CN-122013079-A - Heat treatment method for reducing harmful second phase particles of magnesium-rare earth alloy

Abstract

A heat treatment method for eliminating the harmful second phase particles of Mg-RE alloy includes such steps as overageing the as-cast Mg-RE alloy at low temp to promote the formation of balanced precipitated phase in the meta-aggregation region of solute atoms, heating to medium temp for dissolving the precipitated balanced phase in matrix, cooling to low temp Duan Baowen to form balanced precipitated phase, heating to higher medium temp for dissolving the precipitated balanced phase in matrix, cyclic reciprocation until the unbalanced eutectic in cast state is completely dissolved in matrix, and heating to high temp for dissolving and quenching. The method can effectively inhibit the formation of harmful second phase particles in the solid solution process and reduce the content of the harmful second phase particles. The invention has the advantages of good effect, simple method, no special requirement on equipment and the like, is easy to realize industrial production, and provides a simple and effective way for manufacturing high-performance magnesium-rare earth alloy castings.

Inventors

• TANG CHANGPING
• TANG TAO
• DONG YU
• LIU WENHUI

Assignees

• 湖南科技大学

Dates

Publication Date

20260512

Application Date

20260228

Claims (7)

1. 1. A heat treatment method for reducing harmful second phase particles of magnesium-rare earth alloy comprises the following steps: s1, heating the alloy to a low-temperature section T1, and preserving heat for T1 hours to perform overaging treatment, so as to promote a solute atom segregation region to form a balanced precipitated phase; s2, heating the alloy to a medium temperature section T21, and preserving heat for T21 hours to carry out solid solution so that the precipitated equilibrium phase is dissolved into a matrix; S3, cooling the alloy to a low-temperature section T1, preserving heat for T1 hours, performing overaging treatment, and forming a balanced precipitated phase again; s4, heating the alloy to a medium temperature section T22, and preserving heat for T22 hours to carry out solid solution, so that the precipitated equilibrium phase is dissolved into a matrix; s5, cooling the alloy to a low-temperature section T1, preserving heat for T1 hours, performing overaging treatment, and forming a balanced precipitated phase again; S6, heating the alloy to a medium temperature section T23, and preserving heat for T23 hours to carry out solid solution so that the precipitated equilibrium phase is dissolved into a matrix; s7, repeating the steps from S1 to S6 until the unbalanced eutectic in the cast state is completely dissolved into the matrix; And S8, heating the alloy of the S7 to a high-temperature section T3, preserving heat for T3 hours, and quenching.
2. 2. The heat treatment method according to claim 1, wherein: the temperature of the low-temperature section T1 is 200-400 ℃; The temperature ranges of the medium temperature sections T21, T22 and T23 are 410-500 ℃; the temperature range of the high temperature section T3 is 501-560 ℃.
3. 3. The heat treatment method according to claim 1, wherein: the heat preservation temperature of the latter step is higher than that of the former step in the middle temperature section heat preservation process.
4. 4. A heat treatment method according to claim 3, wherein: The temperature T22 is higher than the temperature T21, the temperature T23 is higher than the temperature T22, and so on until the unbalanced eutectic in the as-cast state is completely dissolved into the matrix, and all the heat preservation temperatures at the stage show increasing trend.
5. 5. The heat treatment method according to claim 1, wherein: The heat preservation time t1 of the low-temperature section ranges from 2h to 72h; the heat preservation time t21, t22 and t23 of the medium temperature section are all in the range of 0.5h-24h; the heat preservation time t3 of the high temperature section ranges from 0.5h to 24h.
6. 6. The heat treatment method according to claim 1, wherein: the heat treatment process is carried out under the protection of inert gas.
7. 7. The heat treatment method according to claim 1, wherein: the quenching medium is water or hot water.

