Mg-co based soluble magnesium alloy containing rare earth elements and method for producing the same

Abstract

The application provides a soluble magnesium alloy with components of Mg-Co-RE1-RE2, wherein the content of Co is 0.5% to 10%, RE1 and RE2 represent two different rare earth elements, specifically, any two of Sc, La, Sm, Pr, Pm, Eu, Tb, Dy, Ho, Tm, Lu, Gd, Y, Nd, Er, Yb and Ce, 0.01 wt.% < RE1 < 20 wt.%, 0.01 wt.% < RE2 < 20 wt.% and the rest is Mg. The yield strength of the alloy in a cast state is greater than 120 MPa, the tensile strength is greater than 210 MPa, the elongation is greater than 8% and the hardness is greater than 80 HV, and the dissolution rate in a water solution containing 3% KCl at 93 DEG C is greater than 80 mg / (cm 2 ·h). The yield strength of the alloy in an extrusion and aging state is greater than 240 MPa, the tensile strength is greater than 330 MPa, the elongation is greater than 10%, the hardness is greater than 100 HV and the dissolution rate in a water solution containing 3% KCl at 93 DEG C is greater than 80 mg / (cm 2 ·h). The alloy has a fast dissolution rate and good mechanical properties and can meet the needs of oil exploitation.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metals technology, specifically to a Mg-Co based soluble magnesium alloy containing rare earth elements, its preparation method, and its application fields. Background Technology

[0002] my country boasts some of the world's largest reserves of shale gas and shale oil, with promising future development prospects. Currently, the mainstream horizontal well production utilizes staged fracturing technology, a key component of which is the fracturing tool, including temporary plugging balls, ball seats, and bridge plugs. At present, commonly used fracturing tools are made of soluble magnesium alloys, which can self-dissolve later in service, thus improving operational efficiency. Pure magnesium has poor mechanical properties and a dissolution rate lower than required, therefore, the development of new soluble magnesium alloys is necessary.

[0003] Patent document 1 (CN118256784A) discloses a soluble magnesium alloy, characterized in that the magnesium alloy is composed of 0.05%–3% Mn, 0.05%–1% Ni, 0.05%–1% X, and the balance Mg by mass percentage; wherein X is one or more of Cu, Fe, Gd, and Y; wherein the Mg-Mn-Ni series alloy can achieve the following highest properties in the as-cast state: yield strength 155 MPa, tensile strength 210 MPa, elongation 31%, and dissolution rate of 50 mg / (cm) in a 3% KCl aqueous solution at 93°C. 2 ·h). This alloy series has relatively low strength and a moderate dissolution rate.

[0004] Patent document 2 (CN113025857A) discloses a soluble magnesium alloy comprising Li and M elements, with the following mass percentages: Li: 8.0–14.0 wt.%; M being at least one of Ni and Cu, wherein Ni: 0.01–5.0 wt.%, Cu: 0.01–5.0 wt.%, and the balance being Mg. The alloy series exhibits relatively low mechanical properties, with a maximum yield strength of 119.5 MPa, a maximum tensile strength of 147 MPa, and a maximum dissolution rate of 70 mg / (cm³) in a 3% KCl aqueous solution at 93°C. 2 (h). The dissolution rate of this alloy series is sufficient for application requirements, but the strength is still relatively low.

[0005] Patent Document 3 (CN110863130A) discloses a soluble magnesium alloy. The composition of the soluble magnesium alloy is Mg-Al-Zn-Mn-Ca-Ni-Ag-X, where X represents one or a combination of more than one of the elements Cu, Fe, Zr, Sn, Gd, Y, Nd, Ce, Sr, Er; among which, the room temperature tensile strength of the extruded Mg-6Al-1.2Zn-0.1Mn-0.3Ca-0.25Ni-0.3Ag-0.1Sn alloy is 325 MPa, the yield strength is 213 MPa, and the elongation is 16.3%. At 93 °C, the corrosion rate in a 3% KCl solution is about 56 mg / (cm 2 ·h). The mechanical properties of this alloy series are good, but the dissolution rate still does not meet the requirements. Summary of the Invention

