JPH0372047A - Light al-base composite material and its manufacture - Google Patents

Abstract

PURPOSE:To drastically lighten the composite material in weight, to maintain its thermal strength and wear resistance into good conditions and to improve its machinability by forming the composite material of which a specified ratio of Mg2Si grains having specified grain size are dispersed into Al having specified purity. CONSTITUTION:The Al-base composite material is formed in such a manner that 1 to 40% volumetric rate of Mg2Si grains having <=3mu average grain size as dispersion strengthening grains are uniformly dispersed into pure Al as a matrix. For manufacturing the composite material, mixed powder of Al powder as a matrix and Mg2Si grains as strengthening grains or Al-Mg-Si alloy powder is used as a raw material. The powder is subjected to ball mill treatment into composite powder, which is thereafter subjected to hot forming into a prescribed shape. Since Mg2Si has low specific gravity compared to that of Al, its lightening in weight can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an aluminum-based composite material used for vehicle engine parts, particularly heat-resistant parts such as pistons and connecting rods, in which aluminum is used as a matrix and dispersed in the matrix. The present invention relates to a dispersion-strengthened aluminum matrix composite material in which reinforcing particles are uniformly dispersed, and a method for manufacturing the same.

Conventional technology and issues The heat-resistant parts for internal combustion engines as described above are
Since the parts are used under physically harsh conditions at temperatures as high as ℃, it is important that the materials have excellent heat resistance, toughness, and wear resistance, as well as a low coefficient of thermal expansion. requested.

On the other hand, since the piston and connecting rod reciprocate at high speed, the inertia force becomes large. Therefore, it reduces vibration,
In order to increase engine output and improve responsiveness, it is desirable that the engine be as light as possible.

In response to these demands, we have created a composite material in which a reinforcing particle phase is uniformly dispersed in an aluminum matrix, and in particular, a strong bond between the matrix and the reinforcing particle phase is achieved through a high-energy ball milling process called mechanical alloying. It is known that composite materials manufactured using powder metallurgy techniques using composite powders having the following properties have excellent heat resistance and wear resistance. Therefore, in order to reduce the weight of heat-resistant parts made of A4-based composite materials, in addition to making the walls thinner by taking advantage of their high strength, it is also necessary to reduce the specific gravity of the material itself as much as possible. It is requested that

However, in conventional Ann-based composite materials of this type, /1203 and SIC are generally used as dispersion-strengthening particles, and the specific gravity of these materials is 203:3.97 and 3.97, respectively.
SIC: 3.17, which is relatively larger than the specific gravity of Al, which is 2.70, so the specific gravity of the composite material itself is greater than that of A and 12, which does not necessarily satisfy the request for weight reduction. was not something that could be obtained.

In view of the above-mentioned background, this invention aims to significantly reduce weight and improve heat-resistant strength and abrasion resistance based on the material selection of a specific dispersion-strengthening particle phase that could not be predicted in the conventional membrane. Particle-dispersed Al that can maintain and improve machinability
The purpose is to provide composite base materials.

As a means for solving the problem, the main feature of the present invention is to select Mg251 particles, which have a smaller specific gravity than Ap, as dispersion-strengthening particles, and more specifically, A4 purity of 99. 0% or more of pure aluminum is used as a matrix, and Mg2Si particles with an average particle size of 3 μm or less are used as dispersion-strengthening particles, and the dispersion-strengthening particles are uniformly dispersed at a volume fraction Vf (Mg2Si) of 1 to 40%. This is a lightweight Al-based composite material.

The present invention also provides that the total content of O and C, which are inevitably introduced into the matrix during the manufacturing process of the composite material, particularly during ball milling and are dispersed as fine AU203 and AU+C3 particles, preferably has a volume fraction of Vf. (O+C)
is controlled within the range of 1 to 20%, and the total content of dispersion-strengthening particles and O and C is controlled at a volume fraction Vf (Mg2Si
) is controlled to 40% or less at 10 Vf (O+C).

In addition, the production of the above-mentioned A4-based composite material uses a pre-mixed powder of A4 powder as a matrix and Mg2Si particles as reinforcing particles or A-Mg-St alloy powder as a raw material powder, which is processed by a powerful machine using a ball mill. Mg2Si as a matrix and reinforcing particles
Preferably, a method is adopted in which a composite powder is made in which the particles are strongly bonded and integrated, and the composite powder is hot-molded according to a conventional method to obtain a predetermined molded body.

Specific Description of Configuration Next, each of the above-mentioned configuration items of the present invention will be explained in more detail.

