The present disclosure relates to forged and flow-formed articles including automobile vehicle wheels.
Current processes for forming automobile vehicle alloy wheels include casting an ingot of a metal including magnesium, extruding a magnesium billet, forging a blank from the extruded billet, flow-forming and pre-machining the blank and performing final machining operations such as for example to finish a hub diameter, wheel spokes and lug bores. Aluminum material is also commonly used for automobile vehicle wheels as its intrinsic formability in a flow forming process is excellent without requiring pre-extrusion.
Magnesium alloy materials such as ZK30 comprising a magnesium-zinc-zirconium alloy have also been adapted for this use and provide excellent formability but have a high cost due to addition of zirconium (Zr) material to improve formability in flow forming. ZK30 is therefore presently limited to niche market applications. Known zirconium-free material such as AZ80 comprising a magnesium-aluminum-zinc alloy is inexpensive compared to ZK30 alloy but suffers from insufficient formability and cracking during flow-forming following forging. Low formability precludes use of AZ80 alloy in mass production processes for automobile vehicle wheel applications.
Thus, while current aluminum and magnesium-zinc-zirconium alloy materials achieve their intended purpose, there is a need for a new and improved system and method for forming an axisymmetric article such as an automobile vehicle wheel.
According to several aspects, a method to form a magnesium article includes: heating materials including magnesium, aluminum, manganese and tin in a furnace to create an alloy having a composition of; the magnesium in an amount greater than or equal to 90% by weight of the materials; the aluminum ranging between approximately 2.0% up to approximately 4.0% by weight of the materials; the manganese ranging between approximately 0.43% up to approximately 0.6% by weight of the materials; and the tin ranging between approximately 1% up to approximately 3% by weight of the materials; chill casting the alloy to create a cast billet; and heating the cast billet at a temperature ranging from approximately 380° C. up to approximately 420° C. and maintaining the temperature for a time period between approximately 4 hours to 10 hours to homogenize element distribution.
In another aspect of the present disclosure, the method further includes forging the cast billet in a single-step or multiple-step forging operation to create a forged blank; and flow-forming the forged blank to form a final shape defining a pre-machined blank.
In another aspect of the present disclosure, the method further includes maintaining a forging temperature ranging from approximately 350° C. up to approximately 450° C. when forging the cast billet.
In another aspect of the present disclosure, the method further includes extruding the cast billet at a temperature ranging from approximately 300° C. up to approximately 450° C. with an extrusion ratio ranging from approximately 2 up to approximately 10 to improve formability of the cast billet.
In another aspect of the present disclosure, the method further includes maintaining a forging temperature ranging from approximately 350° C. up to approximately 450° C. when forging the extruded billet.
In another aspect of the present disclosure, the method further includes heating the forged blank to a temperature ranging between approximately 300° C. to 420° C. prior to flow-forming.
In another aspect of the present disclosure, the method further includes quenching after flow-forming the heated forged blank from a working temperature ranging from approximately OC to 100° C.
In another aspect of the present disclosure, the method further includes ageing after flow-forming the heated forged blank at a temperature ranging from approximately 150° C. to 200° C. for 2 to 20 hours.
In another aspect of the present disclosure, the method further includes finish machining the pre-machined blank to create a desired object such as an axisymmetric magnesium article.
In another aspect of the present disclosure, the method further includes when forging the cast billet forging a hub and multiple spokes defining a forged blank having a circumferential rim.
According to several aspects, a method to form an axisymmetric magnesium article by forging and flow forming includes: smelting multiple materials including magnesium (Mg), aluminum (Al), manganese (Mn) and tin (Sn) in a casting process; solidifying the multiple materials from the casting process into a cast ingot; performing a heat treatment process on the cast ingot at a temperature of approximately 400° C. for a time period of approximately 5 hours to induce precipitation of nanoparticles of Al/Mn out of a matrix of the magnesium; forging the cast ingot after the heat treatment process to form a forged blank; and flow forming the forged blank into a pre-machined blank.
In another aspect of the present disclosure, the method further includes dissolving the Sn into the Mg matrix by conducting the flow forming at a temperature ranging from approximately 300° C. up to approximately 420° C.
In another aspect of the present disclosure, the method further includes supersaturating portions of the Sn into the matrix of the Magnesium by quenching after the flow forming.
In another aspect of the present disclosure, the method further includes ageing the flow formed blank at 150° C. to 200° C. for 2 to 20 hours after the quenching to precipitate Mg/Mn particles to enhance strength.
In another aspect of the present disclosure, the method further includes adding zinc (Zn) into the melt in an amount less than 3% by weight.
