JPH1112672A - Aluminum alloy with high toughness and high heat resistance, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy, capable of industrial production and combining toughness higher than heretofore with heat resistance also higher than heretofore, and its manufacture. SOLUTION: The metallic structure, after heating treatment for an aluminum (Al)-base supersaturated solid solution in which a transition metal element and a rare earth element are allowed to enter into solid solution, is a modulated structure in which an intermetallic compound 1 is precipitated into network state in a matrix composed of aluminum(Al) 2. The intermetallic compound 1 precipitated in the aluminum(Al) matrix is in a network state of 10 to 500 nm width (δ), and the spacing (λ) between nets of the network is regulated to 10 to 100 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy having high toughness and excellent heat resistance, applicable to parts and structural materials requiring toughness.

[0002]

2. Description of the Related Art Many studies have been made on high-strength aluminum alloys starting from alloys containing amorphous, supersaturated solid solutions, and fine crystalline materials produced by ultra-quenching. For example, in Japanese Patent Publication No. Hei 6-21326, a general formula: Al _a M _b X _c (where M: Cr, Mn, Fe, Co, Ni,
At least one element selected from Cu, Zr, Ti, Mg, and Si, X: Y, La, Ce, Sm, Nd, Nb, Mm (Misch metal)
At least one element selected from the group consisting of a, b, and c is atomic%
The ternary alloy consisting of a: 50 to 95, b: 0.5 to 35, and c: 0.5 to 25 is rapidly solidified to obtain a tensile strength of 853 to 1010 MPa.
(87~103kgf / mm ^2), yield strength 804~941MPa (82~96kgf / mm
² ) An amorphous or an amorphous and fine crystalline composite is obtained.

[0003] However, although it has twice or more the tensile strength as compared with the conventional Al crystalline alloy, the Charpy impact value is, for example, lower than about 1/5 of the conventional aluminum ingot.

In Japanese Patent Application Laid-Open No. 5-1346, the general formula: Al _a M _b L n _c or Al _a M _b X _d L n _c (where M: Co, Ni, Cu
At least one element selected from the group consisting of: Ln: Y, a rare earth element, at least one element selected from Mm; X: V, Mn, F
e, Mo, Ti, at least one element selected from Zr) by rapidly solidifying an alloy system having a composition represented by
Mechanical properties such as a tensile strength of 875 to 945 MPa (89.2 to 96.3 kgf / mm ² ) and an elongation of 1.7 to 2.9% during a tensile test are obtained.

The metal structure has an average crystal grain size of 0.1 to 80 μm.
The matrix (referred to as a parent phase enclosing another phase; the same applies hereinafter) is Al or a supersaturated solid solution of Al, and has a particle size of 10 to 500 nm comprising a stable phase or a metastable phase of an intermetallic compound. Particles are distributed in the matrix.

[0006]

In the case of an alloy in which fine intermetallic compound particles in units of nanometers (nm) having a supersaturated solid solution as a matrix disclosed in Japanese Patent Application Laid-Open No. 5-1346 are dispersed, Finely dispersed intermetallic compound particles,
Since heat causes enlargement, the toughness is significantly reduced at a certain temperature or higher.

[0007] Accordingly, Japanese Patent Publication No. 6-21326 and
No. 1346 has a problem that it is difficult to use the aluminum alloy as a material for a mechanical part or an automobile part which requires reliability.

To overcome the above problems, the present invention provides a nanostructure (nm) of an aluminum alloy,
The mechanical properties were evaluated and examined. When a conventional supersaturated solid solution is subjected to a heat treatment, a clear crystal grain boundary exists between the precipitated intermetallic compound and the Al matrix, and dislocation fixation is concentrated at that location during plastic deformation to increase toughness. Hinder.

Therefore, in order to prevent dislocation fixation from being concentrated,
We considered using a modulated structure (a metal structure that reflects regular fluctuations in concentration, also referred to as a modulated structure) in which there is no clear boundary between the intermetallic compound and the Al matrix.

[0010] However, although high toughness is exhibited in the precipitation process, the toughness is remarkably reduced when it proceeds further and is completely precipitated. This is because a complete boundary forms a clear boundary (grain boundary) between the Al matrix and the precipitate, and dislocations are concentrated at that location during plastic deformation.

