CN114908280B - A kind of high-strength toughness rapid degradation Mg-Er-Ni alloy for downhole fracturing and preparation method thereof - Google Patents

Abstract

The invention discloses a high-strength and high-toughness fast degradation Mg-Er-Ni alloy for underground fracturing, which comprises the following components in percentage by mass: er:6-15%, ni:1-5%, the molar ratio of Er/Ni is 1.3-1.8, and the balance is Mg and inevitable impurity elements; wherein Mg, ni and Er mainly form Ni-LPSO phase which is layered and blocky and coexists, and the volume fraction of the Ni-LPSO phase is 15-36%. The invention also discloses a preparation method and application of the Mg-Er-Ni alloy. The Mg-Er-Ni alloy provided by the invention takes magnesium as a base material, and Ni and Er are added; and through regulating the molar ratio of Er/Ni, the solution treatment temperature, time and cooling speed and finally homogenizing heat treatment in short time before extrusion, layered LPSO phase which is not precipitated in the Mg matrix in the rapid cooling process is precipitated to prepare alloy containing blocky and layered Ni-LPSO phases, so that brittle Mg is avoided ₂ Ni phase and low potential MgEr rare earth phase are generated, and simultaneously, the synergistic promotion of the obdurability and the degradation characteristic is realized.

Description

A kind of high-strength toughness rapid degradation Mg-Er-Ni alloy for downhole fracturing and its preparation method

technical field

The invention belongs to the technical field of oil and gas exploitation materials, and in particular relates to a high-strength, tough and fast-degradable Mg-Er-Ni alloy for downhole fracturing and a preparation method thereof.

Background technique

my country has abundant reserves of oil and gas resources, but more than 70% of them are unconventional oil and gas, and the current recovery rate of this type of oil and gas is less than 10%. At present, drillable fracturing tools have obvious limitations due to the difficulty of construction, time-consuming and labor-consuming, and high-level defects, while soluble fracturing tools have the advantages of simple construction, low cost, reliability, and complete solubility. , put into the exploitation of unconventional oil and gas. However, in the face of higher efficiency, deeper mining depth, and more complex mining environment requirements for oil and gas extraction, high-strength and fast-degrading fracturing tools are urgently needed to be developed.

At present, the development of soluble fracturing tools is based on magnesium with high specific strength, low density, and low corrosion resistance as the raw material, and a series of alloying and deformation processing methods are used to develop soluble magnesium alloy fracturing tools. The currently developed Mg-Al and Mg-Zn fracturing tools have more or less low strength or poor degradation performance, which cannot meet the needs of high-pressure and complex environment fracturing tools. Although the Mg-RE-Ni alloy containing multiple second phases has a maximum strength of 510MPa, its degradation rate is only 2400mm/a, so it is urgent to develop a magnesium alloy material with high strength and rapid degradation for fracturing.

Contents of the invention

The present invention aims to solve one of the technical problems in the related art at least to a certain extent. Therefore, the main purpose of the present invention is to provide a high-strength, tough and fast-degradable Mg-Er-Ni alloy for downhole fracturing, aiming to solve the problem that existing magnesium alloys cannot balance strength and degradation rate.

The purpose of the present invention is achieved through the following technical solutions:

A Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing, comprising the following components by mass percentage: Er: 6-15%, Ni: 1-5%, and the molar ratio of Er/Ni is 1.3-1.8, the balance is Mg and unavoidable impurity elements; wherein, Mg, Ni and Er mainly form a layered and massive Ni-LPSO phase coexisting, and the volume fraction of the Ni-LPSO phase is 15-36 %.

In some specific embodiments, the Er/Ni molar ratio is 1.4-1.6, and the volume fraction of the Ni-LPSO phase is 24-36%.

The purpose of the present invention is to also provide the preparation method of the aforementioned Mg-Er-Ni alloy, comprising the following steps: uniformly mixing nickel source, magnesium source and erbium source, carrying out alloying treatment, and obtaining high-strength, tough and fast-degradable Mg-Er -Ni alloy.

