Patent Application
20190300990
This application relates to magnesium alloys and, more particularly, to magnesium-zinc-manganese-tin-yttrium alloys.
Magnesium alloys are lightweight materials—they are 30 to 50 percent lighter than aluminum alloys and 70 percent lighter than steels. Additionally, magnesium alloys have good strength characteristics and stiffness, excellent damping and mechanical properties, and they resist corrosion. Therefore, magnesium alloys are used as structural materials in the aerospace, automobile and rail transportation industries, and are used in various products, such as household appliances.
Magnesium alloys are typically divided into two categories: cast magnesium alloys and wrought magnesium alloys. Cast magnesium alloys can have coarse grains and can exhibit compositional segregation. Therefore, cast magnesium alloys often fail to satisfy the stringent physical requirements of today's high-performance structural materials. Wrought magnesium alloys typically exhibit better mechanical properties, such as proof stress, tensile strength and elongation, as compared with cast magnesium alloys. Therefore, wrought magnesium alloys are often considered for use as high-performance structural materials, particularly when weight is an important consideration.
The common wrought magnesium alloys include the magnesium-aluminum-zinc series and the magnesium-zinc-zirconium series. AZ31 is a typical alloy of the magnesium-aluminum-zinc series—AZ31 has moderate strength, but poor high temperature strength performance. ZK60 is a typical alloy of the magnesium-zinc-zirconium series—ZK60 has excellent room temperature and high temperature strength performance, but is relatively expensive.
Accordingly, those skilled in the art continue with research and development efforts in the field of magnesium alloys.
In one embodiment, the disclosed magnesium alloy may include (1) about 2 percent by weight to about 8 percent by weight zinc, (2) about 0.1 percent by weight to about 3 percent by weight manganese, (3) about 1 percent by weight to about 6 percent by weight tin, (4) about 0.1 percent by weight to about 4 percent by weight yttrium, and (5) magnesium.
In another embodiment, the disclosed magnesium alloy may consist essentially of (1) about 2 percent by weight to about 8 percent by weight zinc, (2) about 0.1 percent by weight to about 3 percent by weight manganese, (3) about 1 percent by weight to about 6 percent by weight tin, (4) about 0.1 percent by weight to about 4 percent by weight yttrium, and (5) magnesium, wherein said magnesium comprises a balance of said magnesium alloy.
In yet another embodiment, disclosed is a method for making a magnesium alloy. The method may include the steps of (1) forming a molten mass including about 2 percent by weight to about 8 percent by weight zinc, about 0.1 percent by weight to about 3 percent by weight manganese, about 1 percent by weight to about 6 percent by weight tin, about 0.1 percent by weight to about 4 percent by weight yttrium and magnesium; (2) cooling the molten mass to form a solid mass; (3) annealing the solid mass to form an annealed mass; and (4) extruding the annealed mass.
Other embodiments of the disclosed magnesium-zinc-manganese-tin-yttrium alloy and method for making the same will become apparent from the following detailed description, the accompanying drawings and the appended claims.
Disclosed is a magnesium alloy that includes magnesium (Mg), zinc (Zn), manganese (Mn), tin (Sn) and yttrium (Y). Without being limited to any particular theory, it is believed that the additions of yttrium and tin in the disclosed magnesium alloy may improve mechanical properties (vis-à-vis magnesium-aluminum-zinc series and magnesium-zinc-zirconium series magnesium alloys) by maintaining fine grains after melting and heat treatment, while also enhancing the hot-working temperature and reducing deformation resistance. Significantly, the disclosed magnesium alloys may be manufactured at much lower cost than magnesium-zinc-zirconium series magnesium alloys.
In a first embodiment, the disclosed magnesium alloy may include about 2 percent by weight to about 8 percent by weight zinc, about 0.1 percent by weight to about 3 percent by weight manganese, about 1 percent by weight to about 6 percent by weight tin, about 0.1 percent by weight to about 4 percent by weight yttrium. The balance of the magnesium alloy may be magnesium, as well as any present impurities. In one particular implementation of the first embodiment, the disclosed magnesium alloy may include at most about 0.15 percent by weight impurities (i.e., the impurity content).
As used herein, “impurities” refers to dissolved elements and inclusions other magnesium, zinc, manganese, tin and yttrium. Non-limiting examples of impurities include silicon, iron, copper and nickel.