The purity of the aluminum material used as the matrix is 99.0%
The above limitations are due to the following reasons. In other words, in order to increase the heat resistance strength of an aluminum material, it is common to alloy it, but on the other hand, the strengthening mechanism that determines the heat resistance strength of a particle-dispersed composite material is , the interaction between the ceramic reinforcing particles and fine aluminum oxides and carbides uniformly dispersed in the alumina matrix and the high density of dislocations. That is, since the dispersion-strengthening particles are stable in the matrix even at high temperatures, they maintain the dislocation pinning effect up to high temperatures, thereby preventing a decrease in strength even when the temperature rises. However, alloying elements, for example, are not added to pistons because they are exposed to high temperatures of 150 to 400°C, and as a result, they precipitate and become coarse over time, and they no longer contribute to maintaining strength through the binning effect of dislocations. has no particular meaning. On the contrary,
The harmful effect of forming crystallized substances and precipitates and reducing toughness increases. Therefore, it is advantageous to use high-purity aluminum materials as composite materials for heat-resistant parts such as pistons that must have both heat-resistant strength and toughness, and to avoid the disadvantage of reduced toughness. It is necessary to use pure aluminum with a purity of at least 99.0% for the A-base. Most preferably purity 9
9.5% or more should be used, but 99.9%
Even if a material with a purity higher than that is used, a significant increase in effectiveness cannot be expected, and the disadvantage of an increase in material cost will be greater, so it is necessary and sufficient to use a material with a purity lower than that.

In particular, Mg251 particles are used as dispersion-strengthening particles because they have the required function as a reinforcing phase forming element, and their own specific gravity is smaller than that of 1.99/1.
(This is because an even lighter composite material can be obtained.The particle size and the amount of dispersion of the reinforcing particles are the dominant factors that determine the heat resistance, wear resistance, and cutting tool life of the composite material.

If the average particle size of the Mg251 particles as reinforcing particles is too large, exceeding 3 μm, they act as inclusions and become a source of cracks, making the composite material brittle and reducing its toughness. However, the average particle size is 0. If the diameter is too small (less than 1 μm), wear resistance deteriorates, which is not preferable. Therefore, it is preferable to use particles with an average particle size in the range of 0.1 to 3.0 μm, particularly preferably about 1 μm.

Furthermore, the dispersion content of the Mg251 particles in the composite material is as follows:
If the volume fraction Vf (Mg2Si) is less than 1%, the desired sufficient heat resistance and abrasion resistance cannot be imparted. On the other hand, if the amount of dispersion exceeds 40%, the composite material will become brittle and have poor toughness, and the machinability, especially the life of the cutting tool, will be poor. Therefore, Mg
It is necessary that the 25I particles be dispersed at a volume fraction of Vfl to 40%, preferably Vf5 to 3.
It is preferable to disperse it in a range of about 0%, particularly preferably about 10 to 25%.

Afl base composite material according to the present invention, O introduced into the matrix during the manufacturing process, especially by ball milling
The content of C and C is determined by the volume fraction Vf (O+C) of their total, since they eventually disperse as fine Al220+ and Al4C3 particles with a particle size of 30 μm or less and affect the physical properties of the composite material. It is desirable to control the amount within the range of 1 to 20%. The above volume fraction Vf(O+
C) is obtained by converting the weight surface fraction of the content of O and C using the following formula.

Vf (O+C)-1,71x O* w t%+3. 71XC·wt% If the volume fraction of the total content of O and C (Vf(O+C)) is less than 1%, sufficient heat resistance cannot be imparted to the composite material. On the other hand, if it exceeds 20%, the average interparticle distance in the composite material becomes shorter and the restraining force for dislocation increases, resulting in decreased ductility and embrittlement, making it impossible to obtain the desired high elasticity. Most preferably, the contents of O and C should be controlled to about 5 to 10% in terms of their volume fraction Vf (O+C).

In addition, the total content of Mg2Si particles as reinforcing particles and O and C in the composite material is also the volume fraction V f (Mg
2 Sl) 10V f (O+C) 4
If it exceeds 0%, it is not preferable because it causes a decrease in ductility and embrittlement of the composite material as described above. Therefore, it is also desirable to control this to 40% or less.

The content of O and C as described above can be controlled by adjusting the amount of dispersion aid such as ethanol used during ball milling,
This can also be done by adjusting the oxygen concentration of the atmosphere during the manufacturing process.

In the production of the A4-based composite material according to the present invention, a mixture of separately produced aluminum powder and Mg251 particles may be used as the raw material powder, or alternatively, a mixture of aluminum powder and Mg251 particles produced separately may be used.
Al-Mg-S1 alloy powder whose composition is adjusted so that the volume fraction Vf (Mg2Si) of l is in the range of 1 to 40%,
For example, the atomized powder may be used. Then, in order to improve the uniform dispersibility of the reinforcing particles, the above raw material powder was strongly ground by ball milling to create a composite powder in which the reinforcing particles were combined in a manner that they were wrapped in a matrix. A predetermined molded body shall be obtained by molding.

The above-mentioned forming includes the usual steps of powder metallurgy such as degassing, creating a billet by hot compaction, extrusion from this billet, forging from an extruded material, and further powder forging.

