A method for segregating immiscible alloys to improve microstructure uniformity

Abstract

The present invention discloses a method for improving the uniformity of the structure of an immiscible alloy by segregation, which comprises: subjecting an immiscible alloy sample to a non-equilibrium solidification treatment; subjecting the immiscible alloy sample obtained by the non-equilibrium solidification treatment to a heat treatment process of heating and holding the sample, holding the sample above the melting point of the low-melting-point phase, then powering off and cooling the sample to 1000°C, taking out the immiscible alloy sample, and rapidly quenching the sample to obtain an immiscible alloy sample with a uniform dispersed distribution structure. 50 Co 50 The immiscible alloy was subjected to semi-solid heat treatment, and a specific cooling method was adopted in which the power was turned off and cooled to 1000℃, and then the sample was taken out and quickly quenched. During the entire cooling process, under the synergistic effect of the uniform composition field and high cooling rate, a uniform structure with a dispersed minority phase was formed in the liquid matrix. Finally, by adjusting the process parameters of the semi-solid heat treatment, the microstructure of the immiscible alloy was significantly changed, showing a uniform structure.

Description

Technical Field

[0001] The invention belongs to the technical field of immiscible alloys, and particularly relates to a method for segregating immiscible alloys to improve their structural uniformity. Background Art

[0002] Immiscible alloys are characterized by a miscibility gap in their phase diagram, typically undergoing liquid-liquid phase separation (LLPS). Many of these alloys have broad applications, such as superconductors, electrical contacts, and self-lubricating materials. However, during melt cooling, large density differences between the two separated phases and factors such as melt convection often lead to segregation, limiting their development and industrial application. If immiscible alloys can be prepared with a structure where the minority phase is uniformly dispersed as tiny particles within a matrix, such alloys can meet specialized requirements under demanding conditions. The exceptional mechanical and physical properties exhibited by these immiscible alloys offer promising prospects for industrial application. Therefore, the study of immiscible alloys holds significant theoretical value and enormous potential for industrial applications, attracting widespread attention and becoming a cutting-edge research topic in the field of metal materials.

[0003] Cu-X (X = Co, Fe, Cr, Nb, etc.) is known as a metastable immiscible alloy. When the alloy is undercooled slightly, a liquid-solid phase transition occurs, with the X-rich alloy existing as a solid phase in the matrix. Conversely, when the alloy's undercooling exceeds the critical phase separation threshold, the single-phase alloy melt cools into a liquid-immiscible region, undergoing liquid-liquid phase separation and producing two immiscible phases: a Cu-rich liquid (L1) and an X-rich liquid (L2). During further cooling, factors such as gravity, temperature gradients, concentration gradients, interfacial energy, and convection can cause the immiscible alloy to ultimately develop a segregated solidification structure. Various experimental approaches have been employed to investigate this material prone to heterogeneous microstructures. Some reports have used atomized powder technology to achieve an "egg-shaped" shell-core structure in Cu-Fe-based alloys. However, the small size and high cooling rates make the microstructure difficult to control. There are also some reports that used the dropping tube method to study the phase separation behavior in metastable eutectic Cu-Pb alloys. The studies showed that the alloy is more likely to produce a two-layer core-shell structure at the critical composition, while a three-layer core-shell structure is formed on the left side of the critical composition, and an irregular structure is formed away from the critical composition of the alloy.

[0004] The microstructural evolution of Cu-Co alloys with liquid phase separation is also closely related to the processing conditions. The liquid phase separation process is regulated by adjusting the supercooling state. However, the degree of supercooling during solidification is difficult to control, resulting in the formation of different types of segregation structures in the alloy.