In some specific embodiments, the nickel source is selected from nickel simple substance and/or nickel alloy;

Further, the nickel alloy is selected from magnesium-nickel alloy;

In some specific embodiments, the magnesium source is selected from magnesium element and/or magnesium alloy;

Further, the magnesium alloy is selected from magnesium-nickel alloy;

In some specific embodiments, the erbium source includes at least one of magnesium-erbium alloy and nickel-erbium alloy;

In some specific embodiments, the alloying treatment is smelting casting method and powder alloy method;

Further, alloying treatment is carried out by melting and casting;

In some specific embodiments, the smelting and casting method includes the following steps:

(a) Casting: Mix nickel source, magnesium source and erbium source evenly, carry out smelting and casting, obtain as-cast alloy;

(b) Heat treatment: The as-cast alloy is subjected to homogenization treatment and extrusion deformation treatment in sequence to obtain a Mg-Er-Ni alloy with high strength, toughness and rapid degradation.

Further, in step (a), when performing smelting and casting, first raise the temperature to 760-800°C, keep warm and stir to melt all the raw materials, then keep warm at 760-780°C for 10-20min, and finally pass through 5-10°C brine After rapid cooling in the bath, an as-cast alloy is obtained;

Further, inert gas protection is used during smelting and casting; the inert gas is selected from at least one of helium, argon, carbon dioxide and sulfur hexafluoride;

Further: in step (b), the temperature for homogenization treatment is 380-420°C, and the time is 25-35min.

Further, in step (b), the extrusion ratio during extrusion deformation treatment is 9-15, and the extrusion deformation speed is 0.3-0.4m/min; preferably, the temperature for extrusion deformation treatment is 380-420 ℃.

The object of the present invention is to also provide the application of the aforementioned Mg-Er-Ni alloy in the field of oil and gas development.

Compared with the prior art, the present invention has at least the following advantages:

1) The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention uses magnesium as the base material, and is melted at 760-800°C by adding Ni and Er, 760-780°C, 10-20min Insulation treatment, rapid cooling in 5-10°C brine bath to adjust the structure of the second phase; then by adjusting the molar ratio of Er/Ni, control it to only produce Ni-LPSO phase; finally, through a short-term homogenization heat treatment before extrusion, so that During the rapid cooling process, the unprecipitated layered LPSO phase precipitates in the Mg matrix, and an alloy containing massive and layered Ni-LPSO phases is prepared, which not only avoids the formation of brittle Mg ₂ Ni phases and low-potential MgEr rare earth phases, but also achieves strong toughness and synergistic improvement of degradation characteristics.

2) The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention has a simple process flow, does not need solid solution and aging heat treatment, simplifies the process, reduces the cost, and uses resistance furnaces, extrusion machines and other equipment All are conventional equipment, which is convenient for industrial application.

Description of drawings

In order to illustrate the specific implementation of the present invention more clearly, the following will briefly introduce the drawings that are required for the specific implementation or the description of the prior art.

Fig. 1 is the SEM figure of the Mg-Er-Ni alloy that embodiment 2 provides among the present invention;

Fig. 2 is the ImagePro test figure of the Mg-Er-Ni alloy that embodiment 2 provides among the present invention;

Fig. 3 is the TEM figure of the Mg-Er-Ni alloy that embodiment 2 provides among the present invention;

Fig. 4 is an engineering force diagram of the Mg-Er-Ni alloy provided in Example 1-Example 6 of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and examples. The following examples are only descriptive, not restrictive, and cannot limit the protection scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

In the following examples, pure magnesium, Mg-30wt.% Er and Mg-30wt.% Ni master alloy are purchased from Shandong Ruifeng Metal Products Co., Ltd., carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ) Bought from Chongqing Ruike Gas Co., Ltd., the corrosion rate determination bottle KCl was purchased from Chongqing Huanghui Chemical Dangerous Goods Sales Co., Ltd.