Heat-resistant parts such as pistons and connecting rods for internal combustion engines are manufactured by further performing necessary secondary processing such as forging, cutting, and polishing on the molded bodies obtained as described above.

An An-Mg-S1 alloy produced into powder by an atomization method was used as the raw material powder for the examples. To prepare the above alloy, pure aluminum with a purity of 99.8% is used as the aluminum material as a matrix, and Mg and S are added to it.
1 was added in various amounts in a ratio of 311 mol to 2 mol of Mg.

Then, each of these raw material powders was milled using a ball mill using a steel ball 30 in a gas atmosphere.
A composite powder was prepared by ball milling at rpsx for 1 hour. In this ball milling step, ethanol was added as a dispersion aid at a ratio of 3vt%.

Next, the composite powder obtained above was filled into an Al powder container in an Ar gas atmosphere, and heated to 3×10−3 at 500°C.
torrx After 5 hours of vacuum heating and degassing treatment, 500°C x 700 ONgf/ad using a hot press
The resulting billet was compacted under the conditions of extrusion ratio 1
By extrusion molding at a ratio of 0:1 and an extrusion temperature of 450° C., various aluminum matrix composite materials in the shape of round bars were obtained.

On the other hand, for comparison, A with an average particle size of 0°5 μm was added to the reinforcing particles.
, a composite material containing Q203 powder dispersed in 15 vol 96(7) ratio (sample No. 13), and an aluminum material sample containing no reinforcing particles (sample No. 14)
was also manufactured in accordance with the above.

Then, for the various samples obtained above, the volume ratio Vf1 diameter of the Mg2Si particles dispersed therein was investigated, and the O and C contents were also investigated. The results are shown in Table 1. In addition, the dispersion volume fraction Vf of Mg251 particles (Mg
2 Si) +, t, the solid solution amount of Mg25j is O,
The specific gravity was determined as 1°99.

Table 1 [Margin below] Each of the above samples No. 1 to 16 was examined for tensile strength at 300° C. hot, elongation at room temperature, abrasion resistance, and machinability. The results are shown in Table 2. In addition, the wear resistance test was carried out using an ultra-thin dry abrasion tester using a mating material: Fe.
12. No lubrication, friction speed: 1. 991′rL/S,
Friction distance: 600m, final load: 2. Measured under IK9 conditions. In addition, the cutting workability is as follows: Bit used: 10, Cutting speed = 247TrL/S1 Feed: 0.2m/rev
, Depth of cut = IM1 Number of cuts: 8 times, No lubrication, Sample dimensions:
Cutting was performed under the conditions of 23 m in diameter and 200 m in length, and the width of wear on the flank of the cutting tool was measured.

[Margin below]

Table 2 As can be seen from the results shown in Table 2 above, Mg251 particles with an average particle size of 3 μm or less are used as reinforcing particles, and the volume fraction Vf (Mg2Si) of the dispersed amount is 1 to 40%.
All of the AQ-based composite material samples No. 11 to 10) according to the present invention, which were dispersed in the range of In contrast, sample No. of the comparative example
, Nos. 11 to 16 had serious drawbacks in any one or more of the above-mentioned properties. Moreover, of course, the composite material according to the present invention has a specific gravity smaller than that of aluminum, and sample No. 1 of the comparative example uses A and Q20s particles as reinforcing particles.
It was significantly lighter than the composite material No. 5.

Effects of the Invention As described above, the present invention provides a composite material that has the unique characteristics of a particle-dispersed Afl base composite material, particularly heat resistance, and has excellent wear resistance and cutting tool life. Furthermore, it is possible to provide a lightweight A base material composite material having a specific gravity smaller than Al1. Therefore, the composite material is suitable for use in heat-resistant parts such as pistons and connecting rods of internal combustion engines that are used under severe conditions, and can reduce the weight of the layers.

that's all

Claims (3)

[Claims] (1) Pure aluminum with an Al purity of 99.0% or more is used as a matrix, and Mg_2Si particles with an average particle size of 3 μm or less are used as dispersion-strengthening particles, and the proportion of the dispersion-strengthening particles is 1 to 40% in the volume fraction Vf (Mg_2Si). A lightweight Al-based composite material characterized by being uniformly dispersed. (2) The total content of O and C, which are inevitably present as Al_2O_3 and Al_4C_3 particles, is the volume ratio V
f(O+C) is controlled in the range of 1 to 20%, and the total content of dispersion-strengthening particles and O and C is 40% at their volume fraction Vf(Mg_2Si)+Vf(O+C).
% or less.
Base composite. (3) Mixed powder of Al powder as a matrix and Mg_2Si particles as reinforcing particles or Al-Mg-S
The lightweight Al-based composite according to claim (1) or (2), characterized in that the i-alloy powder is used as a raw material powder to form a composite powder by ball milling, and then the composite powder is hot-formed into a predetermined shape. Method of manufacturing wood.