JPH11236601A - Rapidly solidified aluminum alloy powder, its production, and high strength and high toughness aluminum alloy member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rapidly solidified aluminum alloy powder whose oxidized film on the surface is liable to be broken. SOLUTION: This Aluminum alloy composed of at least one kind of the non-equilibrium phase among the amorphous phase, quasi-crystalline phase, quasi-stable phase and supersaturated solid solution and α-Al with <=500 nm average grain size is incorporated with at least one kind among mg, Li and Ca, and within 1 μm from the surface of the powder, at least one kind among Mg, Li and Ca is contained by 0.05 to 15 wt.%. Then, the quasi-stable phase is composed of at least one kind among Al3 Zr, Al3 Ti and Al3 (Zr, Ti), and the supersaturated solid solution contains at least one kind selected from transition metallic elements and rare earth elements respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rapidly solidified aluminum alloy powder for producing a high-strength and high-toughness aluminum alloy member by hot plastic working such as extrusion or powder forging.

[0002]

2. Description of the Related Art In recent years, high strength and high toughness aluminum alloy members using a rapidly solidified aluminum alloy powder containing an amorphous phase, a quasicrystalline phase, a metastable phase, and a supersaturated solid solution have been put to practical use.

[0003] The rapidly solidified aluminum alloy powder used in the production of these high-strength and high-toughness aluminum alloy members is easily oxidized, and stable alumina (Al) is formed on the surface of the powder.
₂ O ₃ ) oxide film is formed. In particular, in the case of inexpensive gas atomized powder or the like, a thick oxide film is easily formed on the surface of the powder.

As a result, when the aluminum alloy member is manufactured by solidifying the rapidly solidified aluminum alloy powder, the bonding between the powders is insufficient, and the mechanical properties, particularly toughness, of the aluminum alloy member are sometimes insufficient. Therefore, conventionally, various types of mechanical compressive deformation have been applied to the powder compact, and the powder has been subjected to shear deformation, thereby destroying an oxide film on the powder surface and improving the bonding between the powders. Examples of the means of mechanical compression deformation include an extrusion method and a powder forging method.

[0005] In the case of the extrusion method, the powder is deformed to a predetermined extrusion ratio so that the powder is sheared, and at this time, an oxide film on the surface of the powder is broken. As a result, the powders can be strongly bonded together, and the mechanical properties such as the toughness of the aluminum alloy member can be improved.

In the case of the powder forging method, although an aluminum alloy member can be formed in a shape (near net shape) close to the final shape of a machine component, a portion where powder-to-powder bonding is insufficient due to the formation of a complicated shape occurs. In some cases, the toughness of the aluminum alloy member is insufficient.

In order to sufficiently destroy the oxide film on the surface of the powder, for example, Japanese Patent Application Laid-Open No. 1-215901 discloses a method in which a powder agitator such as an attritor or a ball mill is used. A method is disclosed in which a cold work, which is a treatment, is performed on a powder surface to destroy an oxide film on the powder surface. By performing powder forging on the powder that has been subjected to the pretreatment, a portion where bonding between powders is insufficient is eliminated, and an aluminum alloy member having excellent toughness is obtained.

[0008]

SUMMARY OF THE INVENTION Amorphous phase, quasicrystalline phase,
A rapidly solidified aluminum alloy powder containing at least one non-equilibrium phase out of a metastable phase and a supersaturated solid solution needs to contain a large amount of alloying elements in order for the non-equilibrium phase to appear. For this reason, not only an oxide film is formed on the powder surface, but also the hardness of the powder itself increases.

Therefore, in the conventional extrusion method, powder forging method and the like, it becomes difficult to break the oxide film on the powder surface by shearing the powder. Therefore, in a rapidly solidified aluminum alloy member manufactured by an extrusion method, a powder forging method, or the like, there is a problem that bonding between powders is poor, and the mechanical properties thereof are high in strength but insufficient in toughness.

Therefore, in order to improve the toughness of an aluminum alloy member obtained by solidifying a rapidly solidified aluminum alloy powder containing at least one non-equilibrium phase among an amorphous phase, a quasicrystalline phase, a metastable phase, and a supersaturated solid solution, It is necessary to strengthen the bonding between powders.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rapidly solidified aluminum alloy powder which can solve the above-mentioned problems and can easily combine powders without adding a pre-process which can be industrially produced and increases the cost. An object of the present invention is to provide a manufacturing method thereof and a high-strength and high-toughness aluminum alloy member.

