RU2554269C1 - Magnesium-based alloy and product made from it - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: magnesium-based alloy contains the following in wt %: zinc 0.1-3.0; zirconium 0.05-0.9; calcium 0.005-0.1; cadmium 0.001-0.004; silicon 0.005-0.05; beryllium 0.0005-0.01; yttrium 3.5-9.5; neodymium 2.01-2.5; lanthanum 0.05-1.5; magnesium - rest.

EFFECT: increased tension strength, yield strength during compression, improved characteristics of weldability, and increased corrosion resistance of the magnesium-based alloy and products made out of it, provided that high strength is kept.

2 cl, 1 ex, 2 tbl

Description

The invention relates to the field of mechanical engineering and aircraft manufacturing, where welded high-strength and heat-resistant magnesium alloys can be used as lightweight structural material for the manufacture of housing compartments, hardware compartments, brackets, armchair parts, dashboards, control panel parts, control system parts, etc. ., as well as in structures operating at high temperatures.

From the prior art (Patent US 6,767,506 B2, publ. 06/27/2004) known alloy based on magnesium and the product made from it, the following chemical composition, wt.%:

Nd 2.7-3.3 Y 0-2.6 Zr 0.2-0.8 Zn 0.2-0.8 Ca 0.03-0.25 Be 0.00-0.001 Fe ≤0.007 Ni ≤0.002 Cu ≤0.003 Si ≤0.01 Mg rest

The disadvantages of this alloy and its products are a low level of strength properties at room temperature (tensile strength ≤320 MPa) with insufficient yield strength (not more than 225 MPa). The alloy has an insufficient level of heat-resistant properties (at 250 ° C tensile strength σ _in = 135-162 MPa), yield strength under compression (≤228 MPa) and does not weld. Thus, the alloy cannot be used for the manufacture of assemblies and parts operating under load or in working areas with elevated (up to 300 ° C) temperature, and cannot be used to obtain welded structures. This leads to a reduction in the range of parts. Products made from this alloy, for example, brackets, rocking chairs, levers, control system parts, elevator, etc., will have insufficient quality and reliability and durability.

Known alloy based on magnesium and the product made of it (International application (PCT) WO 2011117628 publ. 09/29/2011), the following chemical composition wt.%:

Y 0-10 Nd 0-5

In case of joint doping, the sum of Y + Gd should be at least 0.05%

One or more heavy rare earth metals (hereinafter - REM) selected from the group of Ho, Lu, Tm and Tb with their combined content in the range from 0.5% to 5.5%

Gd 0-3.0 Sm 0-0.2

With an optimal ratio, the alloy also contains one or more elements:

Dy 0-8 Zr 0-1,2 Al 0-7.5 Zn and / or Mn in total 0-2 Sc 0-15 In 0-15 Ca 0-3 Er ≤5.5

The combined content of Er, Ho, Lu, Tm and Tb≤5.5 wt.% And the content of one or more rare-earth metals from heavy rare-earth metals other than Y, Nd, Ho, Lu, Tm, Tb, Dy, Gd and Er, amounts to up to 0.5 wt.%; inevitable impurities - up to 0.3 wt.%

Mg Rest

Products made from this alloy, for example, brackets, rocking chairs, levers, control system parts, elevator, etc., will have insufficient reliability and durability.

The disadvantages of this alloy and its products are the low level of strength properties (tensile strength, yield strength) at room and elevated temperatures, insufficient yield strength under compression, and the inability to obtain welded joints. Thus, the alloy cannot be used in the construction of loaded parts and assemblies, as well as parts operating at elevated temperatures. Products made from this alloy, such as parts of the control system, parts of seats, elevator, etc., will have insufficient durability and reliability.

As a prototype (RF Patent No. 2293784, publ. 02.20.2007), an alloy based on magnesium of the following chemical composition, mass% is proposed.

Zn 0.1-2.0 Zr 0.05-0.9 Ca 0.005-0.1 Cd 0.005-2.0 Si 0.005-0.05 Be 0.0005-0.01 Y 3,5-9,0 Gd and / or Dy 0.005-0.3 Mg Rest

The disadvantages of this alloy, known from the prototype, include the fact that it is characterized by insufficiently high values of tensile strength, compressive yield and low corrosion resistance. Welded joints of the alloy known from the prototype are not sufficiently high strength and crack resistance. Thus, products made from a known alloy will be less stable properties, reliability and durability.

The technical result of the invention is to increase the tensile strength, yield strength under compression, to improve the weldability and increase the corrosion resistance of an alloy based on magnesium and products made from it while maintaining high strength at temperatures up to 300 ° C.

To achieve a technical result, an alloy based on magnesium is proposed, containing zinc, zirconium, calcium, cadmium, silicon, beryllium, yttrium, gadolinium and / or dysprosium, characterized in that it additionally contains rare-earth metals, while elements from the cerium subgroup are used as rare-earth metals containing neodymium and lanthanum, in the following ratio of components, wt.%:

A magnesium-based alloy containing zinc, zirconium, calcium, cadmium, silicon, beryllium, yttrium, characterized in that it additionally contains lanthanum, neodymium in the following ratio, wt.%:

Zn 0.1-3.0 Zr 0.05-0.9 Ca 0.005-0.1 Cd 0.001-0.004 Si 0.005-0.05 Be 0.0005-0.01 Y 3,5-9,5 Nd 2.01-2.5 La 0.05-1.5 Mg rest

The authors found that the joint additional introduction of elements selected from the cerium subgroup of rare-earth elements (hereinafter - REE), namely: neodymium, lanthanum, within the stated limits, increases the tensile strength, yield stress under tension, the yield strength under compression, improves weldability while maintaining high alloy strength at temperatures up to 300 ° C.

