JPS62185857A - Heat resistant and high strength aluminum alloy - Google Patents

Abstract

PURPOSE:To provide the titled alloy having especially superior toughness and Young's modulus, by composing respective ratios of Si, Cu and Mg, further one kind or more among Ni, Cr and Mo. CONSTITUTION:The titled alloy is composed of, by weight 12.0-28.0% Si, 0.8-5.0% Cu, 0.3-3.5% Mg and one kind or more among 3.1-8.0% Ni, 0.2-8.0% Cr, 0.2-8.0% Mo. In the alloy, Si improves Young's modulus and reduces thermal expansion coefft., exhibits heat treating effect by coexistence with Mg, further provides elongation and toughness. Cu improves strength due to heat treatment effect. Mg is used for obtaining heat treating effect due to coexistence with Si and provides elongation and toughness. Ni, Cr and Mg improve high temp. strength and Young's modulus and have effect for possessing elongation and toughness. By specifying compsn. ranges of the above components, the aimed Al alloy having improved strength toughness and Young's modulus can be provided.

Description

[Detailed description of the invention] A0 Purpose of invention (1) Industrial application field The present invention relates to heat resistant, high strength aluminum alloys.

(2) Prior art At present, aluminum alloys are actively used as constituent materials for automobile parts in order to reduce the weight of the parts.

In particular, it is more effective to construct moving parts such as pistons and connecting rods in an internal combustion engine from an aluminum alloy, since this can also reduce inertial force.

Therefore, conventionally, the above-mentioned moving parts have been manufactured by applying a melting method using an aluminum alloy such as JIS AC8A.

(3) Problems to be solved by the invention Since the above-mentioned moving parts are used at high temperatures, they are required to have heat resistance and high strength, as well as excellent toughness and a high Young's modulus. When the melting method is applied, the degree of freedom in selecting additive elements in aluminum alloys is narrow, so there are naturally limits to improving strength, toughness, and Young's modulus.

In view of the above, the present invention focuses on a powder metallurgy method that has a wide degree of freedom in selecting additive elements, and when the above-mentioned moving parts are manufactured using this method, the strength etc. of the moving parts can be further improved compared to conventional ones. It is an object of the present invention to provide the aluminum alloy that can be used.

B0 Structure of the Invention (11 Means for Solving Problems) The heat-resistant, high-strength aluminum alloy according to the present invention contains at least one member selected from the following ranges of Si-, Cu and Mg, and Ni, Cr and MO. It is characterized by containing.

12.0% by weight≦Si≦28.0% by weight0.8% by weight≦
Cu≦5.0wt% 0.3wt%≦Mg≦3.5wt% 3.1wt%≦Ni≦8.0wt%0.2wt%
≦Cr≦8.0wt% 0.2ffilIt%≦Mo≦g, Qii1% (2) Function Si improves Young's modulus and lowers the coefficient of thermal expansion, and exhibits heat treatment effects when coexisting with Mg. It also has the effect of retaining elongation and toughness. however,
If the Si content is less than 12.0% by weight, the above effects cannot be obtained, while if it exceeds 28.0% by weight, elongation and toughness will decrease.

Cu improves the strength due to the heat treatment effect.

However, if the Cu content is less than 0.8% by weight, the above effects cannot be obtained, while if it exceeds 5.0% by weight, the corrosion resistance will decrease.

Mg is used to obtain a heat treatment effect by coexisting with St, and has the effect of maintaining elongation and toughness. However, if the Mg content is less than 0.3% by weight, the above effects cannot be obtained, while if it exceeds 3.5% by weight, elongation and toughness will decrease.

Ni, Cr and Mo have the effect of improving high temperature strength and Young's modulus, as well as retaining elongation and toughness. However, if the content of Ni is less than 3.1% by weight and the content of Cr and Mo is less than 0.2% by weight, the above effect cannot be obtained, while on the other hand, the content of these is more than 8.0% by weight. and elongation and toughness decrease.

For the above reasons, by specifying the composition ranges of various chemical components as described above, it is possible to provide the aluminum alloy with improved strength, toughness, and Young's modulus.

(3) Example When manufacturing moving parts such as pistons using the aluminum alloy according to the present invention, the steps of pulverizing the alloy, powder compacting, heat treatment, and hot extrusion processing are adopted.
Depending on the motion part, extrusion is followed by hot forging.

The aluminum alloy is powdered by applying an air atomization method, and the cooling rate of the powder is set at 102° C./sec or higher. If the cooling rate is lower than this, large amounts of Ni, Cr, and MO are added to obtain high rigidity and high heat resistance, so intermetallic compounds will coarsely crystallize, resulting in an extremely low elongation and impact value. It cannot be put to practical use.

As a powder compacting method, cold isostatic pressing method (CIP) is used.
method) or mold compression molding method is adopted.

In the heat treatment of the billet obtained by compaction,
The temperature is set at 430°C or higher and 520°C or lower. This treatment is carried out in an inert gas atmosphere such as Ar, primarily to remove gases such as H2 contained in the billet, and secondarily to sinter the billet. Since the effect was small, the strength decreased, and sintering did not progress sufficiently.
If it exceeds C, a liquid phase is generated and the strength is reduced, so the significance of adopting rapid solidification during powder production is lost.

