ES2397636A2 - CASTING ALLOY OF THE AIMgSI TYPE - Google Patents

Abstract

Field of the invention: The invention relates to non-ferrous metallurgy, particularly aluminium casting alloys and can be employed for high temperature application. Object of the invention: the prior art use of the known components in combination with new ones. The alloy comprises the following elements, by weight percent (wt. %): 4.0 to 16.0 for magnesium, 2.0 to 9.0 for silicon, 0.05 to 1.5 for manganese, 0.01 to 0.6 for scandium, 0.05 to 0.5 for zirconium, at least one or more elements selected from the group comprising (wt. %): 0.05 to 0.5 for chromium, 0.1 to 2.0 for copper, 0.05 to 1.0 for nickel, 0.01 to 0.6 for hafnium as well as one or more elements selected from the group comprising-(wt. %): 0.05 to 0.6 titanium, 0.005 to 0.05 for boron, 0.01 to 0.85 for yttrium, 0.001 to 0.2 for germanium, wherein 0.001% < (Ti + B + Y + Ge) <1.5%, aluminium as the balance. Technical result: said casting alloy of the AlMgSi type having high strength and wear resistance at temperatures of more than 250 DEG C in combination with high fluidity.

Description

Casting alloy of type AIMgSi

OBJECT OF THE INVENTION

The present invention relates to non-ferrous metallurgy, in particular alloys for cast aluminum, and can be used to produce component parts for applications at high temperatures.

BACKGROUND OF THE INVENTION

Currently, the industry contemplates a wide application of aluminum alloys based on the eutectic of the Al-Si binary system additionally alloyed with Mg, Cu, Zn, Fe, Ni, Mn, Ti and other elements. The improvements of

prior art alloys include: improving its chemical and phase compositions, updating and inventing

foundry technologies, using special additions to refine the melts, modify the structure,

etc. One of the major drawbacks of existing aluminum smelting alloys is the decrease in melting temperature as the number of alloy elements increases. It sets a limit on its use in high temperature internal combustion engines of the prior art.

Depending on the concentration of silicon, complex alloy alloys based on the Al-Si system can be divided into 3 groups: hypoeutectic comprising <12% by weight silicon (356.0, 360.0, AK7, AK9) , eutectic comprising 12-13% by weight of silicon (AK12, AK12M2MrH, Mahle 124) and hypereutectic comprising 14-26% by weight of silicon (390.0, 20 Mahle 138, Mahle 244).

A large number of primary silicon crystals in these alloys results in a decrease in their ductility and their

technological properties and makes it necessary to use expensive casting techniques.

For example, an aluminum alloy (document UA 22435A) containing, in percentage by weight (% by weight): 25 14.0-16.5 silicon, 1.2-2.5 copper, 0.8- 1.5 mg, 0.5-1.3 manganese, 0.05-0.20 titanium, 0.01-0.6 nickel, 0.01-0.5 zinc, 0.7- 1.6 iron, 0.01-0.2 chromium, 0.01-0.4 zirconium, 0.03-0.1 phosphorus and aluminum

like the rest.

Conventionally, the disadvantages of said alloy are its unstable mechanical properties, which are

caused by primary silicon crystals and meltable ternary silicon containing 30 eutectic as well as the environment

contaminated by the production of the alloy and the smelting of ingots due to the phosphorus present in them.

Hypoeutectic and eutectic alloys for widespread use in the industry have good casting capacity, are technologically simpler and easier to treat. However, its use temperature does not exceed 200-230 T.

Another alloy for cast aluminum (RU 2237096) containing, in percentage by weight (% by weight): 5.0-10.0 silicon, 2.0-5.0 copper, 0.3-0, 7 mg, 0.05-0.4 titanium, 0.01-0.3 zirconium, 0.2-0.4 antimony, 0.05-0.6 scandia, 0.1-0, 3% by weight neodymium, 0.3-2.0 calcium and aluminum as the rest.

The disadvantages of said alloy tend to be low resistance to high temperatures and low resistance to use.

There are some more procedures to improve the mechanical properties of materials used in environments

high temperatures. For example, the reinforcement of matrices of eutectic alloys by fibers or filaments of AbO "SiC, C, etc. (the so-called metal matrix compounds -MMC) or the use of the CMC technique (compounds

ceramic matrix). However, the use of such techniques is more expensive than casting. Therefore, they did not win

production popularity.

