Preparation method for heterogeneous Mg alloys bar with high elastic modulus

Abstract

It provides a preparation method of solid-liquid composite casting in a specific mold to produce the heterostructured metallic bars composed of high elastic modulus metal and low elastic modulus Mg alloy. Subsequently, the microstructure of heterogeneous Mg alloys bars is adjusted by the specific deformation and heat treatment. Heterogeneous Mg alloys bars without oxide inclusions and with good interfacial bonding were prepared through this method. The improvement of elastic modulus is obtained by tailoring the heterogeneous microstructure.

Claims

1. A method for preparing heterogeneous Mg alloys bar, which is involved in the following steps: Step 1: pretreating a high elastic modulus metal, which comprises chemically cleaning surfaces of the high elastic modulus metal to remove oil stain and oxide, performing galvanizing treatment on the surfaces of the high elastic modulus metal to obtain a pre-treated solid metal that has a zinc layer with a proper thickness, presetting the pre-treated solid metal in a cavity of a mold, and then, wrapping a heating sleeve around the mold to preheat the pre-treated solid metal and the mold; wherein an elastic modulus of the high elastic modulus metal is at least four times that of Mg, and the high elastic modulus metal is selected from one of high entropy alloys CoCrNi and VCoNi and is solid state; Step 2: performing solid-liquid composite casting operation on the pre-treated solid metal, which comprises under an antioxygen and inert gas shielding atmosphere, removing the heating sleeve, and then performing casting operation on the pre-treated solid metal to obtain a heterogeneous Mg alloy cast ingot, wherein the casting operation comprises pouring liquid Mg or liquid Mg alloy into the mold, and wrapping the heating sleeve around the mold to perform heat preservation on the mold; Step 3: deforming the heterogeneous Mg alloy cast ingot, which comprises cutting the heterogeneous Mg alloy cast ingot to obtain heterogeneous metal bar, and extruding, drawing or rotary forging the heterogeneous metal bar to obtain a deformed heterogeneous metal bar, thereby to eliminate casting defects and improve an interfacial bonding quality; and Step 4: performing heat treatment on the deformed heterogeneous metal bar, which comprises performing vacuum solution on the deformed heterogeneous metal bar to obtain a heterogeneous Mg alloy bar, thereby to eliminate an influence of deformation and tailor a microstructure of heterogeneous metal; wherein: in step 1, the heating sleeve is wrapped around the mold to perform preheating treatment to hold temperature at 650670 C., which is not lower than a melting point temperature of Mg or Mg alloy, for 5-7 hours; in step 2, after pouring, the heating sleeve is quickly wrapped for heat preservation, heat preservation temperature is held at 600700 C. for 28 hours; and in step 3, the heterogeneous metal bar is deformed by extrusion, drawing or rotary forging at a deformation temperature of 250300 C.

2. The method of claim 1, wherein in step 1: a shape of the pre-treated solid metal is coil or disc spring, a quantity of solid metal is placed according to specific actual needs, ranging from 1 to 100, a diameter of the pre-treated solid metal accounts for 1% 99% of a diameter of the mold cavity, and the diameter of the mold cavity ranges from 10100 cm.

3. The method of claim 1, wherein in step 1: galvanizing treatment adopts electroplating, hot dip plating, thermal spraying, or vapor deposition, a thickness of the zinc layer is 0.150 m, and the pre-treated solid metal is passed through a positioning hole of the mold and preset in the mold cavity.

4. The method of claim 1, wherein in step 2: pouring temperature of pouring liquid Mg or liquid Mg alloy is 6501000 C.

5. The method of claim 1, wherein in step 4: the deformed heterogeneous metal bar is treated by vacuum solution to eliminate the influence of deformation and regulate the microstructure of heterogeneous metal, heat treatment temperature is determined by Mg or Mg alloy, and the range is 400900 C., with the time of 112 hours.

Description

DESCRIPTION OF ATTACHED DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is sketch map of pretreatment.

(3) FIG. 2 is sketch map of solid-liquid composite casting.

(4) FIG. 3 is sketch map of cast ingot and deformation.

(5) FIG. 4 is sketch map of heat treatment.

(6) FIG. 5 is curves of mechanical properties.

