CN114540688B - Ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy - Google Patents
Ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy Download PDFInfo
- Publication number
- CN114540688B CN114540688B CN202210185992.4A CN202210185992A CN114540688B CN 114540688 B CN114540688 B CN 114540688B CN 202210185992 A CN202210185992 A CN 202210185992A CN 114540688 B CN114540688 B CN 114540688B
- Authority
- CN
- China
- Prior art keywords
- alloy
- heat treatment
- diameter
- sample
- magnesium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/06—Alloys based on magnesium with a rare earth metal as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Extrusion Of Metal (AREA)
Abstract
The invention relates to the field of alloy processing, and discloses an ultrahigh pressure heat treatment method for Mg-Zn-Zr-Gd alloy, which comprises the following steps: (1) Smelting magnesium alloy in a resistance furnace by using a high-purity magnesium ingot, a high-purity zinc ingot, a Mg-30% Gd intermediate alloy and a Mg-30% Zr intermediate alloy as raw materials to obtain a Mg-Zn-Zr-Gd alloy; (2) softening and heat treating the extruded alloy; (3) extruding the alloy obtained in the step (1); (4) pretreating the extruded alloy; (5) And (5) carrying out ultrahigh pressure heat treatment on the alloy pretreated in the step (4). The invention effectively solves the problems that the number of internal defects is obviously increased after the magnesium alloy is deformed, crystal grains are crushed and deformed, and the diffusion of alloy atoms is obviously inhibited. The invention has the advantages that the strength, the toughness and the corrosion resistance are synchronously and obviously improved.
Description
Technical Field
The invention belongs to the field of alloy processing, and particularly relates to an ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy.
Background
Magnesium alloys have attracted much attention as a research hotspot of biomedical materials in recent years mainly because of the following aspects: 1) The elastic modulus (20-40 GPa) of the magnesium alloy is close to that of human cortical bone (20 GPa), so that the stress shielding effect existing in other metal bone implant materials can be avoided. 2) The magnesium alloy has good biocompatibility and can promote bone cells to attach to the surface of the magnesium alloy to form bone. 3) Magnesium alloys are the most active of the currently used metallic structural materials, and are susceptible to corrosion and degradation, particularly in solutions containing Cl "ions. If the magnesium alloy is used as an implant material, secondary operation can be avoided.
However, the problems troubling researchers at present are that the magnesium alloy has poor durability, so that the degradation speed is too high, the concentration of magnesium ions around bone tissues is too high, the bone dissolving phenomenon is caused, and the healing of fracture is influenced; meanwhile, the degradation speed is too high, so that the mechanical property of the magnesium alloy is reduced too fast, and the magnesium alloy has a fixing effect before fracture healing.
The methods for improving the corrosion resistance of magnesium alloy are divided into three categories: one method is to improve the corrosion resistance of magnesium alloy by surface treatment, deformation treatment and heat treatment without changing the components of magnesium alloy. Another method is to improve the corrosion resistance by optimizing the components. By this method, researchers developed a large number of novel medical magnesium alloys, mainly comprising: mg-Mn-Zn, mg-Zn-Ca, mg-Zn-Zr, mg-Zn, mg-Nd-Zn-Zr and the like, and In addition, rare earth elements such as Y, nd, ce, in and the like can also obviously improve the corrosion resistance of the magnesium alloy; the third method is the purification of alloy components, wherein impurity elements of iron, nickel and copper in the magnesium alloy can form a cathode phase in the magnesium alloy to form galvanic corrosion with a magnesium matrix, and elements such as Mn, zr and the like have remarkable purification effect.
The high pressure heat treatment is a material treatment method which is started in recent years, and under the action of high pressure of GPa level, the diffusion process and the phase change driving force of atoms are changed, so that compared with the conventional heat treatment of metal materials, the structure and the performance are obviously improved, for example, the solid solubility of the alloy can be improved by utilizing high pressure, and the morphology, the size and the like of a precipitated phase can be controlled. But currently there is limited research in this area.
The recrystallization process, the nucleation and growth process of the precipitated phase are obviously changed, the grain size is refined, and the precipitated phase is fine, so that the mechanical property and the corrosion resistance of the alloy are improved. After the magnesium alloy is deformed, the number of internal defects is obviously increased, crystal grains are crushed and deformed, recrystallization can be initiated by subsequent annealing, and alloy atom diffusion is inevitably and obviously inhibited under the action of high pressure, so that the recrystallization process is influenced, but the change mechanism of the recrystallization process of the deformed magnesium alloy under high pressure is rarely reported at present.
Disclosure of Invention
The invention provides an ultrahigh pressure heat treatment method for Mg-Zn-Zr-Gd alloy, aiming at solving the problems that the number of internal defects of the magnesium alloy after deformation is obviously increased, crystal grains are crushed and deformed, alloy atom diffusion can be obviously inhibited, the corrosion resistance of the alloy is reduced, and the mechanical property is not ideal in the prior art.
