JPH07197167A - Sintered aluminum alloy having excellent strength and wear resistance - Google Patents

Abstract

PURPOSE:To develop a sintered Al alloy having excellent strength and wear resistance by dispersing group hard layers as assemblies of fine Si crystal grains in an Al alloy base in such a manner that these layers exist therein in the structure of the sintered Al alloy. CONSTITUTION:The Al powder, Al-Zn alloy powder, Al-Mg alloy powder, Al-Cu alloy powder, Al-Fe alloy powder and Al-high-Si alloy powder in the fine powder form produced by an atomization method are mixed at specific ratios and, thereafter, the mixture is pressurized and molded to a desired shape. This powder mixture molding is sintered at a high temp. and is then subjected to shape correction by recompression. The molding is further subjected to a soln. heat treatment and aging treatment, by which the sintered member of the Al alloy is produced. Such sintered alloy has the structure in which the group hard layers 2 of 20 to 150mum sizes densely assembled with the fine Si crystal grains of an average grain size of 1.5 to 15mum in the base 3 consisting of the Al alloy at a ratio of 10 to 70 area % disperse and exist in the base Al alloy 3 at a ratio of 3 to 50 area % of this alloy. The sintered Al alloy member which is light in weight and has the excellent wear resistance and strength is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered aluminum alloy for manufacturing various machine parts such as gears for oil pumps for passenger cars, cam sprockets for passenger car engines, which are lightweight and require strength and wear resistance. It is about.

[0002]

2. Description of the Related Art Generally, an aluminum alloy containing Si: 8 to 30 wt% as shown in Japanese Patent Publication No. 1-20215 is used for manufacturing a mechanical part which is lightweight and requires strength and wear resistance. Has been. However, this alloy
As described in the official gazette, since it is difficult to manufacture by an ordinary powder metallurgy method, after heating at 300 ° C. to a liquid phase formation temperature or lower or sintering, forging in the above temperature range or strong working of extrusion is performed. , Si with a density ratio of 95 without coarsening
Although the target alloy is obtained by densifying the alloy to more than 10%, there is a drawback that the cost is increased because the above-mentioned steps such as hot forging or extrusion are required.

Therefore, a method of obtaining a sintered aluminum alloy having excellent strength only by a sintering process has been proposed (see Japanese Patent Laid-Open No. 4-365832).

To produce a sintered aluminum alloy by this method, the raw material powder is Si: 16-30% by weight.
Of Al-Si alloy powder containing less than 1% of primary crystal Si crystallized with the remainder substantially consisting of Al, and further pure Al powder, Cu powder and Mg powder are prepared, and these raw material powders are added and mixed. , Molding pressure of the obtained mixed powder: 2.5 to
Molded into a green compact with n / cm ² or more,
Obtained by sintering at ˜570 ° C.

The sintered aluminum alloy thus obtained has Si: 2 to 16% by weight and Cu: 2.0 to 4.5.
%, Mg: 0.2 to 1.5% by weight, the rest has a composition essentially consisting of Al, has a structure in which primary Si is uniformly dispersed, and has a low Si content. However, even if the primary crystal Si is uniformly dispersed, the wear resistance can be favorably maintained.

[0006]

However, in recent years, as the performance of the rotary drive device has been improved, the parts used therefor have come to be used under severe conditions, and under such severe conditions, Parts that are required to withstand use, but have sufficiently satisfactory mechanical properties (particularly strength and wear resistance) in the above-mentioned conventional sintered aluminum alloy having a structure in which primary Si is uniformly dispersed. Could not be manufactured.

[0007]

Therefore, the present inventors have
As a result of conducting research to obtain a Si-containing sintered aluminum alloy that is more excellent in strength and wear resistance than before,
(A) A structure in which the distribution of Si crystal grains greatly affects the strength and wear resistance of the sintered aluminum alloy, the Si crystal grains aggregate to form a group hard phase, and the group hard phase is dispersed in the matrix. The sintered aluminum alloy having No. 1 has improved strength and wear resistance as compared with the conventional sintered aluminum alloy having a structure in which Si crystal grains are uniformly dispersed.

(B) In order to obtain an alloy having a structure in which the above Si crystal grains are aggregated to form a group hard phase, and the group hard phase is dispersed in the matrix, and which is excellent in strength and wear resistance. Is S as a raw material powder for forming a group hard phase.
i: 13 to 60% by weight, cooling rate: 10 ² ° C /
Research results such as that obtained by using an Al alloy powder manufactured in a second or more, preferably an amorphous Al alloy powder, were obtained.