[0006] The purpose of the present invention is to provide a Mg-Co-based soluble magnesium alloy containing rare earth elements and a preparation method thereof. To achieve the above purpose, the present invention provides

[0007] A Mg-Co-based soluble magnesium alloy containing rare earth elements, characterized in that, calculated by mass percentage, the soluble magnesium alloy consists of the following components: Mg-Co-RE1-RE2, where the Co content is 0.5% - 10%; the rare earth elements RE1 and RE2 are specifically any two of Sc, La, Sm, Pr, Pm, Eu, Tb, Dy, Ho, Tm, Lu, Gd, Y, Nd, Er, Yb, Ce, 0.01 wt.% < RE1 < 20 wt.%, 0.01 wt.% < RE2 < 20 wt.%, and the balance is Mg; the soluble magnesium alloy contains a novel long-period stacking ordered (LPSO) phase, the composition of which is (Mg, Co)(RE1, RE2), the width range is 10 - 50 μm, the average spacing is 10 - 40 μm, and the volume fraction accounts for 20 - 40%. This LPSO phase plays a role in increasing the dissolution rate of the alloy, increasing the strength and hardness of the alloy; the soluble magnesium alloy has a dissolution rate greater than 80 mg / (cm 2 ·h) in an aqueous solution containing 3% KCl at 93 °C.

[0008] The preparation method of the soluble magnesium alloy as described above, characterized in that the specific preparation steps are as follows:

[0009] S1 Proportion raw materials: Use pure Mg ingots, pure Co powder with a spherical particle size less than 50 μm, and Mg-30RE1 and Mg-30RE2 master alloys as raw materials, and proportion the raw materials according to the alloy element content;

[0010] S2 casting: First, pure Mg ingots, Mg-30RE1 and Mg-30RE2 master alloys are melted in a melting furnace at 750°C and held for 2-4 minutes. Then, pure Co powder is added, and the furnace temperature is raised to 850°C and held for 1-6 minutes. Electromagnetic stirring is used to ensure that the three alloying elements are mixed evenly in the alloy melt, especially to ensure that the Co powder is fully dissolved. Then, the alloy melt is poured into a graphite mold and cooled to room temperature to obtain the magnesium alloy ingot of the invention.

[0011] Furthermore, the magnesium alloy ingot can be subjected to extrusion deformation and aging heat treatment;

[0012] S3 Solution Treatment: The magnesium alloy ingot is held at 450℃~500℃ for 12~24 hours, and then water quenched.

[0013] S4 extrusion: The ingot treated in step S3 is held at 400℃~550℃ for 0.5~2 h, and then extruded to obtain magnesium alloy rods. The extrusion speed is 0.5~2 mm / s and the extrusion ratio is 16~36.

[0014] S5 Aging Treatment: The rods obtained in step S4 are kept at 150℃~250℃ for 12~72 h. During this process, precipitates are formed in the Mg matrix. The size of the precipitates is less than 100 nm, which can significantly improve the strength of the rods. The average grain size after extrusion is 3~6 μm.

[0015] Furthermore, the as-cast magnesium alloy obtained from S2 exhibits a yield strength greater than 120 MPa, a tensile strength greater than 210 MPa, an elongation greater than 8%, and a hardness greater than 80 HV; its dissolution rate in an aqueous solution containing 3% KCl at 93℃ is greater than 80 mg / (cm³). 2 ·h).

[0016] Furthermore, the aged magnesium alloy obtained from S5 exhibits a yield strength greater than 240 MPa, a tensile strength greater than 330 MPa, an elongation greater than 10%, and a hardness greater than 100 HV; in an aqueous solution containing 3% KCl at 93℃, the dissolution rate is greater than 80 mg / (cm³). 2 ·h).

