Method for manufacturing quasicrystal and alumina mixed particulate reinforced magnesium-based composite material

Abstract

A method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite, includes manufacturing a quasicrystal and alumina mixture particles reinforcement phase, including preparing raw materials for the quasicrystal and alumina mixture particles reinforcement phase including a pure magnesium ingot, a pure zinc ingot, a magnesium-yttrium alloy in which the content of yttrium is 25% by weight, and nanometer alumina particles, the elements having the following proportion by weight 40 parts of magnesium, 50-60 parts of zinc, 5-10 parts of yttrium and 8-20 parts of nanometer alumina particles of which the diameter is 20-30 nm, pretreating the metal raw materials, cutting the pure magnesium ingot, the pure zinc ingot and the magnesium-yttrium alloy into blocks, removing oxides attached on the surface of each metal block, placing the blocks into a resistance furnace to preheat at 180 C. to 200 C., and filtering out the absolute ethyl alcohol after standing, and drying.

Claims

1. A method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite, orderly comprising: manufacturing a quasicrystal and alumina mixture particles reinforcement phase, comprising preparing raw materials for manufacturing the quasicrystal and alumina mixture particles reinforcement phase comprising a pure magnesium ingot, a pure zinc ingot, a magnesium-yttrium alloy in which the content of yttrium is 25% by weight, and nanometer alumina particles, the elements having the following proportion by weight 40 parts of magnesium, 50-60 parts of zinc, 5-10 parts of yttrium and 8-20 parts of nanometer alumina particles of which the diameter is 20-30 nm; pretreating metal raw materials, cutting the pure magnesium ingot, the pure zinc ingot and the magnesium-yttrium alloy into metal blocks, removing oxides attached on a surface of each metal block, and placing the metal blocks into a resistance furnace to preheat and keep at 180 C. to 200 C. for 20 minutes to 30 minutes; pretreating the nanometer alumina particles, including putting the nanometer alumina particles into a beaker, adding absolute ethyl alcohol, placing the nanometer alumina particles in an ultrasonic cleaner to shock for 15 minutes to 20 minutes, and filtering out the absolute ethyl alcohol after standing, and drying in an oven at 590 C. to 610 C. for 5 to 8 minutes so as to completely evaporate the absolute ethyl alcohol where the ultrasonic cleaner has frequency of 20 KHz and power of 1000 W; flux-free smelting under a first shielding gas, including placing the pretreated pure magnesium ingot into a crucible of a melting furnace after the crucible is preheated to dark red, when the temperature of the crucible continues to rise to more than 400 C., continuously providing the first shielding gas to keep the subsequent smelting under protective atmosphere; homogenizing treating an alloy melt including, adding the pure zinc ingot after the pure magnesium ingot is completely melted at 700 C., stirring and homogenizing the alloy melt after the pure zinc ingot is completely melted to separate oxides from the melt and to remove impurities on the surface; continuously heating the alloy melt to 760 C., adding the magnesium-yttrium alloy, stirring to homogenize the alloy melt after the magnesium-yttrium alloy is completely melted; adding of the nanometer alumina particles including, cooling the alloy melt to 700 C., and coating the nanometer alumina particles with a magnesium foil pressed into the alloy melt and stirring for 3 minutes to get diffusion of the nanometer alumina particles in the alloy melt to be fully and uniformly; allowing to stand for 10 to 15 minutes after stirring, removing impurities and oxides on the surface; pouring the alloy melt into a metal mould preheated to 200 C. in advance and removing the quasicrystal and alumina mixture reinforcement phase after solidification; ball-milling the quasicrystal and alumina mixture reinforcement phase, including breaking the quasicrystal and alumina mixture reinforcement phase, adding alloy pieces into a planetary ball mill and milling the alloy pieces; and screening out particles having the size of 100 to 200 mesh using a stainless steel sieve to obtain the quasicrystal and alumina mixture particles reinforcement phase; manufacturing a particles reinforcement phase-magnesium alloy matrix melt mixture slurry, including preparing raw materials for smelting the magnesium alloy matrix comprising a pure magnesium ingot, a pure aluminum ingot, a pure zinc ingot, a magnesium-manganese alloy, a magnesium-silicon alloy and a magnesium-calcium alloy; the elements having the following proportion by weight 1000 parts of magnesium, 90 parts of aluminum, 10 parts of zinc, 1.5-5 parts of manganese, 0.5-1 part of silicon and 0.1-0.5 part of calcium; pretreating metal raw materials, including cutting the pure magnesium ingot, the pure aluminum ingot, the pure zinc ingot, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy into metal blocks, removing oxides attached on a surface of each metal block, and placing the raw materials into a resistance furnace to preheat and keep at 180 C. to 200 C. for 20 minutes to 30 minutes to remove moisture attached on the surface of each metal block; flux-free smelting under a second shielding gas, including placing the pure magnesium ingot and the pure aluminum ingot into a crucible and heating up to 700 C. to melt after the crucible is preheated to dark red, when the temperature rises to more than 400 C., continuously providing the second shielding gas to keep the subsequent smelting under protective atmosphere to prevent a magnesium alloy melt from oxidizing and burning; homogenizing treating of an alloy melt, including adding the preheated magnesium-manganese alloy at 700 C. after the metals are completely melted, adding the preheated pure zinc ingot sequentially at 700 C. after melting, stirring and homogenizing the alloy melt after melting to separate oxides from the melt and to remove impurities on the surface are removed, continuously heating up to 720 C., adding the preheated magnesium-silicon alloy and the preheated magnesium-calcium alloy, thereby obtaining a magnesium alloy matrix melt after melting, and stirring to homogenize the magnesium alloy matrix melt; coating the quasicrystal and the alumina mixture particles reinforcement phase using an aluminum foil and pressing the quasicrystal and the alumina mixture particles reinforcement phase into the magnesium alloy matrix melt, mixing the quasicrystal and alumina mixture particles reinforcement phase with the magnesium alloy matrix melt to be homogenous by staged variable speed stirring, thereby obtaining the particles reinforcement phase-magnesium alloy matrix melt mixture slurry where the weight ratio of the quasicrystal and alumina mixture particles reinforcement phase to the magnesium alloy matrix is (4-8):100; allowing the particles reinforcement phase-magnesium alloy matrix melt mixture slurry to stand for 10 to 15 minutes, so as to separate oxides from the melt, and to remove impurities on the surface; casting ingot by pouring and extrusion, including cooling the particles reinforcement phase-magnesium alloy matrix melt mixture slurry to 700 C. in a crucible of the smelting furnace; preheating a steel mould in an extruder to 180 C. 200 C.; opening a cover of the smelting furnace, and aligning the cover with a pouring gate of the mould of the extruder, and pouring until a cavity is filled; performing die closing and extrusion by the extruder under extrusion pressure of 100 MPa for 15 to 20 seconds; by the pressure of a punch of the extruder, the particles reinforcement phase-magnesium alloy matrix melt mixture slurry in the cavity of the mould generates high pressure solidification and plastic deformation under mechanical static pressure of 100 MPa, cooling the ingot and the mould to room temperature naturally; opening the mould, and pushing out the ingot using an ejector pin device protruding out from a base of the extruder, thereby obtaining the finished product of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite.