In the following examples, the mechanical properties are detected by the electronic universal tensile testing machine (GB/T 1177-2018) (detection method), the equipment model adopted is CMT-5105, and the degradation rate is passed through the immersion test of the alloy (GB/T 1177-2018) (detection method). /T16886.15) (detection method), the equipment used is a digital display constant temperature water bath, its model is HH-2; the volume fraction of the phase body in the alloy is tested by Image Pro phase volume fraction analysis software; SEM and Phase identification was carried out by transmission electron microscopy (TEM).

Example 1

The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention comprises the following components by mass percentage: Er: 6.2%, Ni: 1.5%, and the balance is Mg and unavoidable impurities elements (mass percentage content of unavoidable impurity elements in the alloy is not higher than 0.2%), wherein the molar ratio of Er/Ni is 1.45.

The preparation method of the Mg-Er-Ni alloy with high strength, toughness and fast degradation for downhole fracturing provided by the present invention comprises the following steps:

1) Proportioning according to the composition of the above alloys, weighing commercial pure magnesium blocks and Mg-30wt.% Er, Mg-30wt.% Ni intermediate alloys, grinding the surface of raw materials, removing the surface oxide layer, and placing them in turn In industrial alcohol, put it into an ultrasonic cleaner for cleaning;

2) Set the temperature of the resistance furnace to 760°C, under the protection of the mixed gas of carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ), put the pure Mg block and the Mg-30wt.% Er master alloy into the crucible first , put the crucible into the resistance furnace, after the material is melted, put the Mg-30wt.%Ni intermediate alloy, after it is completely melted, keep it at 760°C for 20min; after the heat preservation is over, take the crucible out of the resistance furnace , and rapidly cooled in a 5°C salt water bath to obtain an as-cast alloy;

3) Turn the as-cast alloy to prepare an extruded ingot with a diameter of 80 mm and a height of 60 mm. After peeling the extruded ingot, preheat the extruded ingot to 380°C for 35 minutes for homogenization treatment, and then place Put it into an extrusion cylinder for extrusion, the extrusion temperature is 380° C., the extrusion ratio is 15, and the extrusion speed is 0.3 m/min to obtain an extruded rod.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-time homogenized state prepared in this example, and a transmission electron microscope (TEM) was used to scan the appearance of the alloy, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It can be seen from the detection that Mg, Er and Ni in the short-time homogenized state alloy form a layered and massive Ni-LPSO-containing phase coexisting, and the volume fraction of this phase is 15.2%.

Example 2

The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention comprises the following components by mass percentage: Er7.6%, Ni: 1.9%, and the balance is Mg and unavoidable impurities elements (mass percentage content of unavoidable impurity elements in the alloy is not higher than 0.2%), and the Er/Ni molar ratio is 1.41.

The preparation method of the Mg-Er-Ni alloy with high strength, toughness and fast degradation for downhole fracturing provided by the present invention comprises the following steps:

1) Proportioning according to the composition of the above alloys, weighing commercial pure magnesium blocks and Mg-30wt.% Er, Mg-30wt.% Ni intermediate alloys, grinding the surface of raw materials, removing the surface oxide layer, and placing them in turn In industrial alcohol, put it into an ultrasonic cleaner for cleaning;

2) Set the temperature of the resistance furnace to 770°C, and under the protection of the mixed gas of carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ), first put the pure Mg block and the Mg-30wt.% Er master alloy into the crucible , put the crucible into the resistance furnace, after the material is melted, put the Mg-30wt.%Ni intermediate alloy, after it is completely melted, keep it at 760°C for 18min; after the heat preservation is over, take the crucible out of the resistance furnace , and rapidly cooled in a 5°C salt water bath to obtain an as-cast alloy;

3) Turn the as-cast alloy to prepare an extruded ingot with a diameter of 80 mm and a height of 60 mm. After peeling the extruded ingot, first preheat the extruded ingot to 400°C for 30 minutes for homogenization treatment, and then place Put it into an extrusion barrel for extrusion, the extrusion temperature is 400° C., the extrusion ratio is 11, and the extrusion speed is 0.3 m/min to obtain an extruded rod.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-time homogenized state prepared in this example, and a transmission electron microscope (TEM) was used to scan the appearance of the alloy, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. Detection, the results are shown in Figure 1, Figure 2 and Figure 3, it can be seen that Mg, Er and Ni in the short-time homogenized alloy form a layered and massive Ni-LPSO phase that coexists, and the volume fraction of this phase is 19.1%, Er/Ni molar ratio is 1.41.