The present invention has been made based on the results of such research, and has a strength having a structure in which Si crystal grains aggregate to form a group hard phase, and the group hard phase is dispersed in the matrix. And a sintered aluminum alloy having excellent wear resistance. in this case,
It is preferable that Si is 0.05 to 2% by weight as a solid solution in the base material.

The structure of the sintered aluminum alloy having excellent strength and wear resistance according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view of a structure obtained by copying a structure photograph of the sintered aluminum alloy of the present invention.

In FIG. 1, 1 is a Si crystal grain. If the average grain size of the Si crystal grains 1 is smaller than 1.5 μm, the effect of contributing to wear resistance is reduced, and if it is larger than 15 μm, the strength of the material decreases,
Moreover, the machinability deteriorates, which is not preferable. Therefore,
Average grain size of Si crystal grains: Determined within a range of 1.5 to 15 μm.

As shown in FIG.
Group hard phase 2 as shown in is formed,
The group hard phase 2 is dispersed (preferably uniformly dispersed) in the matrix 3.

The group hard phase 2 is preferably formed by densely gathering Si crystal grains 1 at a ratio of 10 to 70 area%, because the Si crystal grains 1 are less than 10 area% in abrasion resistance. The effect on sex is not fully obtained, while
If they are densely aggregated over 70 area%, the group hard phase 2 will have a density close to a lump, and the opponent's aggression becomes remarkable,
This is because the strength and machinability are inferior, which is not preferable.

The group hard phase 2 in which the Si crystal grains 1 are densely aggregated at a ratio of 10 to 70 area% preferably has an average size in the range of 20 to 150 μm, because the average size is. This is because if it is less than 20 μm, the effect on the wear resistance is reduced, while if it exceeds 150 μm, the strength of the material is lowered, which is not preferable.

As described above, in the sintered aluminum alloy of the present invention, the Si crystal grains 1 having an average grain size of 1.5 to 15 μm are densely assembled at a ratio of 10 to 70 area% and the group hard phase 2 is formed. However, it is preferable that the group hard phase 2 is dispersed in the matrix 3 at a rate of 3 to 50 area%. The reason is that if it is less than 3% by area, the effect on the wear resistance is reduced, while if it exceeds 50% by area, the strength of the material is significantly reduced, which is not preferable.

As described above, in order to obtain an alloy having a structure in which the group hard phase is dispersed as described above and having excellent strength and wear resistance, Si: 13 to 13 is used as the raw material powder for forming the group hard phase. Cooling rate: 10 containing 60% by weight
Al alloy powder produced at ² ° C./sec or more, preferably,
It can be obtained by using an amorphous Al alloy powder for the following reason.

The Si component in the Al alloy powder for forming a hard phase grows and coarsens as a hard Si crystal by heating during sintering, but the Al alloy produced at a cooling rate of 10 ² ° C / sec or less. In the powder, the Si component in the powder was already crystallized as coarse primary crystal Si, and the Si crystal was further coarsened during sintering, so that the grain size could not be controlled to 15 μm or less, and the particle size was 1.5 to 15 μm. This is because the group hard phase formed by aggregating Si crystals does not form and is dispersed as coarse Si crystals, which causes a decrease in the strength and machinability of the material. From the above reason, as the Al alloy powder raw material for forming the group hard phase, amorphous powder is preferable because it is easier to control the Si crystal grain size during sintering.

[0019]

[Examples] As raw material powders, pure Al powder having a grain size of -100 mesh and Al produced by the atomization method were used.
-50 wt% Zn powder, Al-5 wt% Mg powder, Al
-30 wt% Cu powder, Al-10 wt% Fe powder, and 10 ³ to 10 ⁴ ° C. by an atomizing method having the average particle size and composition shown in Table 1 for forming a group hard phase.
Al-high Si-based powder produced at a cooling rate of 1 / sec and an amorphous Al-high Si-based powder obtained by crushing an amorphous ribbon produced at a cooling rate of 10 ⁵ ° C / sec or more by a single roll rapid solidification method. A powder was prepared.

