CN1980760A - Magnesium-base composite powder, magnesium-base alloy material and method for production thereof - Google Patents

Abstract

Magnesium-based composite powder used as raw material for making _Mg2Si particle dispersion magnesium-based composite material has Mg-based powder (7) as the main component constituting the matrix of magnesium alloy, and _Mg2Si particles attached to its surface by an adhesive (9).

Description

Magnesium-based composite powder, magnesium-based alloy raw material and manufacturing method thereof

technical field

The present invention relates to a magnesium-based composite powder containing Mg ₂ Si with high rigidity, a magnesium-based alloy raw material and a manufacturing method thereof.

Background technique

Magnesium alloys are characterized by light weight effects due to their low specific gravity, and are widely commercialized and put into practical use mainly in casings of mobile phones and Walkmans. In the design of products and components, in addition to the mechanical characteristics of the strength and hardness of raw materials, rigidity is also an important material factor.

For example, when a magnesium alloy is applied to an automatic transmission (AT) case, even if it has the same tensile strength and creep strength as the currently used aluminum alloy (such as ADC12), the existing magnesium The rigidity (Young's modulus) of the alloy is only about 60% of that of aluminum alloy, so bending and deformation will occur when a load is applied under the same size and wall thickness. Therefore, there is still a problem in the practical application of magnesium alloys in that it is necessary to design thicker parts according to the products and parts to be used, and the effect of weight reduction cannot be obtained.

In order to improve the rigidity of metallic materials such as magnesium alloys, it is generally effective to disperse compound particles having higher rigidity than the metallic materials, that is, to use composite materials. For example, the Young's modulus of magnesium silicide (Mg ₂ Si) is 120GPa, which is significantly larger than the Young's modulus (43-44GPa) of general magnesium alloys, so the composite material in which the particles are dispersed in the alloy Rigidity improvement can be expected.

However, when Mg-Si alloys are produced by melting and casting, there is a eutectic point in the vicinity of about 1% Si content on a weight basis, so if Si is added far beyond 1% by weight, the relationship between it and Mg Mg ₂ Si produced by the reaction grows coarsely. In a magnesium alloy containing such coarse Mg ₂ Si, the strength and toughness decrease due to the stress concentration in the particles, and the explosion during the melting process due to the heat generated by the reaction of Mg and Si occurs. dangerous. In addition, the presence of coarse Mg ₂ Si particles degrades the casting performance (castability) into the mold. A problem occurs that there are a large number of defects and voids inside the cast alloy raw material. Therefore, AS21 alloy (Mg-2%Al-1%Si) and AS41 alloy (Mg-4%Al-1%Si) are magnesium alloys containing Mg ₂ Si that can be produced by melting and casting. However, when about 1% by weight of Si is added, the volume fraction of the generated Mg ₂ Si particles is still less than about 1% of the whole, so it is difficult to significantly improve the rigidity of the magnesium alloy.

On the other hand, SKTHAKUR (Source: Metallurgical and Materials Transactions A, Vol.35A, March 2004, p.1167-1176) proposes a method in which three types of mixed powders containing Si powder are solidified in advance (preform) Here, a magnesium alloy containing Mg ₂ Si particles is produced by an infiltration method in which a molten magnesium alloy is impregnated while being pressurized. However, in this method, Mg ₂ Si synthesized by the reaction between the molten Mg alloy and Si grows along with the crystal grains during the reaction process, and as a result, coarse Mg ₂ Si of about 70 to 100 μm exists in the magnesium alloy. . As a result, various performance problems as described above arise.

In Japanese Patent Application No. 2003-2602 (applied on January 8, 2003), the present inventor disclosed a technique for producing a magnesium-based composite material in which Mg ₂ Si particles are dispersed by powder metallurgy. A magnesium composite powder in which fine Si powder or SiO ₂ powder is adhered to the surface of a magnesium-based alloy powder by a mechanical bonding method or a bonding method using an adhesive, and a method for producing the same are proposed. In addition, it is also proposed that such a composite powder be subjected to intertemporal plastic processing, during which Mg and Si or SiO ₂ are used to generate Mg ₂ Si particles in the solid phase reaction, and finally the Mg ₂ Si particles are uniformly dispersed in the interior. magnesium matrix composites.

The magnesium-based composite material obtained by the technology disclosed in Japanese Patent Application No. 2003-2602 exhibits high tensile strength, but requires high-temperature heating (for example, about 400-550° C.) required for the reaction of Mg and Si or SiO ₂ . This is accompanied by coarsening of magnesium crystal grains. In other words, it is effective to lower the heating temperature to achieve higher strength, but it is difficult to heat at a lower temperature of, for example, about 300° C. due to the above-mentioned solid phase reaction.

Contents of the invention

An object of the present invention is to obtain a high-rigidity and high-strength magnesium alloy containing a large amount of Mg ₂ Si particles without performing high-temperature heating.

The inventors of the present application found that it is effective to use a magnesium-based composite powder in which Mg ₂ Si particles exist on the surface of the Mg-based powder and/or inside the matrix in order to manufacture a magnesium-based composite material in which Mg ₂ Si particles are dispersed. And found that instead of using Si particles as disclosed in Japanese Patent Application No. 2003-2602, instead of utilizing its solid-state reaction with Mg powder to synthesize Mg ₂ Si particles, Mg ₂ Si particles are used, and thus obtained The following advantages.

