JP3424156B2 - Manufacturing method of high strength aluminum alloy member - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to the for advantageously produced economically useful high strength aluminum alloy member as various devices and equipment members such as automotive engine components, aluminum alloy powder having excellent workability or The alloy powder and
The present invention relates to a method for producing a high-strength aluminum alloy member by hot plastic working , the raw material powder being a mixture with Lamix powder .

[0002]

2. Description of the Related Art Aluminum alloy has a specific gravity as small as about one third of iron and is widely used as a lightweight material. However, the mechanical properties such as heat resistance and wear resistance are inferior to those of iron-based materials. As a characteristic improvement measure, in recent years, development of a new aluminum alloy by powder metallurgy is in progress. This is an aluminum alloy melt with a large amount of alloy elements added to it by subjecting it to a powder by subjecting it to a quenching spray treatment such as gas atomization,
It is formed into a required shape by a hot extrusion method or the like.
According to the powder metallurgy method, it is difficult to manufacture by the melting and casting method.
It is possible to manufacture an aluminum alloy member containing a large amount of i, Fe, Mn, Ni, etc., and as an effect of enriching the amount of alloy elements,
Provides excellent functional properties.

[0003]

As described above, it is possible to improve the mechanical properties of aluminum alloy parts by applying the powder metallurgy method, but it has not yet become widespread. The reason is that the processing cost including the raw material powder is high. The first of the factors is that the manufacturing yield of the raw material powder is low. In the powder manufacturing method using a gas or the like as a cooling medium, only powders having a particle diameter of 50 μm or less are targeted, and coarse particles exceeding them need to be classified and removed, and the powder yield is extremely low at about 30%. It will be.

The second factor is the poor workability of the powder. That is, since the powder containing a large amount of alloying elements is hard and has heat resistance, the molding process is generally performed at about 500
A high pressure force of 200 MPa or more is required in the temperature range of ℃ or more. Further, because of the high-pressure processing, the service life of the die is short, and it becomes difficult to accurately form a component having a complicated shape. The present invention is intended to solve the above problems, and aluminum alloy powder or the alloy powder
High-speed
It has excellent mechanical properties under the compression plastic working condition of low pressure.
Provided is a method for economically producing a aluminum alloy member .

[0005]

The method for producing an aluminum alloy member according to the present invention comprises one or more elements selected from transition metal elements of Fe, Cr, Ni, Zr and Mn:
1 to 15 wt%, Si: 10 to 30 wt%, Cu: 0.5 to
5% by weight, Mg: 1 to 5% by weight, the balance being substantially Al, having a fine crystal grain size of 2 μm or less, and a powder particle size of 50
Discharge plasma firing of aluminum alloy powder of μm or more
The preformed body that is solidified by binding is
10 ⁻² / sec or more in the temperature range just below the liquidus line of gold
It consists of compression plastic working at a strain rate . Ceramic powder particles are blended with the above aluminum alloy powder, if desired. The ceramic powder is a fine powder having a particle size of 5 μm or less, and the compounding amount is adjusted to be in the range of 1 to 10 vol%.

The above-mentioned aluminum alloy powder and a mixed powder obtained by blending ceramic powder with the aluminum alloy powder (both may be simply referred to as an aluminum alloy hereinafter) may be a powder or a solidified body (sintered body) of an appropriate shape. After being preformed, it is formed into a desired product member by compression plastic working. The formation of the preformed body is suitably achieved by the spark plasma sintering method, as described later.

The aluminum alloy powder of the present invention and its preform have high-speed superplastic properties. As will be described later, the strain processing speed (ε) is 10 ^{-2 in} the temperature range just below the liquidus line.
It is possible to perform high-speed processing of not less than / sec, and under this processing condition, elongation is high at about 200% or more, and its deformation flow stress is extremely low at about 20 MPa or less. Aluminum alloys containing a large amount of alloying elements are generally hard and heat resistant, so plastic working of crystalline materials usually requires a high working force of 200 MPa or more in a high temperature range of 500 ° C. or more, and processing using superplasticity. Process (crystal grain size: about 10 to 100 μm)
Even when applied, the processing speed is about 10 ^-3 to 10 ^-4 / sec
It is low, and high-speed machining of 10 ^-2 / sec or more is impossible and productivity is poor. INDUSTRIAL APPLICABILITY The aluminum alloy powder and its preform of the present invention realize efficient compression plastic working under high speed and low pressure as an effect of the chemical composition, ultrafine crystal structure and powder grain size of the above alloy powder. ing.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The chemical composition of the aluminum alloy powder is defined as described above in order to ensure the mechanical properties required for structural members and the like and to secure the superplastic characteristics. That is, Si, Cu, Mg, etc. are elements that enhance strength, heat resistance, wear resistance, etc. If the content thereof is less than the above lower limit value, the material improvement effect is insufficient,
On the other hand, if the upper limit is exceeded, the material becomes hard and brittle, and superplastic properties cannot be secured.

