JPH01205049A - Member made of heat-resistant and high strength sintered al alloy - Google Patents

Abstract

PURPOSE:To manufacture the title member by quenching an Al alloy contg. specific amounts of Fe, Cr and Zr into powder, subjecting it to molding and sintering and thereafter to an aging treatment at a specific temp. CONSTITUTION:The molten metal of the Al alloy contg., by weight, 1-5% Fe, 5-12% Cr and 0.5-3% Zr is quenched at the cooling speed of about 10<2>-10<6> deg.C/sec by an inert gas atomizing method, a centrifugal spraying method, etc., and is solidified into the powder shape to reduce the size of the intermetallic compounds of Al-Cr, Al-Zr and Cr-Zr deposited at the time of solidification. the Al alloy powder is pressurized and molded into a green compact it is thereafter sintered and the sintered manufactures are subjected to an aging treatment at 350-500 deg.C. The size of the intermetallic compounds in the sintered Al alloy is fined into <=10mum, by which the machine member made of sintered Al alloy having excellent high temp. strength can be obtd.

Description

Detailed Description of the Invention The present invention relates to a member formed by sintering Al alloy powder, which has good hot workability with little strength loss at high temperatures, and is particularly applicable to internal combustion engines. This invention relates to a heat-resistant, high-strength sintered AJI alloy member that is suitably used in locations that are heated to high temperatures, such as connecting rods and valves.

An alloy for pistons (commonly known as Alsil) containing 18 to 25% by weight of SL is known as an Af1 alloy with good quality and excellent heat resistance. This high SL content AJ alloy is a casting alloy, and according to the melting method, coarse primary crystals Sλ crystallize and the necessary strength cannot be obtained. ) to refine the primary crystal S^. However, since there is a limit to its refining effect, the particle size of the primary crystal SL can be suppressed to about several μm by producing hypereutectic Al alloy powder containing high Sλ by the atomizing method, and the compacted powder is produced using the atomizing method. High strength sintered A by hot extrusion processing
A method of obtaining a member made of l-alloy has been proposed. This AJ gold alloy for powder metallurgy has high temperature strength.

Although 2% by weight or more of Fe is added to improve Young's modulus, if Fe and SL coexist in AJ, acicular A
JIs Fe, Altx Fe! Intermetallic compounds such as SL precipitate and inhibit hot forging workability, resulting in poor sinterability and stress resistance JIX! There is a problem in that the II cracking properties deteriorate.

In addition, in recent years, research has been conducted on All-Fe alloys such as Aj-8F8, but AfJ-Fe alloys cannot be strengthened by aging treatment, and combinations with other alloying elements are being explored. There is.

[1< The present invention was created against this technical background, and its purpose is to provide a ρ alloy member for heat-resistant, high-strength sintering that is strengthened by aging treatment. do.

・The purpose of this is to produce a heat-resistant ^ strength sintered member that has been sintered with He1 alloy powder having the following composition and has a rapidly solidified structure, and has been subjected to aging treatment at a temperature of 350 to 500°C. This is achieved by providing a g-alloy member.

Composition of Ω alloy powder: Fe = 1 to 5% by weight.

Or = 5~12fl! i%, Zr=0.5 to 3% by weight, remainder=AJ) and inevitable impurities.

In Al1 alloy containing Cr and Zr, 1)-
Cr-based, AfJ-Zr-based, and Cr-Zr-based intermetallic compounds form a supersaturated solid solution in the α phase, and the intermetallic compounds precipitate and harden due to aging, which is what is called age hardening. Also,
Cr exceeding the solid solubility limit.

If 11 alloys containing Zr are rapidly cooled and solidified from a molten state and then subjected to aging treatment, Al-Cr series, 1l-Zr series, 0r
It is possible to obtain a structure in which -7r-based intermetallic compounds are finely dispersed and precipitated.
It is possible to measure strengthening by solid solution of r and strengthening by crystallization and precipitation of intermetallic compounds.

It should be noted here that when the intermetallic compound becomes coarse, the strength of the material is impaired, so it is necessary to increase the cooling rate from the molten state to room temperature. The required cooling conditions are a cooling rate of 102-b. The size of the intermetallic compound and the intermetallic compound precipitated by aging can be suppressed to 10 μm or less. As a practical matter, it is difficult to obtain a cooling rate of 102~b by the melting method, and the powder is rapidly solidified by the atomization method, in which an inert gas is injected into the molten metal flowing out of the pores, or the centrifugal spray method. , it is necessary to obtain product parts using powder metallurgy.

The reason for adding the alloying element added in the evening is as follows.

(2) Fe (1 to 5% by weight): Fe contributes to improving room temperature strength, high temperature strength, and Young's modulus. However, if it is less than 1% by weight, the effect of addition is small, and if it exceeds 5% by weight, the sensitivity to notches becomes high and the elongation rate becomes too small.

(2) Cr (5 to 12% by weight): Cr is added to improve the room temperature strength and high temperature strength, as well as the creep properties. However, if it is less than 5% by weight, the temperature is 300-400%.
The strength at °C is low, and if it exceeds 12% by weight, hot workability decreases and the elongation rate becomes too small.

■Zr (0.5 to 3% by weight)...Zr is malleable.