An object of the present invention is to solve the above-mentioned problems and to provide an aluminum alloy having both higher toughness and higher heat resistance than the conventional one, which can be industrially produced, and a method for producing the same.

[0012]

In order to slow down the precipitation process, the transition metal element and the rare earth element were dissolved in solid by selecting a refractory metal element that diffuses slowly in the Al matrix as one of the constituent elements. For a metal structure obtained by heat-treating an Al-based supersaturated solid solution, a modulated structure having excellent heat resistance was obtained for the first time. In this modulated structure, the intermetallic compound is precipitated in a mesh on the Al matrix, and the deposited intermetallic compound is a mesh having a width of 10 to 500 nm, and the distance between the meshes is 10 to 500 nm. 100100 nm.

[0013] If the width and spacing of the mesh are out of the above range, the strength or toughness is greatly reduced. When the width and the interval are both smaller than 10 nm, the strength is sufficient but the ductility is poor. When the width and the interval are larger than 500 nm and 100 nm, both the ductility and the strength are greatly reduced. Also, when either one of the width and the interval does not satisfy the above conditions, both the ductility and the strength are reduced.

This modulated structure is considered to be formed by spinodal decomposition during the precipitation process of the intermetallic compound, or by initial nucleation during the precipitation process. In this network, the boundary between the Al matrix and the precipitate is aligned,
The concentrations of the constituent elements of aluminum and the intermetallic compound change continuously across the boundary. This is because the precipitation process does not require nucleation, does not have a latent period due to an increase in concentration fluctuation, and decomposes while maintaining perfect consistency with the Al matrix. Therefore, since there is no clear boundary (crystal grain boundary) between the Al matrix and the precipitate, the fixation of dislocations during plastic deformation hardly concentrates in one place, thereby exhibiting high toughness.

Important points when combining metal elements for forming a modulated structure are: (a) supersaturated solid solution in an Al matrix. (B) Two-phase separation. There are two points. For the former, a combination of elements having an atomic radius close to that of Al was selected, and for the latter, a combination of elements which did not form a solid solution with the former element and formed an intermetallic compound was selected.

A binary phase diagram between X and Z is a two-phase separation type, and a liquid phase aluminum (Al) alloy containing a transition metal element and a rare earth element is cooled at a cooling rate of 10 ² to 10 ⁵ K / sec. An aluminum alloy having a supersaturated solid solution structure obtained by rapid solidification at a high speed,
Heat treatment is performed at a heating rate of 1.5 K / sec or more and a temperature of 473 K or more. Further, the rapid solidification means is a gas atomizing method or a water atomizing method. After the heat treatment, hot plastic working, especially powder forging is performed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The high toughness and high heat resistant aluminum alloy of the present invention has a general formula: Al _a X _b Z _c (X is Ti, V, Cr, Mo, W, N
at least one element selected from b, Ta, Zr, Z is Y, L
a, Ce, Sm, Nd, Mm (Misch metal), at least one selected from the group consisting of a, b, and c in atomic%: a: 90 to 99, b: 0.5 to
5, c: 0.5 to 5) The alloy has a composition represented by 0.5 to 5), and is rapidly solidified to form a supersaturated solid solution in which the refractory metal element X and the element Z to be separated therefrom are forcibly dissolved in an Al matrix.

The cooling rate for rapid solidification to produce a supersaturated solid solution is 10 ² to 10 ⁵ K / se which can be mass-produced on an industrial level.
c is valid. By subjecting this supersaturated solid solution to heat treatment, a modulated structure in the order of nanometers can be obtained.

Next, in the present invention, the atomic% of each of the above elements
The reason why the range of the component is limited will be described. First, when the component of X is more than the above range, an Al-X intermetallic compound is crystallized as a primary crystal in the Al matrix. When the cooling rate is increased, the primary crystals are forcibly dissolved and disappear, but when the cooling rate is lower than the above, the primary crystals are crystallized, and the toughness is remarkably reduced.

On the other hand, when the component of X is less than the above range, the component of X is dissolved in the Al matrix but precipitates as an Al-X intermetallic compound by the heat treatment to prevent formation of a modulated structure. Therefore, the toughness is significantly reduced.

Next, when the Z component is larger than the above range, an Al-Z based amorphous phase appears in the Al matrix, which prevents the formation of a modulated structure. In addition, a large amount of brittle Al-Z based intermetallic compound is finely precipitated by the heat treatment, and the toughness is significantly reduced.

