Patent Application
20110247778
The invention relates to the technical field of novel composite material synthesis, in particular to a novel method of synthesizing particle reinforced metal matrix composite material by in-situ melt reaction in coupling electromagnetic field and ultrasonic field.
Particle reinforced metal matrix composite material has a wide application prospect in the fields of advanced electric and electronic devices, aviation spacecrafts, machine, bridge tunnel engineering, etc. because of its excellent mechanical properties and physical and chemical properties owing to its composite structure and has been one of research hotspots of metal matrix composite material in recent years. Presently, in-situ reaction synthesis method is the primary method of preparing particle reinforced metal matrix composite material, its principle is that alloying elements or compounds which can generate second phase are added in metal matrix melt to produce in situ particle reinforced composite material by generating particle phase by in-situ reaction with metal melt at a certain temperature. Because of in situ formation of particle phase, the composite prepared by the method has clean bonding interfaces between particles and metal matrix, good wettability and high bonding strength. However, the technique has a series of problems of difficult control of reaction process, easy growth even aggregation of particle phase, and uneven distribution.
External field can improve the thermodynamic and dynamic conditions of in-situ synthesis reaction to promote the in-situ reaction and simultaneously control over growth or segregated aggregation of particle phase. Therefore, in-situ synthesis of metal matrix composite material in external field gets more and more attention from researchers. Chinese patent CN 1676641A (Date of publication: 2005.10.5, Title: Magnetic chemical reaction in-situ synthesizing method for preparing metal matrix nano composite material) provides a synthesis method by in-situ magnetic-chemical reaction in magnetic field (stable magnetic field, alternating magnetic field and pulsed magnetic field), the method disclosed by the patent has excellent effect in fining reinforced particles. Chinese patent CN 1958816 (Date of publication: 2007.05.09, Title: technique for preparing composite material of aluminum based surface enhanced by in situ particle through powered ultrasonic method) provides a technique for preparing in situ particle reinforced (Al3Ti phase) aluminum based surface composite material through a powered ultrasonic method, causing reinforced phase to be distributed evenly in the surface layer of matrix and interfaces to be bonded better.
However, the effect of exerting single electromagnetic field or ultrasonic field on synthesizing particle reinforced composite material by in-situ reaction is unsatisfied. When exerting single magnetic filed, the action intensity of the magnetic field in metal decays exponentially due to insurmountable skin effect of the electromagnetic field in metal melt, and the effective depth of the electromagnetic field acting in the melt is limited, especially when employing a large-volume bath or an electromagnetic field with higher frequency, the difference of the effect of the electromagnetic field in the melt is significant, namely, the effect of the electromagnetic field in the melt shows severe nonuniformity, the effect of the electromagnetic field is weak in the central area and strong at the edge area. When exerting single ultrasonic filed, because ultrasonic wave is mechanical sparse-dense vibration wave which belongs to longitudinal wave, ultrasonic wave has obvious directivity, and meanwhile, the ultrasonic wave also decays seriously in metal melt, ultrasonic effect mainly concentrates in the cylindrical area under an amplitude transformer, namely, the effect of the ultrasonic field concentrates on the central area of the melt and is weak at the edge area of the melt.
In order to compensate the deficiencies of exerting single electromagnetic filed or ultrasonic field, the invention provides a novel method of in-situ synthesizing particle reinforced metal matrix composite material by coupling electromagnetic field and ultrasonic field.
An aspect of the invention is to provide a method of synthesizing in situ particle reinforced metal matrix composite material by melt reaction in coupling magnetic field and ultrasonic field, which is used for preparing high-performance in-situ particle reinforced metal matrix composite material.
The basic principle of the invention lies in simultaneously exerting magnetic field and high-energy ultrasonic field during synthesis of in-situ particle reinforced metal matrix composite material, utilizing magnetochemistry principle of magnetic field generating electromagnetic force, magnetization and eddy current induction heat in melt and sonochemistry principle of high-energy ultrasonic field generating ultrasonic cavitation and ultrasonic current impact to perform coupling during synthesizing the composite material so as to achieve the goals of controlling the distribution of particle phase, inhibiting the growth and aggregation of particles and changing the thermodynamic and dynamic conditions of in-situ synthesis reaction, thereby realizing the synthesis of the particle reinforced metal matrix composite material by coupling magnetochemistry of magnetic field and sonochemistry of high-energy ultrasonic filed. The principle of the method is described as follows by combining
Composite material melt 2 is synthesized in a bath (or melting pot) 1 made of thermal-insulating refractory material, a high-energy ultrasonic amplitude transformer 3 is inserted into the upper part of the bath (or melting pot), the melt undergoes ultrasonic treatment, a magnetic field 4 is exerted to the outer side of the bath (or melting pot). The magnetic field can be exerted in different modes according to preparation methods of the composite material and effects required. Therefore, the exerted magnetic field can be high-power pulse magnetic filed, high-frequency oscillating magnetic field or low-frequency alternating magnetic field.