SPECIFIC EMBODIMENTS

(7) Reference will now be made in detail to various embodiments of present invention with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known technologies will be omitted. However, the following embodiments will enable a person having ordinary skill in the art to easily understand the characteristic constitutions and effects of the present invention and put the present invention into practice with no significant difficulties.

Embodiment 1

(8) Embodiment 1 selected a VCoNi medium-entropy alloy as the solid metal and AZ31 as liquid metal. According to embodiment 1, the preparation method for heterogeneous Mg alloys bar with high elastic modulus includes the following four steps.

(9) Firstly, as shown in FIG. 1a, the shape of solid metal is designed as heliciform. The surface of helical VCoNi alloy 1 is chemically cleaned to remove the oil stain and oxide. A zinc layer with a thickness of 30 m is galvanized on the surface of VCoNi alloy. The pre-treated helical VCoNi alloy 1 is placed through the positioning hole 8 of the positioning die 6 and fix in the cavity of the die 4. Then, a heating sleeve 5 is wrapped around the mold to preheat the helical VCoNi alloy 1 and mold at 800 C. for 2 hours.

(10) Secondly, as shown in FIG. 1b, the heating sleeve 5 is removed. Casting is then performed under the antioxygen and inert gas shielding atmosphere. Pouring is carried out at 800 C. with Liquid AZ31 alloy poured from gate 7 and overflowed from riser 2. After pouring, the heating sleeve 5 is quickly wrapped for heat preservation. The temperature is hold at 500 C. for 2 hours to help form a metallurgical bonding of the solid-liquid interface.

(11) Thirdly, as shown in FIG. 2a, the cast ingot 9 with the diameter of 15 cm and the length of 50 cm is produced. The bar 10 with a diameter of 15 cm is cut from the cast ingot 9, as shown in FIG. 2b. FIG. 3a shows that the bar 10 is extruded along the axial direction by the extruder 11. The extrusion temperature is 200 C., and the extrusion ratio is 1:2. After multiple passes of extrusion, the extruded bar 12 with a diameter of 1 cm is obtained, as shown in FIG. 3b.

(12) Finally, as shown in FIG. 4, the extruded bar 12 is subjected to solution treatment at 500 C. for 12 hours in a high-temperature vacuum furnace 13 under argon atmosphere. Heat treatment can eliminate the influence of deformation and regulate the microstructure of heterogeneous metal. FIG. 5 shows the tensile engineering mechanical properties of VCoNi (blue curve) and AZ31 (green dash curve). The elastic modulus of AZ31 is 13 GPa. While the elastic modulus of VCoNi is nearly 16 times of that of AZ31, about 207 GPa. Furthermore, AZ31 exhibits a uniform elongation of approximately 19%, while VCoNi has a similar uniform elongation of close to 20%. This similarity in plasticity between the two materials is advantageous in preserving the overall plasticity of heterogeneous bars. The embodiment 1 successfully produces Mg alloy bars with high elastic modulus through the solid-liquid cast, deformation and heat treatment.

Embodiment 2

(13) Embodiment 2 selected a CoCrNi medium-entropy alloy as the solid metal and AZ31 as liquid metal. According to embodiment 2, the preparation method for heterogeneous Mg alloys bar with high elastic modulus includes the following four steps.

(14) Firstly, as shown in FIG. 1c, the shapes of solid metal are designed as heliciform. The surfaces of multiple helical CoCrNi alloys 1 are chemically cleaned to remove the oil stain and oxide. A zinc layer with a thickness of 30 m is galvanized on the surfaces of CoCrNi alloys. The pre-treated helical CoCrNi alloys 1 are placed through the positioning holes 8 of the positioning die 6 and preset in the cavity of the die 4. Then, a heating sleeve 5 is wrapped around the mold to preheat the helical CoCrNi alloys 1 and the total mold at 800 C. for 2 hours.

(15) Secondly, as shown in FIG. 1c, the heating sleeve 5 is removed. Casting is then performed under the antioxygen and inert gas shielding atmosphere. Pouring is carried out at 800 C. with Liquid AZ31 alloy poured from gate 7 and overflowed from riser 2. After pouring, the heating sleeve 5 is quickly wrapped for heat preservation. The temperature is hold at 500 C. for 2 hours to help form a metallurgical bonding of the solid-liquid interfaces.