After mixing and mixing these raw material powders in the proportions shown in Table 2, a molded body was prepared at a pressing force of 4 ton / cm ² , and the obtained molded body was sintered under the conditions shown in Table 3 and 5 .5 to
corrected with pressure of n / cm ² (the recompression) subjecting, the present invention sintered aluminum alloy by solution treatment and aging treatment (hereinafter, referred to as the present invention alloy) 13 and Comparative sintered aluminum alloy (hereinafter , Comparative alloys) 1 to 8 were produced.

The structures of the obtained alloys 1 to 13 of the present invention and comparative alloys 1 to 10 were observed with a metallographic microscope, and the S
The average grain size of the i crystal grains, the Si crystal grain aggregation density of the group hard phase formed by aggregating Si crystal grains, the average size of the group hard phase, and the dispersion ratio of the group hard phase in the matrix were measured. The measured values are shown in Table 4.

Further, for comparison, an atomized powder having a grain size of -100 mesh, which contains Si: 20% by weight in which normal primary crystal Si is precipitated and the balance is Al and inevitable impurities, and -100 mesh in all cases. Grain size of C
u powder, Mg powder, and pure Al powder were prepared, and the atomized powder was blended at the ratio shown in Table 2, mixed, and then molded at a pressing force of 4 ton / cm ² , and sintered under the conditions shown in Table 3. A conventional sintered aluminum alloy (hereinafter referred to as a conventional alloy) was produced by solution treatment and aging treatment.

The alloys 1 to 13 of the present invention obtained and the comparative alloy 1
~ 8 and conventional alloy, vertical: 10mm, width: 10m
A block having a size of m and a thickness of 40 mm was prepared, and the cast iron (FC250) rotating the block had an outer diameter of 4
A block-on-ring type abrasion test was performed in which a ring having a size of 0 mm, an inner diameter of 30 mm and a width of 15 mm was pressed with a constant load.

The test conditions are as follows.

Load: 30 kgf, Sliding speed: 5 m / sec, Sliding distance: 1,500 m, Lubrication: Engine oil drip (for gasoline engine) The amount was measured and the results are shown in Table 4.

Further, alloys 1 to 13 of the present invention and comparative alloy 1
~ 8 and conventional alloy using JIS standard JISZ255
The tensile test piece based on 0 was produced, the tensile strength was measured using this test piece, and these measured values are shown in Table 4.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

Further, the Si content of the base material was also measured, and the average content is shown in the remarks column of Table 4.

[0032]

From the results shown in Tables 1 to 4, Si crystal grains having an average grain size of 1.5 to 15 μm are densely aggregated at a rate of 40 to 70 area%. The average size of the group hard phase is within the range of 20 to 150 μm, and the group hard phase is 3 to 50 μm in the matrix.
The alloys 1 to 13 of the present invention, which are dispersed in the area% ratio, are superior in tensile strength and wear resistance from the conventional alloy in which Si crystal grains are uniformly dispersed in the base material, because the wear amount is small. It turns out that it is excellent.

However, it is understood that the comparative alloys 1 to 8 out of the above range are inferior in at least either tensile strength or wear resistance.

As described above, when a machine part or the like is manufactured using the sintered aluminum alloy of the present invention, a machine part having mechanical strength superior to the conventional one can be manufactured and it can withstand severe use. Therefore, it can greatly contribute to the performance improvement of the drive device and the like.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view for explaining the structure of a sintered aluminum alloy of the present invention.

[Explanation of symbols]

 1 Si crystal grain 2 group hard phase 3 substrate

Claims (4)

[Claims] 1. Sintered aluminum excellent in strength and wear resistance, characterized by having a structure in which Si crystal grains aggregate to form a group hard phase, and the group hard phase is dispersed in the matrix. alloy. 2. A structure in which Si crystal grains are aggregated at a rate of 10 to 70 area% to form a group hard phase, and the group hard phase is dispersed in the matrix at a rate of 3 to 50 area%. A sintered aluminum alloy having excellent strength and wear resistance, which is characterized in that 3. The group hard phase formed by aggregating Si crystal grains at a ratio of 10 to 70 area% has an average size of 2
A sintered aluminum alloy having excellent strength and wear resistance, characterized in that it has a structure in which the group hard phase is in the range of 0 to 150 μm and is dispersed in the matrix at a ratio of 3 to 50 area%. 4. The Si crystal grains have an average grain size of 1.5 to
The sintered aluminum alloy excellent in strength and wear resistance according to claim 1, wherein the sintered aluminum alloy has a size within a range of 15 μm.