Example 3

The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention comprises the following components by mass percentage: Er: 8.8%, Ni: 2.3%, and the balance is Mg and unavoidable impurities elements (mass percentage content of unavoidable impurity elements in the alloy is not higher than 0.2%), and the Er/Ni molar ratio is 1.33.

The preparation method of the Mg-Er-Ni alloy with high strength, toughness and fast degradation for downhole fracturing provided by the present invention comprises the following steps:

1) Proportioning according to the composition of the above alloys, weighing commercial pure magnesium blocks and Mg-30wt.% Er, Mg-30wt.% Ni intermediate alloys, grinding the surface of raw materials, removing the surface oxide layer, and placing them in turn In industrial alcohol, put it into an ultrasonic cleaner for cleaning;

2) Set the temperature of the resistance furnace to 780°C, and under the protection of a mixed gas of carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ), put pure Mg block and Mg-30wt.% Er master alloy into the crucible first , put the crucible into the resistance furnace, after the material is melted, put the Mg-30wt.%Ni intermediate alloy, after it is completely melted, keep it at 770°C for 15min; after the heat preservation is over, take the crucible out of the resistance furnace , and rapidly cooled in a 6°C salt water bath to obtain an as-cast alloy;

3) Turn the as-cast alloy to prepare an extruded ingot with a diameter of 80 mm and a height of 60 mm. After peeling the extruded ingot, first preheat the extruded ingot to 400°C for 25 minutes for homogenization treatment, and then place Put it into an extrusion cylinder for extrusion, the extrusion temperature is 400° C., the extrusion ratio is 9, and the extrusion speed is 0.3 m/min to obtain an extruded rod.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-time homogenized state prepared in this example, and a transmission electron microscope (TEM) was used to scan the appearance of the alloy, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It can be seen from the detection that Mg, Er and Ni in the short-time homogenized state alloy form a layered and massive Ni-LPSO-containing phase coexisting, and the volume fraction of this phase is 24.2%. ;

Example 4

The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention comprises the following components by mass percentage: Er: 10.6%, Ni: 2.8%, and the balance is Mg and unavoidable impurities elements (mass percentage content of unavoidable impurity elements in the alloy is not higher than 0.2%), wherein the Er/Ni molar ratio is 1.32.

The preparation method of the Mg-Er-Ni alloy with high strength, toughness and fast degradation for downhole fracturing provided by the present invention comprises the following steps:

1) Proportioning according to the composition of the above alloys, weighing commercial pure magnesium blocks and Mg-30wt.% Er, Mg-30wt.% Ni intermediate alloys, grinding the surface of raw materials, removing the surface oxide layer, and placing them in turn In industrial alcohol, put it into an ultrasonic cleaner for cleaning;

2) Set the temperature of the resistance furnace to 790°C, under the protection of a mixed gas of carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ), put pure Mg block and Mg-30wt.% Er master alloy into the crucible first , put the crucible into the resistance furnace, after the material is melted, put the Mg-30wt.%Ni intermediate alloy, after it is completely melted, keep it at 770°C for 13 minutes; after the heat preservation is over, take the crucible out of the resistance furnace , and rapidly cooled in an 8°C salt water bath to obtain an as-cast alloy;

3) Turn the as-cast alloy to prepare an extruded ingot with a diameter of 80 mm and a height of 60 mm. After peeling the extruded ingot, preheat the extruded ingot to 420°C for 25 minutes for homogenization treatment, and then place Put it into an extrusion cylinder for extrusion, the extrusion temperature is 420° C., the extrusion ratio is 12, and the extrusion speed is 0.4 m/min to obtain an extruded rod.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-time homogenized state prepared in this example, and a transmission electron microscope (TEM) was used to scan the appearance of the alloy, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It can be seen from the detection that Mg, Er and Ni in the short-time homogenized state alloy form a Ni-LPSO phase containing layer and block coexisting, and the volume fraction of this phase is 28.3%.