[0005] The main problem in the preparation of immiscible alloys at present is that the microstructure segregation is serious and difficult to control. Although a lot of research has been done on the formation mechanism of microstructure evolution, there is still a lack of methods to control the structure. The alloy structures obtained by existing research methods are mostly core-shell structures and different types of segregation structures. The control of the structure of immiscible alloys depends on the cooling rate and alloy composition. The actual microstructure morphology of the alloy after solidification varies greatly and basically presents a segregation structure. Existing research is mostly through controlling the alloy supercooling, cooling rate, adding external fields, etc., but it is difficult to achieve active control of the uniform morphology of immiscible alloys. Existing technologies have encountered insurmountable bottlenecks in the active control of the uniform structure of immiscible alloys. Therefore, there is an urgent need to explore a new method that can effectively control the uniform structure of immiscible alloys. Summary of the Invention

[0006] To address the problem of microstructural segregation during the preparation of immiscible alloys, this paper proposes a method for manipulating the microstructure of immiscible alloys using semi-solid isothermal heat treatment. This study selected immiscible alloys and found that semi-solid isothermal heat treatment can rapidly and effectively homogenize the segregated secondary phase, resulting in a uniform structure. By manipulating the process parameters of semi-solid isothermal heat treatment, the paper exploits the following advantages: 1) selecting immiscible alloys with phase separation characteristics; 2) maintaining high accuracy by maintaining the heat treatment above the melting point of the low-melting-point phase; and 3) employing a specific cooling method involving power-off cooling to 1000°C and rapid quenching of the sample. Throughout the cooling process, the synergistic effects of a uniform composition field and high cooling rate form a uniform structure with a dispersed minority phase within the liquid matrix. Ultimately, by manipulating the process parameters of semi-solid isothermal heat treatment, the microstructure of the immiscible alloy exhibits a uniform structure, suggesting promising industrial applications.

[0007] Specifically, the present invention provides a method for segregating an immiscible alloy to improve its structural uniformity, comprising:

[0008] The immiscible alloy samples were subjected to non-equilibrium solidification treatment;

[0009] The immiscible alloy sample obtained by the non-equilibrium solidification treatment is subjected to a heating-holding heat treatment process, and is held above the melting point of the low-melting-point phase. The immiscible alloy sample is then turned off and cooled to 1000° C., and then taken out and rapidly quenched to obtain an immiscible alloy sample with a uniformly dispersed distribution structure.

[0010] As a further illustration of the present invention, the non-equilibrium solidification process includes:

[0011] A quartz tube containing an immiscible alloy button ingot is placed into a material processing device and subjected to a heating-insulation-cooling treatment. The heating-insulation-cooling treatment process is repeated multiple times to obtain an undercooling degree of 200K-300K, and then cooled to 1000°C for quenching to complete the non-equilibrium solidification treatment process of the immiscible alloy, thereby obtaining immiscible alloy samples with different types of core-shell structures under large undercooling degrees.

[0012] As a further illustration of the present invention, after the immiscible alloy button ingot is placed in the quartz tube, the surface needs to be covered with B2O3.

[0013] As a further illustration of the present invention, the holding temperature of the non-equilibrium solidification treatment is set at 1400° C.-1440° C., and the holding time is at least 5 minutes.

[0014] As a further illustration of the present invention, the heat treatment is carried out at a holding temperature of 1280° C. to 1360° C. and a holding time of 3 h to 6 h.

[0015] As a further illustration of the present invention, the immiscible alloy is but not limited to Cu 50 Co 50 Immiscible alloys.

[0016] As a further illustration of the present invention, the Cu 50 Co 50 The preparation process of the immiscible alloy includes: using Cu and Co as raw materials, melting in a vacuum non-consumable arc melting furnace, repeatedly turning each sample over and melting multiple times during the melting process to ensure uniform composition of the alloy, thereby obtaining Cu 50 Co 50 Immiscible alloys.