(16) Thirdly, as shown in FIG. 2c, the cast ingot 9 with the diameter of 30 cm and the length of 50 cm is produced. The bar 10 with a diameter of 30 cm is cut from the cast ingot 9, as shown in FIG. 2b. FIG. 3a shows that the bar 10 is extruded along the axial direction by the extruder 11. The extrusion temperature is 200 C., and the extrusion ratio is 1:2. After multiple passes of extrusion, the extruded bar 12 with a diameter of 2 cm is obtained, as shown in FIG. 3b.

(17) Finally, as shown in FIG. 4, the extruded bar 12 is subjected to solution treatment at 500 C. for 12 hours in a high-temperature vacuum furnace 13 under argon atmosphere. Heat treatment can eliminate the influence of deformation and regulate the microstructure of heterogeneous metal. FIG. 5 shows the tensile engineering mechanical properties of CoCrNi (brown curve) and AZ31 (green dash curve). The elastic modulus of AZ31 is 13 GPa. While the elastic modulus of CoCrNi is nearly 16 times of that of AZ31, about 206 GPa. Furthermore, AZ31 displays a uniform elongation of approximately 19%, while CrCoNi exhibits a uniform elongation exceeding 30%. This superior plasticity of CrCoNi compared to low elastic modulus alloys is advantageous in preserving the overall plasticity of heterogeneous bars. The embodiment 2 successfully produces Mg alloy bars with high elastic modulus through the solid-liquid cast, deformation and heat treatment.

Embodiment 3

(18) Embodiment 3 selected a VCoNi medium-entropy alloy as the solid metal and pure Mg as liquid metal. According to embodiment 3, the preparation method for heterogeneous Mg alloys bar with high elastic modulus includes the following four steps.

(19) Firstly, as shown in FIG. 1a, the shape of solid metal is designed as heliciform. The surface of helical VCoNi alloy 1 is chemically cleaned to remove the oil stain and oxide. A zinc layer with a thickness of 30 m is galvanized on the surface of VCoNi alloy. The pre-treated helical VCoNi alloy 1 is placed through the positioning hole 8 of the positioning die 6 and preset in the cavity of the die 4. Then, a heating sleeve 5 is wrapped around the mold to preheat the helical VCoNi alloy 1 and the total mold at 800 C. for 2 hours.

(20) Secondly, as shown in FIG. 1b, the heating sleeve 5 is removed. Casting is then performed under the antioxygen and inert gas shielding atmosphere. Pouring is carried out at 800 C. with Liquid pure Mg poured from gate 7 and overflowed from riser 2. After pouring, the heating sleeve 5 is quickly wrapped for heat preservation. The temperature is hold at 500 C. for 2 hours to help form a metallurgical bonding of the solid-liquid interface.

(21) Thirdly, as shown in FIG. 2a, the cast ingot 9 with a diameter of 15 cm and length of 50 cm is produced. The bar 10 with a diameter of 15 cm is cut from the cast ingot 9, as FIG. 2b shown. As shown in FIG. 3a, the bar 10 is extruded along the axial direction by the extruder 11. The extrusion temperature is 200 C., and the extrusion ratio is 1:2. After multiple passes of extrusion, the extruded bar 12 with a diameter of 1 cm is obtained, as shown in FIG. 3b.

(22) Finally, as shown in FIG. 4, the extruded bar 12 is subjected to solution treatment at 500 C. for 12 hours in a high-temperature vacuum furnace 13 under argon atmosphere. Heat treatment can eliminate the influence of deformation and regulate the microstructure of heterogeneous metal. FIG. 5 shows the tensile engineering mechanical properties of VCoNi (blue curve) and pure Mg (orange dash curve). The elastic modulus of pure Mg is 45 GPa. While the elastic modulus of VCoNi is nearly 5 times of that of pure Mg, about 207 GPa. Furthermore, Mg exhibits a uniform elongation of approximately 20%, while VCoNi has a similar uniform elongation of close to 20%. This similarity in plasticity between the two materials is advantageous in preserving the overall plasticity of heterogeneous bars. The embodiment 3 successfully produces Mg alloy bars with high elastic modulus through the solid-liquid cast, deformation and heat treatment.