CN115323230B - Aluminum-copper-cerium series heat-resistant aluminum alloy and preparation method thereof - Google Patents

Abstract

The invention discloses an aluminum-copper-cerium-based heat-resistant aluminum alloy and a preparation method thereof, comprising Cu 6%-9%, Ce 0.75%-1.5%, Mn 0.5%-1.2%, RE 0.05%- 0.4%, Zr 0.1% ~ 0.5%, the balance is Al, which solves the problem that the θ′-Al ₂ Cu precipitate phase in copper-containing aluminum alloys is easy to coarsen at 300 ° C ~ 350 ° C, and then gradually loses the strengthening effect, resulting in the alloy For the outstanding problem of limited high-temperature life, the volume fraction ratio of the eutectic phase and the precipitated phase has been adjusted, which has significantly improved the long-term service ability of heat-resistant cast aluminum alloys at high temperatures. The enduring strength of 400h at 300°C is 90MPa, and the enduring strength of 100h at 350°C is greater than 70MPa.

Description

A kind of aluminum-copper-cerium heat-resistant aluminum alloy and preparation method thereof

technical field

The invention relates to the field of metal materials, in particular to an aluminum-copper-cerium heat-resistant aluminum alloy and a preparation method thereof.

Background technique

In recent years, the rapid development of aerospace and transportation has put forward a realistic demand for aluminum alloy materials that can serve at higher temperatures. For example, aluminum alloys are used to cast parts such as automobile engine blocks and cylinder heads. However, driven by the improvement of gas engine efficiency and emission standards, the engine needs to further increase the combustion pressure, which means that the operating temperature of the gas turbine will be higher than 250 °C, which exceeds the heat resistance limit of the currently used Al-Si system. In aerospace and other fields, titanium alloy materials are currently mainly used in the temperature range of 250°C to 350°C. If titanium alloy components can be replaced by aluminum alloy materials that have been in stable service for a long time in the temperature range of 250°C to 350°C, the aircraft can be reduced. important design indicators.

At present, the most widely used heat-resistant aluminum alloys in my country are mainly 2-series cast aluminum alloys represented by ZL204A, ZL205A, ZL206, ZL207 and ZL208. Foreign countries mainly include A201, 206 and RR350 alloys in the United States. The mechanical performance indicators that characterize the long-term service ability of materials at high temperatures are mainly high-temperature enduring strength or high-temperature creep strength. Among the above alloys, my country's ZL206 alloy has the best high-temperature enduring strength and creep strength. The chemical composition of ZL206 is Cu: 7.6~8.4wt.%, RE: 1.5~2.3wt.%, Mn: 0.7~1.1wt.%, Zr: 0.1~0.25wt.%, Al is the balance, and RE is mixed rare earth. In the T6 state, the enduring strength of 400h at 300°C is about 60MPa, and the enduring strength of 100h at 350°C is about 50MPa. At 300°C to 350°C, there is a sharp increase in creep rate and a sharp decrease in creep enduring strength. question. The existing high-temperature durable strength performance indicators of aluminum alloy materials have been difficult to meet the latest needs of the current automotive and aerospace fields.

Contents of the invention

Aiming at the outstanding problems that the existing heat-resistant cast aluminum alloys have a sharp increase in creep rate and a sharp decrease in creep durable strength at 300°C to 350°C, the invention provides an aluminum-copper-cerium-based heat-resistant aluminum alloy and a preparation method thereof , significantly improving the long-term service capability of heat-resistant cast aluminum alloys at high temperatures.

The present invention is achieved through the following technical solutions:

An aluminum-copper-cerium heat-resistant aluminum alloy, including Cu 6%-9%, Ce 0.75%-1.5%, Mn 0.5%-1.2%, RE 0.05%-0.4%, Zr 0.1%-0.5% by mass percentage %, the balance is Al.

Preferably, the ratio of Cu and Ce is (4-8):1.

Preferably, the RE is at least one of Y, Er, Sc and Yb.