In another aspect of the present disclosure, the method further includes adding the materials in the following amounts by weight of the materials: the magnesium being greater than or equal to 90% by weight of the materials; the aluminum ranging between approximately 2.0% up to approximately 4.0% by weight of the materials; and the manganese ranging between approximately 0.43% up to approximately 0.6% by weight of the materials.
According to several aspects, an automobile vehicle axisymmetric magnesium article, comprising: multiple materials including magnesium (Mg), aluminum (Al); manganese (Mn), and tin (Sn); the magnesium being present at greater than or equal to 90% by weight of the materials; the aluminum ranging between approximately 2.0% up to approximately 4.0% by weight of the materials; the manganese ranging between approximately 0.43% up to approximately 0.6% by weight of the materials; the tin ranging between approximately 1.0% up to approximately 3.0% by weight of the materials; and a plurality of nanoparticles of Al/Mn precipitated out of a matrix of the magnesium, the plurality of nanoparticles refining a plurality of dynamic recrystallized grains and inhibiting the growth of the dynamic recrystallized grains.
In another aspect of the present disclosure, a rim is flow-formed after pre-heating to a temperature ranging between approximately 300° C. to 420° C.
In another aspect of the present disclosure, an automobile vehicle wheel includes the circumferential rim machined from the pre-machined blank.
In another aspect of the present disclosure, an average equivalent diameter of DRX grains in the circumferential rim after roll forming is more than 10% smaller than in an outboard flange of the automobile vehicle wheel, and an average equivalent diameter of the dynamic recrystallized grains in the circumferential rim being less than 10 um.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
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The cast billet 14 is then transferred, for example by a robot, to a forging station where in a fourth procedure 30, the pre-heated cast billet 14 is subjected to single-step or a multiple-step of forging operation at a forging temperature that may range from approximately 350° C. up to approximately 450° C. The forging operation forms a hub and spokes defining the forged blank 16 having the circumferential rim 18 described in reference to
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The addition of Al is provided for castability and strength. According to several aspects, Al content ranges from 2.0% to 4.0% for a balance between intergranular boundary mobility and castability.
Tin (Sn) solute has weak drag effect on boundary mobility. Therefore, a certain amount of Sn is added to improve castability and strength for the alloy to make up for the reducing Al content. In the flow forming process conducted at temperatures ranging from approximately 300° C. to 452° C., Sn can be dissolved in the Mg matrix. By quenching, Sn can be supersaturated in the Mg matrix. In the following ageing treatment conducted at 150° C. to 200° C. for 2 to 20 hours Mg—Sn particles will precipitate out to enhance strength. To avoid a significant cost increment, Sn addition is controlled to range from 1% to 3%.
Similar to Sn, Zinc (Zn) solute has weak drag effect on boundary mobility. In addition, Zn addition is beneficial for fluidity of the melt in casting when its amount is equal to or less than 3%. Zn addition will also enhance strength properties in the final product owing to a solid solution strengthening effect.
Though calcium and rare earth elements may help modify texture of microstructure and improve formability, calcium and rare earth elements tend to segregate to grain boundaries and have strong drag effect on boundary movement. Therefore, the alloy of the present disclosure is substantially free of calcium and rare earth elements, <0.05%.
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The alloy of the present disclosure produces a high volume of Al—Mn nanoparticles 74 during heat treatment 72 following casting 66 to improve thermal stability for the new Mg—Al alloy. The Al—Mn nanoparticles 74 help refine dynamic recrystallized grains in the forging process 76 and inhibit their growth, which further contributes to intergranular boundary strengthening. Manganese (Mn) is conventionally added in commodity AZ80 and AZ31 alloys for neutralizing negative effect of iron (Fe) brought to corrosion resistance. In the alloy of the present disclosure, Mn is added to generate a high volume of Al—Mn nanoparticles to enhance thermal stability of microstructure in the forged blank. The volume of Al—Mn nanoparticles 74 are larger than comparable particles formed in AZ80 with a preference for low Aluminum and high Manganese. Microalloying of manganese in the casting process is difficult due to limited solubility of manganese in magnesium. Therefore, manganese content in the present alloy is limited to 0.6% considering processability in scale-up production. Adding manganese at higher than 0.6% content may lead to undissolved coarse Mn-containing intermetallic particles 70 in as-cast microstructure which is detrimental for the following forming process and the ductility in the final product.
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A method to form an axisymmetric magnesium article 10 of the present disclosure offers several advantages. These include provision of a magnesium-aluminum alloy chemistry based on a zirconium-free alloy system (Mg—Al—Mn—Sn) that may be flow-formed, a microstructure suitable for flow-forming, and a manufacturing process for producing axisymmetric magnesium components such as automobile vehicle wheels.
The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.
Number | Date | Country | Kind |
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202110932302.2 | Aug 2021 | CN | national |