Example 5

The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention comprises the following components by mass percentage: Er: 13.2%, Ni: 3.4%, and the balance is Mg and unavoidable impurities elements (mass percentage content of unavoidable impurity elements in the alloy is not higher than 0.2%), and the Er/Ni molar ratio is 1.36.

The preparation method of the Mg-Er-Ni alloy with high strength, toughness and fast degradation for downhole fracturing provided by the present invention comprises the following steps:

1) Proportioning according to the composition of the above alloys, weighing commercial pure magnesium blocks and Mg-30wt.% Er, Mg-30wt.% Ni intermediate alloys, grinding the surface of raw materials, removing the surface oxide layer, and placing them in turn In industrial alcohol, put it into an ultrasonic cleaner for cleaning;

2) Set the temperature of the resistance furnace to 790°C, under the protection of a mixed gas of carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ), put pure Mg block and Mg-30wt.% Er master alloy into the crucible first , put the crucible into the resistance furnace, after the material is melted, put the Mg-30wt.%Ni intermediate alloy, after it is completely melted, keep it at 775°C for 13 minutes; after the heat preservation is over, take the crucible out of the resistance furnace , and rapidly cooled in an 8°C salt water bath to obtain an as-cast alloy;

3) Turn the as-cast alloy to prepare an extruded ingot with a diameter of 80 mm and a height of 60 mm. After peeling the extruded ingot, first preheat the extruded ingot to 410°C for 30 minutes for homogenization treatment, and then place Put it into an extrusion barrel for extrusion, the extrusion temperature is 410° C., the extrusion ratio is 13, and the extrusion speed is 0.4 m/min to obtain an extruded rod.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-time homogenized state prepared in this example, and a transmission electron microscope (TEM) was used to scan the appearance of the alloy, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It can be seen from the detection that Mg, Er and Ni in the short-time homogenized state alloy form a layered and massive Ni-LPSO-containing phase coexisting, and the volume fraction of this phase is 32.2%.

Example 6

The Mg-Er-Ni alloy with high strength, toughness and rapid degradation for downhole fracturing provided by the present invention comprises the following components by mass percentage: Er: 14.8%, Ni: 3.9%, and the balance is Mg and unavoidable impurities elements (mass percentage content of unavoidable impurity elements in the alloy is not higher than 0.2%), and the Er/Ni molar ratio is 1.33.

The preparation method of the Mg-Er-Ni alloy with high strength, toughness and fast degradation for downhole fracturing provided by the present invention comprises the following steps:

1) Proportioning according to the composition of the above alloys, weighing commercial pure magnesium blocks and Mg-30wt.% Er, Mg-30wt.% Ni intermediate alloys, grinding the surface of raw materials, removing the surface oxide layer, and placing them in turn In industrial alcohol, put it into an ultrasonic cleaner for cleaning;

2) Set the temperature of the resistance furnace to 800°C, and under the protection of the mixed gas of carbon dioxide (CO ₂ ) and sulfur hexafluoride (SF ₆ ), put the pure Mg block and the Mg-30wt.% Er master alloy into the crucible first , Put the crucible into the resistance furnace, after the material is melted, put the Mg-30wt.%Ni intermediate alloy, after it is completely melted, keep it at 780°C for 10min; after the heat preservation is over, take the crucible out of the resistance furnace , and rapidly cooled in a 9°C salt water bath to obtain an as-cast alloy;

3) Turn the as-cast alloy to prepare an extruded ingot with a diameter of 80 mm and a height of 60 mm. After peeling the extruded ingot, first preheat the extruded ingot to 400°C for 30 minutes for homogenization treatment, and then place Put it into an extrusion barrel for extrusion, the extrusion temperature is 400° C., the extrusion ratio is 11, and the extrusion speed is 0.3 m/min to obtain an extruded rod.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-time homogenized state prepared in this example, and a transmission electron microscope (TEM) was used to scan the appearance of the alloy, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It can be seen from the detection that Mg, Er and Ni in the short-time homogenized state alloy form a Ni-LPSO phase containing layer and block coexistence, and the volume fraction of this phase is 36.0%.