There is another solution to these problems. It includes the use of the eutectic ternary system of AI-Mg-Si instead of the Al-Si binary. The AI-Mg-Si system comprises a quasibinary eutectic used to create new alloys for cast aluminum with improved properties. This eutectic is formed by the a-Al phase and the Mg, Si intermetallic phase, which melts at a higher temperature and is thermodynamically more stable in contrast to silicon. This will guarantee a higher melting temperature of the developed alloys and their conservation to a high degree when introducing alloy elements and will lead to a damping of the diffusion-dependent processes at high

operation temperatures.

For example, the alloy for casting of AIMgSi (US 6,623,570 B2) containing, in percentage by weight (% by weight), 3.0 to 7.0 of magnesium, 1.7 to 3.0 of silicon, 0.2 to 0.48 of manganese, 0.15 to 0.35 of iron, titanium as desired, with a maximum of 0.2%, 0.1 to 0.4 of nickel and aluminum as the rest.

The disadvantages of said alloy tend to be low resistance to high temperatures and low resistance to use.

Cast aluminum alloy of AI / Mg / Si containing scandia (WO 2005/047554 A 1) comprising at least 1.0-8.0% by weight of magnesium (Mg),> 1.0- 4.0% by weight of silicon (Si), 0.01- <0.5% by weight of scandia (Se), 0.005-0.2% by weight of titanium (Ti), 0-0, 5% by weight of an element or group of elements, selected from the group comprising zirconium (Zr), hafnium (Hf), molybdenum (Mo), terbium (Tb), niobium (Nb), gadolinium (Gd), erbium (Er ) and vanadium (Y), 0-0.88% by weight of manganese (Mn), 0-0.3% by weight of chromium (Cr), 0-1.0% by weight of copper (Cu) , 0-0.1% by weight of zinc (Zn), 0-0.6% by weight of iron (Fe), 0-0.004% by weight of beryllium (B) and the rest of aluminum with additional impurities up to max. 0.1% by weight and max. 0.5% total by weight.

The low content of transition metals and copper in said alloy does not guarantee its strength and resistance to high temperature use, while alloy elements such as terbium, gadolinium and erbium make it more expensive.

The alloy for smelting of aluminum (document UA 83776) technically more comparable to the one claimed is that which contains, in percentage by weight (% by weight): 3.0-22.0 mg, 2.8-10.0 silicon, 0.05-1.0 zirconium, 0.52.5 copper, 0.05-1.0 manganese, 0.05-1.5 nickel, 0.05-1.5 cobalt, 0.05-1.0 titanium, 0.05-1.0% iron, 0.05-1.0 boron, 0.05-0.5 carbon, 0.05-1.0 chromium , 0.05-0.3% molybdenum, 0.05-0.5 tungsten, 0.01-0.6 scandia and aluminum like the rest.

The high content of refractory alloy elements in said alloy and the need for considerable overheating and maintaining the melt at temperatures of -800 'C can increase the evaporation of magnesium and scandia and give rise to unstable mechanical properties.

BRIEF DESCRIPTION OF THE INVENTION

The general purpose of the present invention is to provide an improved cast aluminum alloy for

applications at high temperatures (at temperatures> 250 'C) and combines good mechanical and technological properties.

An objective of the invention is to use a combination of known and new components that guarantees good

mechanical properties of said alloy at temperatures of more than 250 'C, more resistance to use and improvement of some of its casting properties, e.g. eg, fluency.

A further objective of the invention is to provide an improved composition of said alloy for cast aluminum, modifying the qualitative and quantitative content in basic and alloy elements and adding germanium, hafnium and yttrium, which improves the mechanical properties without deteriorating the casting .

The aforementioned objective is achieved by providing an aluminum casting alloy that contains,

in percentage by weight, (% by weight):

Magnesium (Mg) 4.0-16.0 Silicon (Si) 2.0-9.0 Manganese (Mn) 0.05-1.5 Scandia (Se) 0.01-0.6 Zirconium (Zr) 0, 05-0.5

at least one or more elements selected from the group comprising:

Chromium (Cr) 0.05-0.5 Copper (Cu) 0.1-2.0 Nickel (Ni) 0.05-1.0 Hafnium (Hf) 0.01-0.6

as well as one or more elements selected from the group comprising:

Titanium (Ti) 0.05-0.6 Boron (B) 0.005-0.05 Itrium (Y) 0.01-0.85 Germanium (Ge) 0.001-0.2

in which 0.001% <(Ti + B + Y + Ge) <1.5%

Aluminum (Al) the rest.

