CN104294109B - Samarium and/or gadolinium-containing heat-resisting cast aluminum alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a heat-resistant cast aluminum alloy containing samarium and/or gadolinium and a preparation method thereof. 1.0%, Mn 0.10-0.50%, Cu 0.01-2%, Ti 0.01-0.2%, impurity element ≤ 0.15%, and the balance is Al. The addition of Gd or Sm elements can refine the grains, increase the yield strength of the alloy, and at the same time generate stable granular Al ₂ Gd or Al ₂ Sm phases near the grain boundaries of the alloy, which can strengthen the grain boundaries and improve the alloy's strength. High temperature creep resistance.

Description

Heat-resistant cast aluminum alloy containing samarium and/or gadolinium and its preparation method

technical field

The invention belongs to the field of metallurgy, and in particular relates to a heat-resistant casting aluminum alloy containing samarium and/or gadolinium and a preparation method thereof.

Background technique

At present, lightweight has gradually become the development direction of modern automobiles, and aluminum alloy, as the most widely used light alloy, will be more widely used in the automobile industry. At present, the aluminum alloy parts of the automotive power system are basically castings. Among the existing cast aluminum alloys, alloys such as A319 and A356 are the most widely used. These aluminum alloys have excellent casting properties, especially excellent mechanical properties at temperatures below 225°C.

With the improvement of fuel economy requirements for automobiles, high power density automobile engines will surely become the mainstream of future automobile engines, but this type of engine must work at a temperature higher than 250°C, but when the temperature exceeds 250°C, the existing problems are The creep performance of the alloy drops sharply, so that it cannot meet the power demand. The heat-resistant aluminum alloys for automobiles currently being researched and developed mainly include alloy systems such as Al-Si and Al-Cu. In the article "The effects of manganese on the T-phase and creep resistance in Al _- Si-Cu-Mg-Ni alloys" published in the journal "Materials Science &EngineeringA" in 2013 by AR _Farkoosh et al. _0.3 Mg _(0.3-1) Adding 0.3% manganese by weight to the Ni alloy improves the plasticity and thermal stability of the T-Al ₉ FeNi phase, making the alloy creep at 300°C and 20MPa after 300 hours reduced to 0.2%. However, since there are many T-Al ₉ FeNi phases in the alloy, and this phase is easily broken under high temperature stress, it seriously affects the heat resistance of the alloy.

Contents of the invention

In view of this, one of the objects of the present invention is to provide a heat-resistant cast aluminum alloy containing samarium and/or gadolinium, the yield strength of the aluminum alloy is enhanced by adding samarium and/or gadolinium, and the alloy has a solid solution strengthening effect , effectively improving the high temperature performance of the alloy; the invention also provides a preparation method of the above alloy.

Technical scheme of the present invention is as follows:

Heat-resistant cast aluminum alloy containing samarium and/or gadolinium, each component by weight percentage is: Si 5.0-8.0%, Mg 0.20-0.50%, Gd and/or Sm 0.1-1.0%, Mn 0.10-0.50%, Cu 0.01-2%, Ti 0.01-0.2%, impurity element ≤ 0.15%, and the balance is Al.

Preferably, the components by weight percentage are: Si 6.2%, Mg 0.34%, Gd 0.7%, Sm 0.7%, Mn 0.33%, Cu 1.5%, Ti 0.12%, impurity elements ≤ 0.15%, and the balance is Al.

Preferably, the components by weight percentage are: Si 7%, Mg 0.31%, Gd 0.5%, Mn 0.1%, Cu 0.1%, Ti 0.18%, impurity elements≤0.15%, and the balance is Al.

Preferably, the components by weight percentage are: Si 5.2%, Mg 0.45%, Gd 0.9%, Mn 0.2%, Cu 1.9%, Ti 0.1%, impurity elements≤0.15%, and the balance is Al.

Preferably, the components by weight percentage are: Si 5.8%, Mg 0.4%, Sm 0.9%, Mn 0.21%, Cu 0.02%, Ti 0.16%, impurity elements≤0.15%, and the balance is Al.

