JPH0474402B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a super heat-resistant and wear-resistant Al alloy, and relates to an aluminum alloy that can be used under severe conditions and a composite powder for producing the alloy. In recent years, materials for automobile engines and aircraft have become smaller, lighter, and have higher output due to the need to save energy and improve performance. It is required to withstand use under severe temperature conditions. Taking automobile pistons as an example, the conventional Al alloy for pistons is an Al-Si cast material such as AC8B. However, in the casting method, increasing the Si content to a high content of 20% or more causes problems of segregation and coarsening of primary crystals, making it difficult to meet the above requirements. Therefore, in recent years, development of heat-resistant and wear-resistant aluminum alloy materials with pore-free, uniform fine crystal grains has begun using quenched high-Si-containing aluminum alloy powder as a starting material and a hot extrusion method. However, when a rapidly cooled powder is used, there are problems such as grain growth due to heating during molding for densification, and there are limits to the manufacturing method. Furthermore, it is technically difficult to add dispersed particles to the rapidly cooled powder.
In other words, it has not been possible to further improve heat and wear resistance by strengthening by adding dispersed particles based only on the quenching method. The present invention has been made to solve the problems of the prior art, and uses a new method called mechanical alloying to preserve the advantages of quenched powders having supersaturated solid solutions and uniform fine crystal grains (or to improve quenched powders). While the same effect is obtained by the mechanical alloying process itself of the mixed powder, the dual effect of the duplication of the dispersion strengthening effect due to the addition of dispersed particles makes it possible to improve the performance of conventional cast materials, ingot materials, and recently developed materials. The purpose of the present invention is to provide an aluminum alloy that has better heat resistance and wear resistance than materials made from quenched powder, and a composite powder for producing the alloy. According to the present invention, such a purpose is to produce quenched Al alloy powder.
99.5 to 90% by volume and 0.5 to 10% by volume of carbon powder (graphite powder) are mechanically alloyed to obtain a powder, which is then processed by embossing and sintering, hot pressing, sintering, forging, etc.
It can be obtained by performing various forming treatments such as powder rolling, hot isostatic pressing, and hot extrusion. Properties similar to those of quenched aluminum alloy powder can be obtained by mechanical alloying of a mixed powder with the same composition and carbon powder (graphite powder). During the mechanical alloying process and subsequent heating before forming, during the heat treatment of the compact, the initial carbon (graphite) becomes a carbide Al ₄ C ₃ ,
This is finely and uniformly dispersed and contributes to strengthening the alloy. Hereinafter, the aluminum alloy of the present invention and the composite powder for producing the alloy will be explained. The present invention significantly improves heat resistance while maintaining wear resistance through the synergistic effect of strengthening the matrix due to the effects of fine crystal grains in the quenched powder and strengthening dispersed particles (Al ₄ C ₃ ) through mechanical alloying. This was done based on the knowledge that it is possible to In the present invention, the reason why the amount of Si is limited to 5 to 30% by weight in the Al-Si quenched powder or mixed powder used as the raw material powder before mechanical alloying treatment is that if the weight ratio is less than 5%Si, the casting method cannot be used. This is because it is easy to manufacture and has low wear resistance.
This is because if the weight ratio exceeds 30% Si, wear resistance increases, but hot forming of the powder and subsequent plastic working becomes difficult. Cu is used for precipitation strengthening due to heat treatment of the alloy.
Mg is added depending on the purpose for solid solution strengthening. If room temperature strength is not important, no additives can be used. The reason why we limited the volume ratio of carbon powder (graphite powder) that becomes carbide particles called Al ₄ C ₄ through mechanical alloying treatment and hot processing to 0.5 to 10% is that dispersion strengthening occurs when the volume ratio is 0.5% or less. This is because if the volume ratio exceeds 10%, it becomes brittle, making hot forming of the mechanical alloying powder and plastic working of the alloy difficult. The reason why we limited the amount of Fe to 2 to 12% by weight in the Al-Fe-based quenched powder or mixed powder is that it is 2% by weight.
This is because if the weight ratio is less than 12% Fe, the effect of heat and wear resistance is small, and if the weight ratio is 12% or more, the hot workability of the powder and the plastic workability of the alloy after mechanical alloying treatment deteriorate. Co, Ni, Cr,
Addition of transition metals such as Mn, Ce, Ti, Zr, Mo, etc.
Although it is desirable to add it to further improve the alloy properties and the moldability of the powder, there is no problem even if it is not added. Added at least 7% by weight
There is no problem at all if the amount is larger than the amount of Fe, but in that case it will be expensive, so
The weight ratio was limited to 7% or less. Mechanical alloying of Al-Si-Fe based quenched powder or mixed powder and carbon powder (graphite powder)
This is based on the knowledge that the effect of combining the excellent properties of both Al-Si and Al-Fe systems can be obtained. In particular, the composition is 10 to 14% Si by weight, 4 to 4% by weight
Mechanical alloying powder with 6% Fe has excellent hot workability and is effective in overcoming the high coefficient of thermal expansion, which is a general weakness of Al alloys, and has the property of low thermal expansion in addition to the characteristics of super heat and wear resistance. Take into consideration. When mechanically alloying aluminum powder, depending on the aluminum alloy composition, the aluminum powder may be granulated and become lumpy before being sufficiently uniformly mechanically alloyed. Normally, the above phenomenon does not easily occur in the case of rapidly solidified powder with high hardness, but it tends to occur in the case of mechanical alloying of pure aluminum powder or mixed powder with other pure metal powder. In such a case,
Pelletization must be prevented by adding appropriate amounts of water, oil, and organic solvents (0.05 to 3% by volume) to ensure sufficient mechanical alloying. The added water, oil, and organic solvent are either removed or dispersed as carbide Al ₄ C ₃ by heating or degassing the mechanical alloying powder or its compact before hot processing. Example 1 Rapidly solidified aluminum alloy powder (composition Al-12Si) of 100 mesh or less produced by gas atomization method
-5Fe-4.5Cu-1Mg) and carbonized powder (carbon black) were mixed at a volume ratio of 97:3 and treated with a dry attritor for 5 hours. The powder is granulated and coarsened by mechanical alloying, with an average particle size of about 1 mm, and the structure has a wavy structure characteristic of mechanical alloying (see Fig. 1). No primary Si crystals are observed. The microvits hardness of the powder exceeds 250. The above powder was placed in an Al sheath, heated at 450°C for 2 hours, and then hot extruded at an extrusion ratio of 10:1.
Table 1 shows the properties of the extruded alloy. It has a microstructure so fine that it cannot be seen with an optical microscope at 1000x magnification, and has a tensile strength of over 30 Kg/mm ² at 300°C. It also has a low coefficient of thermal expansion.

