JPH0651896B2 - Heat and wear resistant aluminum alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat resistant and wear resistant aluminum alloy used in automobiles, aircrafts and the like.

Problems to be solved by conventional techniques and inventionsAl-Si based alloys such as AC8A, AC8B, AC9A have been developed as heat and wear resistant alloys, but these alloys are sufficiently satisfactory in terms of heat resistance. It's not cheap. Recently, Al-Si-Fe and Al-Si-Ni alloys with further improved heat resistance have been developed by powder metallurgy technology. However, although Al-Si-Fe alloys have high heat resistance, they are elongated and inferior in toughness. On the other hand, Al-Si-Ni alloys are superior in elongation and toughness to Al-Si-Fe alloys, but inferior in heat resistance. The present invention replaces a part of Fe and Ni of Al-Si-Fe alloys and Al-Fe-Ni alloys with Ni and Fe, so that the heat resistance of Al-Si-Fe alloys is not significantly impaired and the elongation is improved. It was recalled that the heat resistance and the toughness can be improved without significantly decreasing the elongation of Al-Si-Ni alloys.

In recent years, materials for automobile engines and aircraft have been made smaller and lighter and have higher output because of the need for energy saving and higher performance, and accordingly, the materials used for pistons and the like are
It is required to have high heat resistance and wear resistance that can withstand use under severe conditions of higher load and higher temperature than before.

Taking automotive pistons as an example, Al-Si casting materials such as AC8B are used as conventional piston Al alloys. However, in the casting method, if a large amount of Si, Fe, Ni, etc. is added in order to further improve wear resistance and heat resistance, the properties such as strength, elongation and toughness are remarkably increased due to element segregation and coarsening of primary crystals. And the required characteristics cannot be sufficiently satisfied.
Therefore, in recent years, development of a heat-resistant and wear-resistant aluminum alloy material having non-porous uniform fine crystal grains has been started by a hot extrusion method or the like using a rapidly cooled high Si content aluminum alloy powder as a starting material. The alloy produced in this way is a solid solution of a large amount of elements such as Si, Fe and Ni due to the expansion of the solid solution limit by the effect of rapid solidification, and coarse precipitates such as those found in cast materials, Segregation hardly occurs.

However, when the quenched powder is used, there are problems such as grain growth due to heating at the time of molding for densification, which naturally limits the manufacturing method. For example, a heat-resistant and wear-resistant alloy produced by quenching powder metallurgy mainly contains 20 to 30% by weight of Si.
Highly alloyed aluminum alloys containing 2-10% by weight of transition elements such as Fe and Ni are produced by hot extrusion of rapidly solidified powder. The aluminum alloys thus obtained have improved heat and wear resistance. However, the elongation and toughness are significantly reduced.

The cause of this is an intermetallic compound or a primary crystal precipitate generated during hot extrusion. This low elongation and toughness limits the applications of the highly alloyed aluminum alloys produced by quench powder metallurgy.

Means for Solving the Problems The present invention has been made to improve the toughness and elongation of a highly alloyed aluminum alloy composed of transition elements of Al, Si and Fe, Ni, and Fe contained in the alloy. By including the transition elements Ni and Ni in appropriate proportions, the conventional Al-Si-Fe
Another object is to improve the toughness of the highly alloyed aluminum alloy mainly composed of three elements such as Al-Si-Ni alloy without significantly reducing the heat resistance and wear resistance or the elongation.

The main additive elements of the aluminum alloy of the present invention are Si which is effective in improving wear resistance and Fe and Ni which are effective in improving heat resistance. When a large amount of Si is added to Al, it precipitates as primary crystal Si particles during solidification, and the wear resistance of the alloy is improved. The size and amount of primary Si particles depend on the solidification rate of the alloy, Si
When the solidification rate is high, the Si primary crystal grains become small, but they become coarse as the Si amount increases, depending on the addition amount. The limit is 40%. When the amount of Si exceeds this, primary crystal Si
The particles become coarse, which causes the alloy speed to decrease significantly. If it is less than 5%, the effect of improving wear resistance is very small,
Hard to use as a wear resistant material.