The invention adopts the specific scheme that: an ultrahigh pressure heat treatment method for Mg-Zn-Zr-Gd alloy comprises the following steps:
(1) Melting a magnesium alloy in a resistance furnace using as raw materials a high-purity magnesium ingot, a high-purity zinc ingot, an Mg-30% Gd-effective intermediate alloy and an Mg-30% Zr-effective intermediate alloy to obtain an Mg-Zn-Zr-Gd alloy;
(2) Softening heat treatment is carried out on the extruded alloy;
(3) Extruding the alloy obtained in the step (1);
(4) Pretreating the extruded alloy;
(5) And (4) carrying out ultrahigh pressure heat treatment on the alloy pretreated in the step (4).
In the step (1), the magnesium alloy is smelted under the mixed gas of CO2 at.% and SF60.5 at.%.
Pouring the alloy after smelting at the pouring temperature of 700-800 ℃ into a metal mold preheated to 200-250 ℃ before extruding in the step (3), and softening for 8-12 hours at the temperature of 400-500 ℃.
Cooling the alloy after softening treatment, extruding on a hydraulic press to extrude a bar with the diameter of 10-20mm, wherein the extrusion speed is 22-25mm/s, and the extrusion ratio is 10:1-50 ℃, the mold temperature is 350-380 ℃, and the extrusion temperature is 300-350 ℃.
The pressure condition of the ultrahigh pressure heat treatment in the step (5) is 2-6GPa.
The temperature condition of the ultrahigh pressure heat treatment in the step (5) is 300-400 ℃.
The step (4) of pretreating the extruded alloy comprises the steps of cutting the magnesium alloy into a cylinder with the diameter of 10mm and the height of 8mm by using a wire cutting machine; and (3) polishing the surface of the alloy by using water sand paper, removing oxide skin formed by linear cutting, soaking the alloy in absolute alcohol, cleaning the surface of the sample by using ultrasonic waves, and drying.
Coating a magnesium alloy sample with the diameter of 10mm multiplied by 8mm by a tantalum sheet before the ultrahigh pressure heat treatment in the step (5), putting the magnesium alloy sample into a boron nitride crucible with the inner diameter of 10mm, the outer diameter of 12mm and the height of 8mm, putting the whole crucible into a graphite furnace with the inner diameter of 12mm, the outer diameter of 14mm and the height of 16.6mm, and respectively putting boron nitride sheets with the diameter of 12mm multiplied by 2mm and pyrophyllite sheets with the diameter of 12mm multiplied by 2.3mm above and below the boron nitride crucible put into the graphite furnace; the graphite furnace is integrally placed in a pyrophyllite groove, and graphite flakes and steel caps with the diameter of phi 14mm multiplied by 1mm are respectively placed on the upper side and the lower side of a graphite crucible in the pyrophyllite groove.
Before ultrahigh pressure heat treatment, a boron nitride crucible, a boron nitride sheet, a pyrophyllite sheet, a graphite furnace, a graphite sheet, a pyrophyllite block and a steel cap used for packaging the sample are put into a dryer in advance for drying for 20-24 hours.
And (5) during the ultrahigh pressure heat treatment, firstly raising the pressure to a preset pressure, then quickly raising the temperature to a preset temperature, preserving the heat for 1-1.5h, turning off a power supply to stop heating, naturally cooling to room temperature, releasing the pressure and taking out the sample. Compared with the prior art, the invention has the following beneficial effects:
the invention realizes large deformation by extruding the magnesium alloy, the alloy is subjected to heat treatment at 300 ℃ and 1H after extrusion, the grain size of the alloy is slightly increased, the extruded Mg-Zn-Zr-Gd alloy is subjected to ultrahigh pressure heat treatment, the grain size of the alloy is reduced, the strength of the alloy is increased, and the elongation is increased; the electrochemical corrosion result shows that the corrosion resistance of the alloy is obviously improved after the alloy is subjected to high-pressure heat treatment. The invention solves the problems that the internal defect number is obviously increased after the magnesium alloy is deformed, crystal grains are crushed and deformed to cause the reduction of corrosion resistance, and alloy atom diffusion is inevitably and obviously inhibited under the action of ultrahigh pressure, thereby refining the crystal grain size, precipitating phases (cathode phases) by aging, becoming finer and more uniform, reducing the local corrosion tendency, and obviously improving the strength of the alloy by the dispersion strengthening effect of fine particles.
Drawings
FIG. 1 is a diagram of an experimental apparatus for high pressure heat treatment according to the present invention;
FIG. 2 is a metallographic structure diagram showing the sample in example 1 at a magnification of 100;
FIG. 3 is a metallographic structure drawing showing 100 times that of a sample in example 2;
FIG. 4 is a metallographic structure diagram showing a sample prepared in comparative example 1 by a factor of 100;
FIG. 5 is a metallographic structure diagram showing a sample prepared in comparative example 2 by a factor of 100;
FIG. 6 is a cross-sectional view of the extruded Mg-Zn-Zr-Gd alloy;
FIG. 7 is an EDS analysis chart of the precipitated phase in FIG. 6;
FIG. 8 shows the morphology of precipitated phases in the alloy of example 1 under the action of ultrahigh pressure;
FIG. 9 is a graph showing the relative phase separation of the alloy under normal pressure in example 1;
wherein the reference numerals are respectively:
1-a steel cap; 2-a graphite flake; 3-pyrophyllite tablets; 4-boron nitride sheet; a 5-boron nitride crucible; 6-a graphite furnace; 7-pyrophyllite block.