On the other hand, when the Z component is less than the above range, the Z component dissolves in the Al matrix, but the Al-X intermetallic compound precipitates more than the Al-Z intermetallic compound. The Al-X system precipitates due to the heat treatment, which prevents the formation of a modulated structure. Therefore, the toughness of the aluminum alloy is significantly reduced.

Further, the present invention relates to a method of adding 473K to a rapidly solidified aluminum alloy having a supersaturated solid solution matrix of Al.
The present invention provides a method for producing the high toughness and high heat resistant aluminum alloy, wherein the heat treatment is performed at the above temperature at a heating rate of 1.5 K / sec or more.

Using a rapidly solidified aluminum alloy of the above-mentioned supersaturated solid solution as a starting material, the temperature was raised to a temperature of 473K or higher.
By performing heat treatment at a heating rate of 5 K / sec or more, a modulated structure can be obtained, and high toughness can be obtained. on the other hand,
If less than 473K, precipitation from the supersaturated solid solution is insufficient,
The result is an aluminum alloy with high strength but low ductility and poor toughness. In addition, when the heat treatment is performed at a heating rate of less than 1.5 K / sec, the metal structure of the aluminum alloy is enlarged, resulting in poor toughness.

[0025]

EXAMPLES Examples of the present invention will be described together with comparative examples to clarify the effects of the present invention. (Examples 1 to 15) An aluminum alloy having an alloy composition shown in Table 1 (same in Table 2) was melted in an arc melting furnace to produce a button-shaped ingot (1 gr ingot), and then a single-roll liquid quenching was performed. This ingot was used as a ribbon sample using an apparatus. Note that the numbers 1 to 15 in the column of No. in Table 1 (Table 2 is the same)
In each of Examples 1 to 15, 16 to 20 are comparative examples.

For the preparation of the ribbon-shaped sample, a quartz nozzle having a tip with a diameter of 0.5 mm was installed at a position of 0.5 mm immediately above a copper roll rotating at 2000 rpm, and was placed in the quartz nozzle. The ingot was melted in a high-frequency heating furnace to obtain a liquid phase aluminum alloy. The liquid phase aluminum alloy was injected at an injection pressure of 78 kPa (7.95 × 10 ⁻³ kgf / mm ² ) to obtain a ribbon-shaped sample. The cooling rate during solidification of the liquid phase aluminum alloy at this time is 10 ³ to 10 ⁵ K / sec.

These ribbon samples were heat-treated under the conditions shown in Table 1. Table 2 shows the results of tensile tests performed on the heat-treated ribbon samples using an Instron tensile tester.
Next, the modulated tissue of Example 1 was compared with the resolution SEM (Scanning El
ectron Microscope). In the other examples, SEM photographs of the modulation structure similar to those in FIG. 1 were obtained.

[0028]

[Table 1]

[0029]

[Table 2]

In FIG. 1, the black portion is Al, and the curved white band portion and the mist-like white portion at the lower right of the photograph are the precipitated intermetallic compounds. Here, the “modulated structure in which the intermetallic compound is precipitated in a network in the Al matrix” is a portion formed from Al in the black portion and the intermetallic compound in the curved white portion in the figure. The portion corresponding to the "shape net" is the intermetallic compound in the white portion of the curved strip.

FIG. 2 is a schematic diagram of a tissue in which a part of FIG. 1 is enlarged. The black part 2 is Al and the curved white part 1
Is an intermetallic compound. The “intermetallic compound precipitation interval λ corresponding to the interval between the nets” is the portion of λ in the figure, and is based on the cross-section method based on the actually observed micrograph (perpendicular to the micrograph of the observation visual field). Vertical and horizontal straight lines are drawn, and the average length of each tissue on the straight line is calculated.) On the other hand, the “mesh-like width δ” is the portion of δ in the figure. Tables 2 and 4 show the precipitate spacing λ and the mesh-like width δ for each alloy composition.

Next, in selecting an alloy system for forming a modulated structure in which intermetallic compounds are precipitated in a network,
As mentioned above, it is important that the binary phase diagram between X and Z is a combination that is of the two-phase separation type.