The essential characteristic of said alloy is the presence, in percentage by weight (% by weight): of magnesium (4,016.0), silicon (2.0-9.0), manganese (0.05-1.5), scandium (0.01-0.6) and zirconium (0.05-0.5). The distinctive feature of the

Invention is the presence in it of at least one or more elements selected from! group comprising, in

weight percentage (% by weight): chromium (0.05-0.5), copper (0.1-2.0), nickel (0.05-1.0), hafnium (0.01-0, 6), as well as one or more elements selected from the group comprising: titanium (0.05-0.6), boron (0.005-0.05%), yttrium (0.01-0.85) and

germanium (0.001-0.2), in which in 0.001 <(Ti + B + Y + Ge) <1.5%.

The reason for the percentages mentioned above is explained by the following factors.

A combination of magnesium and silicon used in an aluminum alloy forms an eutectic structure, which provides high temperature resistance, good resistance to use and fluidity. The upper and lower limits of the

Percentage are stipulated by the phase equilibrium of the ternary system of AI-Mg-Si. In combination with others

components, these elements determine the zone of existence of binary eutectic alloys that contain phase

of Mg2Si. Said alloy is characterized by a well differentiated structure provided by the Mg2Si phase located in the a-Al of the metal matrix in the form of fibers and plates. The aforementioned percentage of

Magnesium and silicon in said alloy provides the necessary properties. When the content of magnesium and silicon in an alloy is lower, 4.0% of its mass and 2.0% of its mass, respectively, the part by volume

of Mg2Si in the eutectic is not sufficient to provide the necessary mechanical, tribological and foundry properties. When the magnesium and silicon content in an alloy is greater, 16.0% of its mass and 9.0% of its mass, respectively, form large primary crystals of Mg2Si and the amount of eutectic decreases, which causes the embrittlement of the alloy and deteriorates its casting capacity.

Manganese has a low diffusion rate in aluminum and, consequently, a positive influence on resistance

at high temperatures of the alloys. In addition, manganese slows the diffusion of copper into aluminum, which also improves the properties of alloys. When the manganese content in an alloy is less than

0.05% of its mass, its effect on high temperature resistance and resistance to the use of the alloy is negligible, while its content greater than 1.5% of its mass causes thick intermetallic compounds

that disintegrate the alloy.

The simultaneous introduction of Sc and Zr in the aforementioned proportions results in the formation of nanoparticles of the L12 phase and improves the strength of the alloy, such particles are formed as a result of a heat treatment at high temperatures, are consistent with the matrix of eutectic alloy, they do not react with the eutectic colonies of the alloy and provide uniform ingot structures, allowing the use of

Alloy at high temperatures.

The scandium also provides better thermal stability of the structure, improves its welding capacity and

minimizes its tendency towards the formation of cracks by contraction, in order to provide the necessary

Resistance to high temperatures, the content of scandium should be 0.01 to 0.6% by weight. When the content is

less than 0.01% by weight, the amount of dispersoids of the reinforcement phase is not sufficient and, as a consequence, the dispersion reinforcement is not achieved. When the content of scandia is greater than 0.6% by weight, they form large crystals of their aluminoid, which decreases the mechanical properties of the alloy.

The zirconium, together with the scandium, forms nanoparticles of the AI phase, (Sc, _, Zr,). The zirconium present in the alloy minimizes the tendency of the particle to coagulation, which provides good thermal stability of the structure and properties. When the zirconium content is less than 0.05% by weight, its effect on

High temperature resistance and resistance to use is negligible. When the content is greater than 1.0% in

weight, large crystals of the intermetallic of AI, Zr are formed, which decreases the ductility of the alloy.

The use of at least one or more elements of the group comprising chromium, copper, nickel and hafnium in the aforementioned proportions improves the strength of the alloy at temperatures of more than 250 oC. When he

Chromium content is less than 0.05% by weight, its effect on the mechanical properties of the alloy is negligible, while the chromium content greater than 0.5% by weight causes the formation of eutectic

Multi-phase melts in grain boundaries, which decreases the high temperature resistance of the alloy.