Detailed Description
The present invention will be described in further detail below with reference to the attached drawings, and it should be clearly understood herein that the described embodiments are not all embodiments, but are merely illustrative and not restrictive of the present invention.
The invention provides an ultrahigh pressure heat treatment method for Mg-Zn-Zr-Gd alloy, which comprises the following steps:
(1) Melting a magnesium alloy in a resistance furnace using as raw materials a high-purity magnesium ingot, a high-purity zinc ingot, an Mg-30% Gd-effective intermediate alloy and an Mg-30% Zr-effective intermediate alloy to obtain an Mg-Zn-Zr-Gd alloy;
(2) Softening and heat treating the extruded alloy;
(3) Extruding the alloy obtained in the step (1);
(4) After extrusion, pretreatment is carried out
(5) And (4) carrying out ultrahigh pressure heat treatment on the alloy pretreated in the step (3).
In the step (1), the magnesium alloy is smelted under the mixed gas of CO2 99.5at.% and SF60.5 at.%.
Before the extrusion in the step (1), the alloy after smelting is poured, the pouring temperature is 700-800 ℃, the alloy is poured into a metal mold preheated to 200-250 ℃, and the softening treatment is carried out for 8-12 hours at the temperature of 400-500 ℃.
(3) Cooling the alloy after softening treatment, extruding on a hydraulic press to extrude a bar with the diameter of 10-20mm, wherein the extrusion speed is 20-30mm/s, and the extrusion ratio is 10:1-50 ℃, the die temperature is 350-400 ℃, and the extrusion temperature is 300-350 ℃.
(4) The step of pretreating the extruded alloy is to cut the magnesium alloy into a cylinder with the diameter of 10mm and the height of 8mm by using a wire cutting machine; and (3) polishing the surface of the alloy by using water sand paper, removing oxide skin formed by linear cutting, immersing in absolute alcohol, cleaning the surface of the sample by using ultrasonic waves, and drying.
(5) The pressure condition of the ultrahigh pressure heat treatment in the step (4) is 2-6GPa.
Wherein the melting of the magnesium alloy is carried out in a resistance furnace using as raw materials a high purity magnesium ingot (99.99 wt.%), a high purity zinc ingot (99.99 wt.%), a Mg-30-Gd master alloy and a Mg-30-Zr master alloy, to obtain a Mg-Zn-Zr-Gd alloy; softening and heat-treating the obtained alloy; carrying out extrusion large deformation treatment on the alloy subjected to softening heat treatment; and carrying out ultrahigh pressure heat treatment on the pretreated alloy. The step of pretreating the extruded alloy is to cut the magnesium alloy into a cylinder with the diameter of 10mm and the height of 8mm by using a wire cutting machine; and (3) polishing the surface of the alloy by using water sand paper, removing oxide skin formed by linear cutting, immersing in absolute alcohol, cleaning the surface of the sample by using ultrasonic waves, and drying.
In the step (1), the magnesium alloy is smelted under the mixed gas of CO2 of 99.5at.% and SF of 60.5 at.%. Before the extrusion in the step (3), the alloy after smelting is poured, the pouring temperature is 700-800 ℃, the alloy is poured into a metal mold preheated to 200-250 ℃, and the softening treatment is carried out for 8-12 hours at the temperature of 400-500 ℃. Cooling the alloy after softening treatment, extruding on a hydraulic press to extrude a bar with the diameter of 10-20mm, wherein the extrusion speed is 22-25mm/s, and the extrusion ratio is 10:1-50 ℃, the die temperature is 350-380 ℃, and the extrusion temperature is 300-350 ℃.
TABLE 1 chemical composition (wt.%) of as-extruded Mg-Zn-Zr-Gd alloy
Coating a magnesium alloy sample with phi 10mm multiplied by 8mm by a tantalum sheet before ultrahigh pressure heat treatment in the step (5), putting the magnesium alloy sample into a boron nitride crucible with the inner diameter of 10mm, the outer diameter of 12mm and the height of 8mm, putting the whole crucible into a graphite furnace with the inner diameter of 12mm, the outer diameter of 14mm and the height of 16.6mm, and respectively putting the boron nitride sheet with phi 12mm multiplied by 2mm and the pyrophyllite sheet with phi 12mm multiplied by 2.3mm into the upper part and the lower part of the boron nitride crucible which is put into the graphite furnace; the graphite furnace is integrally placed in a pyrophyllite groove, and graphite flakes and steel caps with the diameter of phi 14mm multiplied by 1mm are respectively placed on the upper side and the lower side of a graphite crucible in the pyrophyllite groove.
The tantalum sheet can protect the magnesium alloy and has the functions of protection and pollution prevention; the boron nitride in the boron nitride crucible plays a role in protecting and transmitting pressure to the magnesium alloy; graphite in the graphite furnace is used as a heating source, and the temperature is controlled by adjusting input voltage; the pyrophyllite sheet has the functions of protection and pressure transmission, and pyrophyllite is a pressure transmission medium; the steel cap plays a role in conducting electricity.