2. The method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite according to claim 1, wherein at least one of the first shielding gas and the second shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, and the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1, the mixture gas is introduced to a position of 1 cm-2 cm above a metal melt surface, the flow rate of the shielding gas is 1 L/min, the exhaust pressure is 0.2 MPa to 0.4 MPa.

3. The method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite according to claim 1, wherein the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are coated with an aluminum foil, and are pressed into the melt by a bell jar prior to stirring.

4. The method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite according to claim 1, wherein stirring in a first stage of the staged variable speed stirring is at the speed of 200 to 300 rpm/min for 5 to 10 minutes; in a second stage, stirring is at the speed of 1200 to 1500 rpm/min for 5 to 10 minutes, and then the speed is reduced to 800 to 1000 rpm/min and stirring is continuously conducted for 5 to 10 minutes; in a third stage, the stirring speed is increased to 1200 to 1500 rpm/min, stirring continuously for 10 to 20 minutes.

5. The method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite according to claim 1, wherein the quasicrystal and alumina mixture particles reinforced magnesium matrix composite comprises a quasicrystal and alumina mixture particles reinforcement phase and a magnesium alloy matrix, and the weight ratio of the quasicrystal and alumina mixture particles reinforcement phase to the magnesium alloy matrix is 6 to 100; the magnesium alloy matrix comprises by weight 1000 parts of magnesium, 90 parts of aluminum, 10 parts of zinc, 3 parts of manganese, 0.7 part of silicon and 0.3 part of calcium; the quasicrystal and alumina mixture particles reinforcement phase comprises by weight 40 parts of magnesium, 55 parts of zinc, 8 parts of yttrium and 14 parts of nanometer alumina particles of which the diameter is 25 nm; and the size of the quasicrystal and alumina mixture particles reinforcement phase is 150 mesh.

6. The method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite according to claim 1, wherein the quasicrystal and alumina mixture particles reinforced magnesium matrix composite has microstructure characteristics of -Mg solid solution, Mg.sub.17Al.sub.12 distributed in a fractured chain form, and the quasicrystal phase and alumina particles diffusively distributed at grain boundaries.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail hereinafter with reference to the drawings.

(2) FIG. 1 is a schematic view of extrusion casting mould device used to prepare the magnesium matrix composite in the present invention.

(3) FIG. 2 is a microstructure view of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite of the present invention.

