US20210062306A1 - High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy - Google Patents
High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy Download PDFInfo
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- 238000002485 combustion reaction Methods 0.000 title abstract description 3
- 229910000861 Mg alloy Inorganic materials 0.000 title description 13
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 141
- 239000000956 alloy Substances 0.000 claims abstract description 141
- 239000011777 magnesium Substances 0.000 claims abstract description 24
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 16
- 238000001125 extrusion Methods 0.000 claims description 48
- 229910052791 calcium Inorganic materials 0.000 claims description 26
- 229910052727 yttrium Inorganic materials 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 23
- 229910052782 aluminium Inorganic materials 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 22
- 229910000765 intermetallic Inorganic materials 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 229910052725 zinc Inorganic materials 0.000 claims description 12
- 229910052748 manganese Inorganic materials 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 238000005242 forging Methods 0.000 claims description 7
- 239000011159 matrix material Substances 0.000 claims description 7
- 238000005096 rolling process Methods 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 150000001875 compounds Chemical class 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 2
- 239000011575 calcium Substances 0.000 description 32
- 230000000052 comparative effect Effects 0.000 description 17
- 239000011701 zinc Substances 0.000 description 17
- 238000007792 addition Methods 0.000 description 15
- 238000005275 alloying Methods 0.000 description 15
- 239000000463 material Substances 0.000 description 15
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 10
- 239000011572 manganese Substances 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- 238000005266 casting Methods 0.000 description 8
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 5
- 229910003023 Mg-Al Inorganic materials 0.000 description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 238000000635 electron micrograph Methods 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 238000001636 atomic emission spectroscopy Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000004512 die casting Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 229910018131 Al-Mn Inorganic materials 0.000 description 1
- 229910018461 Al—Mn Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910021380 Manganese Chloride Inorganic materials 0.000 description 1
- GLFNIEUTAYBVOC-UHFFFAOYSA-L Manganese chloride Chemical compound Cl[Mn]Cl GLFNIEUTAYBVOC-UHFFFAOYSA-L 0.000 description 1
- 229910021323 Mg17Al12 Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910000946 Y alloy Inorganic materials 0.000 description 1
- 238000003483 aging Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- ZFXVRMSLJDYJCH-UHFFFAOYSA-N calcium magnesium Chemical compound [Mg].[Ca] ZFXVRMSLJDYJCH-UHFFFAOYSA-N 0.000 description 1
- 238000009750 centrifugal casting Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 239000003562 lightweight material Substances 0.000 description 1
- MIOQWPPQVGUZFD-UHFFFAOYSA-N magnesium yttrium Chemical compound [Mg].[Y] MIOQWPPQVGUZFD-UHFFFAOYSA-N 0.000 description 1
- 239000011565 manganese chloride Substances 0.000 description 1
- 229940099607 manganese chloride Drugs 0.000 description 1
- 235000002867 manganese chloride Nutrition 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000010118 rheocasting Methods 0.000 description 1
- 238000007528 sand casting Methods 0.000 description 1
- 238000009716 squeeze casting Methods 0.000 description 1
- 238000012956 testing procedure Methods 0.000 description 1
- 238000010119 thixomolding Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- -1 zinc metals Chemical class 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C1/00—Manufacture of metal sheets, metal wire, metal rods, metal tubes by drawing
- B21C1/003—Drawing materials of special alloys so far as the composition of the alloy requires or permits special drawing methods or sequences
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Extrusion Of Metal (AREA)
Abstract
Description
- The present invention relates to high strength wrought magnesium alloys designed for aerospace applications. More specifically, the invention includes a Mg—Al—Zn—Mn—Ca—Y alloy, which is non-flammable and improves on extrudability and mechanical properties of conventional alloys. The invention also includes a method of making the alloy in a selected manufacturing process.
- In automotive and aerospace applications, lightweight materials are increasingly used to replace heavy structural elements in order to increase vehicle fuel efficiency. Titanium and aluminum are common material choices for reducing weight in structural applications, but magnesium alloys are superior because they have the lowest density of any structural metal and can achieve higher specific strengths (strength to weight ratio) than other metals. However, there are significant design challenges which have prevented the implementation of a commercial alloy in aerospace applications.