Before ultrahigh pressure heat treatment, a boron nitride crucible, a boron nitride sheet, a pyrophyllite sheet, a graphite furnace, a graphite sheet, a pyrophyllite block and a steel cap used for packaging the sample are put into a dryer in advance for drying for 20-24 hours. And (5) during the ultrahigh pressure heat treatment, firstly raising the pressure to a preset pressure, then quickly raising the temperature to a preset temperature, preserving the heat for 1-1.5h, turning off a power supply to stop heating, naturally cooling to room temperature, releasing the pressure and taking out the sample.
Example 1
An ultrahigh pressure heat treatment method for Mg-Zn-Zr-Gd alloy comprises the following steps:
(1) Melting a magnesium alloy in a resistance furnace using a high purity magnesium ingot (99.99 wt.%), a high purity zinc ingot (99.99 wt.%), a Mg-30% Gd master alloy and a Mg-30% Zr master alloy as raw materials to obtain a Mg-Zn-Zr-Gd alloy; (2) The casting temperature is 750 ℃, the casting is carried out in a metal die preheated to 200 ℃, the softening treatment is carried out for 10 hours at 420 ℃, the casting is carried out on a 3150KN hydraulic press after cooling, the extrusion is carried out on a bar with the diameter of 15mm, the extrusion speed is 22mm/s, and the extrusion ratio is 10:1, the temperature of a die is 360 ℃, and the extrusion temperature is 340 ℃; (3) Pretreating the extruded alloy, wherein the step (3) of pretreating the extruded alloy comprises the step of cutting the magnesium alloy into a cylinder with the diameter of 10mm and the height of 8mm by using a wire cutting machine; and (3) polishing the surface of the alloy by using water sand paper, removing oxide skin formed by linear cutting, soaking the alloy in absolute alcohol, cleaning the surface of the sample by using ultrasonic waves, and drying. (4) And (4) carrying out ultrahigh pressure heat treatment on the alloy pretreated in the step (3), wherein the ultrahigh pressure heat treatment temperature is 300 ℃, the pressure is 2GPa, and the time is 1 hour.
Coating a magnesium alloy sample with phi 10mm multiplied by 8mm by a tantalum sheet before ultrahigh pressure heat treatment in the step (4), putting the magnesium alloy sample into a boron nitride crucible with the inner diameter of 10mm, the outer diameter of 12mm and the height of 8mm, putting the whole crucible into a graphite furnace with the inner diameter of 12mm, the outer diameter of 14mm and the height of 16.6mm, and respectively putting the boron nitride sheet with phi 12mm multiplied by 2mm and the pyrophyllite sheet with phi 12mm multiplied by 2.3mm into the upper part and the lower part of the boron nitride crucible which is put into the graphite furnace; the graphite furnace is integrally placed in a pyrophyllite groove, and graphite flakes and steel caps with the diameter of phi 14mm multiplied by 1mm are respectively placed on the upper side and the lower side of a graphite crucible in the pyrophyllite groove.
Before ultrahigh pressure heat treatment, a boron nitride crucible, a boron nitride sheet, a pyrophyllite sheet, a graphite furnace, a graphite sheet, a pyrophyllite block and a steel cap used for packaging the sample are put into a dryer in advance for drying for 20 hours. And (4) during the ultrahigh pressure heat treatment in the step (4), firstly raising the pressure to a preset pressure, then rapidly raising the temperature to a preset temperature, keeping the temperature for 1h, turning off a power supply to stop heating, naturally cooling to room temperature, releasing the pressure and then taking out the sample.
Example 2
The difference from example 1 is that in step (4) of this example, the alloy pretreated in step (3) is subjected to ultra-high pressure heat treatment at 400 ℃ under 2GPa for 1 hour.
Comparative example 1
The present comparative example provides an Mg-Zn-Zr-Gd alloy that is obtained by melting a magnesium alloy in a resistance furnace using, as raw materials, a high-purity magnesium ingot (99.99 wt.%), a high-purity zinc ingot (99.99 wt.%), an Mg-30-th Gd intermediate alloy, and an Mg-30-Zr intermediate alloy. (2) Pouring the mixture into a metal die preheated to 200 ℃ at the pouring temperature of 750 ℃, softening the mixture for 10 hours at the temperature of 420 ℃, cooling the mixture, extruding the mixture on a 3150KN hydraulic press to extrude a bar with the diameter of 15mm, wherein the extrusion speed is 22mm/s, and the extrusion ratio is 10:1, the temperature of a die is 360 ℃, and the extrusion temperature is 340 ℃;
(1) Comparative example 2
The comparative example is different from example 1 in that in the step (4), the alloy pretreated in the step (3) is subjected to heat treatment, and the heat treatment is carried out on the alloy under the condition of normal pressure, the temperature is 300 ℃ and the time is 1 hour.
Examples 1-2 the high-pressure test equipment used was a CS-1B type synthetic diamond hydraulic press (high-pressure cubic press). The main technical parameters of the press are shown in table 2.
Table 2: main technical parameters of press
Electrochemical polarization experiments were performed on the above examples and comparative examples.
