WO2022060253A1

WO2022060253A1 - Aluminium casting alloy

Info

Publication number: WO2022060253A1
Application number: PCT/RU2021/050295
Authority: WO
Inventors: Виктор Христьянович МАНН; Александр Николаевич АЛАБИН; Александр Юрьевич КРОХИН; Дмитрий Олегович Фокин
Original assignee: Общество с ограниченной ответственностью "Институт легких материалов и технологий"
Priority date: 2020-09-16
Filing date: 2021-09-15
Publication date: 2022-03-24
Also published as: MX2023003144A; JP2023542129A; RU2745595C1; CA3195581A1; EP4215634A1; KR20230069152A; CN116057193A; US20230212717A1

Abstract

The invention relates to the field of metallurgy, and more particularly to aluminium-based alloys, and can be used for producing thin-walled intricate castings by casting in a metal mold, in particular for automotive components, parts for electronic devices, and the like. The present aluminium-based casting alloy contains: 1.5-5.1 wt% calcium; up to 0.7 wt% iron; up to 1.0 wt% silicon; 0.1-1.8 wt% zinc; and, optionally, one or more of 0.2-2.5 wt% manganese; 0.005-0.1 wt% titanium; 0.05-0.14 wt% zirconium; 0.05-0.15 wt% chromium, wherein calcium and zinc are present in the structure of the alloy predominantly in the form of eutectic particles. The technical result is that of providing the desired combination of technical properties during casting, as well as resistance to corrosion.

Description

CASTING ALUMINUM ALLOY

Technical field

The invention relates to the field of metallurgy, in particular to aluminum-based alloys characterized by high corrosion resistance. The alloy can be used to obtain thin-walled castings of complex shape by casting into a metal mold.

Prior Art

Industrial non-hardened alloys of the A-Si system, for example, A413.2 or AK12pch (GOST 1583), are characterized by high manufacturability during casting and a relatively low level of strength properties, in particular, the yield strength usually does not exceed 60-80 MPa, depending on casting thickness. A higher level of strength properties of castings already in the cast state is provided by the addition of copper, in particular, alloys of the AA383.1 or AK12M2 type are known. The increase in mechanical properties in this case is accompanied by a significant decrease in relative elongation and deterioration in corrosion resistance.

Among thermally non-hardenable corrosion-resistant alloys, alloys based on a solid solution based on the Al-Mg system are known, for example, AMgbl, AMg5K, AMg5Mts (GOST 1583), Magsimal®59 (Rheinfelden Alloys), etc., characterized by satisfactory processability during casting, good corrosion resistance , a good level of strength properties and relative elongation. Among the disadvantages of the alloys of this system, one should single out a high linear shrinkage and insufficiently good tightness of thin-walled castings. The combination of a high level of strength properties, relative to elongation and corrosion resistance is realized in alloys of the Al-Si system with the addition of 0.2-0.5 wt. % magnesium, in particular, alloys such as AK9 (GOST1583), Silafont®36 (Rheinfelden Alloys), trimal®37 (Trimet), etc. are known. quenching in water), change in overall dimensions and the appearance of cracks.

An invention of NUST MISiS is known, disclosed in patent RU2660492. The material for use in the cast state contains (wt.%): 5.4-6.4% calcium, 0.3-0.6% silicon and 0.8-1.2% iron. Among the disadvantages of the proposed invention, one should highlight the low relative elongation, which did not exceed 2.6%, which limits the use of the material in critical cast parts.