In hot extrusion processing, the billet temperature is 300℃
As above, the temperature is set to 450° C. or lower, and the extrusion ratio is set to 5 or more and 35 or less, respectively. If the billet temperature is lower than 300℃, the deformation resistance becomes large and extrusion becomes impossible, and the powder cannot be completely sintered.
If the temperature exceeds 0°C, the structure will become coarser and the strength will decrease.

As for the extrusion method, both direct extrusion (forward extrusion) and indirect extrusion (backward extrusion) can be applied, but if the extrusion ratio is less than 5, the strength will vary;
If it exceeds , deformation resistance increases, moldability deteriorates, and mass productivity becomes difficult.

In the forging process, the forging temperature is 430'C or higher,
The temperature is set at 495°C or lower, preferably 470°C. When the forging temperature is lower than 430"C, the formability deteriorates;
If the temperature exceeds 95°C, a liquid phase tends to occur, causing a decrease in strength.

When manufacturing moving parts through each of the above steps, the optimum range of aluminum alloy is to improve the heat resistance, toughness, and Young's modulus, and to improve hot extrusion workability and hot forging workability during manufacturing. is as follows.

14.0wt%≦Si≦18.0wt%1.6wt%≦
Cu≦3.0wt% 0.3wt%≦Mg≦0.8wt% 3.1wt%≦N, i≦4.5wt%i, o, t
i amount %≦Cr≦ 2.0 weight% 1.0 weight%≦MO≦
2.0% by weight When Nt, Cr, and Mo contain two or more of them, the optimum range is for the sum of them to be 2.0% by weight or more and 8.0% by weight or less.

Table I shows the compositions of aluminum alloys 1 to 1 according to the present invention and conventional aluminum alloys 1 to X.

The conventional aluminum alloy (■) corresponds to JIS AC8A, the same (■) corresponds to AA standard A390D, and the same (X) corresponds to JIS 2017.

Table I Next, an example in which a round bar is manufactured using aluminum alloys I to ① according to the present invention will be described.

An air atomization method is applied to aluminum alloys I to 1 to produce alloy powder at a cooling rate of 10'' to 1O4C/sec.

Mt.) Using each alloy powder, cold isostatic press molding method or mold compression molding method was applied, and the density ratio was 75% and the diameter was 225 mm.
A round bar billet for extrusion of cranes is compacted.

In the cold isostatic press molding method, alloy powder is placed in a rubber tube, and the steps of i, s to 3. Molding is carried out under hydrostatic pressure of OLon/-, and in the mold compression molding method, alloy powder is placed in a mold and heated in air at room temperature for 1.S to 3.
Molding is carried out under Oton/CIA pressure.

(C) Each billet is placed in a soaking furnace with an internal temperature of 500° C. and held for 4 hours, and heat treatment is applied to each billet and the left.

1 dl Each billet is extruded at a billet temperature of 380°C to obtain a round bar with a diameter of 50 fins (extrusion ratio 20).

(el) Each round bar is subjected to T6 treatment consisting of heating at 490°C for 2 hours, cooling with water, and heating at 175°C for 8 hours.

([1) Each round bar is held in an atmosphere of 200°C for 100 hours.

A tensile test piece with a parallel part surface diameter of 5 mm and a parallel part length of 39 mm was cut out from each round bar that had undergone the step (f) above, and a tensile test was conducted on each tensile test piece at 200°C.

Also, from each round bar that has gone through the step (f) above, 10mm long and 1mm wide
A test piece having a length of 00 m and a thickness of 1 m was cut out, and the Young's modulus of each test piece was measured at room temperature by an internal friction method.

Round bars are melted using the conventional aluminum alloys ■ to give Tensile test pieces similar to those described above were cut out from each round bar, and tensile tests similar to those described above were conducted on them. In addition, test pieces similar to those described above were cut out from each round bar, and the Young's modulus of the test pieces was similarly measured.

Table 3 shows the tensile test results and Young's modulus measurement results for each test piece.

Table 2 As is clear from Table 2 above, aluminum alloys 1 to 2 according to the present invention are superior to conventional aluminum alloys 1 to X in terms of strength, toughness, and Young's modulus.

C1 Effect of the Invention According to the present invention, the composition range of essential chemical components consisting of St, Cu and Mg is specified as described above, and Ni
By specifying the composition range of the selected chemical components consisting of % Cr and Mo as described above, it is possible to provide a heat-resistant, high-strength aluminum alloy having particularly excellent toughness and Young's modulus, and which is suitable for internal combustion engine applications. Effective as a component material for parts.

Claims (1)

[Scope of Claims] A heat-resistant, high-strength aluminum alloy containing at least one selected from Si, Cu, and Mg as well as Ni, Cr, and Mo in the following ranges. 12.0% by weight≦Si≦28.0% by weight 0.8% by weight≦Cu≦5.0% by weight 0.3% by weight≦Mg≦3.5% by weight 3.1% by weight≦Ni≦8. 0 weight% 0.2 weight%≦Cr≦8.0 weight% 0.2 weight%≦Mo≦8.0 weight%