Comparative example 1

The composition of the Mg-Er-Ni alloy provided in this comparative example is basically the same as that of Example 2, except that the content of Ni is the same, but the molar ratio of Er/Ni is 1.0, and its preparation method is the same as that of Example 2.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-term homogenized state prepared in this comparative example, and the transmission electron microscope (TEM) was used to conduct morphology scanning analysis, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It is found that the alloy sample not only contains bulk Ni-LPSO phase, but also contains Mg ₂ Ni phase, and the volume fractions of bulk Ni-LPSO phase and Mg ₂ Ni phase are 9.8 and 4.8, respectively.

Comparative example 2

The composition of the Mg-Er-Ni alloy provided in this comparative example is basically the same as that of Example 2, except that the content of Er is the same, but the molar ratio of Er/Ni is 2.8, and its preparation method is the same as that of Example 2.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-term homogenized state prepared in this comparative example, and the transmission electron microscope (TEM) was used to conduct morphology scanning analysis, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It was detected that the alloy sample not only contained bulk Ni-LPSO phase but also MgEr phase, and the volume fractions of Ni-LPSO phase and MgEr phase were 14.1% and 9.4% respectively.

Comparative example 3

The Mg-Er-Ni alloy provided in this comparative example has the same components as in Example 2, and its preparation method is basically the same as in Example 2, except that the extruded ingot is homogenized at a temperature of 380-420°C Treat for 10min.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-term homogenized state prepared in this comparative example, and the transmission electron microscope (TEM) was used to conduct morphology scanning analysis, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It was detected that the alloy sample contained layered and massive Ni-LPSO phases, and the volume fraction of the Ni-LPSO phase was 14.2%.

Comparative example 4

The Mg-Er-Ni alloy provided in this comparative example has the same components as in Example 2, and its preparation method is basically the same as in Example 2, except that the extruded ingot is homogenized at a temperature of 380-420°C Treat for 60min.

Scanning electron microscopy (SEM) was used to scan the appearance of the alloy in the short-term homogenized state prepared in this comparative example, and the transmission electron microscope (TEM) was used to conduct morphology scanning analysis, and Image Pro analysis software was used to analyze the properties of the second phase volume fraction. It was detected that the alloy sample was mainly composed of layered Ni-LPSO phase, and the volume fraction of the Ni-LPSO phase was 22.5%.

Comparative example 5

The Mg-Er-Ni alloy provided by this comparative example has the same components as in Example 2, and its preparation method is the same as in Example 2, except that the as-cast alloy is smelted at 770 ° C, kept at 680 ° C for 18 min, and room temperature (25 ° C). -35°C) brine cooling.

The short-time homogenized state alloy prepared in this example adopts a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to carry out shape scanning analysis, and uses Image Pro analysis software to perform performance detection on the second phase volume fraction. It can be seen that the Mg, Er and Ni in the alloy sample only form a bulk Ni-LPSO phase, and the volume fraction of the Ni-LPSO phase is 19.8%.

Comparative example 6

The Mg-Er-Ni alloy provided by this comparative example has the same components as in Example 2, and its preparation method is the same as in Example 2, except that the as-cast alloy is smelted at 770 ° C, kept at 650 ° C for 18 min, and room temperature (25 ° C). -35°C) brine cold.

The short-time homogenized state alloy prepared in this example adopts a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to carry out shape scanning analysis, and uses Image Pro analysis software to perform performance detection on the second phase volume fraction. It can be seen that the Mg, Er and Ni in the alloy sample only form a bulk Ni-LPSO phase, and the volume fraction of the Ni-LPSO phase is 19.5%.