A casting alloy of the Al-Ni-Mn system is known, intended for the production of structural components for automotive and aerospace applications, which is an alternative to branded silumins, developed by Alcoa and disclosed in patent US6783730B2 (published on August 31, 2004). It is possible to obtain castings from this alloy with a good combination of casting and mechanical properties with a content (wt.%) of 2-6% Ni, 1-3% p, 1% Fe, less than 1% silicon, and also with the content of other unavoidable impurities. Among the disadvantages of the proposed invention, it should be noted that a high level of casting and mechanical properties is ensured by the use of aluminum grades of high purity and with a high nickel content, which significantly increases the cost of the obtained castings. In addition, the proposed material is thermally non-hardening in the entire concentration range, which limits its use. At the same time, in the region of high nickel concentrations, the corrosion resistance of castings is significantly reduced. Known are cast aluminum alloys based on Al-Ni and A1-Ni-Mn systems and a method for producing cast parts from them, which are described in the invention of Alcoa US8349462B2 (publ. 08.01.2013) and application EP201 1055318 of Rheinfelden Alloys GmbH & Co. kg. The invention provides alloy compositions for use in the as-cast state. The common thing in the proposed inventions is a high nickel content of 1-6%, which determines the main disadvantage - a significant decrease in corrosion resistance. With a relatively low content of nickel and manganese, casting alloys have a low level of strength characteristics.

Known material based on the Al-Ni-Mn system proposed by NUST "MISiS" and disclosed in the patent of the Russian Federation 2478131C2 publ. 03/27/2013 The material contains (wt%): l.5-2.5% Ni, 0.3-0.7% Fe, 1-2% Mn, 0.02-0.2% Zr, 0.02% - 0 .12% Sc and 0.002-0.1% Ce. Castings obtained from the alloy after annealing (without using the hardening operation) are characterized by a tensile strength of at least 250 MPa with a relative elongation of at least 4%. The first disadvantage of this alloy is its increased tendency to form concentrated porosity, which makes it difficult to obtain high-quality relatively large castings. The second drawback is associated with the need to use elevated casting temperatures, which cannot always be implemented in foundry conditions.

Closest to the proposed is a material containing (wt.%) Al-3.5%Ca-0.9%Mn-0.5%Fe-0.l%Zr-0.l%Sc, disclosed in the publication https: //doi.Org/10.1016/j.msea.2019.138410. The authors of the publication considered the material as a deformed alloy, in the technological chains of which quenching in water is excluded. It follows from the publication that the use of the alloy specified in the publication for castings and use in the cast state is not obvious. Among the disadvantages of the proposed invention, the presence of expensive scandium should be highlighted, as well as the need to use heat treatment to realize the strengthening effect from the joint addition of zirconium and scandium. Disclosure of invention

The objective of the invention is to create a new cast aluminum alloy designed to produce thin-walled castings by various methods of casting into a metal mold, in particular, gravity, high-pressure casting, low-pressure casting, liquid stamping, but not limited to, satisfying the specified requirements for a set of technological and corrosion characteristics.

The technical result of the invention is to provide a given combination of technological characteristics during casting and corrosion resistance.

The technical result is achieved by the proposed casting alloy based on aluminum, with the following concentrations of alloying elements, wt. %: Calcium 1.5-5.1 Zinc 0.1-1.8 Iron up to 0.7

Silicon up to 1.0 optional, at least one element selected from the group

Manganese 0.2-2.5

Titanium 0.005-0.1

Zirconium 0.05-0.14

Chrome 0.05-0.15

Aluminum and inevitable impurities - the rest

In a private version, calcium and zinc in the structure are presented mainly in the form of eutectic particles. The alloy is made in the form of castings.

Various modifications and improvements are allowed, not going beyond the scope of the invention defined by the first claim. The essence of the invention

Due to the selected combination of alloying elements, the proposed alloy is characterized by a narrow crystallization interval, which, in combination with a large amount of the eutectic phase, provides a good level of casting characteristics, and due to elements that dissolve in the aluminum solid solution, a satisfactory level of strength properties in the cast state. At the same time, with a different combination of selected alloying elements, within the claimed region, corrosion resistance is maintained at a good level.

The main criterion for the acceptable choice of alloying elements was the formation of the desired structure, excluding the presence of coarse primary crystals and/or coarsening of the eutectic phase; the rationale for the concentration range is given below.