(1) High-temperature heating around 400 to 550°C required to promote the above-mentioned Si-Mg reaction is not required, and as a result, the reduction in the strength of the Mg-based alloy can be suppressed by suppressing the coarsening and growth of Mg crystal grains in the matrix .

(2) Coarsening of Mg ₂ Si particles and Mg can be suppressed by avoiding heat generation during the Si—Mg reaction.

In short, magnesium-based alloys can be produced by warm extrusion at about 200 to 400°C without performing the high-temperature heating required for the solid-state reaction of Mg and Si as described above. As a result, a highly rigid and high-strength magnesium-based alloy containing a large amount of fine Mg ₂ Si particles can be obtained.

The magnesium-based composite powder according to the present invention includes the magnesium-based powder and magnesium silicide (Mg ₂ Si) dispersed on at least one of the surface of the magnesium-based powder and the interior of the matrix.

In the above magnesium-based composite powder, the maximum particle diameter of Mg ₂ Si is 50 μm or less, preferably 20 μm or less, more preferably 5 μm or less. In addition, the content of Mg ₂ Si relative to the magnesium-based composite powder is preferably 5 to 60% on a volume basis.

According to the magnesium-based alloy raw material of the present invention, the above-mentioned magnesium-based composite powder is compacted and sintered, so that Mg ₂ Si particles are dispersed in the matrix.

In one embodiment, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of preparing magnesium (Mg)-based powder and magnesium silicide (Mg ₂ Si) particles.

b) A step of coating a binder on the surface of the Mg-based powder.

c) A step of mixing and stirring the Mg-based powder coated with the binder and the Mg ₂ Si particles to bond the surface of the Mg-based powder to the Mg ₂ Si particles.

In other embodiments, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of preparing magnesium (Mg)-based powder and magnesium silicide (Mg ₂ Si) particles.

b) A step of mechanically mixing the Mg-based powder and Mg ₂ Si particles after preparing them, and mechanically bonding the surface of the Mg-based powder to the Mg ₂ Si particles.

In the above method, the method of mechanically combining the surface of the Mg-based powder with the Mg ₂ Si particles is, for example, mechanically mixing using a ball mill, a mixing attritor, a roller compactor, or a rolling mill. Blend powder.

In addition, in other embodiments, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of preparing magnesium (Mg)-based powder and magnesium silicide (Mg ₂ Si) particles.

b) A step of mixing Mg-based powder and Mg ₂ Si particles.

c) A step of compacting the mixed powder in a die to produce a Mg-based compact in which Mg ₂ Si particles are dispersed.

d) A step of sintering the Mg-based compact to produce a Mg-based sintered alloy in which Mg ₂ Si particles are dispersed.

e) A step of mechanically pulverizing or cutting the Mg-based sintered alloy to form a powder.

In addition, in other embodiments, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of preparing magnesium (Mg)-based powder and silicon (Si) particles.

b) A step of mixing Mg-based powder and Si particles.

c) A step of compacting the mixed powder in a die to produce a Mg-based compact in which Si particles are dispersed.

d) A step of heating the Mg-based compact, synthesizing Mg ₂ Si through the reaction of Mg and Si, and producing a Mg-based sintered alloy in which Mg ₂ Si particles are dispersed.

e) A step of mechanically pulverizing or cutting the Mg-based sintered alloy to form a powder.

In addition, in other embodiments, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of adding magnesium silicide (Mg ₂ Si) particles to a magnesium-based melt and stirring.

b) The process of pouring the melt into a mold to make a casting raw material.

c) A process of mechanically pulverizing or cutting the cast raw material to powderize the powder.

In addition, in other embodiments, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of preparing magnesium (Mg)-based powder and magnesium silicide (Mg ₂ Si) particles.

b) A step of mixing Mg-based powder and Mg ₂ Si particles.

c) A step of compacting the mixed powder in a die to produce a Mg-based compact in which Mg ₂ Si particles are dispersed.

d) A step of melting and casting a Mg-based compact to produce a Mg ₂ Si particle-dispersed Mg-based casting raw material.

e) A step of mechanically pulverizing or cutting the Mg-based cast raw material to powderize the powder.

In addition, in other embodiments, the manufacturing method of the magnesium-based composite powder according to the present invention has the following steps.

a) A step of preparing magnesium (Mg)-based powder and silicon (Si) particles.

b) A step of mixing Mg-based powder and Si particles.

c) A step of compacting the mixed powder in a die to produce a Mg-based compact in which Si particles are dispersed.

d) A step of heating the Mg-based compact, synthesizing Mg ₂ Si through the reaction of Mg and Si, and producing a Mg-based sintered alloy in which Mg ₂ Si particles are dispersed.

e) A step of melting and casting a Mg-based sintered alloy to produce a Mg-based casting raw material in which Mg ₂ Si particles are dispersed.

f) A process of mechanically pulverizing or cutting the cast raw material to pulverize the powder.

The manufacturing method of the magnesium-based alloy raw material according to the present invention has the following steps: the step of compacting the above-mentioned magnesium-based composite powder; heating the compacted powder in an inert gas atmosphere or a non-oxidizing gas atmosphere at 200-400°C The step of molding: the step of extruding and densifying the compressed powder molding immediately after heating.