A method for preparing an aluminum-copper-cerium-based heat-resistant aluminum alloy, comprising the following steps:

Step 1. Heat the aluminum alloy ingot at 200°C-300°C for 12h-48h, then raise the temperature to 400°C-500°C for 5h-15h;

Step 2. Heat the aluminum alloy ingot in step 1 at 520° C. to 537° C. for 5 hours to 30 hours and then quench it;

Step 3, heat the aluminum alloy ingot obtained in step 2 at 150°C-200°C for 5h-30h, then raise the temperature to 250°C-300°C for more than 1h, then cool to room temperature to obtain aluminum-copper-cerium-based heat-resistant aluminum alloy.

Preferably, in step 1, an intermediate alloy of elemental aluminum and aluminum alloy is used to prepare an aluminum alloy ingot by melting.

Preferably, the quenching treatment in step 2 is water quenching.

Preferably, the cooling method described in step 3 is air cooling.

Compared with the prior art, the present invention has the following beneficial technical effects:

The invention provides an aluminum-copper-cerium-based heat-resistant aluminum alloy. By controlling the ratio of copper and cerium elements and adding rare earth elements to the aluminum alloy, the long-term service ability of the heat-resistant cast aluminum alloy at high temperature is significantly improved. Its enduring strength at 300°C for 100h is greater than 100MPa, its enduring strength at 300°C for 400h is 90MPa, and its enduring strength at 350°C for 100h is greater than 70MPa.

In the preparation process of the aluminum-copper-cerium heat-resistant aluminum alloy, high-density RE element solute atomic clusters are formed by 200°C-300°C/12h-48h solid solution pretreatment, and 400°C-500°C/5h-15h solid solution pretreatment Treatment, using high-density RE solute atomic clusters as heterogeneous nucleation particles to form high-density Al ₃ Zr nano-precipitated phases, using 520°C to 537°C solid solution treatment to remelt Al ₂ Cu intermetallic compounds, and ensure high-density Al ₃ The Zr nano-precipitation phase is not significantly coarsened, and the 150℃～200℃/5h～30h+250℃～300℃/>1h double-stage aging treatment process is adopted, and the Al ₃ Zr nanoprecipitation phase is used as the heterogeneous nucleation particle to precipitate θ′ -Al ₂ Cu precipitation phase, and promote the segregation of RE and Zr elements at the interface of θ′-Al ₂ Cu precipitation phase, forming a “diffusion barrier layer”, which greatly improves the temperature of θ′-Al ₂ Cu precipitation phase at 300℃～350℃ Excellent thermal stability, which solves the prominent problem that the θ′-Al ₂ Cu precipitate phase in copper-containing aluminum alloys is easy to coarsen at 300 ° C to 350 ° C, and then gradually loses the strengthening effect, resulting in a limited high-temperature service life of the alloy.

Further, the ratio of Cu:Ce should be 4:1 to 8:1, preferably 5.3:1, to optimize the volume fraction ratio of nano-precipitated phase and micro-crystalline phase, wherein the nano-precipitated phase is Cu-containing θ′-Al ₂ Cu precipitated phase, the micron crystalline phase is Cu-containing Al ₂₀ Cu ₂ Mn ₃ , Al ₈ Cu ₄ Ce, Al ₂₄ Cu ₈ Ce ₃ Mn phase, the mechanism of θ′-Al ₂ Cu nano-precipitated phase improving high temperature creep resistance In order to hinder dislocation climbing, the mechanism of micron crystal phase to improve high temperature creep resistance is load transfer. In the case of a certain Cu content, the volume fractions of the Cu-containing nano-precipitated phase and the Cu-containing micro-crystalline phase will ebb and flow, and the relative content is controlled by the Cu:Ce ratio. The preferred Cu:Ce ratio makes the θ′-Al ₂ Cu nano The volume fraction of the precipitated phase and the micro-crystalline phase is reasonably matched, so that the two strengthening mechanisms of hindering dislocation climbing and load transfer can produce the best synergistic effect and improve the high-temperature mechanical properties.

Description of drawings

Figure 1 shows the durability test data of the aluminum-copper-cerium heat-resistant aluminum alloy of the present invention at 300°C, and its comparison with ZL201A, ZL206 and ZL207 alloys.