The transition metal elements Fe, Cr, Ni, Zr and Mn are effective elements for improving mechanical properties.
The purpose of the present invention is to enhance the superplastic property as an effect of the addition. That is, these elements combine with Al,
Precipitation as a fine compound phase suppresses the crystal growth of the aluminum alloy, and makes it possible to obtain the fine crystal structure necessary for the expression of superplasticity properties. The content (the total amount when two or more kinds are contained together) is set to 1 wt% or more in order to make the addition effect sufficient, and 10 wt%
The upper limit of% is that if it exceeds the upper limit, the material becomes hard and the superplastic property is impaired.

The grain size of the aluminum alloy powder is 2 μm
The following is required. The reason for having such an ultrafine structure is to ensure high-speed superplasticity. Further, the reason why the powder particle diameter is limited to 50 μm or more is to improve the compressibility, moldability, and plastic deformability of the powder. This is because the finer the powder produced by ultra rapid solidification, the larger the strain hardening, the more the frictional resistance at the grain interface in the compression plastic working increases, and the lower the plastic deformability. Aluminum alloy powder with this ultra-fine crystal structure and powder grain size is produced by the spinning water atomization process (SWAP method: Spining Water atomi
It can be obtained in good yield by spraying the zation process (cooling rate: 10 ⁴ ° C / sec or more).

Ceramic powder is blended with the aluminum alloy powder, if desired. Ceramic particles are
It disperses in the aluminum alloy matrix to enhance the mechanical properties of the product member and suppresses the crystal growth of the aluminum alloy of the matrix. The grade of ceramics is
Oxides, nitrides, carbides, borides, etc.
One kind or plural kinds thereof are appropriately selected and used. Particularly, it is effective to use silicon carbide (SiC), alumina (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ) or the like alone or in combination.

The ceramic powder needs to be fine particles having a particle size of 5 μm or less. For coarser grain sizes,
This is because the superplastic characteristics of the aluminum alloy powder are deteriorated, high-speed superplastic processing becomes difficult, and finish processing (machining) becomes difficult. The blending amount is 1 to 10
If the content is less than 1 vol%, the compounding effect is poor, and if the content exceeds 10 vol%, a large amount is compounded, which causes embrittlement of the alloy and impairs high-speed superplastic properties.

The aluminum alloy powder (single powder or mixed powder with ceramics) of the present invention is formed into a compacted solidified body (sintered body) having an appropriate shape prior to molding (compression plastic working such as forging) of product members. Is preferred. Although it is possible to obtain the target member by subjecting the powder to compression plastic working as it is, preforming is advantageous for increasing the efficiency of compression plastic working.

The preforming is performed by the spark plasma sintering method (SP
S method: Spark plasma Sintering). In spark plasma sintering, pressure sintering is performed using pulsed current, and internal heat generation type sintering that uses the high energy of high-temperature plasma due to the momentary and intermittent spark discharge that occurs in the powder particle gap. Is the law. Discharge points in the powder sample move and disperse throughout the sample as the current / voltage application is repeatedly turned on and off. Due to the uniform heating effect due to this internal heat generation, it is possible to achieve homogeneous sintering under a processing condition of a short time and at a low temperature (preventing the growth and coarsening of crystal grains from being suppressed).

The sintering treatment temperature is preferably regulated to 500 ° C. or lower. This is to prevent the growth and coarsening of the crystal grains and to maintain the high-speed superplasticity property based on the fine crystal structure.
The processing temperature can be easily controlled by the pulse current, ON / OFF cycle, processing time and the like. Further, the applied pressure is appropriately in the range of about 70 to 180 MPa. If the pressing force is lower than this, high temperature sintering is required, which causes the disadvantage of coarsening the growth of crystal grains. On the other hand, it is not necessary to make the pressure higher than 180 MPa, and an increase in the applied pressure further accelerates the wear of the mold, which is not preferable.

