RU2496899C1 - Method for obtaining boron-containing composite material on aluminium basis - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method for obtaining material in the form of a cast section involves preparation of aluminium melt containing 1-2 wt % of iron and 0.2 - 0.6 wt % of silicon, introduction to the melt at the temperature of 900-1100°°C of boron in the form of boric acid and titanium in the form of chips in the ratio allowing to obtain in cast structure of titanium diboride particles in the amount of 4 to 8 wt %, and crystallisation by casting to a mould.

EFFECT: obtaining boron-containing composite material on aluminium basis, which has high level of absorption of neutron emission in combination with the best mechanical properties and processibility.

5 ex, 2 tbl, 1 dwg

Description

Technical field

The present invention relates to the field of metallurgy, in particular to boron-containing aluminomatrix composite materials, which are required to absorb neutron radiation in combination with a low specific gravity.

State of the art

Alumomatrix composite materials (AKM) containing boron have a unique combination of physical and mechanical properties. Since boron tends to absorb neutron radiation well, they are widely used in nuclear energy [W.K. Barney, G.A. Shemel W.E. Seymour, Nucl. Sci. Eng. 1 (1958) 439-448]. Despite the fact that boron-containing AKMs have been in operation for a long time, their use is associated with a number of problems, in particular, with the technology for their preparation. Since boron has low solubility in liquid aluminum, the classical technologies associated with obtaining a homogeneous melt (without the presence of any solid phases) and the formation of boron-containing compounds during crystallization cannot be practically implemented.

Numerous methods are known for producing boron-containing AKM using powder metallurgy methods. In particular, there is a known method for producing AKM, in which alloys of different systems (1xxx, 3xxx, 6xxx, etc.) are used as an aluminum matrix, and boron carbide (B4C) in the form of a powder 1-60 μm in size (US Pat. US 6602314 B1. Publ. 05.08.03). This method of manufacturing AKM involves sintering under pressure (with preliminary evacuation). The disadvantage of this and all methods associated with powder metallurgy is the difficulty of obtaining large billets intended for rolling. Another disadvantage of this method is that the proposed matrix alloys have a different combination of physicochemical properties, which determines a wide range of characteristics achieved in AKM.

A known method for the production of AKM, developed by Alcan Aluminum Corporation, which includes a liquid-phase process for mixing non-metallic particles into a liquid melt (US Pat. No. 5,531,425 (1996)). According to this method, ingots are obtained in crystallizers, then hot rolling is used to produce plates and sheets. The disadvantage of this method is the difficulty of preventing the clustering of non-metallic particles during the mixing process, which can lead to the formation of an inhomogeneous structure. It should also be noted that the size of non-metallic particles in the AKM is determined by the size of the initial particles and cannot be reduced during mixing into the melt.

Closest to the claimed invention is a method for producing B-containing AKM described in US2008 / 0050270A1 (2008), according to which titanium is introduced into an aluminum melt obtained by melting an industrial aluminum-boron master alloy so as to form a melt whose temperature is maintained in the range from 700 to 850 ° C, particles of titanium diboride (TiB ₂ ), after which crystallization is carried out by casting. In the private claims of this patent, it is proposed to introduce gadolinium and samarium supplements.

This method allows to obtain in the AKM a microstructure with dispersed particles of the TiB ₂ phase, which are formed during the mixing process as a result of phase transformations. However, it requires the use of an aluminum-boron ligature as the initial charge, which leads to a relatively high cost of this process. The presence of gadolinium and samarium additives makes the process even more expensive. The disadvantage of this method is that the original aluminum-boron ligature contains sparingly soluble Al ₂ B particles, which, during aging, can settle to the bottom of the crucible, thus leading to loss of boron.

Disclosure of the invention.

The problem to which the invention is directed, is to provide a method for producing a boron-containing composite material based on aluminum containing boron in an amount of more than 1% in the form of particles of titanium diboride (TiB ₂ ) uniformly distributed in an aluminum matrix. At the same time, the technological process for obtaining such an AKM should be relatively cheap. In particular, it should allow the use of aluminum waste containing more than 1% Fe. and titanium waste in the form of fine chips.

The problem is solved by creating a method for producing a boron-containing composite material based on aluminum in the form of a cast billet, including the preparation of an aluminum melt, introducing boron and titanium into it in the form of solid phases, exposing the melt to form particles of titanium diboride (TiB ₂ ) in it, crystallization by casting, characterized in that

a) from 1 to 2 wt.% iron and from 0.2 to 0.6 wt.% silicon are introduced into the aluminum melt, and its temperature is maintained in the range from 900 to 1100 ° C,

b) boron is introduced into the aluminum melt in the form of boric acid (H ₃ BO ₃ ), and titanium in the form of fine chips in such a ratio that the amount of titanium diboride in the cast structure is from 4 to 8 wt.%.