The principle of coupling magnetic field and ultrasonic field is as follows:
(1) The exerted magnetic field 4 is high-power pulse magnetic filed, namely, high-power pulse magnetic filed is coupled with ultrasonic field. In the melt, the high-power pulse magnetic field generates a pulse electromagnetic force, a pulse magnetizing force and joule heat produced by induced current, which accelerates in-situ chemical reaction and disperses particle phase. However, the pulse magnetic filed decays in a certain extent in the metal melt, and under the effect of the magnetic field, the reaction is strong at the edge area of the melt and weak at the central area, so the magnetic field shall be coupled with the high-energy ultrasonic field which has powered supersonic generating cavitation effect and acoustic streaming impact in the melt, wherein the cavitation effect controls the aggregation of particles, and the acoustic streaming impact plays a role of stirring in micro area. Because the effect of ultrasonic field is strong at the central area and weak at the edge area, the magnetic field and the ultrasonic field just compensate for each other to accelerate in-situ reaction by coupling, achieving the goals of fast formation and dispersion of particle phase.
(2) The exerted magnetic field 4 can be high-frequency oscillating magnetic field which has skin effect in the melt and thus centrally acts on the edge of the melt and generates an electromagnetic force to particles in the composite material melt to control the aggregation of the particles. The ultrasonic field mainly acts on the middle area of the bath.
(3) The magnetic field 4 can be selected as low-frequency stirring magnetic field coupling with power ultrasonic field if the requirements on size and distribution of particles of the composite material are lower. Especially when the amount of metal to be treated is large enough to be in tons, because of the limitations of present high-frequency oscillating magnetic field and high-power pulse magnetic field, coupling low-power stirring magnetic field and high-energy ultrasonic field also can be adopted to obtain an ideal effect. The principle lies in high-energy ultrasonic field generating cavitation effect and acoustic streaming impact in the melt, wherein cavitation effect controls the aggregation of particles, and acoustic streaming impact plays a role of stirring in micro area; the exerted low-frequency stirring magnetic field 4 performs electromagnetic stirring to the whole bath, so the ultrasonic stirring effect is more obvious, and the local effect or concentrated effect of ultrasonic treatment can be controlled.
On the basis of the principle the invention has the following schemes:
A method of synthesizing metal matrix composite material by melt reaction in coupling magnetic field and ultrasonic field comprises: adjusting metal-base melt to the onset reaction temperature after refining, then adding reactant powder which generates reinforced particle phase by in-situ synthesis reaction with melt, simultaneously exerting magnetic field and high-energy ultrasonic field during the synthesis reaction, keeping the reacted melt stand until it is cooled to casting temperature after reaction, and casting.
In the method of the invention, said exerted field can be high-power pulse magnetic field, high-frequency oscillating magnetic field or low-frequency alternating magnetic field. The invention has the following three technical schemes according to different exerted magnetic fields:
(1) Coupling high-power pulse magnetic field and high-energy ultrasonic field
The range of electromagnetic parameters of high-power pulse magnetic field is as follows: pulse current frequency is 0.1 Hz-10 Hz, pulse current density is 1 KA/m2-10 KA/m2, charging voltage is 1 KV-20 kV, and central magnetic field intensity is 0.5-20T. Electromagnetic parameters can be selected according to the size of the melting pot and the type of the melt, and the effect is remarkable if pulse magnetic field intensity in the melt is over 1T.
The frequency of ultrasonic field is 10 kHz-30 kHz, and ultrasonic intensity is 0.5 kW/m2-60 kW/m2.