Fe and Ni improve the heat resistance of aluminum alloys, but the effect is
Fe is larger. However, it has lower elongation and toughness than Ni. Part of Fe and Ni of this Al-Si-Fe and Al-Si-Ni alloy
By replacing with Ni and Fe, an alloy having better characteristics than the original alloy can be obtained. That is, Al-Si-Fe
-Ni alloy has slightly lower heat resistance than Al-Si-Fe alloy but improved elongation, and slightly higher elongation than Al-Si-Ni alloy, but improved heat resistance. Of particular note is that the toughness is higher than either Al-Si-Fe or Al-Si-Ni. The reason for this is considered as follows. Fe, N
In both cases, the solid solution limit to Al is very small, 0.04% by weight, but the solid solution limit is expanded by rapid solidification, and the maximum solid solution range is
It is reported that Fe is 4 to 12% by weight and Ni is 3 to 15% by weight. Of Fe or Ni added to Al, the supersaturated content that exceeds the solid solubility limit expanded by quenching is precipitated as a precipitate of a compound or the like, which significantly reduces the toughness of the alloy. However, by substituting a part of Fe with Ni and a part of Ni with Fe, the supersaturation degree of each element can be reduced, and the precipitate becomes fine and uniform. Therefore, it is considered that the toughness is greatly improved. Although only Fe and Ni are shown here, the same idea can be applied to the combination with other elements, so that the effect of improving toughness by element replacement can be expected. This Al-Si-Fe-Ni alloy is Al-Si-Ni
Fe: Ni ratio that shows almost the same toughness value as the alloy ranges from 1: 4
It is 4: 1. Most preferably, Fe: Ni is 1: 1.
If the amount of Fe + Ni is 12% or more, the toughness and elongation are significantly reduced, so the amount of Fe + Ni is 12% or less. Also Fe + Ni
If the amount is 2% or less, the effect of improving heat resistance is almost lost, so the amount of Fe + Ni is set to 2% or more.

When an Al alloy containing a large amount of Si, Fe, and Ni as described above is manufactured by the conventional melting and casting methods, the solidification rate is slow (1
℃ / sec or less), Si primary crystals and intermetallic compounds become coarse,
Material strength is significantly reduced. As a method for suppressing coarse precipitates, there are a rapid solidification method and a hot top method, but the hot top method has a low limit of the amount of elements added. In the quenching method, when the material is rapidly cooled at a solidification rate of 100 ° C./sec or more, the size of the precipitates becomes about 50 μm at maximum in the range of the element addition amount shown in the scope of the present claims, which causes the material properties to be greatly deteriorated I won't. Such a solidification rate can be easily achieved by converting the molten alloy into powder by an atomizing method or the like. Considering the formability or solidification rate of the powder, the particle size of the powder suitable for use is 40 mesh or less. Since these high alloy powders have high hardness of the powder particles themselves, it is necessary to give strong plastic working such as hot extrusion to form an alloy.

Example 9 Al-Si-Fe prepared by adjusting the composition of an aluminum alloy having a purity of 99.0% or more to have Si, Fe, and Ni as shown in Table 1.
-Ni-based alloy powder was produced by the air atomization method, and these powders were hot extruded at a temperature of 450 ° C to obtain an alloy. The material properties are shown in Table 1. Al-Si-Fe and A produced by the same method for comparison
We also investigated l-Si-Ni alloys. As can be seen from the table, the Al-Si-Fe-Ni alloy has superior impact value and elongation compared to the Al-Si-Fe alloy. It also has improved strength and toughness compared to Al-Si-Ni alloys.

EFFECTS OF THE INVENTION As described above, the aluminum alloy of the present invention is a conventional Al-Si-
The toughness and elongation of Fe-based alloys and the toughness and strength of Al-Si-Ni-based alloys have been improved. Engine parts such as automobiles, connecting rods, etc.
It can be used as a vane for pistons or compressor parts.

Claims (1)

[Claims] 1. An aluminum alloy containing Si, Fe and Ni, wherein the Si element is 5.1% by weight to 40% by weight,
And Fe and Ni elements are (Fe + Ni) 2 to 12% by weight, the ratio of Fe: Ni is 1: 4 to 4: 1 at the same time, the balance is substantially aluminum, and primary crystal Si, A powder metallurgical Al-Si-Fe-Ni-based heat- and wear-resistant aluminum alloy, characterized in that the intermetallic compound has a particle size of 50 µm or less.