RU2496902C1 - Aluminium-matrix composite material with boron-containing filler - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: composite material contains copper, manganese, zirconium, iron, silicon and boron, and has a structure consisting of solid aluminium solution and phases uniformly distributed in it at their further ratio in solid solution, wt %: 6-15 B₄C, 2-6 Al₁₅(Fe,Mn)₃Si₂, 2-6 Al₂₀Cu₂Mn₃, 0.4-0.8 Al₃Zr.

EFFECT: increasing heat resistance of material to heating processes at sufficient level of mechanical properties.

2 cl, 1 tbl, 5 ex

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, in particular in the form of compound B ₄ C, have a unique combination of physical and mechanical properties. Since boron has the ability to absorb neutron radiation well, they are widely used in nuclear energy [WK Barney, GA Shemel, WE 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, for example, susceptibility to corrosion and the problem of inhomogeneity of structure. A promising method for their production, which has a positive effect on the properties of the material used in radiation protective structures, is mechanical alloying [RM Mohanty, K. Balasubramanian, SK Seshadri, // Materials Science and Engineering - 2007. - V.A498. - P.42-52; M. Khakbiz, F. Ahlaghi, // Journal of Alloys and Compounds - 2009. - V.479 - P.334-341].

Known patent GB 2361934 A (publ. 01.03.2001), which describes AKM, based on an alloy of the Al-Mg-Mn system containing boron in an amount of 0.5-10 wt.% And having neutron-absorbing properties. Boron is introduced into aluminum in the form of a compound (boride) with a particle size of not more than 300 microns. In addition to aluminum and boron, AKM contains magnesium, manganese, silicon, and copper in an amount of 0-50 atomic%. A method of manufacturing an alloy is casting, followed by rolling or forging at a temperature of 250-600 ° C or extrusion at a temperature of 400-550 ° C. The disadvantage of this AKM is the presence of magnesium in the composition, which adversely affects the technological properties of the material, due to increased oxidation during processing.

Also known AKM, consisting of an aluminum matrix and boron-containing filler in an amount of 1.5-9 wt.% (US Pat. US 6602314 B1, publ. 05.08.03). As matrix alloys are proposed: technical aluminum (1xxx series), Al-Mn (3xxx series), Al-Mg-Si (6xxx series), Al-Zn-Mg (7xxx series), Al-Fe (with an iron content of 1 -10 wt.%), And boron carbide as a boron-containing filler. The sizes of the initial powders of the aluminum matrix 5-150 microns and boron carbide 1-60 microns. A method of manufacturing a composite material is sintering under pressure, with preliminary evacuation. The disadvantage of this AKM is that the proposed matrix alloys have a different combination of physicochemical properties, which determines a wide range of characteristics achieved in AKM.

Closest to the claimed invention is AKM, described in patent US 7177384 B2 (publ. 13.02.07). This AKM consists of an aluminum matrix and a boron-containing filler. An alloy of the 6xxx series based on the Al-Mg-Si system is proposed as a matrix. And as a boron-containing filler, boron carbide B ₄ C or boron oxide B ₂ O _{3 is used} , the amount of boron in the material varies from 1.5 to 9 wt.%. Also stipulated is the introduction of titanium powders in an amount of 0.2-4.0 wt.% And / or zirconium in an amount of 0.2-2.0 wt.% In the mixture before sintering. A method of manufacturing a composite material is sintering under pressure, with preliminary evacuation, at a temperature of 350-550 ° C and holding for 5-10 minutes. The disadvantage of this alloy is the limited heat resistance. This is due to the fact that alloys of the 6xxx series are greatly softened when heated above 200 ° C. In addition, the production of this AKM requires the use of primary materials in the form of a powder.

Disclosure of invention

The task to which the claimed invention is directed is to create an aluminomatrix composite material containing at least 4 wt.% Boron and having high heat resistance (to heat up to 350 ° C) with a sufficient level of mechanical properties and the possibility of its preparation based on secondary raw materials in the form shavings.

The problem is solved by creating a boron-containing aluminomatrix composite material based on an aluminum alloy containing copper, manganese, zirconium, iron, silicon and boron carbide (B ₄ C), with a hardness of more than 2.7 GPa and characterized by a structure consisting of aluminum solid solution and uniformly the particles of phases B ₄ C, Al ₁₅ (Fe, Mn) ₃ Si ₂ , Al ₂₀ Cu ₂ Mn ₃ and Al ₃ Zr distributed in it, with the following quantity:

Phase Mass fraction,% At _{4 s} 6-15 Al ₁₅ (Fe, Mn) ₃ Si ₂ 2-6 Al ₂₀ Cu ₂ Mn ₃ 2-6 Al ₃ Zr 0.4-0.8

The proposed AKM can be made in the form of deformed semi-finished products in which, after heating at 350 ° C for 10 hours, the following tensile properties are achieved: tensile strength (σ _in ) - at least 450 MPa, yield strength (σ _0.2 ) - not less than 400 MPa, elongation (δ) - not less than 4%.

The technology for producing AKM includes the following main steps:

1) preparation of a matrix melt based on aluminum;

2) obtaining a cast billet by crystallization of the melt;

3) obtaining chips by machining cast billets;

4) grinding chips to the size of flakes no more than 4 mm in diameter;

5) obtaining composite granules by mechanical alloying of crushed chips and boron carbide powder;

6) obtaining AKM by extrusion of composite granules.