The features and effects of the present invention are described in the following items.

Description of drawings

FIG. 1 is a diagram showing an example of a method of attaching Mg ₂ Si particles to the surface of Mg-based powder using a binder.

Fig. 2 is a diagram showing another example of a method of attaching Mg ₂ Si particles to the surface of Mg-based powder by using a binder.

Fig. 3 is a diagram showing an example of a magnesium-based composite powder in which Mg ₂ Si particles are adhered to the surface of the Mg-based powder.

Fig. 4 is a diagram showing another example of a magnesium-based composite powder in which Mg ₂ Si particles are adhered to the surface of the Mg-based powder.

Fig. 5 is a diagram showing an example of a method for producing a magnesium-based composite powder.

Fig. 6 is a diagram showing an example of a magnesium-based composite powder in which Mg ₂ Si particles are dispersed in a matrix of Mg magnesium-based powder.

Fig. 7 is a diagram showing another example of a method of producing a magnesium-based composite powder.

Fig. 8 is a diagram showing yet another example of a method for producing a magnesium-based composite powder.

Fig. 9 is a diagram showing yet another example of a method for producing a magnesium-based composite powder.

Fig. 10 is a diagram showing yet another example of a method for producing a magnesium-based composite powder.

11 is a micrograph showing an example of a cross-sectional structure of a magnesium-based composite powder in which Mg ₂ Si particles are dispersed in a Mg-magnesium-based alloy matrix.

Fig. 12 is a diagram showing an example of the X-ray diffraction results of magnesium-based composite powder.

Fig. 13 is a diagram showing another example of the X-ray diffraction results of the magnesium-based composite powder.

Detailed ways

(1) Magnesium-based composite powder

(A) Content of Mg ₂ Si

When the whole magnesium-based alloy powder is 100%, it contains 5-60% of Mg ₂ Si by volume standard. In addition, from the viewpoint of the machinability (machinability) of the magnesium-based alloy obtained by solidifying the composite powder, the content of Mg ₂ Si is more preferably 20 to 40% by volume. When the content of Mg ₂ Si is less than 5%, a magnesium alloy having sufficient rigidity cannot be obtained. On the other hand, when the content of Mg ₂ Si particles exceeds 60%, segregation and aggregation of Mg ₂ Si particles will occur in the magnesium-based composite powder containing Mg ₂ Si particles, and the magnesium-based alloy obtained by solidifying such powder will suffer Reduced strength and toughness. In order to have a rigidity equivalent to that of an aluminum alloy and to ensure excellent strength and machinability, the content of Mg ₂ Si particles is more preferably 20 to 40% by volume.

(B) Maximum particle size of Mg ₂ Si

The maximum particle size of Mg ₂ Si contained in the magnesium-based composite powder is 50 μm or less, preferably 20 μm or less, more preferably 5 μm or less. When the maximum particle size of Mg ₂ Si exceeds 50 μm, the mechanical properties and machinability of the obtained magnesium-based alloy deteriorate. When this value is 20 μm or less, good machinability can be maintained even when Mg ₂ Si particles are contained in excess of 40 volume %. Furthermore, when the maximum particle size of the Mg ₂ Si particles is 5 μm or less, the machinability of the magnesium-based alloy is improved, and at the same time, the tensile strength of the present alloy is improved due to the dispersion of the fine Mg ₂ Si particles.

(C) Rigidity (Young's modulus)

The Young's modulus of the magnesium-based alloy is 48-90GPa. If the Young's modulus is lower than 48GPa, the increase rate of the Young's modulus relative to the conventional magnesium alloy is 10% or less, and it is difficult to apply to automobile covers, case-related members, and cases for personal computers and mobile devices. Body components etc. On the other hand, as described above, when the Young's modulus exceeds 90 GPa, the content of Mg ₂ Si exceeds 60% by volume, so the toughness and machinability of the alloy raw material decrease.

(2) Manufacturing method of magnesium-based composite powder

(A) Magnesium-based composite powder joined by binder is used

Fig. 1 and Fig. 2 show a method for producing a Mg-based composite powder using a binder solution, and Fig. 3 schematically shows a cross-sectional structure of an Mg-based composite powder obtained by this method.

In this method, a wet granulator and a spray dryer are used to produce composite powders. According to the method shown in FIG. 1 , a mixture 2 of Mg-based powder and Mg ₂ Si particles is put into a container 1 , and warm air 3 is supplied from the lower part of the container 1 to float the mixture 2 . In this state, the binder solution 4 was sprayed from above to the mixture 2 as a spray to apply the binder to the surface of each particle while drying at a high temperature. As a result, as shown in FIG. 3 , Mg ₂ Si particles 8 adhered and bonded to the surface of Mg-based powder 7 via binder 9 .

According to the method shown in Fig. 2, the mixture 2 of Mg-based powder and _Mg2Si particles is floated in the container 1 with a relatively low air volume, and the binder solution is sprayed from the lower part vertically with respect to the wind flow direction in this state. 4.

Also, although not shown in the figure, by mixing and stirring Mg ₂ Si particles in a binder solution and applying the binder solution as a spray to the Mg-based powder floating by warm air, it is also possible to pass The binder enables the Mg ₂ Si particles to attach and bond to the surface of the Mg-based powder.