Preferably, the weight percentage of each element in the impurity elements is ≤0.05%.

Preferably, the impurity element includes Fe element.

The present invention also provides a method for preparing the above-mentioned heat-resistant cast aluminum alloy containing samarium and/or gadolinium. Mn master alloy, then continue to heat to 750 ° C, add Al-Gd and/or Al-Sm master alloy, and Al-Cu master alloy and Al-Ti master alloy, then keep warm and stir, until the alloy is completely dissolved, mix and mix Refining for 30 minutes, finally cooling down to 680-700°C and then casting.

The beneficial effect of the present invention is that the addition of Gd or Sm elements can refine the grains, improve the yield strength of the alloy, and at the same time generate stable granular Al ₂ Gd or Al ₂ Sm phases near the grain boundaries of the alloy to play a role in precipitation strengthening. Effect, improve the room temperature tensile properties and high temperature creep resistance of the alloy. In addition, the addition of Si can improve the casting properties of the alloy, and the combination of Si and Fe can also improve the tensile properties of the alloy; the addition of Cu can improve the room temperature tensile properties and high temperature creep resistance of the alloy; the addition of Ti can refine the grain size. particles, improve the tensile properties of the alloy at room temperature. In the present invention, through the above metal-organic combination, the alloy crystal grains prepared can be smaller than 20 μm, and the shape and size of eutectic Si are significantly improved.

Because the prepared alloy has good casting performance and can work stably under the condition of 250-275°C and 50MPa, it is possible to widely apply the alloy in the automobile industry.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings:

The metal mold schematic diagram that Fig. 1 alloy casting adopts;

The metallographic diagram of the alloy described in Fig. 2 embodiment 1;

The metallographic diagram of the alloy described in Fig. 3 embodiment 2;

The metallographic diagram of the alloy described in Fig. 4 embodiment 3;

The metallographic diagram of the alloy described in Fig. 5 embodiment 4.

detailed description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. For the experimental methods that do not specify specific conditions in the examples, usually follow the conventional conditions or the conditions suggested by the manufacturer.

The alloy preparation method is as follows:

Add Al-Si master alloy and Al-Mn master alloy after heating industrial pure aluminum to 700-715°C, then continue heating to 750°C, add Al-Gd and/or Al-Sm master alloy, and Al-Cu master alloy Alloy and Al-Ti master alloy, then keep warm and stir, after the alloy is completely dissolved, mix and refine for 30 minutes, finally cool down to 680-700°C and cast. Each embodiment and the composition of the A356 alloy are shown in the table below, and the composition content is expressed in weight percentage.

Si Cu Gd SM Mg Ti mn Impurity elements al Example 1 7% 0.1% 0.5% 0 0.31% 0.18% 0.1% ≤0.15% margin Example 2 5.2% 1.9% 0.9% 0 0.45% 0.1% 0.2% ≤0.15%, Fe is 0.01% margin Example 3 5.8% 0.02% 0 0.9% 0.4% 0.16% 0.21% ≤0.15%, Fe is 0.01% margin Example 4 6.2% 1.5% 0.7% 0.7% 0.34% 0.12% 0.33% ≤0.15%, Fe is 0.012% margin A356 7% 0.01% 0 0 0.35% 0.01% 0.1% ≤0.15%, Fe is 0.01% margin

The room temperature tensile strength of the A356 alloy is 273MPa, the yield strength is 241MPa, and the elongation is 2.5%; at 250°C, the yield strength is 184MPa, and the elongation is 3.9%; at 250°C, 50MPa, the 100-hour creep value is 0.24 %.

The metallographic diagram of the alloy described in Example 1 is as shown in Figure 2, the tensile strength of the alloy at room temperature is 307MPa, the yield strength is 258MPa, and the elongation is 2.1%; at 250°C, the yield strength is 204MPa, and the elongation is 3.9%; At 250°C and 50MPa, the 100-hour creep is 0.06%; at 275°C and 50MPa, the 100-hour creep is 0.09%, and the second phase Al ₂ Gd with a high melting point formed on the grain boundary can hinder Grain boundary sliding during creep improves creep resistance.