Electrochemical samples were cut from the above-described squeeze bar and sampled perpendicular to the direction of squeezing. The above samples were embedded in an epoxy resin seal with an exposed surface area of 1cm 2 The surface was sequentially polished with 200-1000# sandpaper and then polished to 1 μm. The electrochemical polarization experiment employed a standard three-electrode system: the reference electrode is a saturated calomel electrode, the auxiliary electrode is a platinum electrode, and the sample is used as a working electrode. The polarization experiment was performed in a beaker containing 300ml of physiological saline, the temperature of the solution being controlled at 37. + -. 1 ℃. The scanning speed was 0.3mV/s.
The microstructure of the above examples and comparative examples was observed.
The microstructure of the extruded alloy and the alloy after high-pressure treatment is observed on a ZEISS-Axiovert 200MAT type metallographic microscope (OM) and a MX2600 type field emission Scanning Electron Microscope (SEM), and a sample is corroded by 5wt.% of picric acid ethanol solution. The microhardness test specimens were phi 10X 8mm columnar specimens cut from the above-mentioned rods. The test was carried out on a microhardness tester, taking an average of 5 points for each sample, at a temperature of 20 ℃. TEM analysis this experiment adopted JEM-2010 high-resolution transmission electron microscope, to study the internal precipitated phase and recrystallization state of the material. The lattice resolution was 0.14nm and the dot resolution 5 was 0.23nm.
With reference to fig. 4, it can be seen that a large number of deformed grains exist on the original alloy matrix of comparative example 1, fine equiaxial grains exist in a local area, and the grain sizes are greatly different; it can be seen that dynamic recrystallization occurs during hot extrusion, and the average grain size of the alloy measured by the node method is 23 μm. It can be seen from the accompanying fig. 5 that the grain size of the alloy matrix after 1 hour of treatment at 300 ℃ is significantly increased, the number of fine grains is significantly reduced, and the calculated average grain size of the alloy is 25 μm. With reference to FIG. 2, under the action of high pressure of 2GPa and heat at 300 ℃, a large number of distorted grains appear on the alloy matrix, and the number of fine granular grains is obviously larger than that of the samples of comparative example 1 and comparative example 2, and the average grain size is calculated to be 20 μm. With reference to fig. 3, it can be seen that under the action of high pressure of 2GPa, when the heat treatment temperature reaches 400 ℃, after one hour of heat preservation, compared with the sample in example 1, the distorted crystal grains on the alloy matrix are obviously reduced, the number of fine granular crystal grains is also obviously reduced, a large number of slender deformed crystal grains are generated, and the average crystal grain size is calculated to be 22 μm.
From the above results, it can be obtained that under the condition of hot extrusion, a large amount of deformed grains exist, and after 1 hour of heat treatment at 300 ℃, the grains in the local area grow up under the action of heat, while under the action of 2GPa high pressure, under the action of 300 ℃ and 400 ℃ heat respectively, the grain size and morphology do not change much compared with the original extruded state after 1 hour of heat treatment.
The SEM morphologies of the samples of examples 1-2 and comparative examples 1-2 were similar, as shown in FIG. 2. As can be seen by combining the attached figure 6, precipitated phases are distributed on the matrix and are in dispersed distribution; table 3 shows the EDS analysis results of the alloy matrix, and it can be seen that the alloy matrix contains Zn element and a small amount of Zr element, in which the content of Zn element reaches 2.67at%, and it is proved that 2.67at% of Zn element is solid-dissolved in the magnesium alloy, and the solid solubility of Zn element in other heat treatment states is also about 2.67at%, and the alloy is in a supersaturated state; the results of the energy spectrum analysis of the precipitated phases of the alloy are shown in Table 4, and it is found that the precipitated phases have similar compositions as found by the study, in which the compositions are Mg, zn and Gd elements, and the content of Mg element is 54.86at%, the content of Zn element is 30.52at%, the content of Gd element is 13.72at%, and a small amount of Zr element is contained.
TABLE 3 alloy base energy spectrum analysis table
TABLE 4 energy spectrum analysis chart of alloy precipitated phase
Referring to the attached figure 8, it can be seen that the mechanical property parameters obtained through calculation are shown in table 5, and it is known that the compressive strength of the alloy in the comparative example 1 is 507MPa, the yield strength is 209MPa, and the elongation is 13%, compared with the sample in the comparative example 1, the compressive strength and the yield strength of the sample in the comparative example 2 are both significantly improved, and respectively reach 558MPa and 242MPa, and the elongation is also improved to 14%, mainly because a large amount of strengthening phases are precipitated after the heat treatment of the extruded sample, so that the effect of dispersion strengthening is achieved, and meanwhile, a large amount of dislocations existing in the extruded state are significantly reduced after the heat treatment, so that the improvement of the elongation is promoted; compared with the sample of the comparative example 2, the tensile strength of the sample of the example 1 is improved, and the yield strength and the elongation are obviously improved, because the growth of crystal grains caused by heat treatment is hindered under the action of the ultrahigh pressure of 2GPa, a large amount of fine recrystallized crystal grains are generated under the action of pressure, and the strength and the toughness of the alloy are obviously improved; the tensile strength, yield strength and elongation of example 2 were all reduced compared to example 1, and it is understood that at an ultra high pressure of 2GPa, the crystal grains and precipitated phases in the alloy grow up when the heat treatment temperature is raised to 400 ℃, resulting in a reduction in tensile strength, yield strength and elongation.