Added to improve creep properties. However, 0
．． If it is less than 5% by weight, there will be little improvement effect, and if it exceeds 3% by weight, the spreadability will decrease.

Next, AJ! of the composition of the present invention! An example of a method for manufacturing sintered crystals using alloy powder will be described.

■Production of powder...1≦Fe≦5% by weight, 5≦Cr≦1
Cr in a composition range of double ω%, 0.5≦Zr≦3% by weight
AJ alloy powder containing , Fe, and Zr (particle size 105 μm
) at a cooling rate of 102 to 101'C/
Manufactured to meet the following conditions:

■Powder compacting...The obtained powder is pressed to a pressure of 4.000 at 9 f/aA using the cold isostatic press method (CIP method).
As a result, a material for extrusion processing with a size of 5011+1φ×100 shoes is obtained.

■Hot extrusion processing (sintering): After degassing the extrusion material, which is a green compact, at a temperature of 450°C for 1 hour, hot extrusion processing is performed at a temperature of 450°C and an extrusion ratio of 12. do. In addition, in consideration of preventing oxidation of the molded product, it is preferable to carry out the hot extrusion process in a non-oxidizing atmosphere such as argon gas or nitrogen gas.

Grave "Shiban" - Sintered crystal (A
, B, C) and comparative examples of baked crystals (a, b, c, d, e, f, g) obtained by the same method.

h) (see Table 1) at a temperature of 300°C.
A tensile test was conducted on the specimens that had been subjected to three types of aging treatment by holding them at 400°C and 550°C for 10 hours each, and those that had not been subjected to aging treatment, and the test results shown in Table 2 were obtained.

Table 1 Table 2 *σ-...Tensile strength (f/Mn')*ε...
・Elongation rate (%) <Evaluation of test results> ■From the comparison of samples A and 8 and samples a and b, Feff1
It can be seen that as the tensile strength increases, the tensile strength improves and the elongation rate decreases, regardless of the presence or absence of aging treatment.

(2) Comparison of samples B, C, and C shows that as Crff1 increases, the tensile strength improves and the elongation rate decreases regardless of whether or not aging treatment is performed.

■Sample 3. From the comparison of d, it can be seen that the addition of Zr increases the tensile strength regardless of the presence or absence of aging treatment, and the strength-improving effect is particularly large for those subjected to aging treatment at a temperature of 400°C.

■Comparing samples c and h with other samples, it was found that when the amount of Cr added is small, the strength improvement effect due to aging treatment is small, and at a temperature of 550
It can be seen that the decrease M in tensile strength when heated to ℃ is large.

■Looking at the differences between all samples depending on whether or not they were aged,
It can be seen that no improvement in tensile strength can be expected at an aging treatment temperature of 300°C, and that the tensile strength decreases at an aging treatment temperature of 550°C.

WJ mouth 1 unit Temperature 25° C. for multiple 161 samples B (see Table 1).

The surface hardness (micro-Vickers hardness Hv
), and the results are shown in Figure 1.

Evaluation of test results> The upper limit of hardness is observed at a heating temperature of 350°C or higher, maximum hardness is reached at a heating temperature of 450°C, and a sufficiently large increase in hardness is observed even at a heating temperature of 500°C.

For multiple samples B (see Table 1) of 11 mouths and 1 unit, the heating temperature (aging temperature) was set to 400°C, 450°C, and 500°C, and the difference in holding time at each temperature was determined as the surface hardness (micro-Vickers hardness). The effect on f-Iy) was investigated and the results are shown in FIG.

<Evaluation of test results> At a heating temperature of 400°C, the maximum hardness Hv was reached after a holding time of 10 hours.
At a heating temperature of 450°C, the maximum hardness H, 214 is reached after a holding time of 1 hour, and at a heating temperature of 500°C, a maximum hardness of -1v211 is reached after a holding time of 15 minutes.

A higher maximum hardness can be obtained by setting the heating temperature lower than by setting it higher, but it requires a longer holding time, so it is advantageous to increase the heating temperature and shorten the holding time to improve productivity. Therefore, the difference in maximum hardness due to the difference in heating temperature is not so large. Note that it is clear that age hardening progresses while the green compact is heated and hot worked, and there is no need to perform a separate aging treatment depending on the preheating time of the material, the time required for processing, and the processing temperature.

As is clear from the above explanation, Fe = 1 to 5% by weight,
The present invention member, which is a sintered crystal of Al1 alloy powder containing Ee, Cr, and 7r with Cr = 5-12ffi1% and Zr = 0.5-3% Because it is hardened, it can obtain great strength from room temperature to high temperature.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between aging temperature and surface hardness (Hv) of a sintered product of He1 alloy in the composition range of the present invention, and Fig. 2 is a graph showing the relationship between aging treatment temperature and surface hardness (Hv) of a sintered product of He1 alloy powder in the composition range of the present invention. processing temperature,
It is a graph showing the relationship between retention time and surface hardness (Hv).

Claims (1)

[Scope of Claims] A heat-resistant, high-strength sintered Al alloy member, which is a member obtained by sintering Al alloy powder having the following composition and having a rapidly solidified structure, and which is subjected to aging treatment at a temperature of 350 to 500°C. Composition of Al alloy powder: [Fe...1 to 5% by weight, Cr...5 to 12% by weight, Zr...0.5 to 3% by weight, balance...Al and inevitable impurities]