(4) FIG. 3 is a shape appearance view of a tensile specimen fracture of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite of the present invention obtained by a scanning electron microscope.

(5) In FIG. 1, the punch is represented by 1; the cavity is represented by 2; the steel mould is represented by 3; the ejector pin device is represented by 4; the base of the extruder is represented by 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment One

(6) A method for manufacturing a magnesium matrix composite reinforced with quasicrystal and alumina mixture particles in the present invention, orderly comprises the following steps of:

(7) (1) manufacturing a quasicrystal and alumina mixture particles reinforcement phase:

(8) {circle around (1)} preparation of raw materials for manufacturing the quasicrystal and alumina mixture particles reinforcement phase: the raw materials are a pure magnesium ingot, a pure zinc ingot, a magnesium-yttrium alloy in which the content of yttrium is 25% by weight, and nanometer alumina particles; each of the elements has the following proportion by weight: 40 parts of magnesium, 50 parts of zinc, 5 parts of yttrium and 8 parts of nanometer alumina particles of which the diameter is 20 nm;

(9) {circle around (2)} pretreatment of the metal raw materials: the pure magnesium ingot, the pure zinc ingot and the magnesium-yttrium alloy are cut into blocks, oxides attached on the surface of each metal block are removed, and followed by being put into a resistance furnace to preheat and keep at 180 C. for 20 minutes, so as to remove moisture attached on the surface of each metal block;

(10) {circle around (3)} pretreatment of the nanometer alumina particles: the nanometer alumina particles are put into a beaker, absolute ethyl alcohol is added, and followed by being placed in an ultrasonic cleaner to shock for 15 minutes, the absolute ethyl alcohol is filtered out after standing, and then drying is conducted in an oven at 590 C. for 5 minutes so as to completely evaporate the absolute ethyl alcohol; the ultrasonic cleaner has frequency of 20 KHz and power of 1000 W;

(11) {circle around (4)} flux-free smelting under a shielding gas: the pretreated pure magnesium ingot in step {circle around (2)} is put into a crucible of a melting furnace after the crucible is preheated to dark red, when the temperature of the crucible continues to rise to more than 400 C., the shielding gas is continuously provided to keep the subsequent smelting under protective atmosphere; the shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1; the mixture gas is introduced to a position of 1 cm above the metal melt surface, the flow rate of the shielding gas is 1 L/min, the exhaust pressure is 0.2 MPa.

(12) {circle around (5)} homogenizing treatment of an alloy melt: the pure zinc ingot is added after the pure magnesium ingot is completely melted at 700 C., the alloy melt is stirred to homogenize after the pure zinc ingot is completely melted, so as to separate oxides from the melt, and then impurities on the surface are removed; followed by continuously being heated up to 760 C., the magnesium-yttrium alloy is added, stirring is conducted to homogenize the alloy melt after the magnesium-yttrium alloy is completely melted;

(13) {circle around (6)} addition of the nanometer alumina particles: the alloy melt of step {circle around (5)} was stood to cool to 700 C., and then the nanometer alumina particles coated by a magnesium foil are pressed into the alloy melt and stirring is conducted for 3 minutes so as to get diffusion of the nanometer alumina particles in the alloy melt to be fully and uniformly; standing is performed for 10 minutes after stirring, and then impurities and oxides on the surface are removed;

(14) {circle around (7)} pouring: the alloy melt was poured into a metal mould preheated to 200 C. in advance and is taken out after solidification, thereby obtaining a quasicrystal and alumina mixture reinforcement phase;

(15) {circle around (8)} ball-milling of the quasicrystal and alumina mixture reinforcement phase: the resulting quasicrystal and alumina mixture reinforcement phase in step {circle around (7)} is physically broken, the alloy pieces are added into a planetary ball mill and are milled, and then particles having the size of 100 mesh are screened out using a stainless steel sieve, thereby obtaining the quasicrystal and alumina mixture particles reinforcement phase;

(16) (2) manufacturing a particles reinforcement phase-magnesium alloy matrix melt mixture slurry:

(17) {circle around (1)} preparation of raw materials for smelting the magnesium alloy matrix: the raw materials are a pure magnesium ingot, a pure aluminum ingot, a pure zinc ingot, a magnesium-manganese alloy, a magnesium-silicon alloy and a magnesium-calcium alloy; each of the elements has the following proportion by weight: 1000 parts of magnesium, 90 parts of aluminum, 10 parts of zinc, 1.5 parts of manganese, 0.5 part of silicon and 0.1 part of calcium;

(18) {circle around (2)} pretreatment of the metal raw materials: the pure magnesium ingot, the pure aluminum ingot, the pure zinc ingot, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are cut into blocks, oxides attached on the surface of each metal block are removed, and followed by being put into a resistance furnace to preheat and keep at 180 C. for 20 minutes, so as to remove moisture attached on the surface of each metal block;

(19) {circle around (3)} flux-free smelting under a shielding gas: the pure magnesium ingot and the pure aluminum ingot are put into a crucible and are heated up to 700 C. to melt after the crucible is preheated to dark red, when the temperature rises to more than 400 C., the shielding gas is continuously provided to keep the subsequent smelting under protective atmosphere, thereby preventing the magnesium alloy melt from oxidizing and burning; the shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, wherein the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1, the mixture gas is introduced to a position of 1 cm above the metal melt surface, flow rate of the mixture gas is 1 L/min and exhaust pressure is 0.2 MPa.

