Abstract
A preparation method for heterogeneous Mg alloys bar with high elastic modulus. 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 preparation method for heterogeneous Mg alloys bar with high elastic modulus, which is involved in the following steps: Step 1 is pretreatment. Selecting two or more metals with much higher elastic modulus than Mg alloys. The metal with higher elastic modulus should be solid state. The surfaces of the solid metal are chemically cleaned to remove the oil stain and oxide. the surfaces are then galvanized to obtain a zinc layer with a proper thickness. The pre-treated solid metal is preset in the cavity of the mold. Then, a heating sleeve is wrapped around the mold to preheat the metals and mold. Step 2 is the solid-liquid composite casting. The heating sleeve removed. Casting is then Performed under the antioxygen and inert gas shielding atmosphere. Step 3 is deformation. The bar is deformed by extrusion, drawing or rotary forging to eliminated the casting defects and improve the interfacial bonding quality. Step 4 is heat treatment. The deformed heterogeneous metal bar is treated by vacuum solution to eliminate the influence of deformation and tailor the microstructure of heterogeneous metal.
2. The method of claim 1, wherein step 1: The elastic modulus of solid metal should be more than twice higher than the liquid ones. The shape of solid metal can be coil or disc spring. The quantity of solid metal can be placed according to specific actual needs, ranging from 1 to 100. The diameter of solid metal accounts for 1%99% of the diameter of mold cavity (10100 cm).
3. The method of claim 1, wherein step 1: Galvanizing treatment adopts electroplating, hot dip plating, thermal spraying, vapor deposition and other methods. The thickness of zinc coating is 0.150 m. The processed solid metal is passed through the positioning hole of the positioning die and preset in the die cavity. Then, a heating sleeve wrapped around the mold to hold temperature at 500800 C. for 1-10 hours.
4. The method of claim 1, wherein step 2: Removing the heating sleeve and casting are Performed under the antioxygen and inert gas shielding atmosphere. The pouring temperature is 6501000 C. After pouring, the heating sleeve is quickly wrapped for heat preservation. The temperature is hold at 500800 C. for 28 hours.
5. The method of claim 1, wherein step 3: The cast bar is deformed by extrusion, drawing or rotary forging at the deformation temperature of 100500 C.
6. The method of claim 1, wherein 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. The temperature is determined by the low elastic modulus metal, and the range is 400900 C., with the time of 112 hours.
7. The method of claim 1: The method is applicable to aluminum alloys, titanium alloys and Mg alloys with low elastic modulus.
Description
DESCRIPTION OF ATTACHED DRAWINGS
[0014] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0015] FIG. 1 is sketch map of pretreatment.
[0016] FIG. 2 is sketch map of solid-liquid composite casting.
[0017] FIG. 3 is sketch map of cast ingot and deformation.
[0018] FIG. 4 is sketch map of heat treatment.
[0019] FIG. 5 is curves of mechanical properties.
SPECIFIC EMBODIMENTS
[0020] 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
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
