PREPARATION METHOD FOR MAGNESIUM MATRIX COMPOSITE

Abstract

The invention relates to a preparation method for a magnesium matrix composite. The preparation method comprises the following steps: (1) preparing magnesium ingots as raw materials and salt flux and reinforcements; (2) placing the salt flux in a crucible, performing heating to prepare salt flux melts, adding the reinforcements; (3) performing pouring into a normal-temperature crucible, and performing cooling to obtain precursors; (4) adding the raw materials in an iron crucible, and performing melting at 953K-1043K; (5) placing the precursors in raw material melt, after stirring, under a condition of 953K-993K, performing standing so that scum and melt are obtained; and (6) removing the scum, lowering temperature to 973K-982K, and performing casting. The method provided by the present invention is simple in process and low in cost. The method can be used for preparing bulk structural members of the magnesium matrix composite, and can be used for automatic production.

Claims

1. A preparation method for a magnesium matrix composite, comprising: (1) preparing magnesium ingots as raw materials; preparing salt flux and reinforcements, wherein the salt flux is a mixture of barium chloride, magnesium chloride, sodium chloride and calcium chloride, the barium chloride accounts for 35-50% of a total mass of the salt flux, the magnesium chloride accounts for 10-20% of a total mass of the salt flux, the sodium chloride accounts for 10-20% of a total mass of the salt flux, a balance is the calcium chloride and impurities, the impurities account for no more than 1% of the total mass of the salt flux, the reinforcements are elementary metal, rare earth oxides, carbides, borides or metal oxides, the elementary metal is W, Mo or Ni, the rare earth oxides are La.sub.2O.sub.3, CeO.sub.2 or Y.sub.2O.sub.3, the carbides are TiC or SiC, the borides are ZrB.sub.2, the metal oxides are MgO or SiO.sub.2, the reinforcements are 0.1%-30% of a total volume of the raw materials, and the reinforcements are 1%-50% of a total volume of the salt flux; (2) placing the salt flux in a clay crucible or a graphite crucible, performing heating to 773K-923K to prepare salt flux melts, placing the reinforcements in the salt flux melts, and performing stirring until the reinforcements are uniformly dispersed to prepare a liquid-solid mixture; (3) pouring the liquid-solid mixture into a normal-temperature clay crucible or graphite crucible, and performing cooling to normal temperature to obtain precursors; (4) preheating an iron crucible until a body of the iron crucible is in a dark red heat, then placing the raw materials in the iron crucible, and performing melting on the raw materials at 953K-1043K to form a raw material melt; (5) placing the precursors in the raw material melt of 953K-1043K, performing stirring until the precursors are dispersed uniformly, under a condition of 953-993K, adding refining agents, performing stirring for refining, after the refining is finished, controlling temperature to 1013K-1023K, and performing standing so that impurity components are separated from composite components, and scum and a composite melt are obtained; (6) removing the scum from a surface of the composite melt, then cooling the composite melt to 973-982K, and performing casting to form the magnesium matrix composite.

2. The preparation method according to claim 1, wherein a purity of the magnesium ingots is greater than or equal to 99.85%.

3. The preparation method according to claim 1, wherein the reinforcements are fibers, particles or whiskers, wherein a particle size of the particles is 300 nm-20 μm, a diameter of the whiskers is 0.1 μm-1 μm, a length is 10 μm-100 μm, a diameter of the fibers is 5 μm-20 μm, and a continuous length is 10 mm-70 mm.

4. The preparation method according to claim 1, wherein in the step (2), a stirring rate is 100 r/min-200 r/min, and a time is 2 min-10 min.

5. The preparation method according to claim 1, wherein in the step (5), a stirring rate is 100 r/min-300 r/min, and a time is 5 min-15 min.

6. The preparation method according to claim 1, wherein in the step (5), a standing time is 10 min-30 min.

7. The preparation method according to claim 1, further comprising in the step (1): preparing the magnesium ingots and other metal components as the raw materials; when the step (4) is performed, placing the magnesium ingots and the other metal components in the iron crucible jointly, performing melting, and preforming stirring and uniform mixing to form a raw material melt, wherein the other metal components are one or more of aluminum ingots, zinc ingots, manganese chloride, magnesium-rare earth alloys, magnesium-zirconium alloys and magnesium-silicon alloys, and aluminum, zinc, manganese, rare earth, zirconium and silicon in the other metal components account for no more than 10% of a total mass of the raw materials.

8. The preparation method according to claim 1, further comprising in the step (4): enabling covering flux to be scattered onto a surface of the raw material melt so as to prevent magnesium from burning, wherein the covering flux is No. 2 flux; when the step (5) is performed, mixing the covering flux with the scum; and when the step (6) is performed, removing the covering flux and the scum together.