The essence of the invention is to realize a structure in which there are particles of the phase TiB ₂ in an amount of from 4 to 8 wt.%, Uniformly distributed in an aluminum matrix. In this case, iron should be predominantly bound into skeletal particles of the Al ₈ Fe ₂ Si phase. This structure allows you to provide the best combination of physico-mechanical properties and manufacturability when processing pressure.

The proposed method does not require the use of aluminum-boron alloys containing sparingly soluble Al ₂ B particles. On the other hand, particles of the TiB ₂ phase are formed in the melt during chemical reactions, which contributes to their uniform distribution.

The lower limit on the amount of TiB ₂ phase is chosen in order to achieve the necessary level of absorption of neutron radiation, and the upper limit in order to achieve the required level of manufacturability, in particular, during cold rolling.

Execution examples

For experimental substantiation of the proposed invention, 5 variants of obtaining boron-containing AKM were implemented, which are shown in table 1.

Initially, aluminum melts with different iron and silicon contents were prepared in a RELTEC induction furnace in a graphite chamotte crucible. As the initial charge was used waste alloys 1xxx and 8xxx series (Al-Fe-Si systems). At a given temperature, boric acid was introduced into the aluminum melt in the form of a crystalline powder, and then titanium in the form of fine chips. After mixing, flux treatment and holding at 1000 ° С, the slag was removed, and then pouring into a water-cooled metal mold was performed, obtaining flat ingots with dimensions of 20 × 80 × 200 mm. Next, metallographic, chemical and x-ray phase analyzes were performed. A typical structure of the composite material obtained by option No. 3 (see table 1) is presented in figure 1.

The criterion for the manufacturability of experimental AKMs was the production of cold-deformed sheets up to 1 mm thick with a degree of deformation of at least 80%.

The mechanical properties of the sheets (tensile strength (σ _in ). Yield strength (σ _0.2 ) and elongation (δ)) under uniaxial tension was determined at room temperature on a Zwick Z250 universal testing machine in accordance with GOST 1497-84. The test speed was 10 mm / min, the estimated length of 50 mm.

As can be seen from table 1, only the proposed method for producing AKM (No. 2-4) provides a given content of titanium diboride in the cast billet AKM. In the method No. 1 (the content of iron and silicon in the aluminum melt, as well as the temperature of the latter below the declared limits), the content of titanium diboride in the cast billet AKM below the specified. In addition, the boron content in the AKM obtained by the method No. 1, below 1%, which does not allow to provide the necessary level of absorption of neutron radiation. In the method No. 5 (the content of iron and silicon in the aluminum melt, as well as the temperature of the latter above the stated limits), the content of titanium diboride in the cast billet is higher than the set value, which negatively affects the processability during cold rolling (the billet was destroyed during cold rolling).

Table 1 The parameters of the preparation of experimental AKM and the content of titanium diboride in the cast billet No. Melt Parameters Injectable solids The amount of TiB ₂ in the cast billet, wt.% Fe, wt.% Si, wt.% Temperature ° C H ₃ IN ₃ , wt.% Ti wt.% one 0.5 1,0 800 7 7 1,6 2 1,0 0.2 900 fourteen 1,5 4.1 3 1,5 0.4 1000 21 2.2 6.2 four 2.0 0.6 1100 28 3.0 7.9 5 3.0 1,0 1200 35 4.0 9.3

The assessment of tensile mechanical properties was carried out on AKM sheets tormented according to option No. 3. The results shown in table 2 show that the proposed method allows to obtain sufficient strength, both in the cured and annealed conditions.

table 2 Typical mechanical properties of sheets of experimental AKM obtained according to option No. 3 (table 1) condition σ _0.2 , MPa σ _in , MPa δ,% caked 200 225 2.0 annealed 120 155 11.6

Claims (1)

A method of producing a boron-containing composite material based on aluminum in the form of a cast billet, comprising preparing an aluminum melt, introducing boron and titanium into it with the formation of particles of titanium diboride (TiB ₂ ) in it, crystallization by casting in a mold, characterized in that the aluminum melt is prepared, containing from 1 to 2 wt.% iron and from 0.2 to 0.6 wt.% silicon, and maintain its temperature in the range from 900 to 1100 ° C, boron is introduced into the obtained melt in the form of boric acid (H ₃ BO ₃ ), and titanium in the form of fine chips in such a ratio shenii that the amount of titanium diboride formed in the cast structure is from 4 to 8 wt.%.

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