JPH02194142A - Al-base alloy powder for sintering - Google Patents

Abstract

PURPOSE:To manufacture an Al-base alloy powder for forming a sintered compact excellent in fatigue characteristics and toughness by incorporating specific percentages of Zr, Cr, and Fe to Al and specifying the total content of Cr and Fe. CONSTITUTION:An alloy having a composition which contains, as essential components, 0.5-2%, by weight, Zr, 2-5% Cr, and 0.5-3% Fe and has the balance Al with inevitable impurities and further contains, if necessary, 0.1-2%, in total, of one or >=2 kinds selected from 0.5-2% Mn, 0.1-0.6% B, 0.1-0.5% W, 0.5-2% Mo, and 0.5-2% Ti and in which total content of Cr and Fe is controlled to 3-6% is refined and formed into fine powder by a rapid solidification process. By using this alloy powder, a superior sintered compact of Al-base alloy powder having high strength at ordinary temp. and high temp. and also having sufficient toughness and fatigue characteristics can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention serves as a raw material for A1-based alloy powder sintered bodies that are widely used in various industrial machinery fields such as automobiles, aircraft, railway vehicles, and ships. This invention relates to Al-based alloy powder for sintering.

[Prior art] In recent years, as a new technology of A1 powder metallurgy, a rapid solidification method has been applied to obtain an A1-based alloy powder in which Al contains various transitional elements, and this Al-based alloy powder is used to sinter. Many techniques have been developed for manufacturing sintered bodies with high hot strength by molding bodies.

In the above technology, when rapidly solidified powder is used, Al-Fe with a composition that cannot normally be obtained in an equilibrium state is produced.
, Al-Cr, Al-Zr, Al-81, and other A1 alloys can be produced by applying rapid solidification technology. According to this method, the size and fineness of crystal grains can be The mixture can be controlled and a new material with excellent heat resistance, abrasion resistance, and embedding strength can be obtained.

For example, Japanese Unexamined Patent Publication No. 59-43802, No. 60-234
No. 936, No. 60-248860, No. 61-
No. 49551, No. 61-96051, No. 51
A number of techniques are disclosed in Japanese Patent No. 130451, and a similar technique is also disclosed in US Pat. No. 4,464,199.

All of the techniques found in the above documents are approximately 8~! In addition to containing 2% Fe, rare earth elements such as Ce or V, Zr,
Al-F containing a transition metal element such as Mo in Al
E-based alloy powder is obtained by a rapid solidification method, and the powder is sintered to form an Al-Fe-X compound (X is Ce or V as described above) in an Al matrix.

The present invention relates to an A1-based alloy powder sintered body in which hot strength and heat resistance are improved by dispersing Zr, Mo, etc.).

Much research and development has been carried out on Al-based alloy powders other than the Al-Fe alloy powders shown above.
Al-Cr-Zr with improved heat resistance by containing r etc.
A sintered body of alloy powder is disclosed.

[ID to be Solved by the Invention] All of the sintered bodies obtained from the Al-Fe alloy powder have high tensile strength in the temperature range from room temperature to about 300°C.

However, when the present inventors conducted various studies on the Al-Fe alloy powder sintered body, it was found that the sintered body had poor fatigue properties under stress concentration conditions.

In other words, it is known that the fatigue strength of metal materials generally decreases at stress concentration parts such as notches, but in Al-Fe alloy powder sintered bodies, the degree of decrease in fatigue strength (notch susceptibility) generally decreases. ) was found to be significantly high.

Moreover, it was found that this sintered body had low toughness.

In the Al-Fe alloy powder sintered body, a large amount of Fe and other elements are added to increase the volume fraction of the dispersed phase for the purpose of improving strength, but this dispersed phase has magical properties and It is thought that the sintered body becomes a crack propagation site and promotes crack propagation, resulting in poor fatigue properties and low toughness of the sintered body.

Furthermore, even if an attempt was made to improve fatigue properties and toughness by lowering the volume fraction of the dispersed phase, there was a problem in that the tensile strength conversely deteriorated. Therefore, in the Al-Fe alloy powder sintered body,
It is extremely difficult to simultaneously satisfy tensile strength, toughness, and fatigue properties. These problems pose a particular problem when applied to various parts, such as connecting rods, which have complex shapes and operate under certain stress concentration conditions.

On the other hand, it is known that the Al-Cr-Zr alloy powder sintered body is a product in which Cr and Zr are forcibly dissolved in Al when the powder is manufactured by a rapid solidification method. Cr and Z
When the rapidly solidified powder in which r is forcibly dissolved is heated at a temperature of 300 to 450°C, CuA17 is removed from the Al matrix.
゜Intermetallic compounds such as ZrA15 are finely precipitated, and precipitation strengthening can be expected. Moreover, the above-mentioned precipitated compounds are formed at the heat treatment temperature (
Since it hardly becomes coarse in the temperature range of 300 to 450°C or lower, it is expected to exhibit high strength in the temperature range of 300°C or lower.

