alloys were added. A radial magnetic field device and an ultrasonic device were turned on with a radial magnetic field power of 110 kW, a current of 45 A, and an ultrasonic field power of 13 kW to conduct a reaction for 30 min. After a melt was cooled to 780° C. to 800° C., B.sub.4C particles with an average particle size of 15 μm were added at a speed of 20 g/min, and after a reaction was completed, a resulting melt was allowed to stand, then subjected to gas removal and slag removal, cooled to 720° C., and casted to finally obtain a (10 vol % B.sub.4C+0.5 vol % CdB)/A356 composite. The composite had a tensile strength of 310 MPa, a yield strength of 220 MPa, and an elongation at break of 7.5%.