In a second embodiment, the disclosed magnesium alloy may include about 5.0 percent by weight to about 6.3 percent by weight zinc, about 0.6 percent by weight to about 1.1 percent by weight manganese, about 2.0 percent by weight to about 4.4 percent by weight tin, about 0.1 percent by weight to about 1.3 percent by weight yttrium. The balance of the magnesium alloy may be magnesium, as well as any present impurities. In one particular implementation of the second embodiment, the disclosed magnesium alloy may include at most about 0.15 percent by weight impurities.
In a third embodiment, the disclosed magnesium alloy may include about 5.7 percent by weight zinc, about 0.9 percent by weight manganese, about 4.4 percent by weight tin, about 0.5 percent by weight yttrium. The balance of the magnesium alloy may be magnesium, as well as any present impurities. In one particular implementation of the third embodiment, the disclosed magnesium alloy may include at most about 0.15 percent by weight impurities.
Referring to
The forming step (block 102) may be performed in a vacuum induction furnace by charging a crucible with a combination of metals and/or metal alloys required to achieve the desired composition. For example, the crucible may be charged with appropriate amounts of pure magnesium, pure zinc, pure tin, Mg-30% Y master alloy and Mg-5% Mn master alloy.
The furnace may heat the crucible and metals/metal alloys until a molten mass is formed. The molten mass may be stirred, such as for about 2 to about 5 minutes. Optionally, an inert gas blanket may cover the metals/metal alloys in the crucible during the forming step (block 102).
At block 104, the molten mass may be cooled to form a solid mass. Cooling may be effected with water (e.g., cold water). For example, during the cooling step (block 104), the crucible holding the molten mass may be removed from the furnace and immersed in water.
At block 106, any oxidization/crust formed on the solid mass may be wiped away. For example, the wiping step (block 106) may be performed with a cloth, a brush or the like.
At block 108, the solid mass may be machined to the desired size. For example, the machining step (block 108) may include passing the solid mass through a rolling mill until an extrudable size has been achieved.
At block 110, the solid mass may be annealed to form an annealed mass. The annealing step (block 110) may be performed homogeneously. For example, the annealing step (block 110) may include maintaining the solid mass at an elevated temperature (e.g., from about 410° C. to about 430° C.) for a period of time (e.g., from about 10 hour to about 14 hours).
At block 112, the annealed mass may be extruded (e.g., into bars). For example, the extruding step (block 112) may include an extruding temperature (e.g., about 350° C. to about 370° C.), an extruding speed (e.g., about 1 to about 2 meters per second (m/sec)), and a reduction ratio (e.g., 25).
At block 114, the extruded, annealed mass may be cooled. The cooling step (block 114) may include rapid cooling. For example, the cooling step (block 114) may include submerging the extruded, annealed mass into cold water. After cooling, the resulting magnesium alloy may optionally undergo solutionizing and aging.
Five magnesium alloys (Examples 1-5) were prepared using the following raw materials: pure Mg; pure Zn; pure Sn; Mg-30% Y master alloy; and Mg-5% Mn master alloy. The chemical compositions of Examples 1-5 are provided in Table 1.
For each of Examples 1-5, appropriate quantities of the raw materials were charged into a crucible and the crucible was heated in a vacuum induction furnace to form a molten mass. An argon blanket covered the surface of the molten mass in the crucible. The molten mass was stirred for 2 to 5 minutes and then quenched in cold water to yield an ingot. Any oxide/crust formed on the surface of the ingot was wiped away and the ingot was machined to a size suitable for extruding.
For each of Examples 1-5, the cooled and sized ingot was annealed at 420° C. for 12 hours and then extruded into bars. The extrusion parameters were as follows: (a) ingot temperature: 360° C.; (b) extruding cabin temperature: 350° C.; (c) mold temperature: 360° C.; (d) speed: 1 to 2 meters per minute; and (e) reduction ratio: 25. After extrusion, the bars were quickly cooled in cold water.
As shown in
For comparison, the ultimate yield strength, the ultimate tensile strength, and the elongation of several magnesium alloys were also measured at room temperature. The results are provided in Table 3. AZ61 and ZK60 are prior art magnesium alloys.
Thus, the disclosed magnesium alloys may have significant commercial value.
Although various embodiments of the disclosed magnesium-zinc-manganese-tin-yttrium alloy and method for making the same have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.
This application is a continuation of U.S. Ser. No. 14/449,449 filed on Aug. 1, 2014.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14449449 | Aug 2014 | US |
| Child | 16445476 | US |
