AT504924A1 - VEHICLE COMPONENT - Google Patents

Description

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vehicle component

The invention relates to a method for producing a particular dynamically loaded vehicle component such as a piston or another part of a 5 internal combustion engine.

Furthermore, the invention relates to a vehicle component.

In use to moving components of internal combustion engines, such as pistons, 10 are made with preference from lightweight materials as possible. Here, inter alia, one resorts to aluminum or its alloys, which are known to have a relatively low density.

In order to impart a high strength to the alloys used, as is necessary for many applications, they are precipitation hardened, so that components can be obtained which have a high tensile strength at room temperature. However, it is often disregarded that the components can be exposed to operating temperatures of several hundred degrees Celsius, especially in extreme situations. In this case, a precipitation-hardened component may lose its high tensile strength at room temperature very rapidly in high-temperature use. Thus, with the frequently used aluminum alloy 2618 at 300 ° C. and a holding time of 20 hours, a decrease in strength of almost 50% is evident. Such a drop in strength and associated risks can only be compensated by a more massive design of components, which in turn precludes the desired principle 25 of a lightweight construction of moving components.

On this basis, the invention has the object to provide a method of the type mentioned, with which a lightweight vehicle component can be provided, which has a consistently high heat resistance.

Another object of the invention is to provide a lightweight vehicle component which has a consistently high thermal stability. 30 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ···············

The method of the invention is achieved in a method of the type mentioned above in that it comprises the following steps: a) providing gas atomized particles of aluminum or an aluminum alloy, wherein an average size of the particles is less than 10 pm 5, b) compacting the particle, optionally in combination with reinforcing particles, to a dimensionally stable block, then c) forming the block at a temperature of at least 250 ° C, d) creating the vehicle component from the formed block or parts thereof. 10

The inventive concept is to provide a compact dimensionally stable or self-supporting block of small aluminum or aluminum alloy particles, which block in the sequence, for example, by drop forging is formed with a degree of deformation of at least fourfold. The intended precompression in step b) is required in order to obtain a substantially dense body after the subsequent forming. During the forming itself, the oxide skins, which are due to the high affinity of aluminum to oxygen on the surfaces of the particles are broken from temperatures of about 250 ° C, so that during the forming, in which also a further compression of the material takes place, oxides 20 finely dispersed in the matrix material or incorporated into this, wherein at the same time the fine particles, which have an average size of less than 10 pm prior to reshaping, can undergo a decrease in size. The oxides finely distributed in the matrix metal prevent or hinder dislocation movements in the grains, which causes a high tensile strength of the material thus produced. The material or the material is thus structurally solidified and retains a high tensile strength even over long periods of time at high temperatures of, for example, 300 ° C. The material is ideal for creating vehicle components with stable high heat resistance.

The particles of aluminum or an aluminum alloy with a size of less than 30 pm may be atomized under oxygen but also under nitrogen. Also in the latter case, the oxide skin desired in the context of the invention forms with a ratio of metal core to oxide skin which is suitable for structural strengthening. It is favorable if the average size of the aluminum or aluminum alloy particles is less is 5 pm, preferably 0.1 gm to 1.5 gm. The smaller the gas atomized particles are, the higher becomes a relative proportion of the oxide skin formed on atomization or thereafter on the total volume of a particle. As a result, a proportion of finely dispersed oxide in the processed material also increases, which in turn benefits effective structural consolidation and thus high heat resistance. An optimum alumina content of the particles is 5% to 12% with respect to a total volume thereof. In order to achieve high tensile strengths it can be provided that in step b), for example, reinforcing particles of an amorphous metal and / or an amorphous alloy are mixed in. Due to a lack of a crystalline structure and thus of slip planes dislocations are even more hampered by such particles, with the advantage that also a strength, in particular 15 heat resistance, is increased. When reinforcing particles of aluminum or an aluminum alloy are used, good incorporation of the reinforcing particles into the matrix-forming particles can be achieved.

If reinforcing particles are used, they preferably have an average size of less than 500 μm, preferably less than 200 μm.

With regard to optimum strength and toughness on the one hand and good processability of the particle mixture on the other hand, it may be appropriate that a volume fraction of the reinforcing particles is 5% to 45%, preferably 15% to 35%, 25.

The inventively provided compression of the gas atomized aluminum or aluminum alloy particles can be done by a known per se cold isostatic pressing.

With regard to a transformation of the block thus produced at a temperature of at least 250 ° C, there are several possibilities: 30 • ················································································ ··· # · ····· · · · · 4

On the one hand, the deformation can be carried out by extrusion or extrusion. In this case, on the one hand, the pressing causes a break-up and distribution of the oxide skins located on the aluminum or aluminum alloy particles. On the other hand, the precompressed block is simultaneously consolidated so that a porosity of the reshaped material can typically be less than one percent by volume.