In addition, as another method, a predetermined amount of Mg-based powder is put into a container, oleic acid as a binder is added thereto, and the ratio of oleic acid to the Mg-based powder is 0.2 to 0.5% by weight, and then the entire container is vibrated or rotated. , thereby coating the surface of the Mg-based powder in the container with oleic acid. Thereafter, Mg ₂ Si particles were added to the container, and the container was again vibrated or rotated to allow the Mg ₂ Si particles to adhere to the surface of the Mg-based powder coated with oleic acid. The Mg-based composite powder shown in FIG. 3 was thus obtained.

(B) Magnesium-based composite powder using mechanical bonding

On the other hand, as a method of mechanical bonding, Mg-based powder and Mg ₂ Si particles are put into a ball mill, a mixing attritor, a roller compactor, or a rolling mill in a mixed state, and the mixed powder is Compression, shear processing, etc. are applied to obtain Mg-based particulate matter in which Mg ₂ Si particles are mechanically bonded and attached to the surface of the Mg-based powder. If necessary, a Mg-based composite powder having a cross-sectional structure as shown in FIG. 4 and a predetermined size and shape can be obtained from the granules by using a crushing and sifting machine. In Mg-based composite powder 15 shown in FIG. 4 , Mg ₂ Si particles 8 are mechanically bonded and adhered to the surface of Mg-based powder 7 .

(C) Magnesium-based composite powder using Mg ₂ Si particle-dispersed Mg-based sintered alloy

(a) The method shown in Figure 5

Prepare Mg-based powder and Mg ₂ Si particles as the initial raw materials, mix and stir them at a specified ratio, fill them into a metal mold, and press and solidify them to produce Mg-based compressed powder with Mg ₂ Si particles dispersed Shaped body.

The above-mentioned green compact is heated in an inert gas or non-oxidizing gas or vacuum at a temperature lower than the melting point of the Mg-based powder to obtain a Mg ₂ Si particle-dispersed Mg-based sintered alloy through solid-phase diffusion between the Mg-based powders.

The above-mentioned Mg ₂ Si particle-dispersed type Mg-based sintered alloy is powdered by processing such as a pulverizer such as a ball mill or a crusher or cutting, thereby obtaining a sintered alloy having a sectional structure as shown in FIG. 6 and having a predetermined size and shape. Mg-based composite powder 16. In the Mg-based composite powder 16 shown in FIG. 6 , Mg ₂ Si particles are mainly dispersed in the matrix of the Mg-based powder 7 .

In addition, in the above-mentioned Mg ₂ Si particle-dispersed type Mg-based sintered alloy, when the content of Mg ₂ Si particles exceeds 60% by volume, the segregation and aggregation of Mg ₂ Si particles occur, and other problems occur during cutting. There is a problem that the tool life is reduced. From this point of view, the content of Mg ₂ Si particles is preferably 60% or less.

(b) The method shown in Figure 7

Prepare Mg-based powder and Si particles as initial raw materials, mix and stir them at a predetermined mixing ratio, fill them into a metal mold, and perform pressure curing to produce a Mg-based powder compact in which Si particles are dispersed.

The above-mentioned green compact is heated in an inert gas or non-oxidizing gas or vacuum at a temperature lower than the melting point of the Mg-based powder, thereby utilizing the solid-state reaction between Si-Mg to synthesize Mg ₂ Si, and at the same time through the Mg-based powder The Mg-based sintered alloy with dispersed Mg ₂ Si particles was obtained by solid phase diffusion.

The above-mentioned Mg ₂ Si particle-dispersed type Mg-based sintered alloy is powdered by processing such as a pulverizer such as a ball mill or a crusher or cutting, thereby obtaining a sintered alloy having a sectional structure as shown in FIG. 6 and having a predetermined size and shape. Mg-based composite powder containing Mg ₂ Si particles.

(D) Magnesium-based composite powder using Mg ₂ Si particle-dispersed Mg-based casting alloy

(a) The method shown in Figure 8

Mg ₂ Si particles prepared as a starting material were poured into a Mg-based alloy melt, stirred, and then poured into a mold. In the Mg-based cast alloy taken out from the mold, the added Mg ₂ Si particles were uniformly dispersed.

By pulverizing the above-mentioned cast alloy by processing such as a pulverizer such as a ball mill or a crusher, or cutting, a Mg matrix containing Mg ₂ Si particles having a sectional structure as shown in FIG. 6 and having a predetermined size and shape is obtained. Composite powder. In addition, the melting temperature of the Mg-based alloy melt after adding Mg ₂ Si particles is lower than the solidus temperature of Mg and Mg ₂ Si in the Si-Mg equilibrium state diagram. Conversely, if heated above the solidus temperature, Mg ₂ Si will be solid-dissolved in the Mg-based alloy melt, causing the problem of coarsening and growth of Mg ₂ Si during the solidification process after casting.

(b) The method shown in Figure 9

Prepare Mg-based powder and Mg ₂ Si particles as the initial raw materials, mix and stir the two at a specified ratio, fill them into a metal mold, and press and solidify to produce Mg-based compacted powder with Mg ₂ Si particles dispersed body. After fully stirring the melt, pour it into the mold.