However, most of the previous studies on Al-Cr-Zr alloy powder sintered bodies have focused on Al-0r-Z
This relates to the rB base alloy material itself, and the current situation is that it has not yet reached a level of strength that is practically sufficient for extruded rods and forged materials. That is, the Al-based alloy powder sintered body was developed based on the above-mentioned purpose, and after sintering and hot forming, it can be processed by hot casting, rolling, extrusion, etc. in the same way as ordinary ingots. Even after these processes, it is necessary to develop a practically sufficient strength level.

As is clear from the above purpose, the "sintered body" in the present invention refers to a molded material (simply referred to as Al) before being processed into a product.
The meaning also includes (generally referred to as base alloy).

The technique disclosed in JP-A-59-116352 further adds Mn to the ternary alloy of Al-Cr-Zr,
Although the resulting sintered body has increased strength, this sintered body has the following problems.

For example, 16j6rials issued in April 1986
Science and Technology, Vo
1, 2, pages 394-399, Al-Cr-Zr-
Research on Mn alloy powder has been published, and it is disclosed that sintered bodies obtained from this alloy powder are easily affected by heating conditions during hot extrusion and the like.

Therefore, in order to develop sufficient strength in the sintered body obtained from this A1-based alloy powder, it is necessary to use a special processing method at relatively low temperatures such as room temperature extrusion, making it difficult to put it into practical use. .

The present invention has been made to solve these technical problems, and its purpose is to create a sintered material that is excellent not only in heat resistance but also in toughness and fatigue properties under stress concentration conditions. The purpose of the present invention is to provide an Al-based alloy powder that is a raw material for the body.

[Means for solving the problem] The Al-based alloy powder of the present invention that achieves the above object is Z
r: 0.5-2%, Cr: 2-5% and Fe
: It contains 0.5 to 3% as an essential component, and the total of C' and Fe is 3 to 6%, and the remainder consists of A1 and inevitable impurities.

In addition to the above components, Mn: 0.5 to 2%, B:
0.1-0.5%, W: 0.1-0.5%, Mo
1f selected from the group consisting of: 0.5-2%, Ti: 0.5-2%! 1 or 2 or more types in total 0°1-2
%, the object of the present invention can be achieved more effectively.

[Function] The present inventors have discovered that the toughness and fatigue properties under stress concentration conditions of the Al-Cr-Zr alloy powder sintered body are as follows.
If we focus on the superiority of the l=Fe alloy powder sintered body and improve the strength of the Al-Cr-Zr alloy powder sintered body, we can create a new heat-resistant A1 with a high overall property balance. Based on the idea that it might be possible to create a sintered body of base alloy powder, we have been conducting intensive research for some time.

As mentioned above, in the Al-Fe alloy powder sintered body, the above-mentioned A
High strength is achieved by the high volume fraction of the dispersed phase formed by the l-Fe-X compound, but according to research by the present inventors, these dispersed phases are also relatively coarse in individual size. It becomes a source of cracks and causes a decrease in toughness and fatigue properties. On the other hand, Al-Cr-Z
In the r-based alloy powder sintered body, since the amount of added elements is smaller than that of the Al-Fe-based material, it is difficult to obtain high strength, but it has good toughness and fatigue properties.

Therefore, the present inventors investigated the effects of adding various elements to this sintered body based on an Al-Cr-Zr% alloy powder sintered body, and found that if an appropriate amount of Fe is added, the toughness and fatigue of the sintered body can be improved. It has been found that strength can be improved without deteriorating properties.

The effects of each component in the A1-based alloy powder according to the present invention and the reasons for limiting their numerical values are as follows.

Zr: 0.5 to 2% Zr, which is forcibly dissolved into a supersaturated solid solution by the rapid solidification method, precipitates in the subsequent process and has the effect of increasing the room temperature and high temperature strength of the sintered body. In order to exhibit this effect, Zr must be 0.
．． It is necessary to add 5% or more, but if it is added in excess of 2%, excessive Zr that is not forcibly dissolved no matter how rapidly it is cooled will crystallize, reducing the toughness of the sintered body.

Cu: 2-5% Fe: 0.5-3% Cr partially precipitates after forced solid solution and contributes to strengthening, and also
It forms a compound with Fe and disperses in the matrix to improve heat resistance. In particular, a compound in which Cr and Fe are added at the same time is difficult to coarsen even at high temperatures, so it exhibits high room temperature and high temperature strength even after hot working. In order to obtain this effect, it is necessary to simultaneously add 2% or more Cr and 0.5% or more Fe (3% or more in total), but if each component exceeds the above upper limit or the total %, the toughness and fatigue properties of the sintered body deteriorate.

Mn: 0.5-2% B: 0.1-0.5% W: 0.1-0.5% Mo: 0.5-2% Ti: 0.5-2% By simultaneously adding Zr, Cr, and Fe, it is possible to satisfy all of the tensile strength, toughness, and fatigue properties of the sintered body. In addition to these components, Mn, B
, W, Mo, and one or two selected from the group consisting of Ti.
The effects of the present invention can be more effectively achieved by containing an appropriate amount of at least one species.