The authors proved that the joint additional alloying with the neodymium and lanthanum elements of the cesium subgroups of rare-earth metals in the stated limits allows us to enhance the effect of their mutual influence (synergistic effect) on the structure, mechanical and corrosion properties of the alloy and weldability by improving the joint solubility of these elements, mainly α-solid solution. The result is an increase in the microhardness (H _µ ) of α - solid solution from ~ 55 to 85-90 Hv. In addition, the formation of new dispersed intermetallic phases with increased microhardness Hµ ~ 270-300 Hv. As a rule, particles of intermetallic phases are fairly uniformly located in the bulk of the grain and partially along the boundaries. This contributes to hardening of the α-solid solution and grain boundaries, which leads to improved corrosion resistance, increased tensile strength and yield strength, causes an increase in compressive strength. Due to the refinement of the structure (dispersed and fairly uniform distribution of intermetallic phases), narrowing of the crystallization temperature, the properties of welded joints are improved. Moreover, the proposed alloy retains high strength properties at high temperatures.

When using the proposed alloy, it is possible to use welded joints, increasing the resource, reliability and durability of products.

Examples of implementation

The proposed alloy and the alloy known from the prototype were prepared under the same conditions. In a gas furnace using VI-2 flux, in accordance with the calculation of the charge, melts were cast, each weighing 10-15 kg. Received round ingots of each alloy. After turning, round ingots are pressed on a press, made: bars ⌀25 mm, wire ⌀3.5 mm and strips with a cross section of 4 × 65 mm. The strips are cut into dimensional blanks, some of which are butt-welded by argon-arc welding.

The comparative mechanical properties of extruded billets and welded joints of the proposed alloy, alloy - prototype in accordance with GOST 1497-76, GOST 6996-76, GOST 25.503-97 are investigated. The microhardness of the phases and the basic α - solid solution was determined on a PMT - 3 device.

Table 1 shows the compositions of the proposed alloy and prototype alloy, their mechanical and corrosion properties. Table 2 - comparative properties of welded joints using the proposed alloy and prototype alloy as the main alloy and filler material.

Table 2 also shows the properties of the welded joints of the proposed alloy and the alloy known from the prototype when used as an additive for welding high-strength serial alloy based on magnesium grade MA 15.

The comparative mechanical properties of extruded rods of the proposed alloy and prototype alloy are studied in accordance with GOST 1497-84, GOST 25.503-97, GOST 6996-76, and corrosion properties are in accordance with GOST 9.019-74.

The results obtained confirm the advantages of the proposed alloy. In terms of compressive yield strength, the proposed alloy is 33% higher than the alloy known from the prototype, in terms of tensile strength at room temperature and elevated to 300 ° C - by 8.0-8.5%. The proposed alloy has a higher margin of ductility: the relative elongation is 1.3 times greater than that of the alloy known from the prototype. The total corrosion resistance of the proposed alloy, determined by the value of the corrosion rate, is 35-40% higher than that of the alloy known from the prototype.

The advantages of the proposed alloy are clearly confirmed by comparing the main characteristics of welded joints: tensile strength and ν _crit . The value of ν _crit characterizes the minimum rate of deformation (tension) of the alloy hardening during welding, which leads to the appearance of a hot crack in the test section. An increase in ν _crit indicates a decrease in the tendency to crack.

The values of ν _crit for the proposed alloy is 39% higher than that of the welded joint of the prototype alloy, using, respectively, the alloys themselves as additives. Welded joints made using the proposed alloy as a filler material, respectively, exceed the strength by 18% -10% in terms of tensile strength of welded joints of an alloy known from the prior art and the proposed alloy made using an alloy or alloy as a filler material known from the prototype and the proposed alloy.

The use of the proposed alloy as a filler material is more profitable in relation to the serial weldable alloy MA15. In this case, an increase in performance by 7-15% is achieved.

The use of the proposed alloy for the manufacture of welded and non-welded internal units and parts in the design of aircraft, including in service panels, dashboards, equipment compartments, brackets, parts of the control system, operating at room and elevated (up to 300 ° C) temperatures, and also for the manufacture of automobile, motorcycle parts, it will provide an increase in the resource, increase the quality and reliability of these products.

Table 1

Alloy Chemical composition, wt.% Mechanical and corrosion properties, ° С No.
p / p Zn Zr Ca Cd Si Be Y Nd La Gd and / or Dy Mg twenty 300 twenty σ _B σ _0.2 δ σ _B V _corr MPa % MPa g / m ² day one Suggested Alloy 0.10 0.05 0.005 0.001 0.005 0,0005 3,5 2.01 0.05 - The basis 353 232 fourteen 182 14.5 2 1,5 0.47 0,053 0.003 0,028 0.0053 6.5 2.45 0.775 - 349 236 16 180 15.7 3 3.0 0.9 0.10 0.004 0.05 0.01 9.5 2,5 1,5 - 352 230 fifteen 183 14.3 four Prototype alloy 1.05 0.475 0,0525 1.00 0.0275 0.0053 6.3 - - 0.153 325 175 eleven 164 22.8

Claims (2)

1. Magnesium-based alloy containing zinc, zirconium, calcium, cadmium, silicon, beryllium, yttrium, characterized in that it additionally contains lanthanum, neodymium in the following ratio, wt.%:
Zn 0.1-3.0 Zr 0.05-0.9 Ca 0.005-0.1 Cd 0.001-0.004 Si 0.005-0.05 Be 0.0005-0.01 Y 3,5-9,5 Nd 2.01-2.5 La 0.05-1.5 Mg rest 2. A product of an alloy based on magnesium, characterized in that it is made of an alloy according to claim 1.