JPH01152229A - Fiber reinforced heat-resistant al alloy powder sintered material - Google Patents

Abstract

PURPOSE:To obtain the above sintered material having excellent strength at ordinary temp. and high temp. strength by mixing inorganic whisker or inorganic short fiber to Al alloy powder having the specific compsn. contg. Cr and Co, Ni, etc., and sintering the same. CONSTITUTION:The inorganic whisker or inorganic short fiber is mixed to the Al alloy powder contg., by weight, 3-20% Cr, one or more kinds among <10% Co, Ni, Mn, Zr, V, Ce, Fe, Ti, Mo, La, Nb, Y and Hf and consisting of the balance Al with inevitable impurities; and the mixture is sintered. The grain size of said Al alloy powder is preferably regulated to <105mum. The grain size of the metallic compounds crystallized out or deposited in the resulting Al alloy matrix is furthermore preferably regulated to <=10mum. The volume ratio Vf of said whisker or short fiber is suitably regulated to 2-30% as well. By this method, the fiber reinforced heat-resistant Al alloy powder sintered material having sufficiently high tensile strength and elongation ratio in the temp. range of ordinary temp. - high temp. is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber-reinforced heat-resistant AtJ alloy that is suitably used for M4 circumferential members that are heated to high temperatures, such as connecting rods between internal combustion condyles or valves. This relates to powder sintered materials.

And 1.

Excellent heat resistance. As one alloy, an alloy for bis]hen (commonly known as arsil) containing 18 to 25 percent SL is known. This high SL content A, l+ alloy is a casting alloy, and according to the casting method, coarse primary SL crystals crystallize and the necessary strength cannot be achieved.
(adding a) to make the initial product S2 finer. However, there is a limit to its refinement effect, and the AfJ alloy obtained by the melting method has the disadvantage of rapidly softening at temperatures above 150°C, so hypereutectic Al alloy powder with high SL content is atomized. A method has been proposed in which the particle size of the primary crystal S= is suppressed to several μmff1 degree by manufacturing by a method, and the compacted product is hot extruded to obtain a high-strength Al alloy sintered material. By a similar method (
The AtJ-8Fe based alloy sintered material has good heat resistance,
It has a tensile strength of about 30 kof/mm2 at a temperature of 300°C.

In order to further improve the strength of this Al-8Fe alloy sintered material, reinforcing fibers may be added to the raw r1 powder. However, materials reinforced with whiskers or short fibers exhibit a significant decrease in strength at high temperatures compared to long fiber reinforced materials, and their high-temperature strength depends on the matrix metal. Fiber volume fraction (Vf) 25
Because it should be kept below %! The strength improvement ω due to I-fiber reinforcement is limited to 1.5 times the strength of the matrix metal alone, so in order to improve the high-temperature strength of materials reinforced with whiskers or short fibers, the high-temperature strength of the matrix metal must be improved. Must be.

The present invention was devised with this technical background in mind, and its purpose is to develop a fiber-reinforced heat-resistant Al having superior room temperature and high temperature strength than Al-8Fe alloys. An object of the present invention is to provide an alloy powder sintered material.

The purpose is to contain 3 to 20% Cr, co, NL.

Mn, Zr, V, Ce, Fe, TL, MO, 1a.

Less than 10% by weight of an alloying element selected from the group consisting of Nb, Y, and Hf, or 10% by weight of two or more alloying elements
and the remainder A and fl containing unavoidable impurities.
This is achieved by providing a fiber-reinforced heat-resistant Δg alloy powder sintered material made by mixing tJ alloy powder with inorganic whiskers or non-1M short fibers and sintering the mixture.

In powder metallurgy, Cr exceeds the solid solubility limit during AfJ.
, Go, NL1Mn and other alloying elements, Δn-cr
Finely dispersed intermetallic compounds such as Δg-2r series and Δg-2r series 1
When dispersed and precipitated, it is possible to strengthen by solid solution of Cr, Go, etc. in the matrix and by crystallization and precipitation of intermetallic compound particles. However, although the precipitated intermetallic compound particles are stable at room temperature,
Both are dissolved in the matrix, and the hardening effect due to precipitation of intermetallic compound particles is gradually lost. In this case, the rate of solid solution of the intermetallic compound particles into the matrix mainly depends on the diffusion coefficient (cm'/sec) of the alloying element in Δρ. That is, in order to improve the heat resistance of the AfJ alloy sintered material, it is necessary to add an intermetallic compound-forming element that has a small diffusion coefficient and a small solid solubility limit. A typical example of an alloy element with a small diffusion coefficient is the diffusion coefficient in Cr (AJ) =
10-'' to 10-''cm27 seconds), and the addition of Cr improves the heat resistance of the Δ1 alloy. In addition, Aρ
Go is an element with a small diffusion coefficient and solid solubility limit in
N.L.

Mn, Zr, V, Ce, Fe, TL, Mo, La.

