JPS62149840A - High strength, heat and wear resistant al alloy - Google Patents

Abstract

PURPOSE:To obtain a high strength, heat and wear resistant Al alloy maintaining its strength even in environment at high temp., having superior strength and wear resistance at ordinary temp. and also having superior hot workability and machinability by adding specific amounts of Si and Cr to Al of further adding other alloying element. CONSTITUTION:An Al-Si alloy having such a high Si content as 12-30wt% as starting material for powder metallurgy is alloyed with 4-10wt% Cr or further alloyed with one or more among 0.5-10wt% Mg, 2-10% Mn, 0.5-10% Fe, 0.5-3% Ni, 0.01-2% Zr and 0.01-2.0% V. An Al alloy having superior strength, wear and heat resistances at high temp. and also having satisfactory formability and machinability is obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention does not cause a decrease in strength in a high-temperature environment, has excellent room temperature strength and wear resistance, and has excellent hot workability, cutting workability, etc. High strength heat resistance and wear resistance A that exhibits its characteristics
This relates to l-alloys.

[Prior Art] There is a strong demand for heavier parts in various vehicles in order to improve fuel efficiency, and various research and development efforts have been made to make heavy parts such as engines and air conditioner compressors made of Al alloys. Al alloying these parts not only improves fuel efficiency, but also has effects such as extending the life of lubricating oil as its thermal conductivity is far superior to cast iron, improving heat dissipation and avoiding temperature rises. Obtainable.

Among Al alloys, Al alloys with a particularly high Si content have excellent wear resistance and a low coefficient of thermal expansion, and are therefore considered promising as Al alloys for axles. However, the high Si-containing Al alloys produced by melting and casting methods that have been developed in the past have problems with cracking during hot working, machinability, and heat resistance.
These improvements were presented as issues to be solved.

[Problems to be Solved by the Invention] Among the above-mentioned problems to be solved, the causes of deterioration in hot workability and cutting workability have been investigated, and solutions have been proposed.

That is, in high Si-containing Al alloys produced by melting and casting, the cooling rate during melting and casting is slow, so giant primary Si grains crystallize, reducing the strength of the material and causing cracks during hot working.

Therefore, as a solution, it is effective to increase the cooling rate in order to prevent the crystallization of giant Si primary crystals, and powder metallurgy methods that can achieve rapid solidification are being applied. In other words, in high-Si-containing Al powder alloys produced using the rapid solidification method, the primary Si grains do not become gigantic and are finely dispersed, which eliminates the above-mentioned problems such as poor hot workability and machinability. It became. Powder metallurgy also makes it possible to achieve a higher Si content than conventional melting and casting methods, and is expected to produce new high-performance alloys.

However, in terms of heat resistance, there is still room for improvement in the high Si-containing Al powder alloy, and in particular, since the heavy parts are continuously used in high-temperature ashes, heat resistance has to be improved to prevent strength loss at high temperatures. It is desired to provide an even better Al alloy. Furthermore, as vehicles and the like are becoming increasingly faster and more sophisticated, there is a demand for Al alloys that have higher performance than ever in terms of not only heat resistance but also strength and wear resistance.

The present invention has been made in view of these circumstances, and is an Al alloy with high Si content produced by a rapid solidification method that has good hot workability and cutting workability, and an Al alloy with excellent heat resistance. The purpose is to provide an Al alloy with excellent strength and wear resistance.

[Means for Solving the Problems] The present invention, which has achieved the above objects, has the following features: Si: 12 to 30 zero (meaning in weight %, the same applies hereinafter) Cr:
The first feature is that it contains 2 to IO zero and the remainder consists essentially of AI and unavoidable impurities, thereby achieving improvement in heat resistance. Further, by blending one or more elements selected from the following alloying element group, the strength and wear resistance could be further improved.

Mg: 0.5-10% Mn: 2-10% Fe: 0.5-10% Ni: 015-3% Zr: 0.01-2% V: 0.01-2% [Function] This invention As a result of various studies regarding the above-mentioned problem, researchers have concluded that the stability of intermetallic compounds generated at high temperatures has a large effect on heat resistance, and that poor stability may lead to a decrease in high-temperature strength. I found out that there is no such thing. Therefore, in order to improve heat resistance (in other words, to stabilize intermetallic compounds), we believe that it is effective to add elements that have a low diffusion rate in the AI matrix.
.

Based on -3i, other alloying elements were appropriately blended, thereby improving heat resistance and achieving further improvements in strength and wear resistance. The effects of the present invention will be explained below by describing the reasons for selecting the types and amounts of alloying elements used in the present invention. As is clear from the above description, the alloy of the present invention is an extension of the technology of manufacturing by powder metallurgy. In other words, the powder metallurgy method that applies the rapid solidification method has the following features: (1) the solid solubility limit of each alloying element can be expanded, and (2) metal particles and various intermetallic compounds can be dispersed finely and uniformly, resulting in improved strength. It is expected that various properties such as wear resistance, hot workability, and cutting workability will be improved, and that the present invention will also contribute to improving heat resistance by promoting fine dispersion of the heat resistance improving element (Cr). It is highly suitable for achieving the objectives of In addition, in the powder metallurgy method, the cooling rate during rapid solidification is 102°C/sec or more, preferably 104°C.
/sec or more is recommended, and not only atomized powder but also powder obtained by crushing quenched flakes or quenched ribbons can be used.