The metallographic diagram of the alloy described in Example 2 is shown in Figure 3, the tensile strength of the alloy at room temperature is 296MPa, the yield strength is 245MPa, and the elongation is 1.8%; at 250°C, the yield strength is 194MPa, and the elongation is 3.6%; At 250°C and 50MPa, the creep value for 100 hours is 0.04%, and at 275°C and 50MPa, the creep value for 100 hours is 0.07%. The second phase Al ₂ Gd with high melting point formed on the grain boundary can hinder the grain boundary sliding during the creep process and improve the creep resistance.

The metallographic diagram of the alloy described in Example 3 is as shown in Figure 4, the tensile strength of the alloy at room temperature is 301MPa, the yield strength is 260MPa, and the elongation is 1.5%; at 250°C, the yield strength is 213MPa, and the elongation is 2.9%; At 250°C and 50MPa, the creep value for 100 hours is 0.05%; at 275°C and 50MPa, the creep value for 100 hours is 0.09%. The formation of the second phases Al ₂ Gd and Al ₂ Sm with high melting point on the grain boundaries can hinder the grain boundary sliding during the creep process and improve the creep resistance.

The metallographic diagram of the alloy described in Example 4 is shown in Figure 5. The room temperature tensile strength of the alloy is 307MPa, the yield strength is 258MPa, and the elongation is 6.5%; at 250°C, the yield strength is 204MPa, and the elongation is 8.9%; At 250°C and 50MPa, the creep value for 100 hours is 0.06%; at 275°C and 50MPa, the creep value for 100 hours is 0.09%. The formation of the second phases Al ₂ Gd and Al ₂ Sm with high melting point on the grain boundaries can hinder the grain boundary sliding during the creep process and improve the creep resistance.

Compared with A356, the high-temperature (250°C) tensile performance and creep resistance performance of the alloy prepared by the invention are significantly improved. This is because the formation of the second phases Al ₂ Gd and Al ₂ Sm with high melting points on the grain boundaries can hinder the grain boundary sliding during the creep process and significantly improve the creep resistance of the alloy.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (6)

1. A heat-resistant cast aluminum alloy, characterized in that, each component is by weight percentage: Si 6.2%, Mg 0.34%, Gd 0.7%, Sm 0.7%, Mn 0.33%, Cu 1.5%, Ti 0.12%, Impurity elements ≤ 0.15%, the balance is Al. 2. A heat-resistant cast aluminum alloy, characterized in that the components by weight percentage are: Si 5.2%, Mg 0.45%, Gd 0.9%, Mn 0.2%, Cu 1.9%, Ti 0.1%, impurity elements ≤ 0.15 %, the balance is Al. 3. A heat-resistant cast aluminum alloy, characterized in that the components by weight percentage are: Si 5.8%, Mg 0.4%, Sm 0.9%, Mn 0.21%, Cu 0.02%, Ti 0.16%, impurity elements ≤ 0.15 %, the balance is Al. 4. A heat-resistant cast aluminum alloy according to any one of claims 1-3, characterized in that the weight percentage of each element in the impurity elements is ≤0.05%. 5. A heat-resistant cast aluminum alloy according to claim 4, characterized in that the impurity element includes Fe element. 6. The method for preparing a heat-resistant cast aluminum alloy according to any one of claims 1-5, characterized in that the specific steps are: heating industrial pure aluminum to 700~715°C, and then adding Al-Si master alloy and Al-Mn master alloy, then continue to heat to 750°C and add Al-Gd and/or Al-Sm master alloy, as well as Al-Cu master alloy and Al-Ti master alloy, then keep warm and stir until the alloy is completely dissolved Mix and refine for 30 minutes, finally cool down to 680-700°C and cast.