FIG. 3 is a phase diagram of a known Ce-Mo binary alloy (The HANDBOOK of BINA by Dr. William G. Moffatt.).
RY PHASE DIAGRAMS '' GENIUM PUBLISHING CORPORAT
Published in ION 1976. It is well known that the temperature display ° C in the figure and the temperature display K of the present invention are K = ° C + 273.16. ). In this state diagram, γ-Ce and Mo are separated on the low temperature side. In the alloy systems shown in Tables 1 to 4, a combination was selected so that X and Z in the general formula Al _a X _b Z _c were separated in this manner.

In order to obtain a modulated structure by heating, the starting material is desirably a supersaturated solid solution. To produce a supersaturated solid solution, the cooling rate when solidifying from a liquid phase aluminum alloy is important, and the alloy composition must be such that a supersaturated solid solution can be obtained at a cooling rate of 10 ⁵ K / sec or less that can be used on an industrial level.

4 and 5 show SEM photographs of the structures of Comparative Examples 17 and 18. In the case of Comparative Example 17 in which the addition amount of the second element X having a narrow solid solubility limit to the Al matrix is large, the intermetallic compound appears as a spherical primary crystal 3 in the Al matrix as shown in FIG.

On the other hand, in the case of Comparative Example 18 in which the amount of Z added is large, the structure is such that fine spherical primary crystals 4 appear in the amorphous phase as shown in FIG. In both cases, the tensile strength and elongation are significantly reduced and the toughness is poor as compared with the examples.

Next, in selecting an alloy composition for forming a modulated structure by heat treatment, the amounts of X and Z added are important. 6 and 7 show SEM photographs of the structures of Comparative Examples 19 and 20. In the case of Comparative Example 19 where the amount of X added is large, the intermetallic compound appears as spherical primary crystals 3 in the Al matrix as shown in FIG.

On the other hand, in the case of Comparative Example 20 in which a large amount of Z was added, a large amount of spherical fine precipitates 5 appeared together with the spherical primary crystals 4 as shown in FIG. This is because an Al-Z amorphous phase was present during rapid solidification and was subjected to a heat treatment at a temperature higher than the crystallization temperature. In both cases, the tensile strength and elongation are significantly reduced and the toughness is poor as compared with the examples.

Next, to measure the heat treatment temperature dependence of the micro-Vickers hardness (mH _V) under a load of 25g for Example 1 in Table 1. The heat treatment time is 5 minutes. As a result, as shown in FIG. 8, the aluminum alloy of the present invention has a small decrease in hardness due to an increase in the heat treatment temperature, and is extremely excellent in heat resistance. In addition, it was confirmed that in Examples other than Example 1, the heat treatment temperature dependency excellent in heat resistance similar to that in FIG. 8 was obtained.

Examples 21 to 26 Aluminum alloy powders having the alloy compositions shown in Table 3 (also in Table 4) were produced using a gas atomizing apparatus. The numbers 21 to 26 in the columns of No. in Table 3 (also in Table 4) are Examples 21 to 26, respectively, and 27 and 28 are comparative examples. Spraying was performed by impinging a nitrogen gas pressurized to 9.8 MPa (100 kgf / cm ² ) on a liquid phase aluminum alloy dropped from a nozzle having a hole diameter of 2 mm.
It should be noted that water atomization can be similarly performed instead of gas atomization.

Further, under the same spray conditions as above, the 2014 Al alloy (J
A powder having the composition of IS H 4000) was prepared, and the cooling rate during solidification of the actual liquid phase aluminum alloy was estimated from the measurement of the dendrite arm (dendritic crystal) interval of the composition. According to that, when an Al alloy powder with a particle size of 65 μm is obtained,
Cooling rate during solidification of liquid phase aluminum alloy is 2 × 10 ⁴ K / se
c.

Next, each Al alloy powder produced by the above-mentioned gas atomizing apparatus was sieved to a powder particle size of less than 65 μm.
After press-molding the powder having a particle size of less than 65 μm, the compact is rapidly heated in an induction heating furnace, and a contact pressure of 883 M
Powder forging was performed at Pa (9 t / cm ² ). The attained temperature and heating rate of the heating conditions of each press-formed body, and the mechanical properties and metal structure at room temperature of the forged material obtained under the manufacturing conditions were examined. Tables 3 and 4 show the results.