[0012]

Means for Solving the Problems Aluminum comprising at least one non-equilibrium phase among an amorphous phase, a quasi-crystal phase, a meta-stable phase, and a supersaturated solid solution and alpha aluminum (α-Al) having an average particle size of 500 nm or less. Alloy powder,
A rapidly solidified aluminum alloy powder containing at least one of magnesium (Mg), lithium (Li), and calcium (Ca), wherein magnesium (Mg),
It is useful that at least one of lithium (Li) and calcium (Ca) is contained at 0.05% by weight or more and 15% by weight or less.

The metastable phase is aluminum 3 zirconium (Al
₃ Zr), at least one of aluminum 3 titanium (Al ₃ Ti) and aluminum 3 zirconium titanium (Al ₃ (Zr, Ti)), and a supersaturated solid solution selected from a transition metal element and a rare earth element. Those containing at least one of them are useful.

The rapidly solidified aluminum alloy powder is made of aluminum (Al), magnesium (Mg), lithium (L
Those having at least one oxide of i) and calcium (Ca) on the surface of the powder are also useful.

Then, the rapidly solidified aluminum alloy powder is formed by gas or water atomization. Further, a high-strength and high-toughness aluminum alloy member obtained by solidifying the rapidly solidified aluminum alloy powder by hot plastic working is useful.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to overcome the above-mentioned problems, the prevention of the formation of an Al ₂ O ₃ oxide film on the surface of the powder and the destruction of the oxide film during the production of the powder were examined from a metallurgical point of view.

As a result, attention was paid to the fact that Mg, Li, and Ca, which are elements having a higher affinity for oxygen than Al, were previously added to Al as a raw material for producing powder. Since these elements have a strong affinity for oxygen, if the added amount is small, these elements form a solid solution in Al inside the powder. On the other hand, when the amount is large, a brittle oxide is formed on the surface of the powder.

Therefore, in the former case, Mg, Li, and Ca, which are elements having a higher affinity for oxygen than Al, are diffused in the surface direction of the powder due to an increase in temperature during hot plastic working, and Al ₂ O By dividing the oxide film of No. _3, the oxide film is destroyed, and an active aluminum surface is exposed from the gap. Then, due to mechanical compression when hot plastic working is performed, the powders are bonded to each other on the active surface.

On the other hand, in the latter case, the oxide film formed preferentially over the Al ₂ O ₃ oxide film, and the brittle oxide film is
It is destroyed by peeling off from the powder surface by mechanical compression when hot plastic working is performed, and thereafter, by exposing the active Al surface, the powder is bonded on the active surface.

However, among the widely used ingot Al alloys (Al alloys by melt casting), Al-Cu-M
g, there is an ingot Al alloy containing an element having a higher affinity for oxygen than Al such as Al-Zn-Mg, and an aluminum alloy using a powder obtained by mechanically pulverizing the ingot Al alloy is obtained. I have.

In these cases, Mg plays a role of solid solution strengthening. Therefore, if Mg is consumed to destroy the alumina oxide film on the powder surface, the tensile strength of the aluminum alloy will be reduced.

On the other hand, in a high-strength and high-toughness aluminum alloy produced by hot plastic working such as an extrusion method or a powder forging method, a high-hardness powder containing an amorphous phase, a quasi-crystal phase, a metastable phase, a supersaturated solid solution, and the like. , An ultra-fine structure in which α-Al crystal grains have an average crystal grain size of 500 nm or less. Therefore, the added Mg, Li, and Ca hardly form a solid solution, and the role of solid solution strengthening cannot be expected.

Here, as a rapidly solidified aluminum alloy powder for producing a high-strength and high-toughness aluminum alloy by hot plastic working such as an extrusion method or a powder forging method,
It is considered effective to improve the bonding between the powders by using the rapidly solidified aluminum alloy powder to which Mg, Li, and Ca are added in advance.