Fig. 2 is the endurance strength test data of the aluminum-copper-cerium-based heat-resistant aluminum alloy of the present invention at 350°C, and its comparison with ZL206 and ZL207 alloys.

Fig. 3 is a photo of the metallographic microstructure of the aluminum-copper-cerium-based heat-resistant aluminum alloy of the present invention, which shows micron-scale crystal phases.

Fig. 4 is a transmission electron micrograph of the aluminum-copper-cerium-based heat-resistant aluminum alloy of the present invention, which shows a nanoscale θ'-Al ₂ Cu precipitated phase.

Fig. 5 is a high-resolution electron micrograph of the aluminum-copper-cerium-based heat-resistant aluminum alloy of the present invention, which shows the segregated structure at the θ'-Al ₂ Cu interface, that is, the "diffusion barrier layer".

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings, which are explanations rather than limitations of the present invention.

An aluminum-copper-cerium heat-resistant aluminum alloy, including Cu 6%-9%, Ce 0.75%-1.5%, Mn 0.5%-1.2%, RE 0.05%-0.4%, Zr 0.1%-0.5% by mass percentage %, the balance is Al.

The RE is a rare earth, specifically one or more of Y, Er, Sc, and Yb.

The ratio of Cu and Ce is (4-8):1, preferably 5.3:1.

The preparation method of the above-mentioned aluminum-copper-cerium heat-resistant aluminum alloy comprises the following steps:

Step 1. According to the mass percentage of aluminum-copper-cerium series heat-resistant aluminum alloy, aluminum and intermediate alloy are prepared, and aluminum alloy ingot is prepared by smelting. The specific method is as follows:

The raw materials are smelted in a resistance furnace, and then the aluminum alloy solution is poured into a mold to form an aluminum alloy ingot after the aluminum alloy solution is fed with an inert gas for refining degassing and slag removal.

The inert gas is nitrogen or argon.

Step 2, performing multi-stage solid solution pretreatment on the aluminum alloy ingot obtained in step 1, the method is as follows:

S21. Heat the aluminum alloy ingot at 200°C-300°C for 12h-48h to form high-density RE element solute atomic clusters (number density greater than 10 ²⁴ m ^-3 ), which are used as heterogeneous nucleation points for Al ₃ Zr phase.

S22. Heat the aluminum alloy ingot obtained in step S21 at 400° C. to 500° C. for 5 hours to 15 hours to form an Al ₃ Zr nano-precipitate phase with high-density RE solute atomic clusters as the core.

Step 3, performing solution treatment and aging treatment on the aluminum alloy ingot obtained in step 2 to obtain an aluminum-copper-cerium heat-resistant aluminum alloy, the specific method is as follows:

S31. Heat the aluminum alloy ingot at 520° C. to 537° C. for 5 hours to 30 hours, and then perform quenching to complete solution treatment, so that the copper-containing intermetallic compound formed during the solidification process is melted back into the aluminum matrix.

S32. Heat the aluminum alloy ingot obtained in step S31 at 150°C-200°C for 5h-30h, then raise the temperature to 250°C-300°C for more than 1h, then air-cool to room temperature, and complete the aging treatment to obtain aluminum-copper-cerium series Heat-resistant aluminum alloy.

The alloy of the present invention uses the Al ₃ Zr nano-precipitation phase as the heterogeneous nucleation particle to precipitate the θ′-Al ₂ Cu precipitation phase, and promote the segregation of RE and Zr elements at the interface of the θ′-Al ₂ Cu precipitation phase to form a “diffusion barrier layer ”, greatly improving the thermal stability of the θ′-Al ₂ Cu precipitated phase at 300°C to 350°C.

Example 1

An aluminum-copper-cerium-based heat-resistant aluminum alloy, comprising 7% Cu, 1% Ce, 0.8% Mn, 0.085% RE, 0.17% Zr, and the balance is aluminum.