[0017] The characteristic of step S1 of this invention is that, because Co has a melting point as high as 1495℃, this invention, through experimental research, selects Co powder with a spherical particle size of less than 50 μm, which, under the process parameters of the subsequent step S2, can achieve a uniform distribution of Co element in the alloy melt of the invention.

[0018] In contrast, existing Co-containing magnesium alloys are usually smelted using Mg-Co master alloys. For example, the literature (WANG Z, CAO H, ZHENG H, et al. Effect of aging treatment on the mechanical property and precipitation transformation of Mg–Co–Y alloy [J]. Materials Science and Engineering: A, 881, 2023, 145322.) uses a Mg-10Co (wt.%) master alloy.

[0019] The characteristics of S2 casting are: the microstructure of the magnesium alloy ingot obtained by pouring into a graphite mold and cooling to room temperature contains a novel long-period structure (LPSO) phase with a composition of (Mg, Co)(RE1, RE2). Compared with the previously reported LPSO phase, this LPSO phase is characterized by the simultaneous presence of Co and two rare earth elements. Compared with similar rare earth soluble magnesium alloys that do not contain Co, the dissolution rate is 3 times or more than that of Mg–10Gd–3Y–0.2Zr–0.8Ni.

[0020] The room temperature tensile mechanical properties of the as-cast magnesium alloy obtained in this step are: yield strength greater than 120 MPa, tensile strength greater than 210 MPa, elongation greater than 8%, and hardness greater than 80 HV; its dissolution rate in an aqueous solution containing 3% KCl at 93℃ is greater than 80 mg / (cm³). 2 ·h).

[0021] Furthermore, the magnesium alloy ingot can be subjected to extrusion deformation and aging heat treatment.

[0022] S5 Aging Treatment: The bar obtained in step S4 is held at 150℃~250℃ for 12~72 h.

[0023] The room temperature tensile mechanical properties of the aged magnesium alloy obtained in this step are as follows: yield strength greater than 240 MPa, tensile strength greater than 330 MPa, elongation greater than 10%, and hardness greater than 100 HV; in an aqueous solution containing 3% KCl at 93℃, the dissolution rate is greater than 80 mg / (cm³). 2 ·h).

[0024] The soluble magnesium alloy of this invention has the following characteristics and advantages:

[0025] (1) The soluble magnesium alloy of the present invention contains a novel LPSO phase (Mg, Co)(RE1, RE2), the width of the layered LPSO phase ranges from 10 to 50 μm, the average spacing is 10 to 40 μm, and the volume fraction is 20 to 40%. This can simultaneously improve strength and dissolution rate.

[0026] (2) The dissolution rate of the soluble magnesium alloy of the present invention in an aqueous solution containing 3% KCl at 93°C is greater than 80 mg / (cm³). 2 ·h), compared with alloys containing the same rare earth elements but without Co, the dissolution rate is more than 3 times that of Mg–10Gd–3Y–0.2Zr–0.8Ni alloy;

[0027] (3) The soluble magnesium alloy of the present invention has good comprehensive properties, and the dissolution rate of the extruded alloy is maintained at 80 mg / (cm³). 2 At the same time, the tensile strength reaches up to 390 MPa and the elongation is greater than 10%. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the novel LPSO phase contained in the alloy of Example 1 of the invention. Detailed Implementation

[0029] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Appropriate modifications can be made to implement the invention without changing its essence.

[0030] Example 1:

[0031] It should be noted that RE1 and RE2 are any two of Sc, La, Sm, Pr, Pm, Eu, Tb, Dy, Ho, Tm, Lu, Gd, Y, Nd, Er, Yb, and Ce, and are not limited to the combinations in the following embodiments. Some examples are selected to further explain the preparation and processing methods and properties of the alloys of the present invention. The alloy composition ratios are expressed as mass fractions as shown in Table 1-1.

[0032] Table 1-1

[0033]

[0034] The casting process of all the inventive magnesium alloys in Table 1-1 is as follows: using pure Mg ingots, pure Co powder with spherical particle size less than 50 μm, Mg-30RE1 and Mg-30RE2 master alloys as raw materials, the raw material ratio is determined according to the content of alloying elements; firstly, the pure Mg ingots, Mg-30RE1 and Mg-30RE2 master alloys are melted in a melting furnace at 750°C and held for 2-4 minutes, then pure Co powder is added, and the furnace temperature is raised to 850°C and held for 1-6 minutes, with electromagnetic stirring to ensure that the three alloying elements are mixed evenly in the alloy melt, especially to ensure that the Co powder is fully dissolved; then the alloy melt is poured into a graphite mold and cooled to room temperature to obtain the inventive magnesium alloy ingot.

[0035] The microstructure of the alloy of Invention Example 1 was observed using a scanning electron microscope (SEM), and the LPSO phase therein was as follows: Figure 1 As shown, the layered LPSO phase has an average width of 30 μm, an average spacing of 40 μm, and a volume fraction of 30%. Energy dispersive spectroscopy (EDS) analysis using a scanning electron microscope revealed that the LPSO phase contains Co and two other rare earth elements. Figure 1 The specific composition results of element content (at.%) at different positions are shown in Table 1-2.

[0036] Table 1-2

[0037]

[0038] Example 2:

[0039] For the alloy obtained in Example 1, the room temperature tensile mechanical properties were evaluated according to the national standard GB / T228.1-2010 "Metallic materials, tensile testing—Part 1: Test methods at room temperature"; the dissolution rate was tested at 93°C using an aqueous solution containing 3 wt.% KCl according to the national standards GB / T19746-2018 "Corrosion salt solution immersion test of metals and alloys" and GB / T16545-2015 "Removal of corrosion products from corrosion specimens of metals and alloys"; the obtained properties are shown in Table 2-1. The highest dissolution rate in Example 1 was 95 mg / (cm³). 2 •h); Invention Example 18 has the best overall performance, with an elongation of 14.4%, and can be used for large deformation treatments.

[0040] Table 2-1

[0041]

[0042] Example 3:

[0043] The alloy ingot obtained in Example 1 is then subjected to further processing, as follows:

[0044] (1) Solution treatment: The magnesium alloy ingot of the invention example is kept at 450℃~500℃ for 12~24 hours (h represents hours thereafter), and then water quenched. The specific process parameters are shown in Table 3-1.

[0045] (2) Extrusion: The alloy ingot of the invention after solution treatment is kept at 400℃~550℃ for 0.5~2 h, and then extruded to obtain bars. The extrusion speed is 0.5~2 mm / s and the extrusion ratio is 16~36. The specific process parameters are shown in Table 3-1.

[0046] (3) Aging treatment: The above extruded bars are kept at 150℃~250℃ for 12~72 h. The specific aging temperature and time are shown in Table 3-1. During this process, precipitates are formed in the Mg matrix. The size of the precipitates is less than 100 nm, which can significantly improve the strength of the bars.

[0047] Table 3-1

[0048]

[0049] Example 4:

[0050] The aged alloys obtained in Example 3 were tested for mechanical properties and dissolution rates according to the method in Example 2. The results are shown in Table 4-1. All alloys exhibited a yield strength greater than 240 MPa, a tensile strength greater than 330 MPa, an elongation greater than 10%, and a hardness greater than 100 HV. In an aqueous solution containing 3% KCl at 93°C, the dissolution rate was greater than 80 mg / (cm³). 2 •h). Invention Example 3 has the highest elongation, reaching 19.8%, and its dissolution rate reaches 93 mg / (cm). 2 ·h).

[0051] Table 4-1

[0052]

[0053] Comparative Example 1:

[0054] The alloy composition is Mg-9.8Gd-2.8Y-0.5Zr. Raw materials are selected according to the proportion of alloying elements. The raw materials are then added together to a vacuum melting furnace, heated to 750℃, and refined at that temperature for 5-10 minutes with electromagnetic stirring to ensure uniform mixing of the alloying elements. The mixture is then poured into a graphite mold and cooled to room temperature to obtain a magnesium alloy ingot.

[0055] The properties of the as-cast alloy obtained in Comparative Example 1, measured according to the test method in Example 2, are as follows: yield strength 164 MPa, tensile strength 220 MPa, elongation 2%, hardness 78 HV, and dissolution rate 1.5 mg / (cm²). 2 •h). In Example 2, Inventive Example 10 (see Table 2-1) had a tensile strength of 247 MPa, an elongation of 8.4%, a hardness of 89 HV, and a dissolution rate of 90 mg / (cm²). 2 •h). In Example 2, the elongation in the as-cast state of all inventive examples was greater than 8%, which was more than 4 times that of Comparative Example 1; the dissolution rate of all inventive examples in Example 2 was greater than 80 mg / (cm). 2 ·h) is more than 50 times that of proportion 1.

[0056] Comparative Example 2:

[0057] The alloy composition is Mg-12Gd-3.5Y-3.8Ni-0.05La-1.2Eu-0.5Yb. Raw materials are selected according to the proportions of the alloying elements. These raw materials are then added together to a vacuum melting furnace, heated to 750℃, and held at that temperature for 5-10 minutes for refining. Electromagnetic stirring is used to ensure uniform mixing of the alloying elements. The mixture is then poured into a graphite mold and cooled to room temperature to obtain a magnesium alloy ingot.

[0058] The alloy obtained in Comparative Example 2, according to the test method in Example 2, exhibited the following properties: yield strength 99 MPa, tensile strength 150 MPa, elongation 3.5%, hardness 75 HV, and dissolution rate 44.6 mg / (cm²). 2 •h). The lowest performance of the as-cast alloy in this invention is Example 3, with a yield strength of 121 MPa, a tensile strength of 213 MPa, an elongation of 12.8%, a hardness of 85 HV, and a dissolution rate of 90 mg / (cm). 2 Therefore, the performance of all the inventive examples is better than that of Comparative Example 2.

[0059] Comparative Example 3:

[0060] The alloy composition is Mg-14Gd-4.2Y-0.1Ni-1.1Zr-1Eu-1.6Yb. Raw materials are selected according to the proportions of the alloying elements. These raw materials are then added together to a vacuum melting furnace, heated to 750℃, and held at that temperature for 5-10 minutes for refining. Electromagnetic stirring is used to ensure uniform mixing of the alloying elements. The mixture is then poured into a graphite mold and cooled to room temperature to obtain a magnesium alloy ingot.

[0061] The alloy obtained in Comparative Example 3, according to the test method in Example 2, exhibited the following properties: yield strength 168 MPa, tensile strength 215 MPa, elongation 0.9%, hardness 80 HV, and dissolution rate 1.1 mg / (cm²). 2 (·h). In this invention, the as-cast alloy has a tensile strength of 215 MPa, an elongation of 13.0%, a hardness of 87 HV, and a dissolution rate of 90 mg / (cm). 2 •h). The elongation of all the invention examples was greater than 10%, which is more than 10 times that of Comparative Example 3; the dissolution rate of all the invention examples was greater than 80 mg / (cm). 2 ·h) is more than 70 times that of ratio 3.

[0062] Comparative Example 4:

[0063] The alloy composition is Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni. Raw materials are selected according to the proportions of the alloying elements. These raw materials are then added together to a vacuum melting furnace, heated to 750°C, and held at that temperature for 5–10 minutes for refining. Electromagnetic stirring is used to ensure uniform mixing of the alloying elements. The mixture is then poured into a graphite mold and cooled to room temperature to obtain a magnesium alloy ingot. The resulting magnesium alloy ingot is homogenized at 470°C for 24 hours and then at 520°C for 24 hours, followed by air cooling. Extrusion is then performed at 450°C with an extrusion ratio of 8:1 and a speed of 0.5 mm / s.

[0064] The alloy obtained in Comparative Example 4, according to the test method in Example 2, exhibited the following properties: yield strength 316 MPa, tensile strength 382 MPa, elongation 7%, hardness 92 HV, and dissolution rate 46.9 mg / (cm²). 2 •h). In Table 4-1, the highest tensile strength is found in Invention Example 16, which has a similar tensile strength of 379 MPa; elongation is 10.4%, an increase of 48.6%; hardness is 124 HV, an increase of 34.6%; and dissolution rate is 89 mg / (cm²). 2 (·h), which increased by 47.3%.

Claims

1. A Mg-Co based soluble magnesium alloy containing rare earth elements, characterized in that, The soluble magnesium alloy, by mass percentage, consists of the following components: Mg-Co-RE1-RE2, where the Co content is 5% to 10%; the rare earth elements RE1 and RE2 are specifically any two of Sc, La, Pr, Pm, Eu, Tb, Dy, Ho, Tm, Lu, 0.01 wt.% < RE1 < 20 wt.%, 0.01 wt.% < RE2 < 20 wt.%, and the balance is Mg; the soluble magnesium alloy contains a long-period LPSO phase with the composition (Mg, Co)(RE1, RE2), the width range is 10 to 50 μm, the average spacing is 10 to 40 μm, and the volume fraction accounts for 20 to 40%. This LPSO phase plays a role in increasing the dissolution rate of the alloy, increasing the strength and hardness of the alloy; the soluble magnesium alloy has a dissolution rate greater than 80 mg / (cm 2 ·h) in an aqueous solution containing 3% KCl at 93°C.

2. The method for preparing the soluble magnesium alloy according to claim 1, characterized in that, The specific preparation steps are as follows: S1 Raw Material Ratio: Pure Mg ingots, pure Co powder with spherical particle size less than 50 μm, Mg-30RE1 and Mg-30RE2 master alloys are used as raw materials, and the raw material ratio is determined according to the content of alloying elements. S2 casting: First, pure Mg ingots, Mg-30RE1 and Mg-30RE2 master alloys are melted in a melting furnace at 750℃ and held for 2-4 minutes. Then, pure Co powder is added, and the furnace temperature is raised to 850℃ and held for 1-6 minutes with electromagnetic stirring to ensure that the three alloying elements are mixed evenly in the alloy melt and that the Co powder is fully dissolved. Then, the alloy melt is poured into a graphite mold and cooled to room temperature to obtain magnesium alloy ingots. Furthermore, the magnesium alloy ingot is subjected to extrusion deformation and aging heat treatment; S3 Solution Treatment: The magnesium alloy ingot is held at 450℃~500℃ for 12~24 hours, and then water quenched. S4 extrusion: The ingot treated in step S3 is held at 400℃~550℃ for 0.5~2 h, and then extruded to obtain magnesium alloy rods. The extrusion speed is 0.5~2 mm / s and the extrusion ratio is 16~36. S5 Aging Treatment: The rod obtained in step S4 is kept at 150℃~250℃ for 12~72 h. During this process, a precipitate phase is formed in the Mg matrix. The size of the precipitate phase is less than 100 nm, which can significantly improve the strength of the rod. The average grain size after extrusion is 3~6 μm.

3. The method for preparing soluble magnesium alloy according to claim 2, characterized in that, The as-cast magnesium alloy obtained from S2 has a yield strength greater than 120 MPa, a tensile strength greater than 210 MPa, an elongation greater than 8%, and a hardness greater than 80 HV; its dissolution rate in an aqueous solution containing 3% KCl at 93℃ is greater than 80 mg / (cm³). 2 ·h).

4. The method for preparing the soluble magnesium alloy according to claim 2, characterized in that, The aged magnesium alloy obtained from S5 exhibits a yield strength greater than 240 MPa, a tensile strength greater than 330 MPa, an elongation greater than 10%, and a hardness greater than 100 HV. In an aqueous solution containing 3% KCl at 93℃, the dissolution rate is greater than 80 mg / (cm³). 2 ·h).

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