A nickel tri-aluminum-based alloy and a heat treatment method for regulating the precipitation behavior thereof

Abstract

This invention discloses a nickel-aluminum alloy with various intragranular and grain boundary precipitation effects. It also discloses a heat treatment method for controlling the precipitation behavior of the nickel-aluminum alloy, comprising: holding the as-cast nickel-aluminum alloy at a first specified temperature T1, then rapidly cooling it to a second specified temperature T2, and subsequently slowly cooling it to a third specified temperature T3. This method for controlling the precipitation behavior of the nickel-aluminum alloy does not require additional aging or mechanical treatment. By controlling the node temperature and cooling rate of the two cooling stages, the size and morphology of intragranular and grain boundary precipitates can be coordinated and controlled. This method has the advantages of high efficiency, energy saving, low cost, and environmental friendliness, and therefore has high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy processing, specifically to a nickel-aluminum alloy and a heat treatment method for controlling its precipitation behavior. Background Technology

[0002] As-cast polycrystalline nickel-aluminum-based superalloys have broad application prospects in aerospace engine hot-end components and other fields due to their advantages such as ease of manufacturing, low density, high-temperature strength, and excellent oxidation resistance. During service, their deformation behavior is mainly controlled by intragranular microstructure, while their fracture behavior is mainly controlled by grain boundary microstructure. The casting process inevitably causes compositional segregation and microstructure inhomogeneity, which not only reduces their mechanical properties but also makes it difficult to predict the service life of the workpiece.

[0003] Currently, solution heat treatment is generally used to eliminate compositional and microstructure segregation. After holding at the solution temperature for a certain period of time, traditional cooling methods such as water cooling, air cooling, or furnace cooling are typically employed. However, nickel-aluminum alloys have complex compositions and microstructures and are particularly sensitive to cooling rates; a single cooling method cannot effectively regulate the diverse intragranular and grain boundary structures. Summary of the Invention

[0004] This invention designs and develops a heat treatment method for regulating the precipitation behavior of nickel-aluminum alloys. The purpose of this invention is to solve the problem of the uniform precipitation behavior of nickel-aluminum alloys prepared in the prior art.

[0005] This invention designs and develops a nickel-aluminum alloy. The purpose of this invention is to solve the problem of the single precipitation behavior of existing nickel-aluminum alloys.

[0006] The technical solution provided by this invention is as follows:

[0007] A heat treatment method for controlling the precipitation behavior of nickel-aluminum based alloys, comprising:

[0008] After holding the as-cast nickel-aluminum alloy at a first specified temperature T1, it is rapidly cooled to a second specified temperature T2, and then slowly cooled to a third specified temperature T3.

[0009] Preferably, the temperature range of the first specified temperature T1 is 1150℃≤T1<1300℃.

[0010] Preferably, the heat preservation time at the first specified temperature T1 is not less than 2 hours.

[0011] Preferably, the cooling rate during the rapid cooling process is not less than 5°C / min.

[0012] Preferably, the temperature range of the second specified temperature T2 is 950℃≤T2≤1050℃.

[0013] Preferably, the cooling rate during the slow cooling process is no greater than 5°C / min.

[0014] Preferably, the temperature range of the third specified temperature T3 is 750℃≤T3≤850℃.

[0015] A nickel-aluminum alloy, obtained by the heat treatment method described above for controlling the precipitation behavior of the nickel-aluminum alloy.

[0016] Preferably, the intracrystalline precipitates of the nickel-aluminum-based alloy are cubic or nearly cubic, uniform in size, and uniformly distributed within the crystals; and

[0017] The grain boundary precipitates of the nickel-aluminum alloy are granular, short rod-shaped, or long strip-shaped, with uniform size and evenly distributed along the grain boundaries.