The preparation method of the aluminum-copper-cerium heat-resistant aluminum alloy is as follows, comprising the following steps:

Step 1. Prepare aluminum and intermediate alloys according to the above mass percentages, and prepare aluminum alloy ingots by smelting. The specific method is as follows:

S11. Melting Al and Al-Mn master alloys in graphite crucibles in a resistance furnace, and keeping the temperature at 720°C-820°C for 2.5h;

S12. Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the metal solution in step S11 for melting, and keep warm at 720°C-820°C for 1.5h;

S13. At 700°C-720°C, pour argon into the aluminum alloy solution obtained in step S12 for refining and degassing, and then put the aluminum alloy solution into a sand mold to form an aluminum alloy ingot after standing still for slag removal.

Step 2. Heat the aluminum alloy ingot at 200°C for 24 hours, then raise the temperature to 500°C for 12 hours.

Step 3. Heat the aluminum alloy ingot obtained in step 2 at 530°C for 15 hours, then perform water quenching, then heat the obtained aluminum alloy ingot at 150°C for 18 hours, then heat it up to 250°C for 50 hours, and then air cool to room temperature to obtain aluminum-copper-cerium heat-resistant aluminum alloy.

The obtained aluminum copper cerium series heat-resistant aluminum alloy is subjected to performance test, and the test index is as follows:

The aluminum-copper-cerium heat-resistant aluminum alloy has a durable strength of 100 MPa at 300° C., a tensile strength of 165 MPa at 300° C., a yield strength of 132 MPa, and an elongation of 8%.

The aluminum-copper-cerium-based heat-resistant aluminum alloy has a durable strength of 60 MPa at 350° C., a tensile strength of 121 MPa at 350° C., a yield strength of 99 MPa, and an elongation of 11%.

The tensile strength at 400° C. of the aluminum-copper-cerium-based heat-resistant aluminum alloy is 71 MPa, the yield strength is 62 MPa, and the elongation is 10%.

The aluminum-copper-cerium heat-resistant aluminum alloy has a tensile strength of 400 MPa, a yield strength of 243 MPa and an elongation of 7% at room temperature.

Example 2

An aluminum-copper-cerium heat-resistant aluminum alloy, by mass percentage, including Cu 8.0%, Ce 1.3%, Mn 0.8%, RE 0.085%, Zr 0.17%, and the balance is aluminum.

The preparation method of the aluminum-copper-cerium heat-resistant aluminum alloy is as follows, comprising the following steps:

Step 1. Prepare aluminum and intermediate alloys according to the above mass percentages, and prepare aluminum alloy ingots by smelting. The specific method is as follows:

S11. Melting Al and Al-Mn master alloys in graphite crucibles in a resistance furnace, and keeping the temperature at 720°C-820°C for 2.5h;

S12. Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the metal solution in step S11 for melting, and keep warm at 720°C-820°C for 1.5h;

S13. At 700°C-720°C, pour argon into the aluminum alloy solution obtained in step S12 for refining and degassing, then let stand for 10-30 minutes, remove slag, and cast the aluminum alloy solution into a sand mold to form an aluminum alloy Ingot.

Step 2. Heat the aluminum alloy ingot at 250°C for 24 hours, then raise the temperature to 450°C for 12 hours.

Step 3. Heat the aluminum alloy ingot obtained in step 2 for 15 hours at 537° C., then perform water quenching, then heat the obtained aluminum alloy ingot at 175° C. for 10 hours, and then heat it up to 250° C. for 24 hours. Copper-cerium heat-resistant aluminum alloy. Before the creep test, the material was tested at 300°C for 24 hours.

Referring to Figures 1-5, the performance test of the obtained aluminum-copper-cerium heat-resistant aluminum alloy is carried out, and the test indicators are as follows:

The aluminum-copper-cerium heat-resistant aluminum alloy has a durable strength of 105MPa at 300°C for 100h, a durable strength of 92MPa at 300°C for 400h, a tensile strength of 178MPa at 300°C, a yield strength of 128MPa, and an elongation of 9.5%. .

The aluminum-copper-cerium heat-resistant aluminum alloy has a durable strength of 70 MPa at 350° C., a tensile strength of 139 MPa at 350° C., a yield strength of 108 MPa, and an elongation of 13%.

The tensile strength at 400° C. of the aluminum-copper-cerium-based heat-resistant aluminum alloy is 72 MPa, the yield strength is 69 MPa, and the elongation is 13%.