Performance Testing:

The present application performs performance tests on the Mg-Er-Ni alloys prepared in Examples 1-6 and Comparative Examples 1-4, wherein the mechanical properties are tested according to GB/T 1177-2018, and the degradation rate adopts GB/T16886.15. 93 ℃, 3wt.% KCl solution is tested, and concrete result is as shown in Figure 4 and Table 1:

Table 1 Mechanical properties and composition phases of Mg-Er-Ni alloys

According to the above table, in the range of Er/Ni molar ratio of 1.3-1.8, melting at 760-800°C, and rapid cooling after heat preservation at 760-780°C for 10-20min, short time at 400°C for 25-35min before extrusion After homogenization, there is only a single phase containing layered and massive Ni-LPSO, and the volume fraction of the Ni-LPSO phase is between 15% and 36%. With the increase of the content of the Ni-LPSO containing phase, Mg - The tensile strength of Er-Ni alloy is from 330-530MPa, and the degradation rate is increased from 85.1mg/cm ² /h to 142.1mg/cm ² /h, but when the Er/Ni molar ratio is not in this range, as in Comparative Example 1 The molar ratio of this specific ratio in the alloy is 1.0, its strength decreases from 360MPa to 345MPa, and its plasticity decreases from 12.6% to 8.1%. The reason is that the Mg ₂ Ni phase not only reduces the strength of the alloy, but also degrades the plasticity of the alloy. , In addition, the formation of this phase, under the same Ni content, only produces a bulk LPSO phase, and at the same time reduces the content of Ni-LPSO, so that the degradation rate of the alloy drops from 94.3mg/cm ² /h to 62.7mg/cm ² /h. In addition, the molar ratio of this specific ratio in Comparative Example 2 is 2.80, and the reason for the decline in its mechanical properties is that there are bulk Ni-LPSO phases and MgEr phases in the alloy, and the content of Ni-LPSO decreases, which cannot be obtained during deformation. The dynamic recrystallization process is suppressed, and the grains are coarsened and grown, so that the strength of the alloy can be reduced from 360MPa to 335MPa. In addition, the low potential of the MgRE phase and the low content of the Ni-LPSO phase reduce the galvanic corrosion characteristics provided by the alloy, making the alloy The degradation rate of 94.3mg/cm ² /h dropped to 33.9mg/cm ² /h.

After changing the homogenization time before extrusion, such as the homogenization treatment 10min before extrusion in Comparative Example 3, the Er/Ni molar ratio is 1.41, and its strength drops from 360MPa to 320MPa. The reason is that due to the short heat treatment time, it cannot be realized The preheating treatment of the alloy, and after a short time treatment, the layered LPSO phase content is less, and the Ni-LPSO phase content is reduced from 19.1% to 14.2%. Under the same Ni content, the Ni-LPSO content is reduced, so The amount of galvanic corrosion that can be provided is less, so that the degradation rate of the alloy drops from 94.3mg/cm ² /h to 82.5mg/cm ² /h. In addition, when the homogenization treatment was performed 60 minutes before extrusion, the Er/Ni molar ratio was 1.41, and its strength increased from 360MPa to 375MPa. The layered LPSO phase is the main phase, in which the layered Ni-LPSO phase increases more nucleation sites, promotes dynamic recrystallization, refines the grains, and plays a short fiber strengthening effect, while due to a large number of layered Ni-LPSO phases Precipitation, a uniform corrosion product film is easy to form during the corrosion process, forming a corrosion barrier, resulting in a decrease in the degradation rate of the alloy from 94.3 mg/cm ² /h to 58.2 mg/cm ² /h.

In addition, when changing the holding time and cooling conditions of the melting thermometer, such as comparative examples 5 and 6, melting at 770°C, holding at 680°C for 18 minutes and 650°C for 18 minutes, and cooling with brine at room temperature, its strength dropped from 360MPa to 320MPa and 300MPa. It is because the melting temperature is low, the cooling rate is slow, there is almost no layered structure in the alloy, and all precipitates form a massive Ni-LPSO phase. During the short-term homogenization process, no layered Ni-LPSO phase precipitates. It is impossible to add more nucleation sites, promote dynamic recrystallization, refine grains, and play a short-fiber strengthening effect, which makes the strength of the alloy drop significantly. In addition, because there is no layered Ni-LPSO phase in the alloy, the alloy The number of corrosion galvanic couples decreased, so that the degradation rate of the alloy decreased from 94.3mg/cm ² /h to 89.3mg/cm ² /h and 83.2mg/cm ² /h.