Copper and nickel increase an alloy grade of the solid aluminum solution and allow the high temperature resistance of the alloy to be achieved while maintaining moderate ductility. The reinforcing effect is achieved by the solid alloy aluminum solution, as well as by the metastable and stable phases present in the structure, which are formed as a result of the partial decomposition of the supersaturated solid solution caused by crystallization or heating at high temperatures These elements influence the mutual diffusive mobility of atoms and the high temperature resistance of the alloy. Copper and nickel concentrations are changed in relation to the concentration and temperature limits of the two-phase eutectic equilibrium of the multi-component system when additional elements are used. When the copper content is less than 0.1% by weight,

Its effect on high temperature resistance is negligible, It is necessary that the copper content is limited

at 2.0% by weight, since in its excess the multi-phase fused eutectic and additional phases are formed, which causes the embrittlement of the alloy and decreases its resistance to high temperatures.

When the nickel content is less than 0.05% by weight, its effect on the high temperature resistance of the

Alloy is insignificant, while the nickel content exceeding 1.0% by weight causes the formation of

Multi-phase fused eutectic, which decreases the high temperature resistance of the alloy.

Hafnium reduces the mismatch between the aluminum matrix network and the L 12 particles, improving its thermal stability. When the hafnium content is less than 0.01% by weight, its effect on high temperature resistance and resistance to the use of the alloy is negligible. The hafnium content exceeding 0.6% by weight results in the formation of large intermetallic crystals, which decreases the ductility of the alloy.

The addition of one or more elements selected from the group comprising, in percentage by weight (% by weight): titanium (0.05-0.6), boron (0.005-0.05), yttrium (0.01-0 , 85) and germanium (0.001-0.2), in which 0.001% <(Ti + B + Y + Ge) <1.5%, modifies the structure, provides increased distribution uniformity of the phases of reinforcement and the optimal correlation of resistance and plasticity caused by it. The elements lose their modifying effect if the lower concentration limit is reduced. The excess of the upper concentration limit may lead to the formation of thick intermetallic crystals, which decreases the melt capacity and ductility. In addition, the

Titanium, together with boron, improves resistance to use.

Test ingots were melted in an electric resistance furnace or induction furnace in AbOs crucibles in air

using protective flows (ICU and UF) in a corresponding 3: 1 ratio or in a protective atmosphere (Ar). The ingots were manufactured from pure fillers and master alloys were produced in induction furnace or from

resistance or using other procedures. The crucibles components must be loaded so that intermetallic crystals do not form. Before using each of the components, the melt was stirred and maintained

until the previous components dissolved completely. The melting and pouring temperatures were respectively (700-750) 'C and (680-720)' C. After dissolution of the components, the melt is

stirred well, refined by an inert gas or special agents, cleaned of slags and molded.

In order to achieve the dispersion reinforcement by means of the LI nanoparticles, the heat treatment of the ingots in an oven of resistance at (200-400) 'C for (2-50) h was carried out. After performing this type of heat treatment, test pieces were prepared to determine the stress and tribological properties.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows the resistance to use of the alloy for cast iron type AIMgSi compared to commercially available alloys 356.0 and 390.0. The resistance to use in quasi-stationary (1,) and dynamic (Id) operations under load at 180 oC and 300 oC was determined.

EXAMPLES

Example 1

In order to demonstrate the tensile strength at elevated temperatures, the type cast alloy was cast

AIMg Yes, in percentage by weight (% by weight):

Magnesium 5.5-7.5 Silicon 2.0-3.5 Manganese 0.1-0.8 Scandium 0.15-0.3 Zirconium 0.08-0.15 Chrome 0.05-0.2 Titanium 0 , 05-0.2 Boron 0.01-0.04 lily 0.03-0.4 Aluminum the rest

200g ingots were manufactured using electric resistance furnaces with AI crucibles, 03 in air and using protective flows. Subsequently, the ingots were subjected to thermal wracking at temperatures of (250-340) 'C for 2-10 h.