The specific steps comprise: adjusting metal-base melt to onset reaction temperature after refining, then adding reagent which generates particle phase by in-situ reaction with the melt, turning on magnetic field, inserting an ultrasonic amplitude transformer below liquid level about 5-6 mm after the magnetic field is stable, turning on an ultrasonic device, ultrasonic treatment time being 60 s-600 s, turning off the ultrasonic device after time out, turning off the magnetic field, keeping the melt stand until it is cooled to the casting temperature, and casting.
The method is especially suitable for preparing metal matrix composite material with small amount and having extremely high requirement for performance.
(2) Coupling high-frequency oscillating magnetic field and high-energy ultrasonic field
The range of electromagnetic parameters of high-frequency oscillating magnetic field is as follows: high-frequency reference wave frequency is 10 kHz-30 kHz, amplitude modulation oscillating wave frequency is 1 Hz-30 Hz, power range is 0-100 kW, electromagnetic parameters can be adjusted according to the amount and type of melt, bath and stirring intensity, higher reference wave frequency is adopted for aluminum-based or copper-based melt, lower reference wave frequency is suitable for Fe-based, Ni-based or Zn-based melt, oscillating wave frequency is determined by the condition of stirring melt and related to the structure of a reactor and the type of the metal melt, preferably there is no strong turbulence in the melt.
The frequency of ultrasonic field is 10 kHz-30 kHz, and ultrasonic intensity is 0.5 kW/m2-60 kW/m2.
The specific steps comprise: adjusting metal-base melt to the onset reaction temperature after refining, then adding reactant powder which generates reinforced particle phase by in-situ synthesis reaction with melt, turning on magnetic field, inserting an ultrasonic amplitude transformer below liquid level about 5-6 mm after the magnetic field is stable, turning on an ultrasonic device, ultrasonic treatment time being 60 s-600 s, turning off the ultrasonic device after time out, turning off the magnetic field, keeping the melt stand until it is cooled to the casting temperature, and casting.
(3) Coupling low-frequency alternating magnetic field and high-energy ultrasonic field The range of electromagnetic parameters of low-frequency alternating magnetic field is as follows: frequency is 0.1 Hz-60 Hz, working current is 1 A-10000 A, electromagnetic parameters can be adjusted according to the amount and type of melt, bath and stirring intensity, higher frequency is adopted for aluminum-based or copper-based melt, lower frequency is suitable for Fe-based, Ni-based or Zn-based melt.
The frequency of ultrasonic field is 10 kHz-30 kHz, and ultrasonic intensity is 0.5 kW/m2-60 kW/m2.
The specific steps comprise: adjusting metal-base melt to the onset reaction temperature after refining, then adding reactant powder which generates reinforced particle phase by in-situ synthesis reaction with melt, turning on magnetic field, inserting an ultrasonic amplitude transformer below liquid level about 5-6 mm after the magnetic field is stable, turning on an ultrasonic device, ultrasonic treatment time being 60 s-600 s, turning off the ultrasonic device after time out, turning off the magnetic field, keeping the melt stand until it is cooled to the casting temperature, and casting.
Additional remarks: low-frequency alternating magnetic field can be rotating stirring magnetic field or travelling wave stirring magnetic field within the above range of parameters, rotating stirring magnetic field is exerted on the side surface of the bath, or travelling wave magnetic field is exerted on the bottom of the bath, the both belong to the technical scheme of the invention.
The method can be used for small-batch production as well as large-scale industrial application.
The invention has the following advantages compared with the prior art:
(1) Because the composite material is synthesized by coupling magnetic field and ultrasonic field, the coupling of magnetic field and ultrasonic field causes particles to be finer and uniformly distributed;
(2) Ultrasonic wave oscillating stirring and electromagnetic stirring improve the dynamic conditions of synthesis, and particle phase fits with metal matrix interface better; and
(3) Magnetochemistry cooperates with sonochemistry to improve the thermodynamic conditions of in-situ reaction, which accelerates the in-situ reaction speed and controls the growth of particle phase.
Wherein, 1 is bath or melting pot made of thermal-insulating refractory material; 2 is composite material melt; 3 is ultrasonic amplitude transformer; 4 is magnetic field; and 5 is spray gun.
Raw material: metal matrix: pure Al; reaction salt: K2ZrF6+KBF4 power, refined deaerating agent and slag skimming agent.