Description

Heat treatment method for reducing harmful second phase particles of magnesium-rare earth alloy Technical Field The invention relates to a heat treatment method for reducing harmful second phase particles of magnesium-rare earth alloy, belonging to the technical field of alloy preparation. Background Magnesium is one of the most abundant elements on earth, has higher content in metal resources on the surface layer of the crust, and has the advantages of high specific strength, high specific rigidity, good shock absorption performance, good magnetic shielding performance, good casting performance, low cost, easy recycling and the like. However, pure magnesium has the disadvantages of low strength, poor heat resistance and the like, and is difficult to directly apply to engineering. The rare earth element is added into the magnesium, so that the room temperature and high temperature strength, corrosion resistance and the like of the magnesium alloy can be obviously improved, and the magnesium alloy has wide application prospect in the field of aerospace. However, magnesium-rare earth alloys tend to form a large number of deleterious second phase particles during heat treatment, which act as crack sources (as shown in fig. 1), thereby limiting the improvement in mechanical properties of the series of alloys. Therefore, development of a novel heat treatment process is urgently needed, formation of the second-phase particles is effectively controlled, and application of the magnesium-rare earth alloy in the aerospace field is enlarged. Disclosure of Invention In view of the above shortcomings, the invention provides a heat treatment method for reducing harmful second phase particles of magnesium-rare earth alloy, which aims to improve the mechanical properties of alloy castings. The process flow of the heat treatment of the invention is shown in figure 2: In order to achieve the technical effects, the invention is realized by the following technical scheme: The invention firstly discloses a heat treatment method for reducing harmful second phase particles of magnesium-rare earth alloy, which comprises the following steps: s1, heating the alloy to a low-temperature section T1, and preserving heat for T1 hours to perform overaging treatment, so as to promote a solute atom segregation region to form a balanced precipitated phase; s2, heating the alloy to a medium temperature section T21, and preserving heat for T21 hours to carry out solid solution so that the precipitated equilibrium phase is dissolved into a matrix; S3, cooling the alloy to a low-temperature section T1, preserving heat for T1 hours, performing overaging treatment, and forming a balanced precipitated phase again; s4, heating the alloy to a medium temperature section T22, and preserving heat for T22 hours to carry out solid solution, so that the precipitated equilibrium phase is dissolved into a matrix; s5, cooling the alloy to a low-temperature section T1, preserving heat for T1 hours, performing overaging treatment, and forming a balanced precipitated phase again; S6, heating the alloy to a medium temperature section T23, and preserving heat for T23 hours to carry out solid solution so that the precipitated equilibrium phase is dissolved into a matrix; S7, repeating the steps S1 to S6 until the unbalanced eutectic in the cast state is completely dissolved into the matrix; S8, heating the alloy to a high temperature section T3, preserving heat for T3 hours, and quenching. As a preferred embodiment of the present invention, the temperature of the low temperature zone is in the range of 200 ℃ to 400 ℃, the temperature of the medium temperature zone is in the range of 410 ℃ to 500 ℃, and the temperature of the high temperature zone is in the range of 501 ℃ to 560 ℃. As a preferred embodiment of the invention, in the heat treatment scheme, the holding temperature of the latter step is higher than that of the former step in the middle temperature section holding process, and all holding temperatures at this stage show increasing trend. As a preferred embodiment of the present invention, in the heat treatment scheme, the heat preservation time t1 of the low temperature section ranges from 2h to 72h, the heat preservation time t2n (n=1, 2, 3.) of the medium temperature section ranges from 0.5h to 24h, and the heat preservation time t3 of the high temperature section ranges from 0.5h to 24h. As a preferred embodiment of the present invention, in the heat treatment scheme, the heat treatment process is performed under the protection of inert gas. As a preferred embodiment of the present invention, in the heat treatment scheme, the quenching medium is water or hot water. The heat treatment scheme has no requirement on the shape and the size of the casting, and can be used for treatment. Compared with the prior art, the invention has the following beneficial effects: The magnesium-rare earth alloy generally adopts a high-temperature single-stage solid soluti