9. The preparation method according to claim 1, wherein in the step (5), the refining agents are the No. 2 flux.

10. The preparation method according to claim 1, wherein raw material components in the magnesium matrix composite account for 80-99.9% of a total volume, and components of the reinforcements account for 0.1-20% of the total volume.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 is an SEM diagram of a lanthanum oxide reinforced magnesium matrix composite in the embodiment 1 of the present invention; in the figure, (b) is the partial enlarged view of (a);

[0032] FIG. 2 is an XRD diagram of the lanthanum oxide reinforced magnesium matrix composite in the embodiment 1 of the present invention; in the figure, (a) is the diffraction peaks of La.sub.2O.sub.3, and (b) is the diffraction peaks of magnesium matrix composite;

[0033] FIG. 3 is an SEM diagram of cerium dioxide reinforced magnesium matrix composite in the embodiment 2 of the present invention; in the figure, (b) is the partial enlarged view of (a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] A detailed description of the preparation method is given below in combination with the embodiments of the present invention.

[0035] In the embodiments of the present invention, temperature is measured with a thermocouple to ensure the measurement accuracy of the temperature.

[0036] The purity of an aluminum ingot and a zinc ingot in the present invention is 98.9%-99.9%.

[0037] Manganese chloride in the present invention is technical pure.

[0038] Magnesium-rare earth alloys, magnesium-zirconium alloys and magnesium-silicon alloys in the present invention are collectively referred to as master alloys, and rare earth, zirconium and silicon in the master alloys account for 10%-40% of the total mass of the master alloys separately.

[0039] The aluminum ingot, the reinforcements and No. 2 flux adopted in the embodiments of the present invention are products purchased on the market.

[0040] Barium chloride, magnesium chloride, sodium chloride and calcium chloride adopted in the embodiments of the present invention are industrial grade products purchased by commercial.

[0041] An electron microscope adopted in the embodiments of the present invention is Shimadzu SSX550.

[0042] X-ray diffraction observation equipment in the embodiments of the present invention is PANalytical B. V. X pertpro.

[0043] The mass percentage of the reinforcements of the magnesium matrix composite in the embodiments of the present invention is analyzed and calculated by using an X-ray fluorescence spectrum, and then converted into volume percentage.

[0044] The purity of the magnesium ingot in the embodiments of the present invention is greater than or equal to 99.85%.

[0045] The reinforcements in the embodiments of the present invention are fibers, particles or whiskers, wherein the particle size of the particles is 300 nm-20 μm; the diameter of the whiskers is 0.1 μm-1 μm, and the length is 10 μm-100 μm; and the diameter of the fibers is 5 μm-20 μm, and the continuous length is 10 mm-70 mm.

[0046] Before refining in the embodiments of the present invention, materials in the iron crucible are degassed by using mixed gas, and the mixed gas is formed by mixing components in percentage by volume of 0.2%-0.3% of sulfur hexafluoride, 25%-50% of carbon dioxide and balance air, and inflation time of the mixed gas is 2 min-5 min.

[0047] The adding quantity of refining agents in the embodiments of the present invention is 0.5%-0.8% of the total mass of all melts in the iron crucible.

Embodiment 1

[0048] A magnesium ingot is prepared as raw materials; salt flux and reinforcements are prepared; the salt flux is a mixture of barium chloride, magnesium chloride, sodium chloride and calcium chloride, wherein the barium chloride accounts for 45% of the total mass of the salt flux; the magnesium chloride accounts for 20% of the total mass of the salt flux, and the sodium chloride accounts for 15% of the total mass of the salt flux; the balance is the calcium chloride and impurities, and the impurities account for no more than 1% of the total mass of the salt flux; the reinforcements are rare earth oxides, namely La.sub.2O.sub.3 particles; the reinforcements account for 0.5% of the total volume of the raw materials; the reinforcements account for 3% of the total volume of the salt flux;

[0049] The salt flux is placed in a clay crucible, and heated to 803K to form salt flux melts; the reinforcements are added to the salt flux melts, and uniformly dispersed by stirring to form a liquid-solid mixture; the stirring rate is 100 r/min, and the stirring time is 10 min; when the reinforcements are added to the salt flux melts, all the reinforcements are added in three times, and the adding amount each time accounts for less than 50% of the total mass of the reinforcements;

[0050] The liquid-solid mixture is poured into the normal-temperature clay crucible, and cooled to normal temperature to obtain precursors;