The aluminum-copper-cerium heat-resistant aluminum alloy has a tensile strength of 412 MPa at room temperature, a yield strength of 225 MPa, and an elongation of 3.0%.

Table 1 shows the performance comparison results between the aluminum-copper-cerium-based heat-resistant aluminum alloy prepared in Example 2 and the existing heat-resistant aluminum alloys of various grades.

figure 1

Alloy type test temperature state 100h lasting strength 400h lasting strength ZL201A 300℃ T5 78MPa -- ZL206 300℃ T6 <100MPa 60MPa ZL207 300℃ T1 90MPa -- Aluminum alloy of the present invention 300℃ T6 >100MPa 92MPa ZL206 350°C T6 50MPa -- ZL207 350°C T1 35MPa -- Aluminum alloy of the present invention 350°C T6 70MPa --

It can be seen that the high-temperature durability strength of the aluminum-copper-cerium-based heat-resistant aluminum alloy of the present invention at 300° C. and 350° C. is significantly higher than that of existing brands of heat-resistant aluminum alloys. The invention realizes the segregation of RE elements and Zr elements at the θ′-Al ₂ Cu precipitation phase interface through the control of alloy composition and combined with multi-stage heat treatment process, improves the high temperature stability of the strengthening phase, and optimizes the precipitation phase and crystal phase The ratio of the volume fraction between them can obtain excellent durable strength (the durable strength of 400 hours at 300°C and the durable strength of 100 hours at 350°C are particularly outstanding).

Example 3

An aluminum-copper-cerium heat-resistant aluminum alloy, by mass percentage, including Cu 6.0%, Ce 0.75%, Mn 0.5%, RE 0.4%, Zr 0.5%, and the balance is aluminum.

The preparation method of the aluminum-copper-cerium heat-resistant aluminum alloy is as follows, comprising the following steps:

Step 1. Prepare aluminum and intermediate alloys according to the above mass percentages, and prepare aluminum alloy ingots by smelting. The specific method is as follows:

S11. Melting Al and Al-Mn master alloys in graphite crucibles in a resistance furnace, and keeping the temperature at 720°C-820°C for 2.5h;

S12. Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the metal solution in step S11 for melting, and keep warm at 720°C-820°C for 1.5h;

S13. At 700°C-720°C, pour argon into the aluminum alloy solution obtained in step S12 for refining and degassing, then let stand for 10-30 minutes, remove slag, and cast the aluminum alloy solution into a sand mold to form an aluminum alloy Ingot.

Step 2. Heat the aluminum alloy ingot at 300°C for 12 hours, then raise the temperature to 400°C for 15 hours.

Step 3. Heat the aluminum alloy ingot obtained in step 2 for 30 hours at 520° C. and then perform water quenching, then heat the obtained aluminum alloy ingot at 200° C. for 5 hours, then heat it up to 300° C. for 50 hours, and then air-cool to room temperature to obtain aluminum-copper-cerium heat-resistant aluminum alloy.

The obtained aluminum copper cerium series heat-resistant aluminum alloy is subjected to performance test, and the test index is as follows:

The aluminum-copper-cerium heat-resistant aluminum alloy has a durable strength of 85 MPa at 300° C. for 100 hours, a tensile strength of 153 MPa at 300° C., a yield strength of 110 MPa, and an elongation of 12%.

The aluminum-copper-cerium-based heat-resistant aluminum alloy has a durable strength of 54 MPa at 350° C. for 100 hours, a tensile strength at 350° C. of 116 MPa, a yield strength of 92 MPa, and an elongation of 16%.

The tensile strength at 400° C. of the aluminum-copper-cerium-based heat-resistant aluminum alloy is 55 MPa, the yield strength is 51 MPa, and the elongation is 17%.

The aluminum-copper-cerium heat-resistant aluminum alloy has a tensile strength of 359 MPa at room temperature, a yield strength of 203 MPa, and an elongation of 3.4%.

Example 4

An aluminum-copper-cerium heat-resistant aluminum alloy, comprising Cu 9.0%, Ce 1.5%, Mn 1.2%, Sc 0.05%, Zr 0.1%, and the balance is aluminum.