[0018] Preferably, the intracrystalline precipitated phase includes an intracrystalline γ′-Ni3Al phase; and

[0019] The grain boundary precipitates include grain boundary M 23 C6 type carbides.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The heat treatment method for regulating the precipitation behavior of nickel-aluminum-based alloys provided by this invention first involves holding the alloy at a specified temperature higher than the γ′-Ni3Al precipitation temperature for a certain period of time to increase the atomic diffusion rate and eliminate segregation and microstructure inhomogeneity caused during the casting process. Then, through a first-stage rapid cooling process, the nucleation rate of the γ′-Ni3Al phase within the grains is increased and its coarsening is suppressed, generating cubic or near-cubic precipitates with uniform size. Finally, through a second-stage slow cooling process, the grain boundary M 23 The precipitation and growth of C6 type carbides generate granular / rod-shaped / strip-shaped reinforcing phases that are uniformly distributed along the grain boundaries;

[0022] 2. By controlling the node temperature and cooling rate in the two stages, nickel-aluminum alloys with various intragranular / grain boundary precipitation effects can be obtained;

[0023] 3. The heat treatment method for regulating the precipitation behavior of nickel-aluminum alloys provided by this invention can coordinate the control of intragranular and grain boundary precipitates. Compared with traditional solid solution treatment methods, the method of this invention breaks through the limitation that it can only control intragranular or grain boundary precipitates. Compared with traditional solid solution + aging treatment methods, the method of this invention can achieve more diverse grain boundary precipitation effects, and is simple to operate, low in energy consumption, and low in cost, and has good application prospects. Attached Figure Description

[0024] Figure 1This is a schematic diagram of the process flow of the heat treatment method for regulating the precipitation behavior of nickel-aluminum alloys according to the present invention.

[0025] Figure 2 This is a diagram illustrating the precipitation effect of an embodiment of the present invention. Figure 2 a, Figure 2 b is a diagram showing the precipitation effect of Example 1. Figure 2 c. Figure 2 d is a graph showing the precipitation effect of Example 2. Figure 2 e Figure 2 f is a graph showing the precipitation effect of Example 3. Figure 2 g、 Figure 2 h is a graph showing the precipitation effect of Example 4. Figure 2 i Figure 2 j is the precipitation effect diagram of Example 5).

[0026] Figure 3 This is a comparative example of the precipitation effect described in this invention. Figure 3 a, Figure 3 b is the precipitation effect diagram of Comparative Example 1. Figure 3 c. Figure 3 d shows the precipitation effect diagram of Comparative Example 2. Figure 3 e Figure 3 f is the precipitation effect diagram of Comparative Example 3. Figure 3 g、 Figure 3 h represents the precipitation effect diagram of Comparative Example 4.

[0027] Figure 4a These are schematic diagrams of creep curves for Example 1, Comparative Example 1, and Comparative Example 2 of the heat treatment method for regulating the precipitation behavior of nickel-aluminum alloys according to the present invention.

[0028] Figure 4b This is a schematic diagram of the creep rate curves of Example 1, Comparative Example 1, and Comparative Example 2 of the heat treatment method for regulating the precipitation behavior of nickel-aluminum alloys according to the present invention. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0030] like Figure 1 As shown, this invention provides a heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys. This method can synergistically control the intragranular and grain boundary strengthening phases to obtain alloy microstructures with different precipitation effects, including the size and morphology of the intragranular and grain boundary precipitates. Specifically, it includes the following steps:

[0031] Step 1: Hold the cut cast nickel-aluminum metal block at a specified temperature T1; wherein, when holding at the specified temperature T1, 1150℃≤T1<1300℃, and the holding time≥2h;

[0032] Step 2: First, rapidly cool to the specified temperature T2, then slowly cool to the specified temperature T3, and then water cool to room temperature; in the first rapid cooling procedure, the cooling rate is ≥5℃ / min, and 950℃≤T2≤1050℃; in the second slow cooling procedure, the cooling rate is ≤5℃ / min, and 750℃≤T3≤850℃.

[0033] The present invention also provides a nickel-aluminum alloy. The precipitation effect of the nickel-aluminum alloy obtained by the heat treatment method of the present invention for controlling the precipitation behavior of nickel-titanium alloy includes, but is not limited to, the following: the intragranular precipitates are cubic or near-cubic, uniform in size and uniformly distributed within the grains; the grain boundary precipitates are granular, short rod-shaped or long strip-shaped and uniformly distributed along the grain boundaries.

[0034] In another embodiment, the types of precipitated phases include intragranular γ′-Ni3Al phase and grain boundary M phase. 23 C6 type carbides.

[0035] Example 1

[0036] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this embodiment includes the following steps:

[0037] Step S1: Cut the pre-cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0038] Step S2: Cool the sample to 1000°C at a cooling rate of 20°C / min, then cool it to 800°C at a cooling rate of 0.25°C / min, and then water cool it to room temperature.