[Table] Example 2 Rapidly cooled powders and mixed powders with various compositions listed in Table 2 and carbon powder (carbon black) or graphite powder were mechanically alloyed for 10 days in a dry ball mill.
After molding the powder with a cold isostatic press of 4t/ ^cm2 ,
Hot extrusion processing was performed by heating at 450°C for 2 hours.
Table 3 shows the density, Rockwell hardness (B scale), and tensile strength at room temperature and 300°C of the obtained alloy. All of them have excellent strength at high temperatures, and are made by mechanical alloying with carbon powder (or graphite powder) rather than alloys made only of quenched powder.
It can be confirmed that it has a tensile strength as high as 10Kg/mm ² or more at 300℃.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 shows a 400 times enlarged micrograph of the powder obtained by mechanical alloying of Example 1 of the present invention.

Claims (1)

[Claims] 1. Quenched aluminum alloy powder or mixed powder (consisting of pure metal powder or master alloy powder) 99.5 to 90% by volume, carbon powder (or graphite powder) 0.5 to 10% by volume, and the total amount of the above In addition, water, oil,
A composite powder for producing a super heat-resistant and wear-resistant aluminum alloy, characterized in that 0.05 to 3% by volume of an organic solvent is added and mixed, and then mechanically alloyed to uniformly and finely disperse the above components. 2 Quenched aluminum alloy powder or mixed powder has a weight ratio of Si5 to 30%, Cu5% or less, Mg2% or less, and the remaining Al composition or weight ratio Fe2 to 12%, Co.
Claim 1, characterized in that the composition consists of 7% or less of one or more selected from the group consisting of Ni, Cr, Mn, Ce, Ti, Zr, and Mo, and the remainder Al. Composite powder for manufacturing super heat-resistant and wear-resistant aluminum alloys. 3 Quenched aluminum alloy powder or mixed powder has a weight ratio of Si5 to 15%, Fe2 to 12%, Cu not more than 5%, Mg2%
Claim 1 below, characterized in that the content is 7% or less of one or more selected from the group consisting of Co, Ni, Cr, Mn, Ce, Ti, Zr, and Mo, and the remainder is Al. Composite powder for producing ultra-heat-resistant, heat-resistant, wear-resistant aluminum alloy as described in . 4 Al ₄ C ₃ and Si, Fe which are solidified by hot working using the powder described in claims 1 to 3 and formed of the entire amount of carbon (or graphite) and Al.
Components other than aluminum are uniformly and finely dispersed in the aluminum matrix, and have a Rockwell B scale hardness of 75 or more and a tensile strength at 300℃.
Super heat-resistant and wear-resistant aluminum alloy of 26Kg/mm ² or more.