The mechanical tension properties were tested using INSTRON. The specimen was kept 5 free of charge for 0.5 h (stabilization time) at the test temperature and the roll was carried up by loading it later. The loading rate amounted to 10 · 3c · ', the diameter of the effective part of the specimen was 3 mm, the length -18 mm.

The alloy has the following properties at 300 oC:

Breaking strength (cra), MPa 150-200 Elasticity limit (cro ,,), MPa 130-155 Elongation (5),% 3.0-6.0.

Example 2. in percentage by weight (% by weight):

Magnesium 7.0-10.0

Silicon 3.0-5.0 Manganese 0.1-0.8 Scandium 0.15-0.3

Zirconium 0.08-0.15

Chrome 0.05-0.2 Copper 0.3-0.7 Nickel 0.1-0.3 Hafnium 0.01-0.6 Titanium 0.05-0.2 Boron 0.01-0.04 Germanium 0 , 01-0.05 Aluminum the rest.

The alloy that was prepared as in Example 1 has the following properties at a temperature of 400 · C:

Breaking strength (as), MPa 110-120 Elasticity limit (ao, 2), MPa 105-111 Elongation (&),% 1,2-2,0

The described properties are superior to those of the alloys presented in patents UA 83776 and US

6,399,020 B 1.

Example 3

To demonstrate the resistance to use, the alloy for cast iron of the AIMgSi type was prepared as in example 1, in percentage by weight (% by weight):

Magnesium 8.4-10.0 Silicon 3.0-5.0 Manganese 0.1-0.8 Scandium 0.15-0.3 Zirconium 0.08-0.15 Chrome 0.05-0.2 Titanium 0 , 05-0.2 Boron 0.01-0.04 Aluminum the rest,

Tribological tests were carried out in the contact circuit of the spherical zone using the original ATCD unit [NA Zenkin, K.E. Grinkevych. Control Diagnostics 6 (2002) 49]. For these purposes, special conditions were created under which the sphere penetrator slid correspondingly over the flat specimen to

defined temperatures The tests were carried out both in the quasi-permanent permanent operation and in the

the dynamic alternative (Id) under load [KE Grinkevych. Friction and Wear, vol. 24, n. ' 3 (2003) 344].

The modulated dynamic component of the normal pressure force! LP was assigned in the form of an oscillation train that is added simultaneously to the static force Po; The value of the dynamic load component assumes 10% taken from the static and is determined from the formula:

A (2JlJ '

¿P = -l-'3eno -, where A -ample load, T -period, t -time.

2T

The modulated load was applied so that the total load was P = Po -flP. ! lP alternates from ° to A.

In addition, one half of the friction band is conventionally charged by quasi-stationary force

another through dynamic impact. The resistance to use is assessed by the depth of the friction bands in the area of the quasi-stationary and dynamic impacts (1 "Id).

The test conditions are as follows: 180 · C and 300 oC, Po = 22H,! LPMá, = A = 5H, 25 Hz, 10 minutes, sphere penetrator R = 8 mm with Si, N4, silicon lubricant. The test results are shown in fig. one.

Example 4

To demonstrate the fluidity, the alloy for cast iron type AIMgSi was prepared as in example 1, in percentage by weight (% by weight):

Magnesium

Silicon

Manganese

Scandia

5

Zirconium

Chrome

Titanium

Boron

Aluminum

10

7.0-10.0 3.0-5.0 0.1-0.8 0.15-0.3 0.08-0.15 0.05-0.2 0.05-0.2 0 , 01-0.04 the rest.

Fluency was determined by using a complex U-shaped sample of Nekhendzi-Kuptsov. A portion of molten metal of 350 9 was poured at temperatures of 40 oC above the liquid state.

The alloy prepared as in Example 1 and the commercially available alloy 356.0 have a flowability, respectively, of 385 mm and 283 mm.

The previous examples show that said alloy for casting of type AIMgSi has a high strength and

resistance to use at temperatures above 250 oC in combination with high fluidity and tends to be a

20 best alternative to cast aluminum alloys of the prior art. Said alloy can be produced.

under conditions of both laboratory and manufacturing.