[0017] As a further illustration of the present invention, the atomic ratio of Cu:Co is 1:1, and the purity of the pure elemental substances of Co and Cu is 99.99 wt.%.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The present invention improves the existing Cu 50 Co 50 The immiscible alloys are subjected to semi-solid heat treatment. The semi-solid treatment does not change the phase composition of the original alloy, and the heat preservation treatment is performed above the melting point of the low-melting-point phase, which has high accuracy. At the same time, a specific cooling method is adopted in which the power is turned off and cooled to 1000℃, and the sample is taken out and quickly quenched. During the entire cooling process, under the synergistic effect of the uniform composition field and high cooling rate, a uniform structure with dispersed minority phases is formed in the liquid matrix. Finally, by adjusting the process parameters of the semi-solid heat treatment, the microstructure of the immiscible alloy is significantly changed, showing a uniform structure.

[0020] In summary, the alloy directly subjected to solidification treatment has a segregated structure, but after the specific semi-solid heat treatment process provided by the present invention, it can be transformed into a uniformly dispersed structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The Cu2O3 under 270K supercooling temperature obtained by the rapid solidification treatment in Example 1 of the present invention is 50 Co 50 Microstructure of immiscible alloys;

[0022] Figure 2 The Cu after semi-solid heat treatment in Example 1 of the present invention 50 Co 50 Microstructure of immiscible alloys;

[0023] Figure 3 The Cu2O3 under 270K supercooling temperature obtained by rapid solidification treatment in Example 2 of the present invention is 50 Co 50 Microstructure of immiscible alloys;

[0024] Figure 4 The Cu after semi-solid heat treatment in Example 2 of the present invention 50 Co 50 Microstructure of immiscible alloys;

[0025] Figure 5 The Cu2O3 under 260K supercooling temperature obtained by rapid solidification treatment in Example 3 of the present invention is 50 Co 50 Microstructure of immiscible alloys;

[0026] Figure 6 The Cu after semi-solid heat treatment in Example 3 of the present invention 50 Co 50 Microstructure of immiscible alloys. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0028] The semi-solid heat treatment process in this embodiment controls the Cu 50 Co 50 The specific process of the method for the microstructure of immiscible alloys is as follows:

[0029] The first step is alloy preparation: Co and Cu with a purity of no less than 99.99% are selected; both solid-state pure materials are used. The Co:Cu ratio is 1:1, representing the atomic ratio. The surface oxide scales of the two pure metals are first polished off on a grinding wheel. After cleaning, the metals are placed in a copper crucible in a vacuum non-consumable arc furnace and melted using a vacuum non-consumable arc method. Each sample is repeatedly turned over and melted four times to ensure uniform alloy composition, resulting in the final button ingot.

[0030] The second step involved sample preparation: the button ingots were cut, polished, and ultrasonically cleaned. Each experimental sample weighed approximately 1 g. The cleaned samples were placed in a quartz tube with an inner diameter of 7 mm, an outer diameter of 12 mm, and a length of 600 mm. A small amount of boron trioxide glass was placed on the sample surface to prevent oxidation.

[0031] The third step is non-equilibrium solidification treatment: the quartz tube with the sample is fixed with a copper mold fixture and placed in the material processing device, and the sample is placed in the highest temperature zone of the heating body, and the sample placed in the device is solidified. The specific process is to turn on the heating power supply, and repeat the heating rate, holding temperature, holding time and cooling rate set by the program to complete the Cu solidification experiment. 50 Co 50 Solidification process of immiscible alloy. Heating to holding temperature 1420℃, holding time 5min, cooling, and then repeated cycles to obtain large undercooling. According to the cooling curve, the undercooling is 262K. Cooling to 1000℃ and quenching in water to obtain Cu 50 Co 50 The sample of the immiscible alloy after solidification. Its microstructure is a segregated structure. The microstructure is as follows Figure 1 The structure shown.