[0039] Example 2

[0040] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this embodiment includes the following steps:

[0041] Step S1: Cut the pre-cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0042] Step S2: Cool the sample to 1050°C at a cooling rate of 20°C / min, then cool it to 850°C at a cooling rate of 0.25°C / min, and then water cool it to room temperature.

[0043] Example 3

[0044] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this embodiment includes the following steps:

[0045] Step S1: Cut the pre-cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0046] Step S2: Cool the sample to 950°C at a cooling rate of 20°C / min, then cool it to 750°C at a cooling rate of 0.25°C / min, and then water cool it to room temperature.

[0047] Example 4

[0048] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this embodiment includes the following steps:

[0049] Step S1: Cut the pre-cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0050] Step S2: Cool the sample to 1000°C at a cooling rate of 5°C / min, then cool it to 800°C at a cooling rate of 0.25°C / min, and then water cool it to room temperature.

[0051] Example 5

[0052] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this embodiment includes the following steps:

[0053] Step S1: Cut the pre-cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0054] Step S2: Cool the sample to 1000°C at a cooling rate of 20°C / min, then cool it to 800°C at a cooling rate of 5°C / min, and then water cool it to room temperature.

[0055] Comparative Example 1

[0056] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this comparative example includes the following steps:

[0057] Step S1, cut the cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0058] Step S2: Cool the sample to room temperature with water.

[0059] Comparative Example 2

[0060] The heat treatment method for controlling the precipitation behavior of nickel-aluminum alloys in this comparative example includes the following steps:

[0061] Step S1, cut the cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0062] Step S2: Cool the sample to 800°C at a cooling rate of 0.25°C / min, and then water cool it to room temperature.

[0063] Comparative Example 3

[0064] The heat treatment method for the nickel-aluminum based alloy in this comparative example includes the following steps:

[0065] Step S1, cut the cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0066] Step S2: Cool the sample to 1000°C at a cooling rate of 20°C / min, then cool it to 800°C at a cooling rate of 15°C / min, and then water cool it to room temperature.

[0067] Comparative Example 4

[0068] The heat treatment method for the nickel-aluminum based alloy in this comparative example includes the following steps:

[0069] Step S1, cut the cast 5×5×2mm 3 The nickel-aluminum metal block was placed in a muffle furnace and held at 1200℃ for 2 hours;

[0070] Step S2: Cool the sample to 1000°C at a cooling rate of 2°C / min, then cool it to 800°C at a cooling rate of 0.25°C / min, and then water cool it to room temperature.

[0071] Test case

[0072] After controlling the precipitation behavior of the nickel-aluminum alloy, the microstructure of the treated nickel-aluminum alloy was observed using a JSM-7800F scanning electron microscope.

[0073] like Figure 2 As shown, in Examples 1, 3, 4 and 5, cubic or near-cubic γ′-Ni3Al phases were precipitated in the crystals. In Example 2, γ′-Ni3Al phases with R-type raft structure were precipitated in the crystals.

[0074] In all embodiments, rod-shaped M-shaped deposits were precipitated at the grain boundaries. 23C6 type carbides; by comparing Examples 1, 2, and 3, it can be found that: 1. Within the corresponding temperature range, the higher the specified temperature T2, the more the γ′-Ni3Al phase tends to undergo directional coarsening (rafting); the lower the specified temperature T2, the more the γ′-Ni3Al phase tends to be cubic; 2. Within the corresponding temperature range, the higher the specified temperature T3, the more M... 23 The larger the size of C6-type carbides, the better.

[0075] By comparing Examples 1, 4, and 5, it can be found that: 1. Within the corresponding cooling rate range, the faster the first-step cooling rate, the smaller the γ′-Ni3Al phase size; 2. Within the corresponding cooling rate range, the slower the second-step cooling rate, the smaller the M... 23 The larger the size of C6-type carbides; 3. The first-stage cooling rate affects the grain boundary M 23 The size and morphology of C6-type carbides are less affected; the faster the cooling rate during this stage, the better the M... 23 The narrower the width of C6-type carbides, the smaller their size; 4. The cooling rate in the second stage has little effect on the size of the γ′-Ni3Al phase. The faster the cooling rate in this stage, the smaller the size of the γ′-Ni3Al phase.