[0024]

EXAMPLES Examples of the present invention will be described together with comparative examples to clarify the effects of the present invention. Examples 1 to 22) Using a gas atomizer, Examples 1 to 22 and Comparative Examples 1 and 2 having compositions shown in Tables 1 and 2.
A rapidly solidified aluminum alloy powder of No. 2 was produced. As a manufacturing method, a molten metal of an aluminum alloy having a corresponding composition dropped from a nozzle (hole) having a diameter of 1.5 mm is pressurized (100 mm).
kgf / cm ² ) was used. Each rapidly solidified aluminum alloy powder produced was sieved to a maximum powder particle size of 75 μm or less.

[0025]

[Table 1]

[0026]

[Table 2]

Table 1 (Examples 1 to 11) shows that quenching is performed when Mg, Li, or Ca, which is an element having a higher affinity for oxygen than Al, is preliminarily added to Al as a raw material for producing powder. Table 3 shows the composition of the solidified aluminum alloy powder (the upper part is atomic%, the lower part is weight%, and Table 2 is the same).
Table 2 (Examples 12 to 22) shows the composition of the rapidly solidified aluminum alloy when the amount of Mg, Li, and Ca added to the raw material Al is large, and shows the main metallographic structure, the added elements, and the state of the powder. It is shown in FIG.

[0028]

[Table 3]

[0029]

[Table 4]

Mg, L, which are elements which have a higher affinity for oxygen than Al and are previously added to Al as a raw material for producing powder.
The experimental results of the oxide film on the powder surface are shown for Example 1 where i and Ca are small.

FIG. 1 shows an HR-SEM (High Reso).
lution-ScanningElectron M
High-performance scanning electron microscope. 2) is a result of microscopic observation of rapidly solidified aluminum alloy powder particles using the method of FIG. As shown in the secondary electron image by HR-SEM, the presence of magnesium oxide (Mg-Al-O spinel or the like) was not confirmed on the surface (room temperature).

Since the amount of added Mg, which is an element having a higher affinity for oxygen than Al, is small, the Mg element is dissolved in Al inside the powder and there is no magnesium oxide on the powder surface. No, Al ₂ O ₃ is present.

SEM-EDX (Scanning El)
electron Microscope-ergy D
ission Xray Spectrosco
Energy dispersive X-ray analysis method. As a result of the qualitative and quantitative analyses, the presence of Mg equivalent to the addition was confirmed within 1 μm from the surface of the powder particles. When the addition of Mg was set to 0.05% by weight or more and 5% by weight or less, it was separately confirmed that 0.05% by weight or more and 5% by weight or less of Mg were present within 1 μm from the surface of the powder particles.

FIGS. 2 to 5 show examples of the structure change of the powder surface in Example 1 due to the temperature rise. Here, FIG. 2 is a secondary electron image of the surface of a rapidly solidified aluminum alloy powder of 638K, and FIG.
Is the secondary electron image of 753K, FIG. 4 is the secondary electron image immediately after cooling from 753K to room temperature, and FIG.
It is the same secondary electron image after 1 hour after cooling from K to room temperature.

As the temperature is gradually increased, as can be seen from the changes in FIGS. 2 to 5, when the temperature exceeds 753K, Mg dissolved in Al inside the powder diffuses toward the powder surface. Then, the Al ₂ O ₃ oxide film is divided, and an active aluminum surface (white portions indicated by arrows in FIGS. 3 and 4) appears on the surface of the powder. However, as shown in FIG. 5, after one hour, it reacts again with oxygen in the atmosphere to form an Al ₂ O ₃ oxide film.

Each of the powders of Examples 1 to 11 and Comparative Examples 1 and 2 shown in Table 1 containing Mg, Li and Ca was prepared by measuring 9.5 in section.
mm and 29 mm in width, and inserted into a square mold having a height of 9.5 mm and cold-formed at a surface pressure of 6 ton / cm ² . The molded body is subjected to a heat degassing treatment, and the cross section is 11 m in length.
m, 31 mm in width, and inserted into a square mold having a height of 11 mm and hot forging at a surface pressure of 8 ton / cm ² by powder forging (forging temperature is 773K, and the temperature rising rate to this temperature is 4K per second).

The forged aluminum alloy was subjected to a tensile test using an Instron tensile tester and a Charpy impact test using an instrumented Charpy impact tester (JIS B7722). As shown in FIG. 6, the shape of the test piece used in the tensile test is 9 mm (M8 thread rolling on the surface, not shown) from both ends of a cylinder having a length of 30 mm and a diameter of 6 mm. 5m in the center
m, a cylinder with a diameter of 3 mm cut into a cylinder with a diameter of 6 mm
Is 3 mm along a circular arc having a radius of 5 mm. The shape of the Charpy impact test specimen was a prism having a length and width of 10 mm and a length of 30 mm, and no cutout portion was set. The surfaces of both test pieces were subjected to a smooth finish.