The preparation comprises two steps:
(1) Melting metal and preparing powder:
Melting 50 g of pure Al in a 60 kW resistance furnace till the temperature raises to 900° C., and then carrying out deaeration and slag skimming Fully drying the reagents at 250° C.-300° C., in which K2ZrF6+KBF4 is ground into fine powder (particle size is less than 200 mesh) and packaged by an aluminum foil for use after weighing, and the weight of the added K2ZrF6+KBF4 powder being 20 percents of the weight of metal.
(2) Synthesizing composite material melt by in-situ reaction:
Refined metal liquid in accordance with reaction starting temperature (900° C.), compressing K2ZrF6+KBF4 into aluminum liquid in a melt pot by a bell jar, putting the melt pot into high-power pulse magnetic field, then turning on the high-power pulse magnetic field with charging voltage of 1 kV and pulse frequency of 1 Hz; next, inserting an ultrasonic amplitude transformer into the aluminum liquid by the depth of about 3 mm, turning on an ultrasonic device with ultrasonic field frequency of 20 kHz and ultrasonic intensity of 2 kW/m2, and ultrasonic treatment time being 5 minutes; after ultrasonic treatment, continually exerting high-frequency magnetic field for 3 minutes, then turning off magnetic field power, keeping the melt stand until temperature falls to 720° C., and casting the melt into a water-cooled copper mould with the diameter of 200 mm to obtain a composite material cast ingot.
Composite material melt has good fluidity, the obtained composite material casting billet has smooth outer surface, dense interior microstructure, and no defects of solidification structure such as porosity, shrinkage cavities, etc., and the size of particle is 0.2-0.6 nm (
Raw material: metal matrix: pure Al; reaction salt: K2ZrF6+KBF4 power, refined deaerating agent and slag skimming agent.
The preparation comprises two steps:
(1) Melting metal and preparing powder:
Melting 50 Kg of pure Al in a 60 kW resistance furnace till the temperature raises to 900° C., and then carrying out deaeration and slag skimming; fully drying the reagents at 250° C.-300° C., in which K2ZrF6+KBF4 is ground into fine powder (particle size is less than 200 mesh) and put into an injecting pot after weighing, and the weight of the added K2ZrF6+KBF4 powder being 20 percents of the weight of metal.
(2) Synthesizing composite material melt by in-situ reaction:
A device as shown in
Composite material melt has good fluidity, the obtained composite material casting billet has smooth outer surface, dense interior tissue, and no defects of loose and shrinkage cavities in frozen tissue, and the size of particle is 1-5 nm (
Raw material: metal matrix: pure Al; solid powder: industrial zirconium carbonate (Zr(CO3)2) power, refined deaerating agent and slag skimming agent.
The preparation comprises two steps:
(1) Melting metal and preparing powder:
Melting 50 Kg of pure Al in a 60 kW resistance furnace till the temperature raises to 900° C., and then carrying out deaeration and slag skimming; fully drying the reagents at 250° C.-300° C., in which (Zr(CO3)2) is ground into fine powder (particle size is less than 200 mesh) and put into an injecting pot, and the weight of the added (Zr(CO3)2) powder being 20 percents of the weight of metal.
(2) Synthesizing composite material melt by in-situ reaction:
Pouring refined metal liquid in accordance with requirement of reaction starting temperature (900° C.) into a thermal-insulated composite material bath 3 from a metal refining thermal-insulating furnace, spraying (Zr(CO3)2) powder into the bath by an Ar gas spray gun, turning on low-frequency stirring magnetic field with electromagnetic parameter of 10 kHz and current of 280 A; after spraying powder, inserting an ultrasonic amplitude transformer into the bath by the depth of about 5 mm, turning on an ultrasonic device with ultrasonic field frequency of 20 kHz and ultrasonic intensity of 10 kW/m2, and ultrasonic treatment time being 5 minutes; after ultrasonic treatment, continually stirring for 3 minutes, keeping the melt stand until temperature falls to 730° C., deslagging, and casting a composite round billet with diameter of 200 mm by semi-continuous casting at 720° C.
Composite material melt has good fluidity, the obtained composite material casting billet has smooth outer surface, dense interior tissue, and no defects of loose and shrinkage cavities in frozen tissue, the size of particle is 1-5 μm (
| Number | Date | Country | Kind |
|---|---|---|---|
| 200810234978.9 | Nov 2008 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN2009/000252 | 3/10/2009 | WO | 00 | 6/30/2011 |