[0032] The fourth step is semi-solid heat treatment: the alloy sample treated by non-equilibrium solidification is cut in half, polished and cleaned, and the cut sample is placed in the material processing device. The sample holding temperature is set to the liquid-solid two-phase region, and the heating power is used to set the program heating, the holding temperature is 1300℃, and the holding time is 6h. After the holding time is reached, the sample is directly taken out and quickly quenched to complete the Cu 50 Co 50 Heat treatment process of immiscible alloys, Cu after semi-solid heat treatment 50 Co 50 For immiscible alloy samples, the quenched samples taken directly out still have segregation structure, and their structure is as follows Figure 2 shown. Example 2

[0033] The semi-solid heat treatment process in this embodiment controls the Cu 50 Co50 The specific process of the method for the microstructure of immiscible alloys is as follows:

[0034] The first step is alloy preparation: Co and Cu with a purity of no less than 99.99% are selected; both solid-state pure materials are used. The Co:Cu ratio is 1:1, representing the atomic ratio. The surface oxide scales of the two pure metals are first polished off on a grinding wheel. After cleaning, the metals are placed in a copper crucible in a vacuum non-consumable arc furnace and melted using a vacuum non-consumable arc method. Each sample is repeatedly turned over and melted four times to ensure uniform alloy composition, resulting in the final button ingot.

[0035] The second step involved sample preparation: the button ingots were cut, polished, and ultrasonically cleaned. Each experimental sample weighed approximately 1 g. The cleaned samples were placed in a quartz tube with an inner diameter of 7 mm, an outer diameter of 12 mm, and a length of 600 mm. A small amount of boron trioxide glass was placed on the sample surface to prevent oxidation.

[0036] The third step is non-equilibrium solidification treatment: the quartz tube with the sample is fixed with a copper mold fixture and placed in the material processing device, and the sample is placed in the highest temperature zone of the heating body, and the sample placed in the device is solidified. The specific process is to turn on the heating power supply, and repeat the heating rate, holding temperature, holding time and cooling rate set by the program to complete the Cu solidification experiment. 50 Co 50 Solidification process of immiscible alloy. Heating to holding temperature 1420℃, holding time 5min, cooling, and then repeated cycles to obtain large undercooling. According to the cooling curve, the undercooling is judged to be 270K. Cooling to 1000℃ and quenching in water to obtain Cu 50 Co 50 The sample of the immiscible alloy after solidification. Its microstructure is a segregated structure. The microstructure is as follows Figure 3 The structure shown.

[0037] The fourth step is semi-solid heat treatment: the alloy sample treated by non-equilibrium solidification is cut in half, polished and cleaned, and the cut sample is placed in the material processing device. The sample holding temperature is set to the liquid-solid two-phase region, and the heating power is set to heat the program, the holding temperature is 1300℃, and the holding time is 3h. After the holding time is reached, the power is turned off and cooled to 1000℃. The sample is taken out and quickly quenched to complete the Cu 50 Co 50 Heat treatment process of immiscible alloys, Cu after semi-solid heat treatment 50 Co 50 Immiscible alloy samples, whose structure is as follows Figure 4 shown. Example 3

[0038] This embodiment provides a method for treating an immiscible alloy using a semi-solid heat treatment process to control its microstructure.

[0039] The semi-solid heat treatment process in this embodiment controls the Cu 50 Co 50 The specific process of the method for the microstructure of immiscible alloys is as follows:

[0040] The first step is alloy preparation: Co and Cu with a purity of no less than 99.99% are selected; both solid-state pure materials are used. The Co:Cu ratio is 1:1, representing the atomic ratio. The surface oxide scales of the two pure metals are first polished off on a grinding wheel. After cleaning, the metals are placed in a copper crucible in a vacuum non-consumable arc furnace and melted using a vacuum non-consumable arc method. Each sample is repeatedly turned over and melted four times to ensure uniform alloy composition, resulting in the final button ingot.

[0041] The second step involved sample preparation: the button ingots were cut, polished, and ultrasonically cleaned. Each experimental sample weighed approximately 1 g. The cleaned samples were placed in a quartz tube with an inner diameter of 7 mm, an outer diameter of 12 mm, and a length of 600 mm. A small amount of boron trioxide glass was placed on the sample surface to prevent oxidation.