In the spark plasma sintering process, various intermetallic compounds (Cu-Al,
Mg-Si, Al-Cu-Fe, Al-Mn, etc.) are formed by precipitation. Although the aluminum alloy powder of the present invention contains a large amount of alloying elements, it is subjected to ultra-rapid solidification treatment such as SWAP method (cooling rate: 10 ⁴ ° C).
/ sec) or more), almost no precipitate is formed, and even if it is precipitated, the amount of formation is small and it is in a supersaturated solid solution state. During the spark plasma sintering process, these elements are precipitated as intermetallic compounds. Since the sintering process is accomplished under conditions of low temperature and short time, the precipitated compound phase is fine (grain size 1
.mu.m or less), and contributes to strengthening the mechanical properties of the aluminum alloy product without impairing the superplastic properties of the powder.

[0017] and compressive plastic working of the preform (mixed powder of elemental powder or ceramic) aluminum alloy powder of the present invention, in the temperature range just below the alloy liquidus (T _liq), strain machining speed 10 ^{- It} is performed under the condition of ² / sec or more. The optimum range of plastic working temperature (T) is T _liq −
35 ° C. ≦ T ≦ T _liq −10 ° C. Figure 1 shows the superplasticity characteristics of aluminum alloy powder (preform) and its flow deformation stress (strain processing speed: 10 ^-1 / sec) (test material:
Chemical composition (wt%) Si 17.1, Cu 0.96, Mg 1.86, Fe 1.92, N
i 1.0, Mo 0.56, Al Bal, crystal grain size 2 μm, powder grain size 50
μm, liquidus line 550 ℃). As shown in the drawing, in the high strain rate processing in the temperature range (about 515 to 540 ° C.) immediately below the liquidus line, it exhibits high ductility with an elongation rate of 200% or more, and its deformation flow stress is remarkably low of 20 MPa or less.

As described above, the aluminum alloy powder of the present invention and its preform enable efficient compression plastic working under high speed and low pressure, and enhance the productivity of various members by powder metallurgy. It is possible to reduce and alleviate the wear of the mold, improve the service life of the mold, and increase the accuracy of the shape of a member having a complicated shape.

[0019]

EXAMPLE Aluminum alloy powder (single powder and mixed powder) is preformed and subjected to forging to manufacture a member. (1) Aluminum alloy powder A powder obtained by the SWAP method and a powder obtained by the gas atomizing method are used. The SWAP powder has a particle size of 50 to 420 μm, and the gas atomized powder has a coarse particle size (powder particle size: 50
~ 420 μm) and a fine particle size (the same: <50 μm) were prepared. (2) Ceramic powder a: Silicon carbide (SiC) b: Alumina (Al ₂ O ₃ ) c: Silicon nitride (Si ₃ N ₄ )

(3) Preforming (Formation of Formed Solidified Body) A cylindrical block (φ 60 × 30 l, mm) is formed by spark plasma sintering or hot extrusion processing. [SPS Sintering / Sintering] Sintering temperature 400 ℃, processing time 20 min, pressure 1.5tf / cm
² . [Hot extrusion molding] Molding temperature 480 ℃, extrusion ratio 11.

(4) By a compression plastic working hydraulic press machine, a piston member (outer diameter: 62, length:
65, wall thickness: molded top 3, side 5, 5). Machining speed: 10 ^-1 / sec Machining temperature: Liquidus −35 to 10 ℃

The raw material powders, molding / processing conditions, processing results, etc. are shown in Tables 1 and 2. In the table, “W” in the “Type of alloy powder” is SWAP powder, “G” is gas atomized powder, is powder particle size: 50 to 420 μm, is powder particle size: <50
μm. Also, the crystal grain size of W powder ≦ 1 μm, the crystal grain size of G powder ≧ 1 μm, and the crystal grain size of G powder <1 μm. The "forging result" is an inspection result by visual observation and a color check of the member obtained by forging, and the mark "○" indicates that there is no crack and the quality is sound. The blanks (No. 114, No. 115) in the same column indicate that the forging could not be carried out in the preforming step because a preform which could be used for forging could not be formed.

In the comparative example, No. 101 (excessive amount of Si in aluminum alloy powder), No. 103 (excessive amount of Cu), No. 105 (Mg)
Excessive amount) and No. 107 (excessive amount of transition metal element) caused cracks in the forged member because the alloy powder was hardened by the excessive content of the alloying element and the cracking susceptibility of the material increased. No.102 (insufficient amount of Si in aluminum alloy powder), No.104
(Insufficient amount of Cu), No. 106 (insufficient amount of Mg), No. 108 (insufficient amount of transition metal element) are forging with low processing stress due to coarsening of the crystal grain size due to insufficient element content of the alloy powder. Despite the conditions, cracks have occurred. This is because the optimum processing speed region has shifted to the low speed side. No.109 and No.1
The reason why the forged parts of 10 are cracked is that the ceramic powder was excessively compounded in the former case and the ceramic particle size was coarse in the latter case, so that the superplastic characteristics of the preformed body were impaired. .