TABLE 5 compression Performance parameters of different Heat treatment processes
And testing the corrosion behavior of the Mg-Zn-Zr-Gd alloy.
Referring to FIG. 9, after the electrochemical polarization curves are calculated by fitting and the electrochemical parameter values are shown in Table 6, the self-corrosion potential of the alloy No. 1 sample in the extrudable state is-1.4364V, and compared with the self-corrosion potential of the sample of comparative example 1, the sample of comparative example 2, the sample of example 1 and the sample of example 2 is increased to-1.3923, -1.4214 and-1.4115; it is known that both normal pressure heat treatment and high pressure heat treatment can improve the thermodynamic stability of the alloy, which mainly means that structural defects such as dislocation and the like on a matrix after heat treatment are obviously reduced, and the stability of the alloy is improved; the corrosion rate of the alloy after heat treatment is also obviously reduced, wherein the corrosion rate of the samples of the examples 1 and 2 subjected to high-pressure heat treatment is most obviously reduced because the heat preservation can inhibit the growth of precipitated phases in the heat treatment process under high pressure, and compared with the samples of the examples 1 and 2, the samples of the examples 1 and 2 are known to have serious lattice distortion and the quantity of possible deformation twin crystals or dislocation is obviously higher than that of the heat treatment at 300 ℃ under 400 ℃ although crystal grains are refined.
TABLE 6 electrochemical parameters of different heat treatment processes
The microstructure observation of three recrystallization treatment processes on the extruded Mg-Zn-Zr-Gd alloy shows that the recrystallization behavior is more sufficient under normal pressure. However, as the result of abnormal growth of crystal grains, coarse crystal grains appear in local areas, 2GPa high-pressure treatment is introduced in the crystallization annealing process, the internal distortion of the alloy structure caused by high pressure is increased to provide a favorable part for the formation of new crystal nuclei, and the critical free energy required by the formation of the crystal nuclei is reduced by the high pressure, so that the nucleation rate of the new crystal grains is improved. On the other hand, the diffusion of atoms is difficult under an excessively high pressure, and the growth of crystal nuclei is suppressed, so that the grain size of the alloy obtained after the high-pressure treatment of 2GPa is smaller than that obtained under normal pressure. The annealing is carried out under the high-pressure condition of 2GPa at the temperature of 300 ℃, so that the crystal lattice of the alloy is distorted under the action of the high pressure, and the distortion is more remarkable under the interaction with particles.
After the extruded Mg-Zn-Zr-Gd alloy is subjected to heat treatment for 1 hour at 300 ℃ under normal pressure and high pressure, the corrosion resistance is obviously improved, wherein the corrosion resistance is obviously improved after the heat treatment for 1 hour at 300 ℃ under the high pressure.
Comparing the appearance, size and volume fraction of aging precipitation particles in the annealing process under normal pressure and ultrahigh pressure conditions by combining the attached drawings:
firstly, after heat preservation and pressure maintaining are carried out for 1h at 2GPa and 300 ℃, a high-pressure annealing precipitated phase can be seen, and the size is obviously reduced to be lower than that of a normal-pressure annealing precipitated phase; under general conditions, the cathode effect of the fine precipitated phase is lower than that of the coarse precipitated phase, and the fine dispersed precipitated phase has stronger dispersion strengthening effect. For Mg-Zn-Zr alloy, the aging precipitation process is as follows: SSSS → GP zone → beta '1 → beta '2, wherein beta '2 is MgZn2 phase, rare earth or Cu and other elements are added to promote the process, and the size of precipitated phase is obviously reduced by high pressure action, thereby improving the strength and corrosion resistance of the alloy.
Secondly, in the extrusion deformation process, a dislocation and substructure enrichment region exists in a deformation region, the configuration of the dislocation and substructure enrichment region can be changed under the action of ultrahigh pressure and heat, the movement form can be changed, the recrystallization process is obviously affected, and the dislocation and substructure enrichment region can generate nanocrystalline under the action of ultrahigh pressure and has the characteristic of continuous recrystallization.
In conclusion, the extrusion Mg-Zn-Zr-Gd alloy is subjected to ultrahigh pressure heat treatment, so that the strength of the alloy is increased, the elongation is increased, the strength is increased, and the elongation is obviously reduced; the electrochemical corrosion result shows that the corrosion resistance of the alloy is obviously improved after the alloy is subjected to heat treatment. The invention solves the problems that after the magnesium alloy is deformed, the number of internal defects is obviously increased, crystal grains are crushed and deformed, the subsequent annealing can initiate recrystallization, and the diffusion of alloy atoms is obviously inhibited under the action of high pressure. The advantages are that the strength, the toughness and the corrosion resistance are all obviously improved.