In the Mg-based cast alloy taken out from the mold, the added Mg ₂ Si particles are uniformly dispersed, and the alloy is powdered by pulverizers such as ball mills and crushers or cutting, thereby obtaining the alloy shown in Figure 6. Mg-based composite powder containing Mg ₂ Si particles having a cross-sectional structure as shown and having a predetermined size and shape.

(c) The method shown in Figure 10

Mg-based powder and Si particles were prepared as starting materials, mixed and stirred at a predetermined mixing ratio, filled into a metal mold, and pressurized and solidified to produce a Mg-based compact in which Si particles were dispersed.

The above-mentioned green compact is heated in an inert gas or non-oxidizing gas or vacuum at a temperature lower than the melting point of the Mg-based powder, thereby utilizing the solid-state reaction between Si-Mg to synthesize Mg ₂ Si, and at the same time through the Mg-based powder The Mg-based sintered alloy with dispersed Mg ₂ Si particles was obtained by solid phase diffusion.

The above-mentioned sintered alloy was put into a crucible and heated to prepare a Mg-based alloy melt in which Mg ₂ Si particles were dispersed. After fully stirring the melt, pour it into the mold. In the Mg-based cast alloy taken out from the mold, the added Mg ₂ Si particles are uniformly dispersed, and the alloy is powdered by pulverizers such as ball mills and crushers or cutting, thereby obtaining the alloy shown in Figure 6. Mg-based composite powder containing Mg ₂ Si particles having a cross-sectional structure as shown and having a predetermined size and shape.

In addition, since the cutting oil used in the cutting process adheres to the Mg-based composite powder, it is used as a raw material after the cutting oil is decomposed by cleaning treatment.

(3) Magnesium-based alloy raw materials

A Mg-based alloy in which Mg ₂ Si particles are dispersed is obtained by forming and solidifying the above-mentioned Mg-based composite powder containing Mg ₂ Si particles as a starting material.

After compacting the Mg-based composite powder, it is heated and subjected to extrusion processing, forging processing, or rolling processing. However, the heating temperature of the compact at this time is preferably about 200 to 400°C. If it is lower than 200°C, extrusion processing may become difficult. On the other hand, if it exceeds 400° C., the temperature of the raw material after extrusion increases as the extrusion speed increases, and the strength may decrease due to coarsening of crystal grains.

In the matrix of the Mg-based alloy obtained as described above, fine Mg2Si particles are uniformly dispersed. Since the particle size of the _Mg2Si particles dispersed in the alloy is the same as that in the Mg-based composite powder, the maximum particle size of the _Mg2Si particles in the Mg-based alloy is 50 μm or less, preferably 20 μm or less, more preferably 5 μm or less. In addition, the content of Mg ₂ Si in the Mg-based alloy is 5 to 60% by volume. As a result, it becomes possible to manufacture a Mg-based alloy with high rigidity and high strength.

Example 1

Prepare pure Mg powder (purity 99.9%, average particle size 350 μm) and Si powder (purity 99.9%, average particle size 22 μm), after allocating two kinds of powders with Mg:Si=2:1 (molar ratio), carry out 30 with ball mill minutes to mix. The mixed powder was placed in a spark plasma sintering apparatus in a state filled with a carbon mold (inner diameter: 35 mm), and sintered for 15 minutes by adjusting the pressure to 100 MPa and the sample temperature to 600° C. in a vacuum. As a result, a disk-shaped sample made of Mg ₂ Si with an outer diameter of 35 mm and a thickness of 12 mm was obtained.

The above disk-shaped sample was pulverized with a jet mill, finely pulverized and sieved to have a maximum particle diameter of 15 μm or less, to produce Mg ₂ Si particles as a starting material. On the other hand, as the Mg-based powder, an AZ31 (nominal composition Mg-3Al-1Zn/mass%) alloy powder having a diameter of about 2 mm was prepared as a starting material.

Based on the method shown in FIG. 5 , AZ31 powder and Mg ₂ Si particles were first mixed at a predetermined ratio and filled into a metal mold with a diameter of 60 mm_, and a pressure of 400 MPa was applied to produce a compacted powder. The compact was sintered at 550° C. for 1 hour in a nitrogen atmosphere to obtain an AZ31 sintered alloy in which Mg ₂ Si particles were dispersed. Then, a Mg-based composite powder having a diameter of about 0.5 to 3 mm is produced from the sintered alloy by cutting.

FIG. 11 shows the observation results of the cross-sectional structure of the composite powder when the Mg ₂ Si particle content is 16% by volume relative to the entire Mg-based composite powder. Mg ₂ Si particles with a particle size of 15 μm or less do not segregate and agglomerate, but are uniformly dispersed in the AZ31 matrix, thereby obtaining the Mg-based composite powder according to the present invention.

Example 2

Based on the method shown in Figure 7, first prepare pure Mg powder (purity 99.9%, average particle size 350 μm) and Si powder (purity 99.9%, average particle size 22 μm), after blending the two powders at a specified ratio, use a ball mill Mix for 30 minutes. The mixed powder was filled into a metal mold with a diameter of 60 mm, and a pressure of 400 MPa was applied to produce a compacted powder.