No. 111 [Fine crystal SWAP powder (powder particle size ≧
50 μm) Use] has cracks in the forged member,
This is because the crystal grains become coarse during the preforming (hot extrusion) process, and the superplastic deformability of the preform is reduced. No.112 forged parts cracked due to alloy powder (gas atomized powder)
Due to the coarse crystal grains (grain size> 2 μm) and the low preplasticability of the preform. As shown in No. 113, even if spark plasma sintering is applied as a preforming method, the preforming body has a low superplastic deformability, and cracking during forging cannot be avoided. Also, like No. 114 and No. 115,
When a fine powder (powder particle size <50 μm) is used as the alloy powder, the powder has poor compressibility and moldability, and a preform that can be used for forging cannot be formed.

On the other hand, in the invention example, under the condition of high working speed (working speed: 10 ^-1 / sec), the forging process was efficiently achieved with the low pressurizing force of 20 MPa or less, and the sound parts without cracks were obtained. ing. Mechanical properties are also good, for example, the tensile strength of No. 2 member is 398 MPa, that of No. 5 is 376 MPa.
And the improved high strength required for structural members such as piston members for automobile engines.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

According to the present invention, various structural members that are required to have high strength, such as pistons and gears of automobile engines, and other various electric machines and precision machine parts, can be processed at high speed.
It can be efficiently manufactured under processing conditions of low pressure. High-speed machining enables a significant improvement in productivity, and low machining stress is effective in reducing die wear and improving the service life, while improving product shape precision and improving material yield through net-shape machining.・ The effect of shortening the process is brought about. As described above, the present invention not only enhances the functional characteristics of the high-strength aluminum alloy member, but also greatly contributes to energy saving and cost reduction.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the plastic deformability of aluminum alloy powder and the processing temperature.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22C 21/02 C22C 21/02 32/00 32/00 R (72) Inventor Yoshino Tadashi 5-6 Mukaidai, Ryugasaki-shi, Ibaraki Co., Ltd. Kubota Institute for Fundamental Technology (56) References JP-A-5-70879 (JP, A) JP-A-2-285044 (JP, A) JP-A-5-93205 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) C22C 1/04-1/05 C22C 21/00-21 / 18,32 / 00 B22F 3 / 14,3 / 24

Claims (5)

(57) [Claims] 1. One or more elements selected from transition metal elements of Fe, Cr, Ni, Zr and Mn: 1 to 1
5wt%, Si: 10-30wt%, Cu: 0.5-5wt
%, Mg: 1 to 5 wt%, the balance consisting essentially of Al, and a preformed body obtained by solidifying aluminum alloy powder having a crystal grain size of 2 μm or less and a powder grain size of 50 μm or more by spark plasma sintering. A method for producing a high-strength aluminum alloy member, which comprises performing compression plastic working at a strain rate of 10 ⁻² / sec or more in a temperature range immediately below a liquidus line of an aluminum alloy. 2. One or more elements selected from transition metal elements of Fe, Cr, Ni, Zr and Mn: 1 to 1
5wt%, Si: 10-30wt%, Cu: 0.5-5wt
%, Mg: 1 to 5 wt%, the balance substantially consisting of Al, and a crystal grain size of 2 μm or less, a powder grain size of 50 μm or more, and an aluminum alloy powder of 1 to 10 vol% of a ceramic powder of 5 μm or less. A preformed body obtained by solidifying the mixed powder obtained by spark plasma sintering treatment was used for 10 ⁻² / sec in a temperature range immediately below the liquidus line of the aluminum alloy.
A method for producing a high-strength aluminum alloy member, which comprises performing compression plastic working at the above strain rate. 3. The method for producing a high-strength aluminum alloy member according to claim 2, wherein the ceramic powder is one or more kinds of powder selected from alumina, silicon carbide, and silicon nitride. 4. The method for producing a high-strength aluminum alloy member according to claim 1, wherein the discharge plasma sintering treatment temperature is 500 ° C. or lower. 5. The compression plastic working is performed by T _Liq −35 ° C. ≦ T ≦ T.
Production of the high-strength aluminum alloy member according to any one of claims 1 to 4, which is carried out in a temperature range of _Liq -10 ° C [T: compression plastic working temperature, T _Liq : liquidus temperature of aluminum alloy]. Method.