The drawings and the explanation are only for one embodiment of the present invention, but the specific protection scope of the present invention is not limited to the above explanation, and any simple replacement or change within the technical idea of the present invention and the technical solution according to the present invention should be within the protection scope of the present invention.
Claims (2)
1. An ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy is characterized by comprising the following steps:
(1) Melting a magnesium alloy in a resistance furnace using as raw materials a high-purity magnesium ingot, a high-purity zinc ingot, an Mg-30% Gd-effective intermediate alloy and an Mg-30% Zr-effective intermediate alloy to obtain an Mg-Zn-Zr-Gd alloy;
(2) Softening and heat-treating the Mg-Zn-Zr-Gd alloy;
(3) Extruding the alloy obtained in the step (2);
(4) Pretreating the extruded alloy;
(5) Carrying out ultrahigh pressure heat treatment on the alloy pretreated in the step (4);
pouring the smelted alloy at 700-800 deg.c into metal mold preheated to 200-250 deg.c for 8-12 hr to soften at 400-500 deg.c;
cooling the alloy after softening treatment, extruding on a hydraulic press to extrude a bar with the diameter of 10-20mm, wherein the extrusion speed is 22-25mm/s, and the extrusion ratio is 10:1-50 ℃, the die temperature is 350-380 ℃, and the extrusion temperature is 300-350 ℃; the step (4) of pretreating the extruded alloy comprises the steps of cutting the magnesium alloy into a cylinder with the diameter of 10mm and the height of 8mm by using a wire cutting machine; polishing the alloy surface by using water sand paper, removing oxide skin formed by linear cutting, soaking in absolute alcohol, cleaning the surface of a sample by using ultrasonic waves, and drying; coating a magnesium alloy sample with the diameter of 10mm multiplied by 8mm by a tantalum sheet before the ultrahigh pressure heat treatment in the step (5), putting the magnesium alloy sample into a boron nitride crucible with the inner diameter of 10mm, the outer diameter of 12mm and the height of 8mm, putting the whole crucible into a graphite furnace with the inner diameter of 12mm, the outer diameter of 14mm and the height of 16.6mm, and respectively putting boron nitride sheets with the diameter of 12mm multiplied by 2mm and pyrophyllite sheets with the diameter of 12mm multiplied by 2.3mm above and below the boron nitride crucible put into the graphite furnace; putting the graphite furnace into a pyrophyllite groove integrally, and putting graphite flakes and steel caps with the diameter of phi 14mm multiplied by 1mm into the upper side and the lower side of a graphite crucible in the pyrophyllite groove respectively; before ultrahigh pressure heat treatment, putting a boron nitride crucible, a boron nitride sheet, a pyrophyllite sheet, a graphite furnace, a graphite sheet, a pyrophyllite block and a steel cap used for packaging a sample into a dryer in advance for drying for 20-24 hours; and (5) during the ultrahigh pressure heat treatment, firstly increasing the pressure to 2-6GPa, then quickly increasing the temperature to 300-400 ℃, preserving the heat for 1-1.5h, turning off a power supply to stop heating, naturally cooling to room temperature, releasing the pressure and taking out the sample.
2. The Mg-Zn-Zr-Gd alloy ultra-high pressure heat treatment method according to claim 1, characterized in that in the step (1), the magnesium alloy is smelted in CO 2 99.5at.% with SF 6 0.5 at.% of mixed gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210185992.4A CN114540688B (en) | 2022-02-28 | 2022-02-28 | Ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210185992.4A CN114540688B (en) | 2022-02-28 | 2022-02-28 | Ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114540688A CN114540688A (en) | 2022-05-27 |
| CN114540688B true CN114540688B (en) | 2022-12-16 |
Family
ID=81679178
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210185992.4A Active CN114540688B (en) | 2022-02-28 | 2022-02-28 | Ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114540688B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115449679A (en) * | 2022-09-23 | 2022-12-09 | 牡丹江师范学院 | Preparation method of high-damping high-strength and high-toughness magnesium-lithium alloy with synergistically improved damping and mechanical properties |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008127639A (en) * | 2006-11-21 | 2008-06-05 | Kobe Steel Ltd | Magnesium alloy material, and method for producing the same |
| CN101880845A (en) * | 2010-06-11 | 2010-11-10 | 燕山大学 | Method for thinning AM60B cast magnesium alloy grains |
| CN106244882A (en) * | 2016-10-14 | 2016-12-21 | 南京工程学院 | Mg Gd Zn (Ca) medical magnesium alloy with LPSO structure and preparation method thereof |
| CN106756370A (en) * | 2016-12-10 | 2017-05-31 | 哈尔滨工业大学 | A kind of anti-flaming Mg Gd Y Zn Zr alloys of high-strength anticorrosion and preparation method thereof |