The preparation method of the aluminum-copper-cerium heat-resistant aluminum alloy is as follows, comprising the following steps:

Step 1, according to the above-mentioned mass percentage, prepare aluminum and master alloy altogether 50Kg alloy, adopt the method for smelting to prepare aluminum alloy ingot, specific method is as follows:

S11. Melting Al and Al-Mn master alloys in graphite crucibles in a resistance furnace, and keeping the temperature at 720°C-820°C for 2.5h;

S12. Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the metal solution in step S11 for melting, and keep warm at 720°C-820°C for 1.5h;

S13. At 700°C-720°C, pour argon into the aluminum alloy solution obtained in step S12 for refining and degassing, then let stand for 10-30 minutes, remove slag, and cast the aluminum alloy solution into a sand mold to form an aluminum alloy Ingot.

Step 2. Heat the aluminum alloy ingot at 300°C for 48 hours, then raise the temperature to 500°C for 5 hours.

Step 3. Heat the aluminum alloy ingot obtained in step 2 at 537°C for 5 hours, then perform water quenching, then heat the obtained aluminum alloy ingot at 175°C for 30 hours, then heat it up to 250°C for 24 hours, then air cool to room temperature to obtain aluminum-copper-cerium heat-resistant aluminum alloy. Before the creep test, the material was tested at 300°C for 24 hours.

The obtained aluminum copper cerium series heat-resistant aluminum alloy is subjected to performance test, and the test index is as follows:

The aluminum-copper-cerium heat-resistant aluminum alloy has a durable strength of 91 MPa at 300° C. for 100 hours, a tensile strength at 300° C. of 162 MPa, a yield strength of 116 MPa, and an elongation of 10.5%.

The aluminum-copper-cerium heat-resistant aluminum alloy has a durable strength of 61 MPa at 350° C. for 100 hours, a tensile strength at 350° C. of 122 MPa, a yield strength of 95 MPa, and an elongation of 14.2%.

The tensile strength at 400° C. of the aluminum-copper-cerium-based heat-resistant aluminum alloy is 63 MPa, the yield strength is 60 MPa, and the elongation is 15.3%.

The aluminum-copper-cerium heat-resistant aluminum alloy has a tensile strength of 384 MPa at room temperature, a yield strength of 258 MPa, and an elongation of 2.76%.

The above content is only to illustrate the technical ideas of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solutions according to the technical ideas proposed in the present invention shall fall within the scope of the claims of the present invention. within the scope of protection.

Claims (4)

1. An aluminum-copper-cerium heat-resistant aluminum alloy, characterized in that, by mass percentage, it includes Cu 6% ~ 9%, Ce 0.75% ~ 1.5%, Mn 0.5% ~ 1.2%, RE 0.05% ~ 0.4 %, Zr 0.1% ~ 0.5%, the balance is Al, the ratio of Cu and Ce is (4 - 8): 1; The RE is at least one of Y, Er, Sc and Yb; The preparation method of the aluminum-copper-cerium heat-resistant aluminum alloy comprises the following steps: Step 1. Heat the aluminum alloy ingot at 200 ℃ ~ 300 ℃ for 12 h ~ 48 h, then raise the temperature to 400 ℃ ~ 500 ℃ for 5 h ~ 15 h; Step 2, heat the aluminum alloy ingot in step 1 at 520°C~537°C for 5h~30h and then quench it; Step 3. Heat the aluminum alloy ingot obtained in step 2 at 150 ℃ ~ 200 ℃ for 5 h ~ 30 h, then raise the temperature to 250 ℃ ~ 300 ℃ for more than 1 h, then cool to room temperature to obtain aluminum copper cerium Heat-resistant aluminum alloy. 2. An aluminum-copper-cerium heat-resistant aluminum alloy according to claim 1, characterized in that, in step 1, an intermediate alloy of elemental aluminum and aluminum alloy is used to melt and prepare an aluminum alloy ingot. 3 . The aluminum-copper-cerium-based heat-resistant aluminum alloy according to claim 1 , wherein the quenching treatment in step 2 is water quenching treatment. 4 . 4 . The aluminum-copper-cerium heat-resistant aluminum alloy according to claim 1 , wherein the cooling method in step 3 is air cooling.

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