Claims (20)

1. Alloy for cast iron type AIMgSi containing, in percentage by weight (% by weight): Magnesium 4.0 to 16.0 Silicon 2.0 to 9.0 Manganese 0.05 to 1.5 Scandium 0.01 to 0.6 Zirconium 0.05 to 0.5 at least one or more elements selected from the group comprising: Chromium 0.05 to 0.5 Copper 0.1 to 2.0 Nickel 0.05 to 1.0 Hafnium 0.01 to 0.6 as well as at least one or more elements selected from the group comprising: Titanium 0.05 to 0.6 Boron 0.005 to 0.05 Itrium 0.01 to 0.85 Germanium 0.001 to 0.2 in which 0.001% <(Ti + B + Y + Ge) <1.5% Aluminum the rest. 2. Alloy according to claim 1 comprising 5.0 -13.0% by weight of magnesium and e12.1 -7.0% by weight of silicon, which varies mainly from 6.0 to 12, 0% by weight of magnesium and from 2.2 to 6.0% by weight silicon.

3.

Alloy according to claims 1-2 comprising 0.08-1.2% manganese, which varies mainly from 0.1 to 1.0% by weight.

Four.

Alloy according to claims 1-3 comprising 0.05-0.5% scandium, which varies mainly from 0.1 to 0.4% by weight.

5. Alloy according to claims 1 ~ 4 comprising 0.06-0.3% zirconium, which varies mainly from 0.08 to 0.2% by weight. 6. Alloy according to claims 1-5 comprising at least one or more elements selected from the group comprising chromium, copper, nickel and hafnium.

7.

Alloy according to claims 1-6 comprising 0.05-0.2% by weight of chromium.

8.

Alloy according to claims 1-6 comprising 0.3-1.0% by weight of copper.

9.

Alloy according to claims 1-6 comprising 0.1-0.4% by weight nickel.

10.

Alloy according to claims 1 -6 comprising 0.3-0.6% by weight of hafnium.

eleven.

Alloy according to claims 1-10, wherein 0.001% by weight <(Ti + B + Y + Ge) <1.5% by weight.

12.

Ingot production means for the casting alloy according to items 1 to 11 include the

 following stages: a) heating the components of the alloy for foundry type AIMgSi, which is claimed in point 1, to the melting temperature at such a loading sequence of components of the load that prevents the formation of crystals  thick intermetallic phases; b) use flows or a protective means to prevent oxidation of the components; c) refine the melt of nonmetallic components and gases; d) cooling the melt to a sufficient speed for the preservation of doping elements that guarantee the formation of dispersed particles of the reinforcement phase L 1, in the solid solution by subsequent heat treatment. 13. Alloy according to claims 1-12, which in the foundry state is essentially two-phase and contains the eutectic primary crystals (a-AI + Mg, Si) of Mg, Si and the primary dendrites of a-Al. 14. Alloy according to claims 1-13, which retains the two-phase eutectic structure (010 AI + Mg, Si) that is formed by the growth mechanism coupled in a wide range of rates of crystallization. 15. Alloy according to claims 1-14, whose two-phase eutectic consists of lamellae and fibers of Mg, Si located in the matrix of a-Al. fifteen 16. The ingot heat treatment process of the alloy according to claims 1-15, wherein the alloy is coated in air at temperatures of 200-400 · C for 2-50 h, mainly between 250-350 OC for 2-10 h, for the formation of dispersed nanoparticles of a phase with the structure L 1, in the solid solution of a-Al that are consistent with its network. 17. Alloy according to claims 1-16, whose a-Al of the solid solution contains reinforcing particles of the phase that has the structure L 12, are consistent with its network and its chemical composition differs from those of the phases that form the eutectic. 18. Alloy according to claims 1-17, wherein the reinforcing particles do not interact with the phases that form the eutectic in the long-term high temperature annealing process at temperatures from 200-400C. 19. The application of the alloy for foundry type AIMgSi according to claims 1-11, 13-15 and 1730 18 for the manufacture of castings under high thermal stress which are subjected to heat treatment after molded as ingots by the method according to claim 16. 20. Aluminum alloy according to claims 1-19 applied for the manufacture of parts with enhanced use resistance containing 8.4 -13.0% by weight of Mg and 2.4 -6.0% by weight of Si. 35 21. Application of the AIMgSi type alloy according to claims 1-20 characterized by excellent casting properties together with superior mechanical and trobolic properties in the temperature range of 250-400 oC in the manufacture of sectional parts transverse variables (such as pieces of automotive engines).