JPH06172907A - Aluminum alloy excellent in strength at high temperature and its molding - Google Patents

Abstract

PURPOSE:To obtain an Al alloy having more excellent strength at high temp. than the conventional strength and to provide a molding of the Al alloy. CONSTITUTION:This powdery Al alloy consists of 15-25wt.%, in total, of one of >=2 kinds among Fe, Mn, Ni and Cr as transition metals and the balance essentially Al and contains a fine lump transition metal-Al compd, dispersed uniformly in a matrix. Among the transition metals, Fe is preferable because it is less expensive than Al and raw material for Fe is easily available, as well. This Al alloy may contain <=3wt.%, in total, of one or >=2 kinds among Mo, V, Ti and Zr besides the above-mentioned alloying components. This Al alloy is formed into the objective prescribed molding by hot plastic working.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy excellent in high temperature strength and a molded product thereof.

[0002]

2. Description of the Related Art Parts used in internal combustion engines such as automobiles and motorcycles, such as pistons, connecting rods, brake rotors, and the like, must have strength to withstand vigorous motion at high temperatures. On the other hand, in recent years, weight reduction of parts has been desired from the viewpoint of weight reduction of automobiles and energy saving. For this reason, aluminum alloys (JIS 2000 series high-strength aluminum alloys) are also used for parts requiring high-temperature strength.

Since the ingot alloy has a limit in alloy content and a limit in high temperature strength, further, in order to improve high temperature strength, a Fe-aluminum alloy (Al alloy) powder containing Fe in a supersaturated state is prepared. Fe-Al alloys, which are hot plastic working materials, are being researched and developed. The extruded material and the forged material which are hot-formed by such a powder have excellent material properties that the ingot material does not have, and are suitable as materials for heat-resistant mechanical parts and the like.

[0004]

However, it is said that the Fe content in the Al alloy is limited to 10% by weight. Conventionally, Al alloy powder has been produced by a gas atomizing method, but even if He gas, which has excellent cooling ability, is used as a spray medium, if it exceeds 10 wt%, needle-like Fe-Al compound (FeAl ₃ ) is produced. This is because the needle-shaped compound causes a decrease in the high temperature strength of the extruded material or the forged material.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an Al alloy having a high-temperature strength superior to conventional ones and a molded body thereof.

[0006]

The Al alloy powder of the present invention contains a total of 15 to 25 wt% of one or more transition metals consisting of Fe, Mn, Ni and Cr, and the balance is substantially Al. The fine lump-shaped transition metal-Al compound is uniformly dispersed in the matrix. Of the above transition metals, Fe is cheaper than Al, and the raw material is easily available, which is preferable. In addition to the above alloy components, Mo, V, Ti,
One or two or more types of Zr can be contained in a total amount of 3 wt% or less. The above Al alloy is formed into a predetermined compact by hot plastic working such as hot extrusion and hot forging.

[0007]

The Al alloy of the present invention is made of Fe, Mn, Ni, Cr.
15 to 25 wt in total of one or more transition metals consisting of
%, A large amount of transition metal-Al compound such as Fe-Al compound is generated in the matrix, and the high temperature strength is improved. If it is less than 15%, the amount of Al compound is small, and a remarkable improvement in high temperature strength cannot be expected as compared with the conventional case. On the other hand, if it exceeds 25%, the amount of Al compound becomes excessive, the material becomes brittle, and the shape of the compound becomes acicular, resulting in deterioration of strength. Al
Since the form of the Al compound formed in the alloy is a fine lump, even if a large amount is formed in the matrix, the strength is unlikely to deteriorate. In addition to the above alloy components, Mo, V, Ti, Z
By containing one or two or more of r in a total amount of 3 wt% or less, the high temperature strength can be further improved.
Since these metals are high melting point materials, they can be kept at 3% or less in consideration of the ease of melting the Al alloy powder raw material. still,
Cr is also a high-melting point material by itself, but when alloyed with Al, the melting point is remarkably lowered, and it is handled like Fe. By the way, the melting point of Al-15wt% Fe is 975 ℃, Al-15wt%
That of Cr is 980 ° C.

In order to obtain the transition metal supersaturated raw material powder according to the alloy of the present invention, it is necessary to increase the cooling rate to 10 ⁵ ° C / sec or more. Due to such cooling rate, transition metal-Al
The morphology of the compound becomes a lump, and its size becomes a fine particle of about several μm.

[0009]

EXAMPLE An Al alloy powder having an average particle size of 200 μm and having the composition shown in Table 1 was produced by a swirling water flow method or an Ar gas atomizing method. The rotary water flow method is disclosed in JP-A-4-176.
As disclosed in Japanese Patent Laid-Open No. 05-2005, a cooling water layer that flows down while swirling is formed on the inner peripheral surface of a cooling cylinder, and a jet of a molten metal flow is supplied to the cooling water layer and swirling this. This is a method of obtaining a metal powder by dividing the material into cooling liquid layers and rapidly solidifying. According to this production method, a cooling rate of 10 ⁵ ° C / sec or more can be easily obtained even with relatively large particles having an average particle diameter of 200 µm.