Examples include Nb, Y, Hf, etc., all of which improve the heat resistance of the AN alloy.

It should be noted that when the intermetallic compound becomes coarse, the mechanical properties (strength, elongation properties) of the AIJ alloy sintered material decrease to 1.
Therefore, the cooling rate from the molten state should be sufficiently increased to produce the powder.

The required cooling condition is a cooling rate of 102-b, and this cooling rate allows the size of the intermetallic compound to be crystallized or precipitated to be suppressed to 10 μm or less.

On the other hand, as a whisker to be mixed with Al alloy powder, Teha, S
=C, SLs N4, 20 ・6T, LCh.

Various whiskers such as Al20s can be mentioned, and examples of short fibers (including those cut from long fibers) include SλC,
Various fibers such as AN 20s can be mentioned. The whiskers and short fibers are uniformly mixed with Al alloy powder and made into a sintered material by compaction and subsequent hot extrusion. In addition, whiskers.

In order to uniformly mix (disperse) the short fibers in the Al1 alloy powder, it is preferable that the ratio of the powder particle diameter to the lI fiber diameter (powder particle diameter/fiber diameter) be less than 1,500. However, if the diameter ratio is less than 1/200, the powder is too fine and requires heavy handling.

Next, the reason for adding alloying elements to AfJ with respect to Al alloy powder will be explained.

■Cr (3 to 20 ffi ffi%)...Cr is an essential additive component, and is added to improve the room temperature strength and high temperature strength, and improve the creep property. However, 3
If it is less than fnfn%, the strength at room temperature and 200°C is low (tensile strength <30 kgf/mm2), and 20tfn%.
Exceeding this value not only makes it extremely brittle and makes hot working difficult, but also increases the specific gravity and lowers the specific heat resistance, which is disadvantageous.

■Co, NL, Mn, etc. - Co, Nx, Mn.

Zr, V, Ce, Fe, TJ, Mo, La, Nb.

Y, l(f contributes to improvement of room temperature strength and high temperature strength.

However, excessive addition inhibits malleability and makes hot working difficult. The total amount of one or more of the alloying elements added is less than 10% by weight, and if this range is exceeded, malleability is impaired.

Next, an example of a method for manufacturing a sintered material using Al alloy powder having the composition of the present invention will be described.

■ Powder production: AtJ alloy powder having the composition of the present invention (particle size less than 105 μm) is atomized using He gas,
It is manufactured using a centrifugal spraying method or the like so as to satisfy the condition of a cooling rate of 10 2 -b/sec.

■Powder compacting...1rI powder is given a predetermined fiber volume ratio (
V+) whiskers or short fibers are mixed uniformly, and this is heated to a pressure of 4 by cold isostatic press molding (CIP method).
,000 kgr/cm 2 , degassed, and further subjected to hot isostatic press molding (IIIP method) to obtain a material for extrusion processing.

■Hot extrusion processing (sintering): The material for extrusion processing is placed in a soaking furnace with an internal temperature of 450°C, held for 1 hour, and then hot extruded at a temperature of 450°C and an extrusion ratio of 14. Perform processing. In addition, if we consider the prevention of oxidation of molded products,
It is preferable to perform the processing in a non-oxidizing atmosphere such as argon gas or nitrogen gas.

Sintered materials (A, B, C, D, E, F , G, I-1°1) (Table 1) and a sintered material as a comparative example (a.

b, c, d, e, f, Q, h) (Table 1) were subjected to a tensile test, and the test results in Table 2 were obtained. In the table, “
O゛° has a tensile strength of 30kgf at a temperature of 200℃
/mm2 or more, the elongation rate is more than 1%, and the hot workability is good. ゛△゛ means that the above tensile strength condition is not satisfied but the other conditions are satisfied. Those that do not meet the criteria were designated as X11. Incidentally, for convenience, the sintered material (A-1') is referred to as an example of the present invention. The sintered material was manufactured in accordance with the method for manufacturing the fiber-reinforced sintered material.

(Hereafter, margin) Table 1 Table 2 <Evaluation of test results> ■Examples of the present invention (A, B, C, D, E, F, G, H.

From the comparison between (2) and comparative examples (a, b, c, d, e, f, g, h), the alloys in the specified composition range for the present invention have small particle sizes of crystallized substances and precipitates, and It can be seen that the strength at 200°C is sufficiently large. At a temperature of 300''C, all the alloys in the specified composition range for the present invention except the present invention example (A) have a tensile strength of 30 kgf/mm2 or more.

In addition, the examples of the present invention had an elongation rate exceeding 1% and was J3, and had good hot workability.

■Comparing the present invention example (A) and the comparative example (a), Mn,
The addition of Zr and TL was carried out at 200°C, 30°C.
It can be seen that the tensile strength at 0°C is significantly improved and the elongation rate is also significantly improved.