The concentration (wt.%) of calcium in the range of 1.5-5.1% and zinc in the range of 0.1-1.8% provide good casting properties due to the fact that calcium and zinc mainly form a sufficient amount of the eutectic phase. The main effect of the joint introduction of calcium and zinc is the formation of a joint eutectic phase A14(Ca,Zn), where the zinc atom replaces the calcium atom. As a result, the level of strength properties is further increased. If the calcium content is less than the declared level, it will lead to a decrease in casting characteristics. When zinc is reduced below the stated level, there will be no significant increase in strength properties. The content of calcium and zinc above the stated level will lead to the formation of a rough structure and a significant decrease in mechanical properties.

The content of iron and silicon is primarily determined by the purity of the aluminum used in the preparation of the alloy. However, iron and silicon can also be used as alloying elements, due to the fact that silicon in an amount of up to 1.0 wt.% is redistributed between the solid solution and the eutectic, which, on the one hand, provides an increase in strength properties due to additional solid solution hardening in the cast state, and on the other hand, it positively affects the casting characteristics of the alloy due to an increase in the amount of eutectic. With a higher content of silicon, the morphology of the eutectic phase worsens, which generally reduces the strength characteristics. Iron in an amount of up to 0.5 wt.% predominantly forms phases of eutectic origin, which positively affects the casting characteristics of the alloy due to an increase in the amount of eutectic. With an increase in the concentration of iron above 0.5 wt.%, coarsening of the eutectic phase is possible and, as a result, a decrease in mechanical properties.

Manganese in an amount of up to 2.5 wt % is necessary to improve the strength properties, primarily in the cast state, by providing solid solution strengthening. When the manganese content is above 2.5 wt.% in the structure, primary crystals of the Alb(Te, Mn) phase can be formed, which can lead to a decrease in mechanical characteristics. The content of manganese is less than 0.2 wt.% will not lead to significant solid-solution hardening and, as a consequence, a weak increase in strength characteristics.

Zirconium and chromium within the stated limits (wt.%) 0.05-0.14% and 0.05-0.15%, respectively, are necessary to ensure solid solution strengthening. At lower concentrations of these elements, a significant increase in strength characteristics in the cast state is not achieved. For large quantities, it will be necessary to increase the casting temperature above the typical level, which will reduce the durability of the casting molds, otherwise, there will be a high probability of the formation of primary crystals of the AlCr and AlsZr phase, which will not lead to an increase in the level of mechanical properties from the introduction of these elements.

Titanium in the amount of 0.005-0.1 wt.% is necessary for modifying the aluminum solid solution. With a higher content of titanium in structure, the appearance of primary crystals is possible, which will reduce the overall level of mechanical properties, and at a lower level, the positive effect of the influence of this element will not be realized. Titanium can be introduced in the form of a multicomponent alloy, such as Al-Ti-B and/or Al-Ti-C, so in this case, the presence of boron and carbon in compounds with titanium is possible in the alloy, in amounts proportional to the content of the corresponding alloy. Boron and carbon, as independent elements, did not have a significant effect on the mechanical and casting properties in relation to the range under consideration. In addition, in the presence of titanium, in some cases, a decrease in the tendency to form hot cracks during casting is noted.

Example of a specific implementation

For the preparation of alloys, the following charge materials were used (wt.%): A99 and A8 grade aluminum, TsO grade zinc, calcium in the form of calcium metal and A1-6Ca master alloys, manganese in the form of A1-10% Mn master alloy, Al-10% Zr master alloy , Al-10%Cr, Al-5%Ti.

EXAMPLE 1

To assess the effect of alloying elements on the structure and properties in laboratory conditions, 13 alloy compositions were prepared (Table 1).