The essence of the invention is to realize a structure with uniformly distributed particles of thermally stable phases. This structure allows you to provide the best combination of physico-mechanical properties and manufacturability.

The lower limit on boron carbide is chosen in order to achieve the necessary level of absorption of neutron radiation, and the upper limit is in order to provide the necessary level of manufacturability. Since in the process of mechanical alloying (ML) the B ₄ C phase does not interact with the aluminum alloy, its amount is determined by the introduction of ML before the start of the process.

The Al ₁₅ (Fe, Mn) ₃ Si ₂ phase is formed during the crystallization of the matrix aluminum alloy. Its amount is determined by the ratio of manganese, iron and silicon in this alloy. At further technological stages, only a change in the morphology of particles of this phase occurs.

The phases Al ₂₀ Cu ₂ Mn ₃ and Al ₃ Zr are formed in the form of secondary precipitates during the process of heating before extrusion. Their quantities are determined by both the composition of the aluminum alloy and the process parameters.

Execution examples

For experimental substantiation of the proposed invention, AKMs based on 5 aluminum alloys with different contents of copper, manganese, zirconium, iron and silicon were prepared. Alloys (in the form of flat ingots with dimensions of 15 × 60 × 180 mm) were prepared in an electric resistance furnace in graphite chamotte crucibles based on waste aluminum wire grade A5E and other branded aluminum alloys, as well as double alloys (Al-Mn and Al-Zr). Next, the chips obtained by turning the ingots were used.

To obtain AKM, we used: a) shavings of matrix alloys in the form of thin flakes with a width of not more than 4 mm and a thickness of 0.5 mm; b) boron carbide powder (B ₄ C) with an average particle size of about 100 microns. The initial chips and powder were ground, and then loaded into a planetary mill to carry out the ML process. Next, the granules were compacted and then extruded on a press to obtain a preform with a diameter of 25 mm and a height of 10 mm. Sheet metal was also made from pressed blanks to determine the tensile mechanical properties.

Metallographic studies were performed using light (NEOPHOT 32) and electron (HITACHI TM1000) microscopy. The phase composition of the samples was determined using x-ray analysis (DRON-4.0-07) and local chemical analysis (JEOL JSM-6610LV with the local microanalysis system INCA).

Mechanical properties (tensile strength (σ _in ), yield strength (σ _0.2 ) and elongation (δ)) under uniaxial tension (according to GOST 1497-84) and Vickers hardness measurement (according to GOST 2999-75) were determined at room temperature on the Zwick Z250 universal testing machine and the Wilson Wolpert 930N universal hardness tester, respectively.

As can be seen from table 1, only the proposed AKM (No. 2-4) provides a high combination of hardness, heat resistance and manufacturability. In AKM containing particles of phases B ₄ C, Al ₁₅ (Fe, Mn) ₃ Si ₂ , Al ₂₀ Cu ₂ Mn ₃ and Al ₃ Zr below the stated limits (No. 1), the required level of hardness is not achieved. The presence of these phases above the declared limits (No. 5) leads to an unacceptable decrease in manufacturability (destruction during extrusion).

Table 1 Structural characteristics of experimental AKM and hardness values before and after heating No. Mass fraction of phase,% Hardness, HV ¹ GPa At _{4 s} Al ₁₅ (Fe, Mn) ₃ Si ₂ Al ₂₀ Cu ₂ Mn ₃ Al ₃ Zr Hv ₀ Hv ₃₅₀ ΔHV one 3 (2,3) ² one one 0.2 1.4 0.8 0.6 2 6 (4.7) 2 6 0.8 2,8 2.6 0.2 3 10 (7.8) four four 0.6 3.0 2,8 0.2 four 15 (11.7) 6 2 0.4 3.2 3,1 0.1 5 20 (15.7) 8 8 1,0 The destruction of the workpiece during extrusion ¹ HV ₀ - hardness in the initial state; HV ₃₅₀ - hardness after heating at 350 ° C for 10 hours; ΔHV - change in hardness ² boron content in AKM, wt.%

Using composition No. 2 as an example, the tensile properties of 2 mm of the sheet annealed at 350 ° C for 10 hours were determined. The results show that the following average uniaxial tensile properties are achieved in deformed semi-finished products: tensile strength (σ _in ) - 465 MPa, yield strength (σ _0.2 ) - 420 MPa, elongation (δ) - 4.2%.

Claims (2)

1. An aluminum matrix composite material based on an aluminum alloy containing copper, manganese, zirconium, iron, silicon, boron, characterized in that it has a hardness of more than 2.7 GPa and is characterized by a structure consisting of an aluminum solid solution and particles uniformly distributed in it phases B ₄ C, Al ₁₅ (Fe, Mn) ₃ Si ₂ , Al ₂₀ Cu ₂ Mn ₃ and Al ₃ Zr in the following ratio in solid solution, wt.%:
B ₄ C 6-15 Al ₁₅ (Fe, Mn) ₃ Si ₂ 2-6 Al ₂₀ Cu ₂ Mn ₃ 2-6 Al ₃ Zr 0.4-0.8 2. The aluminomatric composite material according to claim 1, characterized in that it is made in the form of deformed semi-finished products, which after heating at 350 ° C for 10 hours have a temporary resistance (σ _in ) of at least 450 MPa, yield strength (σ _{0, 2} ) at least 400 MPa, elongation (δ) of at least 4%.