[0051] An iron crucible is preheated until the body of the iron crucible is in a dark red heat, then the raw materials are placed in the iron crucible, and melting is performed on the raw materials at 973K to form a raw material melt; the covering flux is scattered onto the surface of the raw material melt, and used for preventing the magnesium from burning, and the covering flux is the No. 2 flux;

[0052] Firstly, the precursors are crushed into particles with the particle size of no more than 5 cm, then placed in the raw material melt of 973K, and stirred until the precursors are dispersed uniformly; next, refining agents are added at 973K, and stirred for refining; the refining agents are the No. 2 flux, the stirring rate is 100 r/min, the stirring time is 15 min, and the temperature rises to 1013K after completion of refining; the precursors stand so that impurity components are separated from composite components to obtain scum and a composite melt; the standing time is 30 min;

[0053] The scum is removed from the surface of the composite melt, and then the composite melt is cooled to 973K, and cast to form the magnesium matrix composite; and the reinforcement components in the magnesium matrix composite account for 0.41% of the total volume, and the balance is the raw material components.

[0054] The SEM diagram of the magnesium matrix composite (lanthanum oxide reinforced magnesium matrix composite) is shown as FIG. 1, the XRD diagram is shown as FIG. 2, and as shown in the figures, La.sub.2O.sub.3 phases are uniformly distributed in the matrix.

[0055] Under the same conditions, the quantity of the reinforcements is regulated for parallel test, and the reinforcements are respectively 1%, 3%, 5%, 7%, 9%, 15% and 20% of the total volume of the raw materials; and in the lanthanum oxide reinforced magnesium matrix composite which is formed finally, 80%-90% of the total mass of the reinforcements are reserved in the matrix.

Embodiment 2

[0056] The method is the same as that in the embodiment 1, the differences include:

[0057] (1) In salt flux, barium chloride accounts for 50% of the total weight of the salt flux, magnesium chloride accounts for 10% of the total weight of the salt flux, and sodium chloride accounts for 20% of the total weight of the salt flux;

[0058] (2) Reinforcements are rare-earth oxides, namely CeO.sub.2 particles;

[0059] (3) The reinforcements are 1% of the total volume of raw materials, and are 5% of the total volume of the salt flux;

[0060] (4) The salt flux is placed in a graphite crucible, and heated to 773K to form salt flux melts; the stirring rate is 200 r/min, and the stirring time is 2 min; when the reinforcements are added to the salt flux melts, all the reinforcements are added in four times;

[0061] (5) A liquid-solid mixture is poured into the normal-temperature graphite crucible;

[0062] (6) Raw materials in the iron crucible are molten at 953K to form raw material melt;

[0063] (7) Precursors are placed in the raw material melt at 953K after being crushed, refining agents are added at 953K, and stirred for refining, the stirring rate is 300 r/min, the stirring time is 5 min, the temperature rises to 1023K after completion of refining, and the standing time is 10 min;

[0064] (8) The composite melt is cooled to 982K, and cast to form the magnesium matrix composite; and the reinforcement components in the magnesium matrix composite account for 0.85% of the total volume, and the balance is the raw material components.

[0065] The SEM diagram of the magnesium matrix composite (lanthanum oxide reinforced magnesium matrix composite) is shown as FIG. 3, and CeO.sub.2 phases are uniformly distributed in the matrix.

Embodiment 3

[0066] The method is the same as that in the embodiment 1, the differences include:

[0067] (1) Magnesium ingots and other metal components are prepared as the raw materials, wherein the other metal components are aluminum ingots and account for 5% of the total mass of the raw materials; in salt flux, barium chloride accounts for 35% of the total weight of the salt flux, magnesium chloride accounts for 15% of the total weight of the salt flux, and sodium chloride accounts for 10% of the total weight of the salt flux;

[0068] (2) Reinforcements are borides namely ZrB.sub.2;

[0069] (3) The reinforcements are 10% of the total volume of raw materials, and are 15% of the total volume of the salt flux;

[0070] (4) The salt flux is placed in a graphite crucible, and heated to 883K to form salt flux melts; the stirring rate is 150 r/min, and the stirring time is 5 min; when the reinforcements are added to the salt flux melts, all the reinforcements are added in five times;

[0071] (5) A liquid-solid mixture is poured into the normal-temperature graphite crucible;

[0072] (6) The magnesium ingots and other metal components are placed in the iron crucible together, and the raw materials in the iron crucible are molten at 1043K to form raw material melt;

[0073] (7) Precursors are placed in the raw material melt at 1043K after being crushed, refining agents are added at 1043K, and stirred for refining, the stirring rate is 200 r/min, the stirring time is 10 min, the temperature is cooled to 1013K after completion of refining, and the standing time is 20 min;

[0074] (8) The composite melt is cooled to 978K, and cast to form the magnesium matrix composite; and the reinforcement components in the magnesium matrix composite account for 8.1% of the total volume, and the balance is the raw material components.