[0042] The third step is non-equilibrium solidification treatment: the quartz tube with the sample is fixed with a copper mold fixture and placed in the material processing device, and the sample is placed in the highest temperature zone of the heating body, and the sample placed in the device is solidified. The specific process is to turn on the heating power supply, and repeat the heating rate, holding temperature, holding time and cooling rate set by the program to complete the Cu solidification experiment. 50 Co 50 Solidification process of immiscible alloy. Heating to holding temperature 1420℃, holding time 5min, cooling, and then repeated cycles to obtain large undercooling. According to the cooling curve, the undercooling is judged to be 260K. Cooling to 1000℃ and quenching in water to obtain Cu 50 Co 50 The microstructure of the sample after solidification of the immiscible alloy is a segregated structure. Figure 5 The structure shown.

[0043] The fourth step is semi-solid heat treatment: the alloy sample treated by non-equilibrium solidification is cut in half, polished and cleaned, and the cut sample is placed in the material processing device. The sample holding temperature is set to the liquid-solid two-phase region, and the heating power is set to heat the program, the holding temperature is 1300℃, and the holding time is 6h. After the holding time is reached, the power is turned off and cooled to 1000℃. The sample is taken out and quickly quenched to complete the Cu 50 Co 50Heat treatment process of immiscible alloys, Cu after semi-solid heat treatment 50 Co 50 Immiscible alloy samples, whose structure is as follows Figure 6 shown. Example 4

[0044] This embodiment provides a method for treating an immiscible alloy using a semi-solid heat treatment process to control its microstructure.

[0045] The semi-solid heat treatment process in this embodiment controls the Cu 50 Co 50 The specific process of the method for the microstructure of immiscible alloys is as follows:

[0046] The first step is alloy preparation: Co and Cu with a purity of no less than 99.99% are selected; both solid-state pure materials are used. The Co:Cu ratio is 1:1, representing the atomic ratio. The surface oxide scales of the two pure metals are first polished off on a grinding wheel. After cleaning, the metals are placed in a copper crucible in a vacuum non-consumable arc furnace and melted using a vacuum non-consumable arc method. Each sample is repeatedly turned over and melted four times to ensure uniform alloy composition, resulting in the final button ingot.

[0047] The second step involved sample preparation: the button ingots were cut, polished, and ultrasonically cleaned. Each experimental sample weighed approximately 1 g. The cleaned samples were placed in a quartz tube with an inner diameter of 7 mm, an outer diameter of 12 mm, and a length of 600 mm. A small amount of boron trioxide glass was placed on the sample surface to prevent oxidation.

[0048] The third step is non-equilibrium solidification treatment: the quartz tube with the sample is fixed with a copper mold fixture and placed in the material processing device, and the sample is placed in the highest temperature zone of the heating body, and the sample placed in the device is solidified. The specific process is to turn on the heating power supply, and repeat the heating rate, holding temperature, holding time and cooling rate set by the program to complete the Cu solidification experiment. 50 Co 50 Solidification process of immiscible alloy. Heating to holding temperature 1410℃, holding time 5min, cooling, and then repeated cycles to obtain large undercooling. According to the cooling curve, the undercooling is judged to be 200K. Cooling to 1000℃ and quenching in water to obtain Cu 50 Co 50 Sample of immiscible alloy after solidification.

[0049] The fourth step is semi-solid heat treatment: the alloy sample treated by non-equilibrium solidification is cut in half, polished and cleaned, and the cut sample is placed in the material processing device. The sample holding temperature is set to the liquid-solid two-phase region, and the heating power is set to heat the program, the holding temperature is 1350℃, and the holding time is 4h. After the holding time is reached, the power is turned off and cooled to 1000℃. The sample is taken out and quickly quenched to complete the Cu 50 Co 50 Heat treatment process of immiscible alloys, Cu after semi-solid heat treatment 50 Co 50 Immiscible alloy samples.