For mechanical properties, a tensile test was performed using an Instron tensile tester in the same manner as in Examples 1 to 15, and the tensile strength (UTS) and elongation of each forged powder were measured. Using a Charpy tester (JIS B 7722), the Charpy impact value (J / c) of each powder forged body (however, notch is not set)
m ² ) was also measured and the results are shown in Table 4. As shown in Table 4, the powder forged body according to the example has both high tensile strength and elongation and a high Charpy impact value as compared with the comparative example, and the powder forged body according to the example has a ribbon. It is understood that the same structure and mechanical properties as the material were obtained.

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

According to the present invention, an Al alloy in which the metal structure after heat treatment of an Al-based supersaturated solid solution is a modulated structure in which precipitation of an intermetallic compound in an Al matrix is a network-like structure is an Al alloy having both excellent toughness and heat resistance. Can be provided.

[Brief description of the drawings]

FIG. 1 is an SEM photograph showing a modulated structure in which an intermetallic compound is precipitated in a network.

FIG. 2 is a diagram schematically showing a modulated tissue.

FIG. 3 is a phase diagram of a Ce-Mo binary system.

FIG. 4 is an SEM photograph of Comparative Example 17.

FIG. 5 is a SEM photograph of Comparative Example 18.

6 is an SEM photograph of Comparative Example 19. FIG.

FIG. 7 is a SEM photograph of Comparative Example 20.

FIG. 8 is a diagram showing a relationship between a micro Vickers hardness value and a heat treatment temperature.

[Explanation of symbols]

 1: Intermetallic compound 2: Aluminum 3, 4: Spherical primary crystal 5: Fine precipitate

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C22F 1/00 630 C22F 1/00 630B 650 650A 681 681 683 683 683 687 687 691 691B 691A 692 692A (72) Inventor Toshihiko Kaji Itamiichi, Hyogo 1-1-1, Kita, Sumitomo Electric Industries, Ltd., Itami Works (72) Inventor ▲ Taka ▼ Yuji, 1-1-1, Koyokita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd., Itami Works

Claims (8)

[Claims] 1. A metal structure of an aluminum (Al) alloy containing a transition metal element and a rare earth element, wherein the intermetallic compound has a modulated structure in which the intermetallic compound is precipitated in a network in an aluminum (Al) matrix. Heat resistant aluminum alloy. 2. The high toughness and high heat-resistant aluminum alloy according to claim 1, wherein the metal structure of the aluminum (Al) alloy is a modulated structure obtained by heat-treating an aluminum (Al) -based supersaturated solid solution. 3. The intermetallic compound deposited on the aluminum (Al) matrix has a mesh structure having a width of 10 to 500 nm, and a distance between the mesh networks is 10 to 100 nm. The high toughness and high heat-resistant aluminum alloy according to claim 1 or 2, wherein: 4. The composition of the aluminum (Al) alloy is represented by _a general formula Al _a X _b Z _c , wherein X is the element titanium (Ti),
At least one selected from vanadium (V), chromium (Cr), molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta) or zirconium (Zr); Z is the element yttrium (Y), lanthanum (La), cerium (Ce), samarium (Sm), neodymium (Nd) or misch metal (Mm), wherein a, b, and c represent atomic%;
4. The method according to claim 1, wherein 90 to 99 atomic%, b is 0.5 to 5 atomic%, and c is 0.5 to 5 atomic%.
High-toughness and high heat-resistant aluminum alloy according to the item. 5. The high toughness and high heat-resistant aluminum alloy according to claim 4, wherein the binary phase diagram of the combination between X and Z is a two-phase separation type. 6. A liquid-phase aluminum (Al) alloy containing a transition metal element and a rare earth element is rapidly solidified at a cooling rate of 10 ² to 10 ⁵ K / sec, and the rapidly solidified aluminum (Al) -based supersaturated solid solution is obtained. The method for producing a high toughness and high heat resistant aluminum alloy according to any one of claims 1 to 5, wherein the heat treatment is performed at a temperature rising rate of 1.5K / sec or more and a temperature of 473K or more. 7. The high toughness and high heat-resistant aluminum alloy according to claim 6, wherein said means for rapid solidification is a gas atomization method or a water atomization method, and hot plastic working is performed after said heat treatment. Production method. 8. The method according to claim 7, wherein the hot plastic working is powder forging.