Embodiment 4

[0075] The method is the same as that in the embodiment 1, the differences include:

[0076] (1) Magnesium ingots and other metal components are prepared as the raw materials, wherein the other metal components are zinc ingots and account for 2% of the total mass of the raw materials;

[0077] (2) Reinforcements are elementary metal W;

[0078] (3) The reinforcements are 15% of the total volume of raw materials, and are 25% of the total volume of the salt flux;

[0079] (4) The salt flux is placed in a graphite crucible, and heated to 923K to form salt flux melts, the stirring rate is 120 r/min, and the stirring time is 8 min;

[0080] (5) A liquid-solid mixture is poured into the normal-temperature graphite crucible;

[0081] (6) The magnesium ingots and other metal components are placed in the iron crucible together, and the raw materials in the iron crucible are molten at 1043K to form raw material melt;

[0082] (7) Precursors are placed in the raw material melt at 1043K after being crushed, refining agents are added at 1043K, and stirred for refining, the temperature is cooled to 1018K after completion of refining, and the standing time is 15 min;

[0083] (8) The composite melt is cooled to 980K, and cast to form the magnesium matrix composite; and the reinforcement components in the magnesium matrix composite account for 13.3% of the total volume, and the balance is the raw material components.

Embodiment 5

[0084] The method is the same as that in the embodiment 1, the differences include:

[0085] (1) Magnesium ingots and other metal components are prepared as the raw materials, wherein the other metal components are magnesium-rare earth alloys and account for 4% of the total mass of the raw materials; in salt flux, barium chloride accounts for 40% of the total weight of the salt flux, magnesium chloride accounts for 20% of the total weight of the salt flux, and sodium chloride accounts for 20% of the total weight of the salt flux;

[0086] (2) Reinforcements are carbides namely TiC;

[0087] (3) The reinforcements are 22% of the total volume of raw materials, and are 40% of the total volume of the salt flux;

[0088] (4) The salt flux is placed in a graphite crucible, and heated to 828K to form salt flux melts; the stirring rate is 180 r/min, and the stirring time is 3 min; when the reinforcements are added to the salt flux melts, all the reinforcements are added in four times;

[0089] (5) A liquid-solid mixture is poured into the normal-temperature graphite crucible;

[0090] (6) The magnesium ingots and other metal components are placed in the iron crucible together, and the raw materials in the iron crucible are molten at 988K to form raw material melt;

[0091] (7) Precursors are placed in the raw material melt at 988K after being crushed, refining agents are added at 988K, and stirred for refining, the stirring rate is 300 r/min, the stirring time is 5 min, the temperature rises to 1023K after completion of refining, and the standing time is 25 min;

[0092] (8) The composite melt is cooled to 979K, and cast to form the magnesium matrix composite; and the reinforcement components in the magnesium matrix composite account for 18.6% of the total volume, and the balance is the raw material components.

Embodiment 6

[0093] The method is the same as that in the embodiment 1, the differences include:

[0094] (1) Magnesium ingots and other metal components are prepared as the raw materials, wherein the other metal components are magnesium-zirconium alloys and magnesium-silicon alloys, and zirconium and silicon account for 10% of the total mass of the raw materials; in salt flux, barium chloride accounts for 50% of the total weight of the salt flux, magnesium chloride accounts for 10% of the total weight of the salt flux, and sodium chloride accounts for 10% of the total weight of the salt flux;

[0095] (2) Reinforcements are metal oxides namely SiO.sub.2;

[0096] (3) The reinforcements are 26% of the total volume of raw materials, and are 45% of the total volume of the salt flux;

[0097] (4) Heating is performed to 873K to form salt flux melts, the stirring rate is 160 r/min, the stirring time is 4 min, and when the reinforcements are added to the salt flux melts, all the reinforcements are added in five times;

[0098] (5) The magnesium ingots and other metal components are placed in the iron crucible together, and the raw materials in the iron crucible are molten at 993K to form raw material melt;

[0099] (6) Precursors are placed in the raw material melt at 993K after being crushed, refining agents are added at 993K, and stirred for refining, the stirring rate is 200 r/min, the stirring time is 10 min, the temperature rises to 1013K after completion of refining, and the standing time is 25 min;

[0100] (7) The composite melt is cooled to 976K, and cast to form the magnesium matrix composite; and the reinforcement components in the magnesium matrix composite account for 21.1% of the total volume, and the balance is the raw material components.