The above-mentioned compacted powder is heat-treated at 590°C for 1 hour in a vacuum, thereby synthesizing _Mg2Si particles by the solid-state reaction of Si and Mg, and at the same time promoting sintering between Mg powders to obtain _Mg2Si particle dispersion Mg sintered material. Then, the sintered material was pulverized by a ball mill to produce Mg-based composite powder with a diameter of about 0.3 to 1 mm.

FIG. 12 shows the X-ray diffraction results of the composite powder when the Mg ₂ Si particle content is 7% by volume relative to the entire Mg-based composite powder. Only the peaks of Mg and _Mg2Si were detected, since there was no peak of Si used for the starting material, it completely reacted with Mg and was consumed in the synthesis of _Mg2Si . In addition, since there is no MgO peak, oxidation during sintering does not occur.

In addition, as a result of observation of the structure based on an optical microscope, the average particle size of Mg ₂ Si dispersed in the powder matrix is about 24 μm, which is equivalent to the particle size of the Si powder used as the starting material, so in the above-mentioned reaction process with Mg No significant coarse-grain growth occurred in . As a result, a Mg-based composite powder in which the Mg ₂ Si particles specified in the present invention are uniformly dispersed in the matrix is obtained.

Example 3

Prepare pure Mg powder (purity 99.9%, average particle size 350 μm) and Si powder (purity 99.9%, average particle size 22 μm), after allocating two kinds of powders with Mg:Si=2:1 (molar ratio), carry out 30 with ball mill minutes to mix. The mixed powder was placed on a spark plasma sintering apparatus in a state filled with a carbon mold (inner diameter: 35 mm), and sintering was performed for 30 minutes by adjusting the pressure to 100 MPa and the sample temperature to 600° C. in a vacuum. As a result, a disk-shaped sample made of Mg ₂ Si with an outer diameter of 35 mm and a thickness of 12 mm was obtained.

The above-mentioned disk-shaped sample was pulverized by a jet mill, finely pulverized and sieved to a maximum particle size of 10 μm or less, and Mg ₂ Si particles were produced as a starting material.

Based on the method shown in FIG. 8 , first, an AZ61 (nominal composition Mg-6Al-1Zn/mass%) alloy melt was prepared in a carbon crucible. In the state of controlling the melt at 720-740°C, the above-mentioned _Mg2Si particles were added in a predetermined ratio, stirred well, and then poured into a metal mold to produce an AZ61 cast alloy raw material in which _Mg2Si particles were dispersed.

Mg-based composite powder made of AZ61 alloy with a diameter of about 0.5 to 3 mm was produced from the above-mentioned cast alloy by cutting. Table 1 shows the content (volume basis) of Mg ₂ Si particles relative to the entire cast alloy raw material. In addition, the results of observation of the cross-sectional structure of the obtained composite powder and the operation status of the cemented carbide tool in the process of making the powder are shown in the same table.

In Sample Nos. 1 to 5 which are examples of the present invention, since an appropriate amount of Mg ₂ Si is contained, segregation and aggregation of Mg ₂ Si particles do not occur in the Mg-based composite powder, and the Mg ₂ Si particles are uniformly dispersed in the In the matrix. In addition, regarding the tool wear (damage condition) when producing the Mg-based composite powder by cutting, although some to slight scratches were confirmed, they did not pose a problem.

On the other hand, in sample No. 6 as a comparative example, since the Mg ₂ Si content was as high as 65%, aggregation of Mg ₂ Si particles occurred in the powder matrix, and when the powder was produced by cutting, the casting The alloy contains a large amount of hard Mg ₂ Si, so deep damage occurs on the tool, and at the same time, there is a problem of Mg agglomeration in the damaged part.

[Table 1]

  Sample No. Mg ₂ Si content (volume fraction) Dispersion of Mg ₂ Si particles Tool damage 1 7   Evenly dispersed in the matrix good tool surface 2 12 ditto ditto 3 28 ditto ditto 4 38 ditto few minor abrasions 5 57 ditto minor scratches 6 65 Agglomeration of Mg ₂ Si particles occurs Deep damage has Mg coagulation in its part

Example 4

Prepare pure Mg powder (purity 99.9%, average particle size 350 μm) and Si powder (purity 99.9%, average particle size 22 μm), mix the two powders with Mg:Si=2:1 (molar ratio), and use a ball mill Mix for 30 minutes.

The above-mentioned mixed powder was placed on a spark plasma sintering device in a state filled with a carbon mold (inner diameter: 35 mm), and the pressure was adjusted to 100 MPa in a vacuum, and the sample temperature was adjusted to 600° C. and sintered for 15 minutes. As a result, a disk-shaped sample made of Mg ₂ Si with an outer diameter of 35 mm and a thickness of 12 mm was obtained.

The above disc-shaped sample was pulverized with a jet pulverizer. At this time, the pulverization processing conditions were changed to produce Mg ₂ Si particles having different maximum particle diameters.

Based on the method shown in Fig. 9, as a Mg-based powder, an AM60 (nominal composition Mg-6Al-0.5Mn/mass%) alloy powder with a diameter of 3mm was prepared as a starting material, and it was mixed with _Mg2Si particles at a predetermined ratio , Filled into a metal mold with a diameter of 60mm_ and applied a pressure of 400MPa to produce a compressed powder compact.