That is, these components promote the precipitation strengthening effect of Cr and Zr and contribute to strengthening the sintered body. In order to exhibit this effect, it is necessary to add within the above range, but adding beyond these ranges will result in a decrease in toughness.

As mentioned above, the A1-based alloy powder according to the present invention is made by turning a melted alloy into a fine powder by rapid solidification in order to add a large amount of an element with a small solid solubility limit in an equilibrium state. Various atomization methods can be used as examples, but the method is not limited in any way, but in order to obtain the desired fine powder, it is preferable to set the quenching rate to 102 deg/sec or more.

[Example] Alloys having various compositions shown in Table 1 below were melted and rapidly solidified by N2 gas atomization to obtain powders with a particle size of 74 μm or less. The cooling rate at this time was determined to be 10' based on microstructure observation of 7075 alloy powder prepared by the same method.
Table 1 (%) Each of the obtained powders was mixed into a 70IIIlφ aluminum alloy (
The powder was filled into a capsule manufactured by AA Standard 5052), and while the capsule was heated to 300° C., the inside was vacuum-evacuated through a degassing tube provided at one end of the capsule, and the powder was vacuum-sealed into the capsule. The time required for deaeration was approximately 2 hours.

Next, the capsules are heated at 350°C for about 1 hour to undergo hot extrusion processing, and the outer skin of the capsules is lathed from the resulting extruded rod.
Removed round rod of approximately 15mmφ (Al-based alloy powder sintered body)
I got it. The capsule temperature during extrusion was approximately 330°C.
Also, the extrusion ratio was about 15.

Among the obtained round bar samples, No. 1 containing Cr and Zr at the same time
, 1-9. Each of the sintered bodies No. 11 to 13 was further heat-treated at 350° C. for 24 hours. Test pieces were taken from these extruded rods, and the following various tests were conducted.

Normal temperature tensile test> ASTM 8557M (smooth test piece) and ASTM
602 (notched test piece), measure the 0.2% proof stress (σ., 2) 1 strength (a6) and elongation at break (δ) of a smooth test piece at room temperature and the strength (σ87!) of a notched test piece. did. Then, the proof stress (cj, ,) and strength (σ
Based on the measurement results of NTg), (5Nrs/σo,z) was calculated and used as a toughness evaluation parameter.

High Temperature Tensile Test> In accordance with ASTM E2m, the test temperature was 250°C and the test pieces were preheated at 250°C for 100 hours (70, 2+06 and δ were measured).

<Rotating bending fatigue test> Using a test piece with an annular notch with a stress concentration factor of 6, the number of repetitions until rupture (rupture cycle) at a stress amplitude (σ, ) of 10 kgf/mm2 was measured, and the fatigue properties were determined. was evaluated.

These results are shown in Table 2 below in correspondence with the raw material powder No. As is clear from the results, the sintered body (No.

Nos. 1 to 8) exhibit good values with well-balanced room temperature/high temperature strength, toughness, and fatigue properties.

In contrast, the conventional Al-Fe-Ce shown in No. 15
Sintered bodies obtained from Al-Cr-Zr based alloy powders are inferior to Al-Cr-Zr based alloy powder sintered bodies in terms of toughness and fatigue properties. Moreover, the sintered bodies obtained from the Al-Cr-Zr-Mn alloy powders of No. 14 are inferior in strength at room temperature and high temperature compared to the sintered bodies obtained from the A1-based alloy of the present invention.

On the other hand, No. 10. It is clear from a comparison of the sintered body shown in No. 11 and the sintered body obtained from the Al-based alloy powder of the present invention that sufficient strength cannot be obtained even if either Zr or Fe is missing, and A decrease in fatigue properties, which appears to be due to strength, is observed. Furthermore, as is clear from the characteristics of the sintered body shown in No. 9° 12.13, when the amounts of Fe and Or added exceed the upper limit defined by the present invention, a decrease in toughness and fatigue properties is observed.

[Effects of the Invention] As described above, according to the present invention, by using the Al-based alloy powder having the above composition, an excellent Al having high strength at room temperature and high temperature and sufficient toughness and fatigue properties can be obtained.
A base alloy powder sintered body can be realized. This sintered body is ideal for various engine parts such as connecting rods that are subjected to repeated loads in high-temperature environments, exterior materials for aircraft and various flying objects that are exposed to high-temperature environments, and is also suitable for use in various other industrial machinery parts. It is expected to have wide application.

Claims (2)

[Claims] (1) Zr: 0.5-2% (meaning of weight %, same below)
, Cr: 2 to 5% and Fe: 0.5 to 3% as essential components, and the total of Cr and Fe is 3 to 6%,
An Al-based alloy powder for sintering, characterized in that the remainder consists of Al and inevitable impurities. (2) Mn: 0.5-2%, B: 0.1-0.5%, W
:0.1~0.5%, Mo:0.5~2%, Ti:0.
A for sintering according to claim (1), wherein the A for sintering according to claim 1 contains a total of 0.1 to 2% of one or more selected from the group consisting of 5 to 2%.
L-based alloy powder.