Si: 12-30% If Si is less than 12%, the amount of Si particles dispersed by the rapid solidification method becomes extremely small, making it impossible to obtain the desired strength and wear resistance. On the other hand, if it exceeds 30%, even if the rapid solidification method is used, it will not be possible to prevent the primary Si particles from becoming large, resulting in a decrease in toughness and impact value, as well as deterioration in machinability and formability during hot working. also deteriorates significantly. Furthermore, processing pressure increases significantly and solidification formability deteriorates.

Cr: 2-10% Cr has a low diffusion rate in Al, and the intermetallic compounds finely dispersed by rapid solidification do not become coarse even at high temperatures. be effective. Further, the Cr-based fine intermetallic compound significantly improves room temperature strength and wear resistance. However, Cr
If the amount is less than 2%, the amount of the intermetallic compound produced is so small that desired characteristics cannot be achieved. On the other hand, if it exceeds 10%, the intermetallic compound becomes coarser and the toughness deteriorates.

The common effects of one or more of Mg, Mn, Fe, Ni, Zr, and V are mainly the improvement of strength at room temperature and high temperature, and the improvement of wear resistance due to the finely dispersed phase. In order to effectively exhibit the effect, it is necessary to add 0.5% or more for each of Mg, Fe, and Ni, 2% or more for Mn, and 0.01%LJ each for Zr and ■. . However, Mg
, Mn and Fe are each 10%, Nf is 3%, Zr and V
If each exceeds 2%, the dispersed phase becomes coarser and various properties such as toughness, wear resistance, and heat resistance are deteriorated. In particular, Mg has the disadvantage that it reacts with Si to form an intermetallic compound of Mg2Si, which consumes Si, which is an element that improves wear resistance, inhibits the expression of this effect, and further reduces toughness. has the disadvantage of forming Al--Mn-based giant compounds and deteriorating hot workability, and in order to prevent these defects, the upper limit must be strictly observed.

[Example] Molten Al alloys having various compositions shown in Table 1 were heated at 103°C/se.
The mixture was rapidly solidified at a cooling rate of e to obtain an alloy powder. Next, these were compacted in a warm state and further hot extruded at an extrusion ratio of 14 to obtain an extruded material of 20 mm. Each extruded material was then heat treated at 400°C for 2 hours. In addition, the cast A390 used as a comparison material was heated at 500°C for 4 hours.
After the solution treatment, an aging treatment was performed at 170°C for 10 hours.

Next, the following tests were conducted on these extruded materials or cast materials (A 390).

Friction and wear test The Dalian friction and wear test was conducted under the following conditions.

Mating material: Fe12 Friction speed: 1.97 m/sec Friction distance: 100 m ■Slip: None Load: 2.2 kg After the wear test, the amount of wear was measured from the wear marks. The wear resistance comparison between each sample was determined as the value when the wear amount of Al-20St (comparison material No. 1.1) made by powder metallurgy was set to 1.0, and the results shown in Table 1 were obtained. Ta.

Room temperature and high court tensile test Tensile tests were conducted at room temperature, 100°C, 200°C, and 300°C using a test piece with a parallel section of 6 m and a gage length of 30 am, and the tensile strength and room temperature elongation at each temperature were determined. . The results are also listed in Table 1.

No. 1.2.3 (invention material) and No. 11.14
(comparative material) and No. 4.5 (invention material) and No.
.

As is clear from the comparison with No. 16 (comparative material), adding an appropriate amount (2% or more) of Cr can significantly improve high temperature strength, low temperature strength, and wear resistance.On the other hand, N
In No. 15 (comparative material), the elongation at room temperature was extremely reduced due to the excessive amount of Cr added. Further, No. 12 (comparative material) with a small amount of Si added has insufficient wear resistance, while No. 13 with an excessive amount of Si added shows an extreme decrease in elongation at room temperature. Further M
g.

The effect of adding Mn, Fe, Ni, Zr and V is No.

This was confirmed from the materials of the present invention Nos. 4 to 10, and further improvements in abrasion resistance, room temperature strength, and high temperature strength can be obtained. However, those in which the blending amount of these alloying elements exceeds the upper limit (No.
Regarding Nos. 17 to 19), a decrease in wear resistance or elongation due to coarsening of the intermetallic compound was observed. In addition, when compared with A390 material (No. 20) manufactured by the melt casting method, the superiority of the present alloy can be clearly understood.

[Effects of the Invention] The present invention is configured as described above, and can provide an Al alloy that has excellent strength, wear resistance, and heat resistance, and also has good formability and cutting workability.

Claims (2)

[Claims] (1) Si: 12-30% (weight %, the same applies hereinafter) Cr: 2-10%, with the remainder consisting essentially of Al and inevitable impurities. Abrasive Al alloy. (2) Contains Si: 12-30% Cr: 2-10%, and further includes Mg: 0.5-10% Mn: 2-10% Fe: 0.5-10% Ni: 0.5-3% Contains one or more alloying elements selected from the group consisting of Zr: 0.01-2% V: 0.01-2%,
A high-strength, heat- and wear-resistant Al alloy, wherein the remainder consists essentially of Al and inevitable impurities.