Next, the pressed powder molded body is put into the prepared AM60 alloy melt (melt temperature: 720-740°C) in a carbon crucible, stirred well, and poured into a metal mold to produce AM60 casting in which Mg ₂ Si particles are dispersed. Alloy raw material. Then, Mg-based composite powder (diameter: about 0.5 to 3 mm) made of AM60 alloy was produced from the cast alloy by cutting. In addition, the content of Mg ₂ Si in the obtained Mg-based cast alloy was 22% by volume.

In order to calculate the maximum particle size of the _Mg2Si particles dispersed in the above-mentioned Mg-based composite powder matrix, the cross-sectional structure of the composite powder was observed with an optical microscope, and the maximum particle size of the _Mg2Si particles was obtained by image analysis based on the results. The results are shown in Table 2. In addition, the damage state of the cemented tool during the cutting process when producing the Mg-based composite powder from the cast alloy is shown in the same table.

In Sample Nos. 7 to 10, which are examples of the present invention, since the cast alloy contains Mg ₂ Si with an appropriate particle size, tool wear and damage do not occur when making powder by cutting, and a good surface is exhibited. traits.

On the other hand, in Sample Nos. 11 to 12 as comparative examples, since the maximum particle size of Mg ₂ Si contained in the cast alloy exceeded 50 μm, deep damage occurred on the tool during cutting, and at the same time, the damage Some problems such as Mg aggregation occurred.

[Table 2]

  Sample No. Mg ₂ Si maximum particle size (μm) Tool damage 7 3 good tool surface 8 12 ditto 9 26 ditto 10 42 Deep damage has Mg coagulation in its part 11 75 Deep damage has Mg coagulation in its part 12 92 Deep damage has Mg coagulation in its part

Example 5

Using the Mg-based composite powder described in the above-mentioned Example 3 and Example 4 as a starting material, a green compact of each powder was produced by molding with a metal mold. After each green compact was heated and held for 5 minutes in a nitrogen atmosphere controlled at 350° C., extrusion processing (extrusion ratio 37) was immediately performed to produce an extrusion raw material. Tensile test pieces were produced from each extruded raw material, and the tensile properties (tensile strength and elongation at break) at normal temperature were evaluated, and the Young's modulus was measured. Table 3 shows the results.

In samples Nos. 1 to 5 and Nos. 7 to 10 as examples of the present invention, magnesium-based alloys with excellent strength and toughness can be obtained, especially samples Nos. 4 and 5 have properties comparable to aluminum alloys. of high rigidity. In addition, as shown in Sample Nos. 7 and 8, when the maximum particle size of the Mg ₂ Si particles dispersed in the alloy is as fine as less than 5 μm or 20 μm, in addition to the strength, the elongation also increases significantly.

On the other hand, in sample No. 6 as a comparative example, since the Mg ₂ Si content was large, the Mg-based alloy became brittle, and it was difficult to produce a tensile test piece by machining. In addition, in Sample Nos. 11 to 12 as comparative examples, since the maximum particle diameter of Mg ₂ Si was too large to exceed 50 μm, the toughness of the Mg-based alloy was lowered, and the tensile strength was also lowered.

[table 3]

  Sample No. Tensile strength (MPa) Elongation at break (%) Young's modulus (GPa) refer to 1 278 18 49 2 293 16 53 3 314 13 63 4 322 9 70 5 326 5 82 6 - - 109 Failed to take due to brittle tensile test 7 310 19 59 8 307 17 58 9 303 15 59 10 294 12 58 11 221 7 57 12 206 4 57

Example 6

Prepare pure Mg powder (purity 99.9%, average particle size 350 μm) and Si powder (purity 99.9%, average particle size 22 μm), mix the two powders with Mg:Si=2:1 (molar ratio), and use a ball mill Mix for 30 minutes. The mixed powder was placed on a spark plasma sintering apparatus in a state filled with a carbon mold (inner diameter: 35 mm), and sintering was performed for 30 minutes by adjusting the pressure to 100 MPa and the sample temperature to 600° C. in a vacuum. As a result, a disk-shaped sample made of Mg ₂ Si with an outer diameter of 35 mm and a thickness of 18 mm was obtained.

The above-mentioned disk-shaped sample was pulverized with a jet pulverizer, pulverized and sieved to have a maximum particle diameter of 10 μm or less, to produce Mg ₂ Si particles as a starting material.

Next, 200 g of pure Mg powder (purity: 99.9%) with a particle size of 0.5 to 2 mm was put into a plastic container with a volume of 350 ml, and the container was vibrated for 15 minutes with 0.6 g of oleic acid added to the container using a vibration ball mill. Minutes, so that the surface of the pure Mg powder in the container is uniformly coated with oleic acid. Then add the above-mentioned Mg ₂ Si particles (13% by volume standard relative to the whole mixed powder) in the container, and then apply vibration for 15 minutes to make the Mg ₂ Si particles adhere to the surface of the pure Mg powder, thus making this product. The Mg-based composite powder specified by the invention.

The X-ray diffraction results of the Mg-based composite powder obtained as described above are shown in FIG. 13 . Only the peaks of Mg and Mg ₂ Si were detected as input raw materials, and in the results of scanning electron microscope observation, it was also confirmed that Mg ₂ Si particles were uniformly attached to the surface of the coarse Mg powder. From the above, it was confirmed that when When oleic acid is used as a binder, Mg-based composite powder can also be produced.