Table 5 shows the mechanical properties of the aluminum alloy manufactured by powder forging for each of the examples and comparative examples. Comparing the mechanical properties of Examples 1 and 2 and the comparative example, the Mg-added Example has a good elongation value (%) and a good Charpy impact value (J / cm ² ). High tensile strength is also maintained. Examples 3 to 9 also show good properties in tensile strength, elongation, and Charpy impact value. Further, as shown in the examples in which Li and Ca were added to Examples 10 and 11, it is shown that the addition is effective similarly to Mg.

[0039]

[Table 5]

Next, in Examples 1 to 9 to which Mg was added, the structure of each rapidly solidified aluminum alloy powder was considered, and the state of the oxide film was considered. It is considered that Examples 10 and 11 in Li and Ca are similar to Mg.

Examples 1, 2, 10, and 11 are cases in which an amorphous phase is contained in a rapidly solidified aluminum alloy powder, and an Al-Ni-Mm-based alloy which is a typical alloy system for forming an amorphous phase is used. , Mg, Li, and Ca were added. As a result of X-ray diffraction measurement, ultrafine α-Al crystal grains were scattered, not a single phase of the amorphous phase.

Mg, which is an additional element, is contained not only in the amorphous phase but also in the dispersed α-Al crystal grains. The alumina oxide film on the powder surface formed initially by atomization of the gas atomizing device is destroyed by the separation of the alumina oxide film during heating to the forging temperature of powder forging, which is hot plastic working. The destruction is caused by Mg dissolved in α-Al crystal grains and Mg dissolved in α-Al crystal grains by crystallization of the amorphous phase to form a solid solution.
However, it is considered to be due to diffusion to the surface of the powder particles.

When the powder contains a supersaturated solid solution,
Examples 3 and 4 will be described. Al-Mo-Mm, Al which is a supersaturated solid solution containing aluminum as a main component containing a transition metal element and a rare earth element and which forms a modulated structure
In this case, Mg was added as an additive element to the Cr-Mm alloy. Destruction of the Al ₂ O ₃ oxide film due to fragmentation during heating to the forging temperature of powder forging, which is hot plastic working, causes solid solution in α-Al crystal grains like other transition metal elements and rare earth elements. This is probably due to the diffusion of Mg into the powder surface.

Examples 5 and 6 show the case where the powder contains a quasicrystalline phase. This is a case where Mg is added as an additive element to Al-Mn-Mm and Al-Cr-Mm alloys, which are typical alloys that form a quasicrystalline phase. Similarly,
Destruction of the alumina oxide film due to fragmentation during heating is mainly due to α-
This is probably due to the diffusion of Mg dissolved in Al.

Examples 7, 8, and 9 show cases in which the powder contains a metastable phase. Al ₃ Zr, Al ₃ Ti, Al ₃ (Zr, Ti) serving as nuclei of α-Al crystal grains
Al-Zr-Mm, Al-Ti-M forming a metastable phase
m, Al-Zr-Ti-Mm alloy in which Mg is added as an additional element. Most of Mg is dissolved in α-Al surrounding each metastable phase. Similarly, the destruction of the Al ₂ O ₃ oxide film due to the separation during heating is caused by α-
It is considered that the main cause is the diffusion of Mg dissolved in Al.

Next, M, which is an element having a higher affinity for oxygen than Al, was previously added to Al as a raw material for producing powder.
Examples 12 to 2 shown in Table 2 when g, Li, and Ca are large.
About 0, microstructure observation using HR-SEM and SEM-
As a result of qualitative analysis by EDX, the presence of a magnesium oxide such as Al-Mg-O on the surface of the rapidly solidified aluminum alloy powder was confirmed. Note that an Al ₂ O ₃ oxide film exists.

As shown in Examples 12 to 20, M
g of the rapidly solidified aluminum alloy powder on which an oxide film was formed was cold-formed in the same manner as in Examples 1 to 11, and then heated and degassed to obtain powder forging (forging temperature of 77).
At 3K, the rate of temperature rise to this temperature is 4K per second. ) Was done. The obtained high strength aluminum alloy as a forged body was subjected to a tensile test using an Instron tensile tester and a Charpy impact test using an instrumented Charpy impact tester. The shape of the test piece is the same as in Examples 1 to 11.

Table 2 shows the composition of the rapidly solidified aluminum alloy powder, Table 4 shows its main metal structure, added elements and the states of the elements, and Table 5 shows the mechanical properties of the high-strength aluminum alloy produced by powder forging. Examples are shown for each of Examples 12 to 20. Both elongation and Charpy impact value are good, and tensile strength is sufficiently high. Examples 21 and 22 containing Li and Ca
Is considered to be similar to Mg.

Oxide films of these elements formed preferentially over oxide films of Al ₂ O ₃ are brittle, and are broken by peeling off from the powder surface by mechanical compression during hot plastic working. Then, by exposing the highly active Al surface, it is considered that the powder is bonded on the active surface and exhibits good mechanical properties as shown in Table 5.

It is to be noted that M, which is an element having a higher affinity for oxygen than Al, is added in advance to Al as a raw material for producing powder.
It is considered that the boundary value of the added component weight% between the case where the amount of g, Li and Ca is small and the case where the amount of Mg, Li and Ca added to the raw material Al is large is around 5% by weight. The minimum value when the amount of the added component is small is 0.05% by weight, and the maximum value when the added component is large is 15% by weight based on the result of examining the phase diagram.
It is.

[0051]

By using the rapidly solidified aluminum powder according to the present invention, an oxide film on the surface of the powder is destroyed in an ordinary powder forging method which is an effective method for manufacturing an extrusion method and a near-net-shape mechanical part. By increasing the bond between powders, a high-strength and high-toughness aluminum alloy having excellent tensile strength (UTS), elongation, and Charpy impact value can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram of a secondary electron image of the powder surface (room temperature) of the present invention.

FIG. 2 is a view of a secondary electron image of the powder surface (638K) of the present invention.

FIG. 3 is a view of a secondary electron image of the powder surface (753K) of the present invention.

FIG. 4 is a view of a secondary electron image of the powder surface of the present invention (immediately after cooling from 753K to room temperature).

FIG. 5 is a view of a secondary electron image of the powder surface of the present invention (one hour after cooling from 753K to room temperature).

FIG. 6 is a view showing a tension test piece.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 21/00 C22C 21/00 N (72) Inventor Yoshinobu Takeda 1-1-1, Kunyokita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Inside the Itami Works

Claims (7)

[Claims] An amorphous phase, a quasicrystalline phase, a metastable phase,
At least one non-equilibrium phase of the supersaturated solid solution and alpha aluminum having an average particle size of 500 nm or less (α-A
1) A rapidly solidified aluminum alloy powder characterized in that at least one of magnesium (Mg), lithium (Li), and calcium (Ca) is contained in the aluminum alloy powder of (1). 2. At least one of magnesium (Mg), lithium (Li) and calcium (Ca) is contained in an amount of 0.05% by weight or more and 15% by weight or less within 1 μm from the surface of the rapidly solidified aluminum alloy powder. The rapidly solidified aluminum alloy powder according to claim 1, wherein 3. The metastable phase is at least one of aluminum 3 zirconium (Al ₃ Zr), aluminum 3 titanium (Al ₃ Ti), and aluminum 3 zirconium titanium (Al ₃ (Zr, Ti)). The rapidly solidified aluminum alloy powder according to claim 1, characterized in that: 4. The rapidly solidified aluminum alloy powder according to claim 1, wherein the supersaturated solid solution contains at least one selected from a transition metal element and a rare earth element. 5. The rapidly solidified aluminum alloy powder,
2. The quenching according to claim 1, wherein at least one oxide selected from aluminum (Al), magnesium (Mg), lithium (Li), and calcium (Ca) is provided on the surface of the rapidly solidified aluminum alloy powder. Solidified aluminum alloy powder. 6. The method for producing a rapidly solidified aluminum alloy powder according to claim 1, wherein the powder is formed by a gas or water atomization method. 7. A high-strength and high-toughness aluminum alloy member obtained by solidifying the rapidly solidified aluminum alloy powder according to claim 1 by hot plastic working.