Considering the strength and degradation characteristics of the alloy comprehensively, the alloy is melted at 760-800°C at an Er/Ni molar ratio of 1.3-1.8, kept at 760-780°C for 10-20min, rapidly cooled in a low-temperature salt water bath, and 400°C before extrusion. ℃ 25-35min after homogenization for a short time, there is only a single phase containing layered and massive Ni-LPSO, and the volume fraction of the Ni-LPSO phase is between 15% and 36%, which has the best mechanics and degradation characteristic.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be applied to the foregoing embodiments Modifications are made to the technical solutions described, or equivalent replacements are made to some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the various embodiments of the present invention, and all of them shall be included in Within the scope of the claims and description of the present invention.

Claims (12)

1. The high-strength and high-toughness rapidly-degradable Mg-Er-Ni alloy for underground fracturing is characterized by comprising the following components in percentage by mass: er:6-15%, ni:1-5%, the molar ratio of Er/Ni is 1.3-1.8, and the balance is Mg and inevitable impurity elements; wherein Mg, ni and Er mainly form a Ni-LPSO phase which is layered and blocky and coexists, and the volume fraction of the Ni-LPSO phase is 15-36%; the Mg-Er-Ni alloy is prepared by the following method: (a) casting: uniformly mixing a nickel source, a magnesium source and an erbium source, and smelting and casting to obtain an as-cast alloy; (b) heat treatment: carrying out homogenization treatment and extrusion deformation treatment on the as-cast alloy in sequence to obtain the high-strength high-toughness rapidly-degradable Mg-Er-Ni alloy; wherein in the step (a), when smelting and casting are carried out, the temperature is firstly raised to 760-800 ℃, the temperature is preserved, the raw materials are stirred to be completely melted, then the temperature is preserved for 10-20min at 760-780 ℃, and finally the raw materials are rapidly cooled by adopting a brine bath at 5-10 ℃ to obtain an as-cast alloy; in step (b), the homogenization treatment is carried out at 380-420 ℃ for 25-35min.

2. The Mg-Er-Ni alloy of claim 1, wherein said Er/Ni molar ratio is 1.4-1.6 and the volume fraction of said Ni-LPSO phase is 24-36%.

3. The Mg-Er-Ni alloy of claim 1, wherein said nickel source is selected from elemental nickel and/or a nickel alloy.

4. The Mg-Er-Ni alloy of claim 3, wherein said nickel alloy is selected from the group consisting of magnesium-nickel alloys.

5. The Mg-Er-Ni alloy of claim 1, wherein said magnesium source is selected from the group consisting of elemental magnesium and/or magnesium alloys.

6. The Mg-Er-Ni alloy of claim 5, wherein said magnesium alloy is selected from magnesium alloys.

7. The Mg-Er-Ni alloy of claim 1, wherein said erbium source comprises at least one of a magnesium erbium alloy and a nickel erbium alloy.

8. The Mg-Er-Ni alloy of claim 1, wherein said melting and casting is carried out with an inert gas blanket.

9. The Mg-Er-Ni alloy of claim 8, wherein said inert gas is selected from at least one of helium, argon, carbon dioxide and sulfur hexafluoride.

10. The Mg-Er-Ni alloy according to claim 9, wherein in step (b), the extrusion deformation treatment is carried out at an extrusion ratio of 9 to 15 and an extrusion deformation speed of 0.3 to 0.4m/min.

11. The Mg-Er-Ni alloy of claim 10, wherein said extrusion temperature is 380 to 420 ℃.

12. Use of a Mg-Er-Ni alloy according to any of claims 1 to 11 in the field of oil and gas development.

Images