(2) A comparison between Inventive Example (8) and Comparative Example (b) shows that the addition of TL slightly improves the tensile strength at room temperature, 200°C, and 300°C, and improves the elongation rate.

■From Comparative Examples (a, b), Zr and Mn were added at room temperature.

It can be seen that the tensile strength at 200°C and 300°C is improved.

(2) From the examples (A, B) of the present invention, it can be seen that as Crff1 increases, although the elongation rate decreases within the allowable range, the tensile strength significantly improves in the temperature range from room temperature to high temperature.

■A comparison between the present invention example (B) and the comparative example (C) shows that even if the additive element content is the same, the particle size of the crystallized substances and precipitates is excessive (grains of crystallized substances and precipitates in the melted material). It can be seen that if the diameter is about the same as the diameter), it becomes extremely brittle.

■Comparative examples (a, b) show that although the elongation rate is high unless alloying elements other than Cr are added,
It can be seen that the necessary tensile strength cannot be obtained in the temperature range down to 0°C.

■Comparative examples (d, e) show that excessive Cr addition causes significant embrittlement and that Fe and TL additions occur at room temperature, 2
It can be seen that the tensile strength at 00°C and 300°C is improved.

②Comparative Examples (a, h) show that excessive amounts of additive elements other than Cr cause significant embrittlement.

Fiber-reinforced sintered material (J, Ni, Shi) as an example of the present invention obtained according to the above-mentioned manufacturing method (Table 3) and a fiber-reinforced sintered material as a comparative example obtained by the same method (Table 3) Reinforced sintered material (i,
A tensile test was conducted on sample j), and the test results shown in Table 4 were obtained.

Table 3 (Hereinafter, blank space) Table 4 Evaluation of test results> ■From the comparison between the inventive examples (J, ni, L) and the comparative examples (i, j>), the sintered material strengthened with SλC whiskers has 71 −
Even if the composition of Rix△1 alloy is different, there is no difference in tensile strength at room temperature after steaming, but as the temperature rises, a difference appears,
It can be seen that at high temperature 4 (300° C.), the strength of the comparative examples decreases significantly, whereas the strength of the examples of the present invention does not decrease after steaming.

In addition, the present invention example (Δ) and the present invention example (J
), it can be seen that the tensile strength of the fiber-reinforced sintered material approaches that of the matrix Al alloy simple sintered material with increasing temperature. This means that in order to improve the high-temperature strength of the fiber-reinforced Δ1 alloy sintered material, the high-temperature strength of the matrix Al alloy should be avoided.

■Looking at the change in elongation rate due to temperature in Invention Examples LJ, L), the elongation rate increases with the upper temperature limit, indicating that the elongation characteristics at high temperatures depend on the matrix Al alloy, and the matrix Al alloy It can be seen that the hot workability is good. On the other hand, in the comparative example (i, j>), the elongation rate decreases as the temperature increases, indicating that the matrix A9 alloy tends to become brittle due to heating.

As is clear from the above description, 3 to 20% by weight of Cr, .co, Ni, Mn, Zr, V, and Ce.

Less than 10% by weight of an alloying element selected from the group consisting of Fc, TL, Mo, S=, La, Nb, Y, 1-1f, or less than 10% by weight of two or more alloying elements, and unavoidable impurities. A fiber-reinforced, heat-resistant Al alloy powder sintered material has been proposed, which is made by mixing and sintering an Al alloy powder consisting of .

Matrix Af applied to this fiber-reinforced sintered material
J alloy has sufficiently high tensile strength and elongation in the temperature range from room temperature to high temperature, so the sintered material has large tensile strength as a fiber reinforcement material at room temperature and is heat resistant at high temperatures. Depending on the high temperature strength of the matrix AfJ alloy, it has a sufficiently large high temperature tensile strength and also has good hot workability.

Claims (4)

[Claims] (1) 3 to 20% by weight of Cr, Co, Ni, Mn, Zr
, V, Ce, Fe, Ti, Mo, La, Nb, Y, Hf
Mixing inorganic whiskers or inorganic short fibers with Al alloy powder consisting of less than 10% by weight of one alloying element selected from the group consisting of or less than 10% by weight in total of two or more alloying elements, and the balance Al containing inevitable impurities. Fiber-reinforced heat-resistant Al alloy powder sintered material made by sintering. (2) The fiber-reinforced heat-resistant Al according to claim 1, wherein the grain size of the intermetallic compound crystallized or precipitated in the Al alloy matrix is 10 μm or less.
Alloy powder sintered material. (3) Volume fraction of the whiskers or short fibers (V_f)
The fiber-reinforced heat-resistant Al alloy powder sintered material according to claim 1, wherein the fiber-reinforced heat-resistant Al alloy powder sintered material is 2 to 30%. (4) The fiber-reinforced heat-resistant Al alloy powder sintered material according to claim 1, wherein the particle size of the Al alloy powder is less than 105 μm.