[0050] Experimental test analysis:

[0051] The Cu obtained by different semi-solid heat treatment processes in Example 1, Example 2 and Example 3 were 50 Co 50 The immiscible alloy was cold mounted longitudinally and ground gradually to 2000# sandpaper. It was then polished using a 1.5# diamond paste on a polishing machine at an appropriate speed until no scratches appeared on the surface. Etching was performed using a mixture of ferric chloride (5g) + hydrochloric acid (10ml) + ethanol (100ml). The sample's microstructure was observed using a GX71 OLYMPUS optical microscope. Figure 2 、 4 As shown in FIG6, through the semi-solid heat treatment of the present invention, Cu 50 Co 50 The microstructure of the immiscible alloy has undergone significant changes. After rapid solidification, the structure is a segregated structure. The semi-solid heat treatment is performed with the heat treatment temperature set in the liquid-solid two-phase region of the alloy. At the same time, a special cooling treatment is adopted in which the power is turned off and cooled to 1000°C and the sample is taken out for rapid quenching. During the entire cooling process, under the synergistic effect of the uniform composition field and the high cooling rate, a uniform structure with a dispersed minority phase is formed in the liquid matrix. Finally, after adjusting the process parameters of the semi-solid heat treatment, the microstructure of the immiscible alloy has undergone significant changes, and the segregated structure is transformed into a structure with a uniform distribution of the second phase. Although semi-solid heat treatment is also used in Example 1, since it adopts an ordinary cooling method, it is impossible to form the coupling effect of the uniform composition field and the high cooling rate, and ultimately the segregated structure cannot be eliminated.

[0052] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0053] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for segregating immiscible alloys to improve their structural uniformity, characterized in that: include: The immiscible alloy sample is subjected to non-equilibrium solidification treatment. The immiscible alloy is Cu 50 Co 50 Immiscible alloys; The immiscible alloy sample obtained by the non-equilibrium solidification treatment is subjected to a heating-holding heat treatment process, and is held above the melting point of the low-melting-point phase. The immiscible alloy sample is then turned off and cooled to 1000° C., and then taken out and rapidly quenched to obtain an immiscible alloy sample with a uniformly dispersed distribution structure.

2. The method for improving the microstructure uniformity of the segregated immiscible alloy according to claim 1, wherein: The non-equilibrium solidification process comprises: A quartz tube containing an immiscible alloy button ingot is placed into a material processing device and subjected to a heating-insulation-cooling treatment. The heating-insulation-cooling treatment process is repeated multiple times to obtain an undercooling degree of 200K-300K, and then cooled to 1000°C for quenching to complete the non-equilibrium solidification treatment process of the immiscible alloy, thereby obtaining immiscible alloy samples with different types of core-shell structures under large undercooling degrees.

3. The method for improving the structural uniformity of an immiscible alloy by segregation according to claim 2, wherein: After the immiscible alloy button ingot is placed in the quartz tube, the surface needs to be covered with B2O3.

4. The method for improving the structural uniformity of an immiscible alloy by segregation according to claim 2, wherein: The holding temperature of the non-equilibrium solidification treatment is set at 1400° C.-1440° C., and the holding time is at least 5 minutes.

5. The method for improving the microstructure uniformity of segregated immiscible alloys according to claim 1, wherein: The heat treatment is carried out at a holding temperature of 1280° C. to 1360° C. and for a holding time of 3 h to 6 h.

6. The method for improving the microstructure uniformity of segregated immiscible alloys according to claim 1, wherein: The Cu 50 Co 50 The preparation process of the immiscible alloy includes: using Cu and Co as raw materials, melting in a vacuum non-consumable arc melting furnace, repeatedly turning each sample over and melting multiple times during the melting process to ensure uniform composition of the alloy, thereby obtaining Cu 50 Co 50 Immiscible alloys.

7. The method for improving microstructure uniformity by segregating immiscible alloys according to claim 6, wherein: The atomic ratio of Cu:Co is 1:1, and the purity of Co and Cu pure elements is 99.99 wt.%.

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