(20) {circle around (4)} homogenizing treatment of an alloy melt: the preheated magnesium-manganese alloy is added at 700 C. after the metals are completely melted, the preheated pure zinc ingot sequentially is added at 700 C. after melting, the alloy melt is stirred to homogenize after melting, so as to separate oxides from the melt, and then impurities on the surface are removed; followed by continuously being heated up to 720 C., the preheated magnesium-silicon alloy and the preheated magnesium-calcium alloy are added, thereby obtaining a magnesium alloy matrix melt after melting, and then stirring is conducted to homogenize the magnesium alloy matrix melt; when operating, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are coated with an aluminum foil, and are pressed into the melt by a bell jar, and then stirring is conducted, by which exposure can be avoided during adding to prevent them from generating serious oxidation loss, and by which loss of alloy elements caused by density difference can also avoided.

(21) {circle around (5)} the quasicrystal and the alumina mixture particles reinforcement phase in step (1) is coated using an aluminum foil and then is pressed into the magnesium alloy matrix melt, whereafter, the quasicrystal and alumina mixture particles reinforcement phase is mixed with the magnesium alloy matrix melt to be homogenous by staged variable speed stirring, thereby obtaining the particles reinforcement phase-magnesium alloy matrix melt mixture slurry; the weight ratio of the quasicrystal and alumina mixture particles reinforcement phase to the magnesium alloy matrix is 4:100. Stirring in the first stage of the staged variable speed stirring is conducted at the speed of 200 rpm/min for 5 minutes, a slow speed stirring can avoid lifting the melt level too quickly and can add the aluminum foil in which the mixture particles reinforcement phase is coated into a smelting furnace; in the second stage, firstly, a high speed stirring is conducted at a speed of 1200 rpm/min for 5 minutes, next, stirring speed is reduced to an intermediate speed, the intermediate speed stirring is continued at 800 rpm/min for 5 minutes, this moment, the melt level drops, a large enough vortex is formed on the surface thereof, and the particles reinforcement phase enters into the melt depending on negative pressure suction of the vortex; in the third stage, the stirring speed is increased again to 1200 rpm/min, and stirring is continuously conducted for 10 minutes to sufficiently disperse the particles reinforcement phase having entered the melt.

(22) {circle around (6)} the particles reinforcement phase-magnesium alloy matrix melt mixture slurry was allowed to stand for 10 minutes, so as to separate oxides from the melt, and then impurities on the surface are removed;

(23) (3) casting ingot by pouring and extrusion:

(24) {circle around (1)} the particles reinforcement phase-magnesium alloy matrix melt mixture slurry is cooled to 700 C. in the crucible of the smelting furnace;

(25) {circle around (2)} a steel mould 3 in an extruder is preheated to 180 C.;

(26) {circle around (3)} a cover of the smelting furnace is opened, followed by being aligned with a pouring gate of the mould of the extruder, and then pouring is conducted until the cavity 2 is filled;

(27) {circle around (4)} the extruder performs die closing and extrusion under extrusion pressure of 100 MPa for 15 seconds; by pressure of the punch 1 of the extruder, the particles reinforcement phase-magnesium alloy matrix melt mixture slurry in the cavity of the mould generates high pressure solidification and plastic deformation under mechanical static pressure of 100 MPa; the mould is opened after the ingot and the mould are cooled to room temperature naturally, as shown in FIG. 1, and then an ejector pin device 4 protrudes out from a base of the extruder 5 and pushes out the ingot, thereby obtaining the finished product of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite. The finished product has the microstructure characteristics of -Mg solid solution, Mg.sub.17Al.sub.12 distributed in a fractured chain form, and the quasicrystal phase and alumina particles diffusively distributed at grain boundaries.