Alternatively, on the other hand, it is also possible and preferred in terms of mechanical properties if, for the time being, in step b) a hot isostatic pressing is carried out and then the forming of the block is carried out by forging at a temperature of at least 250 ° C. In hot isostatic pressing, a further compression of the already cold isostatically precompressed block takes place. During the subsequent forging, the already described breaking up of the oxide skins and a finely dispersed distribution of oxide fragments in the material are achieved with further densification thereof. In comparison with an extrusion process, it is advantageous that the oxide skins break up homogeneously over the entire cross section of the block, whereas in the case of extrusion at block diameters of, for example, 95 by 40 millimeters, in some cases only cracking of oxide skins in the region of the block edge is observed these areas can be set for further processing. One explanation is probably that during die forging the processed or processed material, in contrast to extruding has no alternative and the forming energy can be optimally distributed over the entire cross-section of the material introduced into this. In connection with a hot isostatic pressing, it has surprisingly also been found that at least partially amorphous reinforcing particles of aluminum or an aluminum alloy, such as strips of an at least partially amorphous aluminum alloy, for example, from a melt spun and increasingly cooled bands of so-called "rapidly solidified Alg ^ Fea with amorphous, crystalline and quasicrystalline fractions, this process step with respect to a structure substantially unchanged survive and therefore can be used as reinforcing particles. • ···························································································································································································

A temperature between 350 ° C and 500 ° C, preferably 350 ° C to 400 ° C, has proved to be a particularly favorable temperature window for forming the optionally hot isostatically pressed block. At temperatures of less than 350 ° C, it may happen that the individual oxide-coated particles slide off each other or roll without causing the oxide skins to break up.

On the other hand, if a temperature is more than 400 ° C., in particular more than 500 ° C., processing may be impeded because softening of the matrix material no longer permits decomposition of the oxide skins. The further object of the invention is achieved by a vehicle component, such as a piston of an internal combustion engine, by compacting particles of aluminum or an aluminum alloy having an average size of less than 10 μm, optionally together with reinforcing particles, into a block and then forming the block at a temperature of at least 250 ° C with a forming rate 15 of, for example, 4: 1 or more.

The advantages achieved with a vehicle component according to the invention are to be seen in particular in that it has a high heat resistance, even with prolonged Einsatzdauem at elevated temperatures of, for example, 300 ° C. Due to a high tensile strength at high temperatures over long periods of time as well as good flexural fatigue strength and Zugdruckwechselfestigkeit now components can be created that are less massive than components according to the prior art and yet meet desired safety criteria. In other words, over-dimensioning of components in order to compensate for a loss of strength at elevated use temperatures is no longer necessary or not necessary to the extent hitherto required.

As already described, it is advantageous if an average size of the particles made of aluminum or an aluminum alloy is less than 5 μm and 30 is preferably in a range of 0.1 μm to 1.5 μm.

Furthermore, it can be provided that the vehicle component comprises reinforcing particles of an amorphous metal and / or an amorphous alloy. • • • • • • • • • • · · · · · · · · · · · · · · · · · t 6

Because of the compatibility of the aluminum or aluminum alloy particles with the reinforcing material, the amorphous alloy is desirably an aluminum alloy. The reinforcing particles themselves preferably have an average size of less than 500 .mu.m, preferably less than 200 .mu.m. In this case, a volume fraction of the reinforcing particles is preferably 5% to 45%, in particular 15% to 35%.

Further advantages, features and effects of the invention will become apparent from the context of the description and the following embodiments. 10

Show it

1: a TEM image (TEM ... transmission electron microscope) of a microstructure of a piston blank in the edge region;

Fig. 2: A TEM image in the center of the piston blank of Fig. 1. 15

Commercially available particles of aluminum vaporized under nitrogen with an average size of approx. 1 μm (dso, arithmetic mean) were pressed cold-isostatically into self-supporting bolts. The thus prepared bolts with a relative density of about 0.8 were then subjected to a vacuum heat treatment 20 and then hot isostatically pressed at about 475 eC and thereby compressed to a relative density of greater than 0.95. Subsequently, material thus prepared was forged at about 350 ° C with a degree of deformation of greater than four times on blank dimensions of an engine piston, the material underwent a final compression and the aluminum particles were mutually verschert and welded together. 25

The as-prepared piston blanks to be finalized by milling had an average hardness of greater than 80 HB at 25 ° C when viewed across the cross-section, which corresponded to a tensile strength of ≈7 ° C to 4 ° C at 25 ° C. The blanks were then held for 20 hours at a temperature of 300 ° C before tensile tests were carried out on the thus treated blanks at 300 ° C. In these tensile tests it was found that a tensile strength Rm for all blanks was more ateigOO'MPäVetrug. For the yield strengths Rpo, 2 values of more than TT5 ^ MPa | were obtained. In comparison with this, a piston made of an alloy 2618, despite a higher tensile strength at 25 ° C., produced II j. •. wmmm 7 (440 MPa) after soaking at 300 ° C only 110 MPa, which value decreased again after a holding time of 20 hours at this temperature by about 45%.