Table 1 - Chemical composition of experimental alloys (wt.%)

The content of other elements typically did not exceed 0.05 wt.%. The chemical composition of the alloy was chosen from the condition of obtaining a structure consisting of an aluminum solid solution and a eutectic component. Casting of samples was carried out by gravity method in a metal mold "Separately cast sample". Form temperature - could fluctuate in the range of 20 -60 °C. The casting was a tensile specimen with a diameter of 10 mm and a calculated length of 50 mm, which was tested for tension (with the determination of the yield limit, tensile strength, and relative elongation) immediately after casting without machining. The structure of the samples was evaluated from the sample heads.

Table 2 - Mechanical properties as-cast

(gravity casting in a metal mold)

* - compositions of table 1

An analysis of the structure of the studied alloys showed that the structure of the considered compositions in Table 1 mainly consists of an aluminum solid solution and eutectic phases formed by the corresponding elements. At the same time, calcium and zinc in all experimental alloys are predominantly presented in the form of eutectic particles.

For use in the as-cast state, compositions 2, 5 and 12 are most preferred due to the good yield strength to elongation ratio. The most desirable structure of the alloy, on the example of composition 5 (table 1), is shown in Fig.1.

EXAMPLE 2

Evaluation of corrosion resistance on the example of compositions 2, 5, 8 and 11 of the proposed alloy (table 1) was carried out according to the method of accelerated corrosion tests were carried out by the method of exposure to neutral salt fog according to the program: 1 cycle - exposure in a salt fog chamber when spraying 5% NaCl solution for 8 hours and a temperature of 25±1 °C, then holding at a temperature of 35±3 °C without spraying the solution for 16 hours; total: 7 cycles. The result was evaluated by the change in the appearance of the surface of the samples and by the depth of corrosion damage (metallographic method). As a reference, an alloy of the ADC6 type was used, which is characterized by the highest corrosion resistance among cast aluminum alloys.

From a comparative analysis of the results, it follows that during the test, the surface color of the considered compositions and the standard changed from silver to silver-yellow, as well as single surface damage up to 10 microns without significant corrosion damage.

EXAMPLE 3

Casting characteristics were evaluated in terms of hot brittleness (HB) using "casting harp", where the best indicator is to obtain a casting with the maximum length of the "rod" (figure 2). The hot cracking susceptibility was assessed using the example of alloys 2, 4 and 12 (Table 1). As a comparison, an alloy of the type AD6. The absence of cracks in alloys 2, 4 and 12 (Table 1) is shown, which is a good indicator at the level of most alloys of the Al-Si system, in contrast to the ADC6 alloy, in the casting from which about 40% of the cores were destroyed, starting from the maximum length.

EXAMPLE 4

To evaluate the mechanical properties of alloy 12 (Table 1), plates 2 mm thick were cast by injection molding (HPDC). Casting was carried out with mold vacuuming. The mold temperature was about 150°C. Melt temperature - 710 °C. The results of the tensile test of samples cut from a cast plate are shown in Table 3.

Table 3 - Tensile Test Results of 2mm HPDC Cast Plate (As-Moulded)

Claims

CLAIM

1. Cast alloy based on aluminum with the following distribution of alloying elements, May. %:

Calcium 1.5-5.1

Zinc 0, 1-1, 8

Iron up to 0.7

Silicon up to 1.0 optional, at least one element selected from the group

Manganese 0.2 -2.5

Titanium 0.005-0.1

Zirconium 0.05-0.14

Chrome 0.05-0.15

Aluminum and inevitable impurities - the rest

2. An alloy according to claim 1, characterized in that it contains alloying elements during their next redistribution, May. %:

Calcium 2, 8-5, 0

Manganese 0.2- 1.2

Iron up to 0.5

Silicon up to 1.0

Zinc 0, 1-1, 6

3. An alloy according to claim 1 or 2, characterized in that calcium and zinc are present in it mainly in the form of eutectic particles.

4. An alloy according to any one of claims 1-3, characterized in that it is made in the form of a casting.