Embodiment Two

(28) A method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite in the present invention, orderly comprises the following steps of:

(29) (1) manufacturing a quasicrystal and alumina mixture particles reinforcement phase:

(30) {circle around (1)} preparation of raw materials for manufacturing the quasicrystal and alumina mixture particles reinforcement phase: the raw materials are a pure magnesium ingot, a pure zinc ingot, a magnesium-yttrium alloy in which the content of yttrium is 25% by weight, and nanometer alumina particles; each of the elements has the following proportion by weight: 40 parts of magnesium, 55 parts of zinc, 8 parts of yttrium and 14 parts of nanometer alumina particles of which the diameter is 25 nm;

(31) {circle around (2)} pretreatment of the metal raw materials: the pure magnesium ingot, the pure zinc ingot and the magnesium-yttrium alloy are cut into blocks, oxides attached on the surface of each metal block are removed, and followed by being put into a resistance furnace to preheat and keep at 190 C. for 25 minutes, so as to remove moisture attached on the surface of each metal block;

(32) {circle around (3)} pretreatment of the nanometer alumina particles: the nanometer alumina particles are put into a beaker, absolute ethyl alcohol is added, and followed by being placed in an ultrasonic cleaner to shock for 18 minutes, the absolute ethyl alcohol is filtered out after standing, and then drying is conducted in an oven at 600 C. for 7 minutes so as to completely evaporate the absolute ethyl alcohol; the ultrasonic cleaner has frequency of 20 KHz and power of 1000 W;

(33) {circle around (4)} flux-free smelting under a shielding gas: the pretreated pure magnesium ingot in step {circle around (2)} is put into a crucible of a melting furnace after the crucible is preheated to dark red, when the temperature of the crucible continues to rise to more than 400 C., the shielding gas is continuously provided to keep the subsequent smelting under protective atmosphere; the shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1; the mixture gas is introduced to a position of 1.5 cm above the metal melt surface, the flow rate of the shielding gas is 1 L/min, the exhaust pressure is 0.3 MPa.

(34) {circle around (5)} homogenizing treatment of an alloy melt: the pure zinc ingot is added after the pure magnesium ingot is completely melted at 700 C., the alloy melt is stirred to homogenize after the pure zinc ingot is completely melted, so as to separate oxides from the melt, and then impurities on the surface are removed; followed by continuously being heated up to 760 C., the magnesium-yttrium alloy is added, stirring is conducted to homogenize the alloy melt after the magnesium-yttrium alloy is completely melted;

(35) {circle around (6)} addition of the nanometer alumina particles: the alloy melt of step {circle around (5)} was stood to cool to 700 C., and then the nanometer alumina particles coated by a magnesium foil are pressed into the alloy melt and stirring is conducted for 3 minutes so as to get diffusion of the nanometer alumina particles in the alloy melt to be fully and uniformly; standing is performed for 13 minutes after stirring, and then impurities and oxides on the surface are removed;

(36) {circle around (7)} pouring: the alloy melt was poured into a metal mould preheated to 200 C. in advance and is taken out after solidification, thereby obtaining a quasicrystal and alumina mixture reinforcement phase;

(37) {circle around (8)} ball-milling of the quasicrystal and alumina mixture reinforcement phase: the resulting quasicrystal and alumina mixture reinforcement phase in step {circle around (7)} is physically broken, the alloy pieces are added into a planetary ball mill and are milled, and then particles having the size of 150 mesh are screened out using a stainless steel sieve, thereby obtaining the quasicrystal and alumina mixture particles reinforcement phase;

(38) (2) manufacturing a particles reinforcement phase-magnesium alloy matrix melt mixture slurry:

(39) {circle around (1)} preparation of raw materials for smelting the magnesium alloy matrix: the raw materials are a pure magnesium ingot, a pure aluminum ingot, a pure zinc ingot, a magnesium-manganese alloy, a magnesium-silicon alloy and a magnesium-calcium alloy; each of the elements has the following proportion by weight: 1000 parts of magnesium, 90 parts of aluminum, 10 parts of zinc, 3 parts of manganese, 0.7 part of silicon and 0.3 part of calcium;

(40) {circle around (2)} pretreatment of the metal raw materials: the pure magnesium ingot, the pure aluminum ingot, the pure zinc ingot, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are cut into blocks, oxides attached on the surface of each metal block are removed, and followed by being put into a resistance furnace to preheat and keep at 190 C. for 25 minutes, so as to remove moisture attached on the surface of each metal block;

(41) {circle around (3)} flux-free smelting under a shielding gas: the pure magnesium ingot and the pure aluminum ingot are put into a crucible and are heated up to 700 C. to melt after the crucible is preheated to dark red, when the temperature rises to more than 400 C., the shielding gas is continuously provided to keep the subsequent smelting under protective atmosphere, thereby preventing the magnesium alloy melt from oxidizing and burning; the shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, wherein the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1, the mixture gas is introduced to a position of 1.5 cm above the metal melt surface, flow rate of the mixture gas is 1 L/min and exhaust pressure is 0.3 MPa.)