| CN109280829A (en) * | 2018-12-14 | 2019-01-29 | 东北大学秦皇岛分校 | A kind of high-strength casting Mg-Zn-Cu-Zr alloy and preparation method thereof |
| CN109355540A (en) * | 2018-12-14 | 2019-02-19 | 东北大学 | A kind of high intensity Mg-Zn-Cu-Zr-Cr-Ca alloy and preparation method thereof |
| CN110093523A (en) * | 2019-04-25 | 2019-08-06 | 黑龙江科技大学 | A kind of new medical metal material and its super-pressure preparation method |
| CN112458349A (en) * | 2020-11-06 | 2021-03-09 | 重庆大学 | Low-rare earth high-strength wrought magnesium alloy containing neodymium and yttrium and preparation method thereof |
-
2022
- 2022-02-28 CN CN202210185992.4A patent/CN114540688B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008127639A (en) * | 2006-11-21 | 2008-06-05 | Kobe Steel Ltd | Magnesium alloy material, and method for producing the same |
| CN101880845A (en) * | 2010-06-11 | 2010-11-10 | 燕山大学 | Method for thinning AM60B cast magnesium alloy grains |
| CN106244882A (en) * | 2016-10-14 | 2016-12-21 | 南京工程学院 | Mg Gd Zn (Ca) medical magnesium alloy with LPSO structure and preparation method thereof |
| CN106756370A (en) * | 2016-12-10 | 2017-05-31 | 哈尔滨工业大学 | A kind of anti-flaming Mg Gd Y Zn Zr alloys of high-strength anticorrosion and preparation method thereof |
| CN109280829A (en) * | 2018-12-14 | 2019-01-29 | 东北大学秦皇岛分校 | A kind of high-strength casting Mg-Zn-Cu-Zr alloy and preparation method thereof |
| CN109355540A (en) * | 2018-12-14 | 2019-02-19 | 东北大学 | A kind of high intensity Mg-Zn-Cu-Zr-Cr-Ca alloy and preparation method thereof |
| CN110093523A (en) * | 2019-04-25 | 2019-08-06 | 黑龙江科技大学 | A kind of new medical metal material and its super-pressure preparation method |
| CN112458349A (en) * | 2020-11-06 | 2021-03-09 | 重庆大学 | Low-rare earth high-strength wrought magnesium alloy containing neodymium and yttrium and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114540688A (en) | 2022-05-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Peng et al. | Plastic deformation and heat treatment of Mg-Li alloys: a review | |
| Yu et al. | Microstructure evolution and mechanical properties of as-extruded Mg-Gd-Y-Zr alloy with Zn and Nd additions | |
| Zhao et al. | Influence of extrusion conditions on microstructure and mechanical properties of Mg-2Gd-0.3 Zr magnesium alloy | |
| CN114182147B (en) | High-strength high-thermal-conductivity magnesium alloy and preparation method thereof | |
| CN114540688B (en) | Ultrahigh-pressure heat treatment method for Mg-Zn-Zr-Gd alloy | |
| CN113637931B (en) | Method for controllably adjusting solid solubility and corrosion rate of biological zinc alloy by using GPa-grade ultrahigh pressure | |
| Ma et al. | Achieving high strength-ductility in a wrought Mg–9Gd–3Y–0.5 Zr alloy by modifying with minor La addition | |
| CN109161828A (en) | A kind of processing technology and aluminium alloy extrusions for reducing T5 state aluminium alloy Surface of profile coarse-grain | |
| CN110643911A (en) | Thermal mechanical treatment method of eutectic high-entropy alloy | |
| Gerashi et al. | Improved corrosion resistance and mechanical properties of biodegradable Mg–4Zn–xSr alloys: effects of heat treatment, Sr additions, and multi-directional forging | |
| CN112680641A (en) | Solid-solution Zn-containing two-phase magnesium-lithium alloy and preparation method and application thereof | |
| Nie et al. | Microstructure, tensile properties and work hardening behavior of an extruded Mg–Zn–Ca–Mn magnesium alloy | |
| CN108588602A (en) | It is a kind of reduce black line ratio 7075 aluminium alloy flats row manufacturing method and 7075 aluminium alloy flats row and application | |
| JP4061211B2 (en) | Titanium alloy used for cathode electrode for producing electrolytic copper foil and method for producing the same | |
| Dvorský et al. | Structure and mechanical characterization of Mg-Nd-Zn alloys prepared by different processes | |
| CN112251659A (en) | AlCrFe2Ni2C0.24High-entropy alloy and preparation method thereof | |
| US4747884A (en) | High strength aluminum-base alloy containing lithium and zirconium and methods of preparation | |
| CN116676521A (en) | CrCoNi-based medium entropy alloy with heterogeneous grain heterostructure and preparation method thereof | |
| CN106676352B (en) | The low cost and high performance high Ca/Al ratio Mg-XAl-YCa-ZZn alloy of one kind and preparation method | |
| CN114250391A (en) | Anodic oxidation high-magnesium aluminum alloy material and preparation method thereof | |
| CN112301262A (en) | Preparation method of fine-grain biological magnesium-zinc alloy plate | |
| Jia et al. | Pre-deformation and aging characteristics of Cu-3Ti-2Mg alloy | |
| CN112301261A (en) | Preparation method of ultrafine crystal or nanocrystalline magnesium-zinc alloy | |
| Wei et al. | Effect of extrusion temperature on microstructure, mechanical properties and corrosion resistance of Mg-6Sn-3Al-1Zn alloy | |
| CN113234978B (en) | Extruded magnesium-yttrium alloy and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |