CN102071439A - Method for directly preparing Mg-Zn-Zr alloy through electrolyzing molten salts - Google Patents

Abstract

The invention provides a method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis. Anhydrous MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are 30%-45%, 45%-55%, 5-8%, 5.3-15%, 2- 4%, 1-2%, grind and mix evenly, heat and melt in the electrolytic cell; use inert metal molybdenum as the cathode, graphite as the anode, at an electrolysis temperature of 510-630°C, adopt the sinking cathode method, and the pole distance is 4cm , the cathode current density is 3-12A/cm ² , the cell voltage is 5.7-8.2V, after 2-4 hours of electrolysis, the Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell. The composition of the alloy obtained by the invention is uniform; heat energy consumption is significantly reduced; the electrolysis temperature is 510-630°C, which is lower than the melting point of magnesium and far lower than the melting point of zirconium; the production process is shortened, the smelting cost is reduced, and the economic benefits are very significant.

Description

A method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis

technical field

The invention relates to an electrometallurgy method. Specifically, it is a method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis.

Background technique

Magnesium alloys are called "green alloys". They have the advantages of low density, high specific strength and specific stiffness, good thermal conductivity, excellent mechanical and chemical properties, and recyclability, making them widely used in aerospace, automobiles, notebook computers, military, etc. The field has been widely used, and its usage has a tendency to increase significantly. Magnesium alloys can be divided into zirconium-containing magnesium alloys and zirconium-free magnesium alloys according to whether they contain zirconium.

The grain size of Mg-Zn binary alloy is coarse, it is easy to form micropores, and its mechanical properties are low, so it is rarely used in industry. Zr is the most effective grain refining element in Mg-Zn alloys, and can slow down the diffusion rate of alloying elements and prevent grain growth. Mg-Zn-Zr alloys are widely used forging and deformation magnesium alloys. Adding 0.6%-0.8% Zr to Mg-Zn alloy can reduce the grain size to 0.65-6.50μm, which has the greatest effect of refining grains and improving mechanical properties. Therefore, zirconium-containing magnesium alloys have been increasingly widely used.

At present, the production method of Mg-Zn-Zr alloy mostly adopts the mixing method, which is formed by mixing high-purity zinc, magnesium and magnesium-zirconium master alloy in a certain proportion in a molten state. This method has long production process, complex process, high energy consumption, easy segregation of alloy components, and high production cost. At present, to obtain good quality Mg-Zn-Zr alloy is mainly prepared by vacuum melting method, and this method will increase the melting cost of Mg-Zn-Zr alloy, and also put forward higher requirements for its equipment.

The preparation of alloys by the method of doping proposed in the prior art, for example, in the patent "Mg-Zn-Zr deformed magnesium alloy preparation method" with the patent application number 200710046148.9, discloses a method of heating industrially pure magnesium under the protection of gas. After the magnesium is completely melted, add industrially pure Zn and Mg-Zr intermediate alloys, and stir after the alloys are completely melted to make the alloy composition uniform. The ingot is homogenized and plastically deformed on an extruder. After extrusion, the extruded ingot is placed in a heat treatment furnace for annealing heat treatment; the patent application number is 200810236147.5, and the name is "a kind of Mg-Zn-Zr-Nd magnesium Alloy and its preparation method” discloses a method of directly preparing an ingot with high strength and corrosion resistance by adjusting the content of Zn and Zr and adding a trace of rare earth element Nd, using a resistance furnace or a reverberatory furnace for smelting.

Contents of the invention

The purpose of the present invention is to provide a method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis with simple process, energy consumption reduction and uniform composition of the prepared Mg-Zn-Zr alloy.

The purpose of the present invention is achieved like this:

Dry KCl and K ₂ ZrF ₆ at a temperature of 600°C for 72 hours, dry anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF in a vacuum at 130°C for 24 hours; dry anhydrous MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are 30%-45%, 45%-55%, 5-8%, 5.3-15%, 2-4%, 1-2% by mass percentage, finely ground After mixing evenly, heat and melt in the electrolytic cell; use the inert metal molybdenum (Mo) as the cathode, graphite as the anode, and at an electrolysis temperature of 510-630°C, adopt the sinking cathode method, the pole distance is 4cm, and the cathode current density is 3- 12A/cm ² , cell voltage 5.7-8.2V, after electrolysis for 2-4 hours, Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell.

The theoretical basis of the invention is that magnesium-zinc-zirconium alloys with different components can be prepared by controlling the concentration of Mg ²⁺ , Zn ²⁺ , Zr ⁴⁺ and the cathode current density. And the low eutectic MgCl ₂ -KCl molten salt is used as the electrolyte, which can be electrolyzed at a lower temperature.

The outstanding substantive features and significant progress of the technical solution of the present invention are mainly reflected in: the present invention uses metal compounds as raw materials to directly prepare Mg-Zn-Zr alloys, and the alloy composition is uniform; heat energy consumption is significantly reduced, and the electrolysis temperature is 510-630°C , lower than the melting point of magnesium (650°C), far lower than the melting point of zirconium (1852°C); the production process is shortened, the smelting cost is reduced, and the economic benefits are very significant.

Description of drawings

Figure 1a and Figure 1b are the X-ray diffraction analysis (XRD) of the alloy samples prepared in Examples 7 and 6, respectively. XRD analysis shows that the alloy is composed of Mg phase, Mg ₇ Zn ₃ phase, and Zr phase.

Fig. 2a-Fig. 2d are scanning electron microscopy (SEM) (point scanning) and attached energy dispersive spectroscopy (EDS) (corresponding point) analysis of the alloy sample prepared in Example 6. EDS analysis shows that the compounds of magnesium and zinc and elemental zirconium are distributed at the grain boundaries.

3a-3d are scanning electron microscopy (SEM) (point scanning) and attached energy dispersive spectroscopy (EDS) (corresponding point) analysis of the alloy sample prepared in Example 5.

4 is a scanning electron microscope (SEM) photo and a surface scanning (EPMA) photo of the alloy sample prepared in Example 5. It can be seen from the surface distribution that there is no segregation of zirconium in the alloy obtained by this method.

Fig. 5 is a scanning electron microscope (SEM) photograph of the prepared alloy sample. From the SEM photos, it can be seen that the grain refinement degree of Mg-Zn-Zr alloys with different Zr content increases with the increase of zirconium element content. (a: SEM photo of Mg-31Zn×100; b: SEM photo of Mg-11Zn-0.1Zn×100; c: SEM photo of Mg-13Zn--0.2Zr×100; d: Mg-18Zn-1.3Zr× 100 SEM photos)

Detailed ways

List below and describe the present invention in more detail:

Example 1: Dry KCl, K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , graphite as the anode, at the electrolysis temperature of 510°C, the sinking cathode method is adopted, the pole distance is 4cm, the cathode current density is 6A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 6.1-7.2V, after 2 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 32.7%, 66.1%, and 1.2%.

Example 2: Dry KCl, K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , graphite as the anode, electrolysis temperature 540 ℃, adopt the sinking cathode method, the pole distance is 4cm, the cathode current density is 3A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 5.1-6.2V, after 2 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 45.9%, 53.1%, and 1.0%.

Example 3: Dry KCl, K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , graphite as the anode, electrolysis temperature 570 ℃, adopt the sinking cathode method, the pole distance is 4cm, the cathode current density is 6A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 6.1-7.2V, after 2 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 82.4%, 16.7%, and 0.9%.

Example 4: Dry KCl, K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , graphite as the anode, at the electrolysis temperature of 570°C, the sinking cathode method is adopted, the pole distance is 4cm, the cathode current density is 12A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 7.2-8.2V, after 2 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 52.2%, 47.4%, and 0.4%.

Example 5: Dry KCl and K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , graphite as the anode, electrolysis temperature 600 ℃, adopt the sinking cathode method, the pole distance is 4cm, the cathode current density is 9A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 6.4-7.5V, after 2 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 88.9%, 11.0%, and 0.1%.

Example 6: Dry KCl, K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , graphite as the anode, electrolysis temperature 600 ℃, adopt the sinking cathode method, the pole distance is 4cm, the cathode current density is 12A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 7.1-8.2V, after 4 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc, and zirconium are respectively: 80.3%, 18.4%, and 1.3%.

Example 7: Dry KCl, K ₂ ZrF ₆ at 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , and KF at 130°C for 24 hours in vacuum; use MgCl ₂ +KCl+ KF+K ₂ ZrF ₆ +ZrO ₂ +ZnCl ₂ is the electrolyte system, the mass percentage of each component is 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, and the inert metal molybdenum (Mo) is used as the cathode , with graphite as the anode, at an electrolysis temperature of 630°C, the sinking cathode method is adopted, the pole distance is 4cm, the cathode current density is 6A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage is 5.3-6.6V, after 2 hours Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc, and zirconium are respectively: 75.9%, 23.9%, and 0.2%.

Claims (8)

1. A method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis, which is characterized in that: KCl, K ₂ ZrF ₆ are dried at a temperature of 600°C for 72 hours, anhydrous MgCl ₂ , anhydrous ZnCl ₂ , KF was vacuum dried at 130°C for 24 hours; anhydrous MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ were 30%-45%, 45%-55%, 5-8%, 5.3-15%, 2-4%, 1-2%, grind and mix evenly, heat and melt in the electrolytic tank; use inert metal molybdenum as cathode, graphite as anode, electrolysis temperature 510-630℃ Next, take the sinking cathode method, the pole distance is 4cm, the cathode current density is 3-12A/cm ² , the cell voltage is 5.7-8.2V, after 2-4 hours of electrolysis, Mg is deposited near the cathode in the molten salt electrolytic cell - Zn-Zr alloys. 2. the method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis according to claim 1 is characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, electrolysis temperature 510°C, cathode current density 6A/cm ² , anode current density 0.5A/cm ² , cell voltage 6.1-7.2V, after After 2 hours of electrolysis, a Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 32.7%, 66.1%, and 1.2%. 3. The method for directly preparing Mg-Zn-Zr alloys by molten salt electrolysis according to claim 1 is characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, electrolysis temperature 540°C, cathode current density 3A/cm ² , anode current density 0.5A/cm ² , cell voltage 5.1-6.2V, after After 2 hours of electrolysis, a Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 45.9%, 53.1%, and 1.0%. 4. the method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis according to claim 1 is characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, the electrolysis temperature is 570°C, the sinking cathode method is adopted, the cathode current density is 6A/cm ² , the anode current density is 0.5A/cm ² , the cell voltage 6.1-7.2V, after 2 hours of electrolysis, a Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc, and zirconium are respectively: 82.4%, 16.7%, and 0.9%. 5. The method for directly preparing Mg-Zn-Zr alloys by molten salt electrolysis according to claim 1, characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, electrolysis temperature 570°C, cathode current density 12A/cm ² , anode current density 0.5A/cm ² , cell voltage 7.2-8.2V, after After 2 hours of electrolysis, a Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 52.2%, 47.4%, and 0.4%. 6. The method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis according to claim 1, characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, electrolysis temperature 600°C, cathode current density 9A/cm ² , anode current density 0.5A/cm ² , cell voltage 6.4-7.5V, after After 2 hours of electrolysis, a Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 88.9%, 11.0%, and 0.1%. 7. The method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis according to claim 1, characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, electrolysis temperature 600°C, cathode current density 12A/cm ² , anode current density 0.5A/cm ² , cell voltage 7.1-8.2V, after After 4 hours of electrolysis, a Mg-Zn-Zr alloy was deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc, and zirconium were 80.3%, 18.4%, and 1.3%, respectively. 8. The method for directly preparing Mg-Zn-Zr alloy by molten salt electrolysis according to claim 1, characterized in that: the mass percentages of MgCl ₂ , KCl, KF, K ₂ ZrF ₆ , ZrO ₂ and anhydrous ZnCl ₂ are respectively 34.2%, 51.4%, 5.7%, 5.3%, 2.3%, 1.1%, electrolysis temperature 630°C, cathode current density 6A/cm ² , anode current density 0.5A/cm ² , cell voltage 5.3-6.6V, after After 2 hours of electrolysis, a Mg-Zn-Zr alloy is deposited near the cathode in the molten salt electrolytic cell, and the contents of magnesium, zinc and zirconium are respectively: 75.9%, 23.9%, and 0.2%.

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