(42) {circle around (4)} homogenizing treatment of an alloy melt: the preheated magnesium-manganese alloy is added at 700 C. after the metals are completely melted, the preheated pure zinc ingot sequentially is added at 700 C. after melting, the alloy melt is stirred to homogenize after melting, so as to separate oxides from the melt, and then impurities on the surface are removed; followed by continuously being heated up to 720 C., the preheated magnesium-silicon alloy and the preheated magnesium-calcium alloy are added, thereby obtaining a magnesium alloy matrix melt after melting, and then stirring is conducted to homogenize the magnesium alloy matrix melt; when operating, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are coated with an aluminum foil, and are pressed into the melt by a bell jar, and then stirring is conducted, by which exposure can be avoided during adding to prevent them from generating serious oxidation loss, and by which loss of alloy elements caused by density difference can also avoided.

(43) {circle around (5)} the quasicrystal and the alumina mixture particles reinforcement phase in step (1) is coated using an aluminum foil and then is pressed into the magnesium alloy matrix melt, whereafter, the quasicrystal and alumina mixture particles reinforcement phase is mixed with the magnesium alloy matrix melt to be homogenous by staged variable speed stirring, thereby obtaining the particles reinforcement phase-magnesium alloy matrix melt mixture slurry; the weight ratio of the quasicrystal and alumina mixture particles reinforcement phase to the magnesium alloy matrix is 6:100. Stirring in the first stage of the staged variable speed stirring is conducted at the speed of 250 rpm/min for 8 minutes, a slow speed stirring can avoid lifting the melt level too quickly and can add the aluminum foil in which the mixture particles reinforcement phase is coated into a smelting furnace; in the second stage, firstly, a high speed stirring is conducted at a speed of 1300 rpm/min for 8 minutes, next, stirring speed is reduced to an intermediate speed, the intermediate speed stirring is continued at 900 rpm/min for 8 minutes, this moment, the melt level drops, a large enough vortex is formed on the surface thereof, and the particles reinforcement phase enters into the melt depending on negative pressure suction of the vortex; in the third stage, the stirring speed is increased again to 1300 rpm/min, and stirring is continuously conducted for 15 minutes to sufficiently disperse the particles reinforcement phase having entered the melt.

(44) {circle around (6)} the particles reinforcement phase-magnesium alloy matrix melt mixture slurry was allowed to stand for 13 minutes, so as to separate oxides from the melt, and then impurities on the surface are removed;

(45) (3) casting ingot by pouring and extrusion:

(46) {circle around (1)} the particles reinforcement phase-magnesium alloy matrix melt mixture slurry is cooled to 700 C. in the crucible of the smelting furnace;

(47) {circle around (2)} a steel mould 3 in an extruder is preheated to 190 C.;

(48) {circle around (3)} a cover of the smelting furnace is opened, followed by being aligned with a pouring gate of the mould of the extruder, and then pouring is conducted until the cavity 2 is filled;

(49) {circle around (4)} the extruder performs die closing and extrusion under extrusion pressure of 100 MPa for 18 seconds; by pressure of the punch 1 of the extruder, the particles reinforcement phase-magnesium alloy matrix melt mixture slurry in the cavity of the mould generates high pressure solidification and plastic deformation under mechanical static pressure of 100 MPa; the mould is opened after the ingot and the mould are cooled to room temperature naturally, as shown in FIG. 1, and then an ejector pin device 4 protrudes out from a base of the extruder 5 and pushes out the ingot, thereby obtaining the finished product of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite. The finished product has the microstructure characteristics of -Mg solid solution, Mg.sub.17Al.sub.12 distributed in a fractured chain form, and the quasicrystal phase and alumina particles diffusively distributed at grain boundaries.

Embodiment Three

(50) A method for manufacturing a quasicrystal and alumina mixture particles reinforced magnesium matrix composite in the present invention, orderly comprises the following steps of:

(51) (1) manufacturing a quasicrystal and alumina mixture particles reinforcement phase:

(52) {circle around (1)} preparation of raw materials for manufacturing the quasicrystal and alumina mixture particles reinforcement phase: the raw materials are a pure magnesium ingot, a pure zinc ingot, a magnesium-yttrium alloy in which the content of yttrium is 25% by weight, and nanometer alumina particles; each of the elements has the following proportion by weight: 40 parts of magnesium, 60 parts of zinc, 10 parts of yttrium and 20 parts of nanometer alumina particles of which the diameter is 30 nm;

(53) {circle around (2)} pretreatment of the metal raw materials: the pure magnesium ingot, the pure zinc ingot and the magnesium-yttrium alloy are cut into blocks, oxides attached on the surface of each metal block are removed, and followed by being put into a resistance furnace to preheat and keep at 200 C. for 30 minutes, so as to remove moisture attached on the surface of each metal block;

(54) {circle around (3)} pretreatment of the nanometer alumina particles: the nanometer alumina particles are put into a beaker, absolute ethyl alcohol is added, and followed by being placed in an ultrasonic cleaner to shock for 20 minutes, the absolute ethyl alcohol is filtered out after standing, and then drying is conducted in an oven at 610 C. for 8 minutes so as to completely evaporate the absolute ethyl alcohol; the ultrasonic cleaner has frequency of 20 KHz and power of 1000 W;

(55) {circle around (4)} flux-free smelting under a shielding gas: the pretreated pure magnesium ingot in step {circle around (2)} is put into a crucible of a melting furnace after the crucible is preheated to dark red, when the temperature of the crucible continues to rise to more than 400 C., the shielding gas is continuously provided to keep the subsequent smelting under protective atmosphere; the shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1; the mixture gas is introduced to a position of 2 cm above the metal melt surface, the flow rate of the shielding gas is 1 L/min, the exhaust pressure is 0.4 MPa.

(56) {circle around (5)} homogenizing treatment of an alloy melt: the pure zinc ingot is added after the pure magnesium ingot is completely melted at 700 C., the alloy melt is stirred to homogenize after the pure zinc ingot is completely melted, so as to separate oxides from the melt, and then impurities on the surface are removed; followed by continuously being heated up to 760 C., the magnesium-yttrium alloy is added, stirring is conducted to homogenize the alloy melt after the magnesium-yttrium alloy is completely melted;

(57) {circle around (6)} addition of the nanometer alumina particles: the alloy melt of step {circle around (5)} was stood to cool to 700 C., and then the nanometer alumina particles coated by a magnesium foil are pressed into the alloy melt and stirring is conducted for 3 minutes so as to get diffusion of the nanometer alumina particles in the alloy melt to be fully and uniformly; standing is performed for 15 minutes after stirring, and then impurities and oxides on the surface are removed;

(58) {circle around (7)} pouring: the alloy melt was poured into a metal mould preheated to 200 C. in advance and is taken out after solidification, thereby obtaining a quasicrystal and alumina mixture reinforcement phase;

(59) {circle around (8)} ball-milling of the quasicrystal and alumina mixture reinforcement phase: the resulting quasicrystal and alumina mixture reinforcement phase in step {circle around (7)} is physically broken, the alloy pieces are added into a planetary ball mill and are milled, and then particles having the size of 200 mesh are screened out using a stainless steel sieve, thereby obtaining the quasicrystal and alumina mixture particles reinforcement phase;

(60) (2) manufacturing a particles reinforcement phase-magnesium alloy matrix melt mixture slurry:

(61) {circle around (1)} preparation of raw materials for smelting the magnesium alloy matrix: the raw materials are a pure magnesium ingot, a pure aluminum ingot, a pure zinc ingot, a magnesium-manganese alloy, a magnesium-silicon alloy and a magnesium-calcium alloy; each of the elements has the following proportion by weight: 1000 parts of magnesium, 90 parts of aluminum, 10 parts of zinc, 5 parts of manganese, 1 part of silicon and 0.5 part of calcium;

(62) {circle around (2)} pretreatment of the metal raw materials: the pure magnesium ingot, the pure aluminum ingot, the pure zinc ingot, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are cut into blocks, oxides attached on the surface of each metal block are removed, and followed by being put into a resistance furnace to preheat and keep at 200 C. for 30 minutes, so as to remove moisture attached on the surface of each metal block;

(63) {circle around (3)} flux-free smelting under a shielding gas: the pure magnesium ingot and the pure aluminum ingot are put into a crucible and are heated up to 700 C. to melt after the crucible is preheated to dark red, when the temperature rises to more than 400 C., the shielding gas is continuously provided to keep the subsequent smelting under protective atmosphere, thereby preventing the magnesium alloy melt from oxidizing and burning; the shielding gas is a mixture gas of air, carbon dioxide and tetrafluoroethane, wherein the volume ratio of air, carbon dioxide and tetrafluoroethane in the mixture gas is 74:25:1, the mixture gas is introduced to a position of 2 cm above the metal melt surface, flow rate of the mixture gas is 1 L/min and exhaust pressure is 0.4 MPa.

(64) {circle around (4)} homogenizing treatment of an alloy melt: the preheated magnesium-manganese alloy is added at 700 C. after the metals are completely melted, the preheated pure zinc ingot sequentially is added at 700 C. after melting, the alloy melt is stirred to homogenize after melting, so as to separate oxides from the melt, and then impurities on the surface are removed; followed by continuously being heated up to 720 C., the preheated magnesium-silicon alloy and the preheated magnesium-calcium alloy are added, thereby obtaining a magnesium alloy matrix melt after melting, and then stirring is conducted to homogenize the magnesium alloy matrix melt; when operating, the magnesium-manganese alloy, the magnesium-silicon alloy and the magnesium-calcium alloy are coated with an aluminum foil, and are pressed into the melt by a bell jar, and then stirring is conducted, by which exposure can be avoided during adding to prevent them from generating serious oxidation loss, and by which loss of alloy elements caused by density difference can also avoided.