Structural investigations by transmission electron microscopy (TEM) showed that the blanks in the marginal area (Fig. 1) as well as in the center (Fig. 2) with a non - porous structure of aluminum particles (light) and oxides distributed in these or at the particle boundaries Sub-micrometer range (appearing black in Figs. 1 and 2). A vehicle component produced according to the invention has the following useful potential: - Weight reduction of components with the same safety - Higher operating temperatures with temperature-loaded components - Tighter Einsatzdauem at elevated temperatures without significant decrease of 15 material properties - With respect to engines or pistons higher efficiencies - Good damping properties for reduction a sound emission

Claims (22)

• • • • • • • δ claims 1. A method for producing a particular dynamically loaded vehicle component, such as a piston or another part of a 5 internal combustion engine, comprising the following steps: a) providing gas atomized particles of aluminum or an aluminum alloy, wherein an average size of the particles wt wt is w, b) Compacting the particles, optionally in combination with reinforcing particles, into a dimensionally stable block, then c) reshaping the block at a temperature of at least 250 ° C, d) creating the vehicle component from the formed block or parts thereof. 2. The method of claim 1, wherein an average size of the particles of aluminum or an aluminum alloy is less than 5 pm. 3. The method according to claim 1 or 2, wherein an average size of the particles of aluminum or an aluminum alloy is 0.1 pm to 1.5 pm. 4. The method according to any one of claims 1 to 3, wherein the particles of aluminum or an aluminum alloy have an alumina content of 5 percent by volume to 12 percent by volume. 5. The method according to any one of claims 1 to 4, wherein in step b) reinforcing particles 25 are added from an amorphous metal and / or an amorphous alloy. 6. The method of claim 5, wherein reinforcing particles of aluminum and / or an aluminum alloy are used. A method according to claim 5 or 6, wherein the reinforcing particles have an average size of less than 500 μm, preferably less than 200 μm. • · · · · ·. · • · * 9 8. The method according to any one of claims 5 to 7, wherein a volume fraction of the reinforcing particles is 5% to 45%, preferably 15% to 35%. 9. The method according to any one of claims 1 to 8, wherein the compression in step b) is carried out by 5 cold isostatic pressing. 10. The method according to any one of claims 1 to 9, wherein step b) comprises a hot isostatic pressing. 11. The method of claim 10, wherein the vehicle component is created in step d) by forging and optionally subsequent machining. 12. The method according to any one of claims 1 to 11, wherein the treatment of the block in step c) takes place at a temperature between 350 ° C and 500 ° C. 15 13. Vehicle component, in particular piston of an internal combustion engine, by compacting particles of aluminum or an aluminum alloy with an average size of less than 10 pm, optionally together with reinforcing particles, into a block and then forming the block at 20 a temperature of at least 250 ° C. at a forming rate of, for example, 4: 1 or more. 14. The vehicle component of claim 13, wherein an average size of the particles of aluminum or an aluminum alloy is less than 5 pm. 25 15. The vehicle component according to claim 13 or 14, wherein an average size of the particles of aluminum or an aluminum alloy is 0.1 pm to 1.5 pm. 16. Vehicle component according to one of claims 13 to 15, wherein 30 reinforcing particles of an amorphous metal and / or an amorphous alloy are provided. 17. The vehicle component of claim 16, wherein the amorphous alloy is an aluminum alloy. • • • • • • • • • • ··· «· · · · · · 10 18. Vehicle component according to claim 16 or 17, wherein the reinforcing particles have an average size of less than 500 pm, preferably less than 200 pm. 19. Vehicle component according to one of claims 16 to 18, wherein a volume fraction of the reinforcing particles is 10% to 45%, preferably 15% to 35%. 20. Vehicle component according to one of claims 13 to 19, wherein the vehicle component is forged and optionally created by subsequent machining 10 processing. 21. The vehicle component according to any one of claims 13 to 20, wherein the Fahrzugkomponente after 20 hours at 300 ° C has a tensile strength Rm of more than 200 M a. 15 22. Use of hot isostatically pressed primary material containing gas atomized particles of aluminum and / or an aluminum alloy with an average particle size of less than 10 pm and optionally reinforcing particles for forging piston blanks. 20 Capital Technology Beteiligungs GmbH represents « Dipl Ing. Dt G. WIRNSBERGER 6 00Leoben, Mühlgasse 3 pi Ing. Dt G. 1 (OOLeoben, Leoben, March 8, 2007