[0010]

[Table 1]

Microstructure photograph of the Fe-Al alloy powder of Example 1 containing 15% of Fe produced by the rotating water flow method (magnification: 3300)
Is shown in FIG. From the figure, needle-like Fe-Al is present in the base.
No compound was observed, and it was observed that the compound in the form of fine lumps was dispersed in the matrix in a substantially uniform manner.

The Al alloy powder was heated to 540 ° C. and extruded at an extrusion ratio of 4. When the extrusion temperature is raised to a high temperature, Fe-
Since the Al compound is transformed into a needle-shaped one, it is preferable to keep it at 550 ° C or lower. Take a tensile test piece from the extruded material,
The mechanical strength at room temperature and various high temperatures was investigated. The results are shown in Table 2. From the conventional example and the comparative example 1, it can be seen that in gas atomization, the room temperature strength does not improve so much even if the Fe content is increased. On the other hand, in Examples having a high cooling rate, the strength is improved as the content of transition metals such as Fe and Ni is increased and the content of elements such as Mo and V is contained. Further, it can be seen that even with the same Fe content, Example 1 has significantly higher strength than Comparative Example 1. Also,
In the example, the high temperature strength at 300 ° C is also 238 MPa (24.2 kgf / m
m ² ) or more, and has excellent high temperature strength. Also,
In Comparative Examples 2 and 3 containing Si, even if 15% Fe is contained, the strength is low, the elongation is small, and the impact resistance is difficult to expect. However, Si-containing alloys can be used for those that do not require such impact resistance.

[0013]

[Table 2]

Further, a hardness test piece was sampled from the extruded material, heated to a predetermined temperature, and the surface hardness (Vickers hardness) in a temperature rising state was measured. The results are shown in Table 3. It can be seen from Table 3 that in the examples, even when heated to about 400 ° C., the hardness of the conventional example is maintained at room temperature, and the examples have good heat resistance. Comparing Example 1 and Comparative Examples 2 and 3 having the same Fe content, the comparative example containing Si has generally better heat resistance, but as described above, it is difficult to expect impact resistance.

[0015]

[Table 3]

Next, a hardness test piece was sampled from the extruded material, and in order to examine the thermal stability, the holding temperature was variously changed and the sample was held for a predetermined time, and then the hardness at room temperature after cooling (Vickers hardness) was measured. The results are shown in Table 4. From Table 4, in Example 1, the hardness is Hv11 even when heated to 500 ° C. and 100 hr.
It is very high as 0 or more, which is equal to or higher than the room temperature hardness of the conventional example, the rate of decrease in hardness is lower than that of the conventional example, and the thermal stability is excellent. By the way, 500 ℃, 100 h
In the case of holding r, the hardness of the conventional example is 67% at room temperature, whereas it is 84% in Example 1.

[0017]

[Table 4]

In the heat stability hardness test, Fe 15%
Of the extruded material of Fe-Al alloy powder according to Example 1 of
Photograph of the metal structure of the same material after holding for 2 hours (magnification 3300
2) is shown in FIG. From the same picture, Fe-A that had aggregated
It is observed that the 1-compound is uniformly dispersed in the matrix with a fine size of 1 to 3 μm. Further, in this embodiment,
Needle-like Fe-A even when kept at a high temperature of 500 ° C
It can be seen that the l-compound is not deposited and the hardness is less likely to decrease.

[0019]

As described above, the aluminum alloy of the present invention contains 15 to 25 wt% of a specific transition metal such as Fe or Ni.
%, Optionally containing elements such as Mo and Ti in an amount of 3 wt% or less, and the balance substantially consisting of Al, and since a fine lumpy transition metal-Al compound is uniformly dispersed in the matrix, It is possible to generate a large amount of Al compound in the matrix, and since the form is a fine lump, it is possible to secure excellent high-temperature strength without causing a decrease in strength.

[Brief description of drawings]

FIG. 1 is a photograph of a metal structure of a Fe—Al alloy powder according to an example (magnification: 3300 times).

FIG. 2 is a metallographic photograph (magnification: 3300 times) of an extruded material extruded using an Fe—Al alloy powder according to an example containing 15% of Fe, which was held at 500 ° C. for 2 hours.

Claims (4)

[Claims] 1. An excellent high temperature strength characterized by containing 15 to 25 wt% of Fe, the balance being substantially Al, and fine lumped Fe-Al compounds uniformly dispersed in the matrix. Aluminum alloy. 2. A fine lumpy transition metal in a matrix, containing one or two or more kinds of transition metals consisting of Fe, Mn, Ni and Cr in a total amount of 15 to 25 wt%, and the balance substantially consisting of Al. An aluminum alloy excellent in high-temperature strength, characterized in that an Al compound is uniformly dispersed. 3. A total of 15 to 25 wt% of one or more transition metals consisting of Fe, Mn, Ni and Cr, and Mo,
V, Ti, or Zr is contained in a total amount of 3 wt% or less, and the balance substantially consists of Al, and a fine lump of transition metal-Al compound is uniformly dispersed in the matrix. Aluminum alloy with excellent high temperature strength. 4. An aluminum alloy compact formed by hot plastic working using the aluminum alloy according to claim 1, 2 or 3.