As mentioned above, although embodiment of this invention was described referring drawings, this invention is not limited to embodiment shown in figure. Various modifications and changes can be added to the illustrated embodiments within the same or equivalent scope as this invention.

Industrial Utilization Possibility

The magnesium-based alloy obtained according to the present invention can greatly improve the low rigidity of existing magnesium alloys, which is a problem in performance, and can be advantageously used in automotive parts such as engine parts and transmission parts and structural members. for the required use.

Claims (14)

1. a magnesium base composite powder wherein, has: the magnesium based powders; Be scattered in the either party's at least of the surface of described magnesium based powders and matrix inside magnesium silicide Mg ₂Si.

2. magnesium base composite powder according to claim 1, wherein, described Mg ₂The maximum particle diameter of Si is below the 50 μ m.

3. magnesium base composite powder according to claim 1, wherein, described Mg ₂The maximum particle diameter of Si is below the 20 μ m.

4. magnesium base composite powder according to claim 1, wherein, described Mg ₂The maximum particle diameter of Si is below the 5 μ m.

5. magnesium base composite powder according to claim 1, wherein, with respect to the described Mg of this magnesium base composite powder ₂The content of Si counts 5～60% with dimension criteria.

6. the former material of magnesium base alloy wherein, carries out press-powder to the described magnesium base of claim 1 composite powder and is shaped and sintering, makes Mg ₂The Si particle is dispersed in the matrix.

7. the manufacture method of a magnesium base composite powder wherein, has:

Prepare Mg based powders and Mg ₂The operation of Si particle;

Operation at the surperficial coating adhesive of described Mg based powders;

The Mg based powders and the described Mg of described adhesive will be coated with ₂Si mix particles, stirring make Mg ₂The operation that the Si particle combines with the surface of Mg based powders.

8. the manufacture method of a magnesium base composite powder wherein, has:

Prepare Mg based powders and Mg ₂The operation of Si particle;

At described Mg based powders of allotment and described Mg ₂Mechanically mix behind the Si particle, make Mg ₂The operation that Si particle and the surface of Mg based powders mechanically combine.

9. the manufacture method of a magnesium base composite powder wherein, has following operation:

Prepare Mg based powders and Mg ₂The operation of Si particle;

Mix described Mg based powders and described Mg ₂The operation of Si particle;

In metal die, described mixed-powder press-powder is shaped, makes being dispersed with described Mg ₂The operation of the Mg base press-powder formed body of Si particle;

The described Mg base of sintering press-powder formed body makes being dispersed with described Mg ₂The operation of the Mg base sintered alloy of Si particle;

Described Mg base sintered alloy is mechanically pulverized or machining and carry out the operation of powder powdered.

10. the manufacture method of Mg base composite powder wherein, has:

Prepare the operation of Mg based powders and Si particle;

The operation of mixing described Mg based powders and described Si particle;

In metal die, described mixed-powder press-powder is shaped, makes the operation of the Mg base press-powder formed body that is dispersed with described Si particle;

Heat described Mg base press-powder formed body, by the synthetic Mg of the reaction of Mg and Si ₂Si makes simultaneously and is dispersed with Mg ₂The operation of the Mg base sintered alloy of Si particle;

Described Mg base sintered alloy is mechanically pulverized or machining and carry out the operation of powder powdered.

11. the manufacture method of a magnesium base composite powder wherein, has:

In magnesium base liquation, drop into Mg ₂Si particle and the operation that stirs;

Described liquation is poured in the mould to make the operation of the former material of casting;

The former material of described casting is mechanically pulverized or machining and carry out the operation of powder powdered.

12. the manufacture method of a magnesium base composite powder wherein, has:

Prepare Mg based powders and Mg ₂The operation of Si particle;

Mix described Mg based powders and Mg ₂The operation of Si particle;

In metal die, described mixed-powder press-powder is shaped, makes being dispersed with described Mg ₂The operation of the Mg base press-powder formed body of Si particle;

Described Mg base press-powder formed body is fused, casts, make Mg ₂The operation of the former material of Mg base casting that the Si particle disperses;

The former material of described casting is mechanically pulverized or machining and carry out the operation of powder powdered.

13. the manufacture method of a magnesium base composite powder wherein, has:

Prepare the operation of Mg based powders and Si particle;

The operation of mixing described Mg based powders and described Si particle;

In metal die, described mixed-powder press-powder is shaped, makes the operation of the Mg base press-powder formed body that is dispersed with described Si particle;

Heat described Mg base press-powder formed body, by the synthetic Mg of the reaction of Mg and Si ₂Si makes simultaneously and is dispersed with Mg ₂The operation of the Mg base sintered alloy of Si particle;

Described Mg base sintered alloy is fused, casts, make Mg ₂The operation of the former material of Mg base casting that the Si particle disperses;

The former material of described casting is mechanically pulverized or machining and carry out the operation of powder powdered.

14. the manufacture method of the former material of magnesium base alloy wherein, has:

The described magnesium base of claim 1 composite powder is carried out the operation that press-powder is shaped;

The operation of the described press-powder formed body of heating in 200～400 ℃ inert gas atmospheres or non-oxidizing gas atmosphere;

After described heating, immediately described press-powder formed body is carried out extrusion process and makes its densified operation.

Images