[0076] like Figure 3 As shown, in Comparative Example 1, spherical Ni3Al phases precipitated within the grains, while no M phases were observed at the grain boundaries. 23 C6-type carbides precipitated; in Comparative Example 2, coarse, irregularly shaped γ′-Ni3Al phases precipitated within the grains, with strip-shaped M at the grain boundaries. 23 C6-type carbides precipitated; in Comparative Example 3, cubic Ni3Al phase precipitated within the grains, with fine M particles at the grain boundaries. 23 C6-type carbides precipitated; in Comparative Example 4, coarsened cubic Ni3Al phase precipitated within the grains, with rod-shaped M at the grain boundaries. 23 C6 type carbides precipitate.

[0077] By comparing the microstructures of the examples and comparative samples, it can be found that the first cooling procedure (rapid cooling) of the examples suppressed the coarsening of the intragranular γ′-Ni3Al phase; the second cooling procedure (slow cooling) of the examples promoted the coarsening of the grain boundary M 23 C6-type carbides precipitate. When the first stage cooling rate is lower than the set range, the intragranular γ′-Ni3Al phase coarsens and may even become irregular; when the second stage cooling rate is higher than the set range, the grain boundaries M... 23 C6 carbides become so small that they may not even precipitate.

[0078] Creep performance test:

[0079] In accordance with the requirements of GB / T 2039-2012 "Metallic Materials - Uniaxial Tensile Creep Test Method", the samples of Example 1, Comparative Example 1, and Comparative Example 2 were prepared into circular cross-section specimens, and creep tests were conducted using a CRIMS RDL50 high-temperature creep testing machine. The test temperature was 800℃, and the stress was 200MPa.

[0080] The test results are as follows:

[0081] As shown in Figure 4, the creep life of the Comparative Example 1 specimen was 168 h, the elongation at break was 1.21%, and the minimum creep rate was 4.55 × 10⁻⁶. -5 h -1 The creep life of the sample in Comparative Example 2 was 221 hours, the elongation at break was 8.59%, and the minimum creep rate was 3.40 × 10⁻⁶. -4 h -1 The creep life of the sample in Example 1 was 369 hours, the elongation at break was 4.16%, and the minimum creep rate was 9.49 × 10⁻⁶. - 5 h -1 Clearly, the creep rate and elongation at break of the example sample were between those of the two pairs of ratios, but its lifespan was much longer than that of the two pairs of ratios. This indicates that after two-stage cooling heat treatment, the γ′-Ni3Al phase within the nickel-aluminum alloy and the M phase at the grain boundaries... 23 C6-type carbides achieve coordinated control that is beneficial to creep performance.

[0082] The method for controlling the precipitation behavior of nickel-aluminum alloys of the present invention does not require additional aging or mechanical treatment. By controlling the node temperature and cooling rate of the two-stage cooling process, the size and morphology of intragranular and grain boundary precipitates can be controlled in a coordinated manner. This method has the advantages of high efficiency, energy saving, low cost, and environmental protection, and therefore has high industrial application value.

[0083] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A heat treatment method for controlling the precipitation behavior of nickel-aluminum based alloys, characterized in that, include: After holding the as-cast nickel-aluminum alloy at a first specified temperature T1, it is rapidly cooled to a second specified temperature T2, and then slowly cooled to a third specified temperature T3. The temperature range of the first specified temperature T1 is 1150 °C ≤ T1 < 1300 °C; The heat preservation time at the first specified temperature T1 shall not be less than 2 hours; The cooling rate during the rapid cooling process is not less than 5 °C / min; The temperature range of the second specified temperature T2 is 950 °C ≤ T2 ≤ 1050 °C; The cooling rate during the slow cooling process shall not exceed 5 °C / min; The temperature range of the third specified temperature T3 is 750 °C ≤ T3 ≤ 850 °C; The intragranular precipitates of the nickel-aluminum alloy are cubic or nearly cubic, uniform in size and evenly distributed within the grains; and the grain boundary precipitates of the nickel-aluminum alloy are granular, short rod-shaped or long strip-shaped, uniform in size and evenly distributed along the grain boundaries. The intracrystalline precipitates include an intracrystalline γ′-Ni3Al phase; and the grain boundary precipitates include grain boundary M 23 C6 type carbides.

2. A nickel-aluminum based alloy, characterized in that, The nickel-aluminum-based alloy was obtained using the heat treatment method for controlling the precipitation behavior of the nickel-aluminum-based alloy as described in claim 1.

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