(65) {circle around (5)} the quasicrystal and the alumina mixture particles reinforcement phase in step (1) is coated using an aluminum foil and then is pressed into the magnesium alloy matrix melt, whereafter, the quasicrystal and alumina mixture particles reinforcement phase is mixed with the magnesium alloy matrix melt to be homogenous by staged variable speed stirring, thereby obtaining the particles reinforcement phase-magnesium alloy matrix melt mixture slurry; the weight ratio of the quasicrystal and alumina mixture particles reinforcement phase to the magnesium alloy matrix is 8:100. Stirring in the first stage of the staged variable speed stirring is conducted at the speed of 300 rpm/min for 10 minutes, a slow speed stirring can avoid lifting the melt level too quickly and can add the aluminum foil in which the mixture particles reinforcement phase is coated into a smelting furnace; in the second stage, firstly, a high speed stirring is conducted at a speed of 1500 rpm/min for 10 minutes, next, stirring speed is reduced to an intermediate speed, the intermediate speed stirring is continued at 1000 rpm/min for 10 minutes, this moment, the melt level drops, a large enough vortex is formed on the surface thereof, and the particles reinforcement phase enters into the melt depending on negative pressure suction of the vortex; in the third stage, the stirring speed is increased again to 1500 rpm/min, and stirring is continuously conducted for 20 minutes to sufficiently disperse the particles reinforcement phase having entered the melt.

(66) {circle around (6)} the particles reinforcement phase-magnesium alloy matrix melt mixture slurry was allowed to stand for 15 minutes, so as to separate oxides from the melt, and then impurities on the surface are removed;

(67) (3) casting ingot by pouring and extrusion:

(68) {circle around (1)} the particles reinforcement phase-magnesium alloy matrix melt mixture slurry is cooled to 700 C. in the crucible of the smelting furnace;

(69) {circle around (2)} a steel mould 3 in an extruder is preheated to 200 C.;

(70) {circle around (3)} a cover of the smelting furnace is opened, followed by being aligned with a pouring gate of the mould of the extruder, and then pouring is conducted until the cavity 2 is filled;

(71) {circle around (4)} the extruder performs die closing and extrusion under extrusion pressure of 100 MPa for 20 seconds; by pressure of the punch 1 of the extruder, the particles reinforcement phase-magnesium alloy matrix melt mixture slurry in the cavity of the mould generates high pressure solidification and plastic deformation under mechanical static pressure of 100 MPa; the mould is opened after the ingot and the mould are cooled to room temperature naturally, as shown in FIG. 1, and then an ejector pin device 4 protrudes out from a base of the extruder 5 and pushes out the ingot, thereby obtaining the finished product of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite. The finished product has the microstructure characteristics of -Mg solid solution, Mg.sub.17Al.sub.12 distributed in a fractured chain form, and the quasicrystal phase and alumina particles diffusively distributed at grain boundaries.

(72) At room temperature, performance test is performed for the quasicrystal and alumina mixture particles reinforced magnesium matrix composites of embodiments one to three of the present invention, ZM5 magnesium alloy and magnesium alloy matrix of the present invention, the obtained performance parameters and comparison result are shown in Table 1.

(73) TABLE-US-00001 TABLE 1 Tensile Elongation Strength (MPa) (%) ZM5 magnesium alloy 108.3 4.12 magnesium alloy matrix of embodiment 94.5 2.68 2 of the present invention magnesium matrix composite of embodiment 193.9 6.25 1 of the present invention magnesium matrix composite of embodiment 194.5 6.51 2 of the present invention magnesium matrix composite of embodiment 195.8 6.83 3 of the present invention average value of the magnesium matrix 194.7 6.53 composites of the present invention
As can be seen from table 1, tensile strength of the magnesium alloys of the present invention reaches 194.7 MPa at room temperature, elongation also reaches 6.53% while the tensile strength is increased, both of which are increased sharply compared with those of ZM5 magnesium-based alloy and the magnesium alloy matrix.

(74) FIG. 2 is a microstructure view of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite of embodiment two of the present invention. As can be seen from FIG. 2, metallurgical microstructure has good compactness.

(75) FIG. 3 a shape appearance view of a tensile specimen fracture of the quasicrystal and alumina mixture particles reinforced magnesium matrix composite of embodiment two of the present invention obtained by a scanning electron microscope. As can be seen from FIG. 3, in the shape appearance of the tensile specimen fracture, there are a large number of dimples of which the diameter becomes small and has a great depth, and cleavage plane becomes tiny, thereby having an obvious quasi cleavage fracture feature.

(76) The above-described content is only preferably practicable embodiments of the present invention without limitation for the protective scope of the present invention. Besides the above-mentioned embodiments, the present invention may also have other embodiments. All of technical solutions formed by equivalent replacement or equivalent transformation fall within the claimed scope of the present invention. No described technical features in the present invention may be achieved by or using the prior art, therefore, they are not repeated here.