- There are several distinct challenges for magnesium alloys in aerospace applications. The main challenges include strength, workability, cost, and flammability. Strength requirements are straightforward; because magnesium competes mainly with higher strength aluminum and titanium alloys, it must have high strength in order to substitute into any existing application. Workability and cost requirements are interrelated and are dependent on alloy strengths. Most aerospace components have complex shapes with high strength or stiffness to weight ratios. These shape and strength/stiffness requirements, as well as differing wall thicknesses, all necessitate a highly workable alloy. Alloys with moderate or low workability must be extruded at higher temperatures and lower speeds in order to make these complex shapes; this translates into high process costs. While not a consideration for other structural metals, magnesium alloys in commercial aerospace applications must also be nonflammable or self-extinguishing if ignited. Flammability resistance is required due to stringent safety regulations that mandate aggressive testing of magnesium alloys. All of these criteria must be met in order for a magnesium extrusion alloy to be commercially viable for the aerospace industry.
- Individually, solutions exist for each of these challenges, but the solutions are often incompatible or contradictory. For example, high alloying content of aluminum or zinc results in high strength, but reduces workability, as visible in commercial alloy AZ80, which is not extrudable in tube, and alloy ZK60, which is extrudable only very slowly in any form factor. Calcium additions contribute to the flammability resistance of magnesium alloys, but they can also lower the strength, ductility, and/or toughness of the alloy. Significant additions of yttrium and rare earth elements, as in alloy WE43, result in high strengths and flammability resistance; however, such additions are detrimental to workability and are cost-prohibitive. Lean alloys that have little alloying content are easily workable and inexpensive, but they fail all other design criteria. There remains a need for an alloy which satisfies all essential design criteria: good mechanical properties, combustion resistance, and workability and low cost.
- The present invention relates to magnesium alloys that are ideally suited for applications in aerospace and automotive applications. The alloys have good flammability resistance, and extrudability, as well as superior as-fabricated mechanical properties to similar conventional alloys.
- The present invention provides for embodiments that incorporate different ranges of alloying content which gives flexibility and a good balance of options for processing and mechanical properties.
- According to one aspect of the invention, the alloys may lie in composition ranges (by weight) of between about 7.0 to 11.0% aluminum, 0.1 to 0.8% zinc, 0.15 to 0.65% manganese, 0.6 to 1.5% calcium, and 0.05 to 0.6% yttrium with remainder of magnesium and incidental or unavoidable impurities.
- According to one preferred embodiment of the invention, it may be considered a magnesium-based extrusion alloy composition comprising, by weight: 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidable impurities.
- There are a number of additional optional features of the first preferred embodiment. One optional feature is wherein a content of said Mn is between about 0.15 wt % to 0.3 wt % of said alloy.
- Another optional feature is wherein a content of said Zn is between about 0.1 wt % to 0.35 wt % of said alloy.
- Another optional feature is wherein a content of said Zn is between about 0.4 wt % to 0.6 wt % of said alloy.
- Another optional feature is wherein a content of said Al is between about 8.3 wt % to 10 wt % of said alloy.
- Another optional feature is wherein a content of said Ca and Y is between about 0.75 wt % to 1.5 wt % of said alloy.
- Another optional feature is wherein a total combined content of said Al, Ca, and Y does not exceed 11 wt % of said alloy.
- Another optional feature is wherein said Ca and said Y are provided in intermetallic compounds.
- Another optional feature is wherein said intermetallic compounds of Ca and Y comprise Mg—Al—Ca compounds and Al—Mn—Y compounds, respectively.
- Another optional feature is wherein said Mg—Al—Ca intermetallic compound comprises up of up to 57 wt % Al and up to 43 wt % Ca.
- Another optional feature is wherein said Al—Mn—Y intermetallic compound comprises 40 wt % Al, 40 wt % Mn and 20 wt % Y.
- Another optional feature is wherein said Ca and Y intermetallic compounds contribute to flammability resistance of wrought products made from said alloy.
- Another optional feature is wherein said alloy comprises Ca in the form of intermetallic particles; said particles having an average diameter of about less than 1 μm and finely distributed within said alloy.
- Another optional feature is wherein said intermetallic particles are formed in a wrought process, including extrusion, rolling, or forging.
- Another optional feature is wherein when said alloy is provided in a matrix phase, particles making up said alloy have an average diameter of about 10 μm or less.
- Another optional feature is wherein said alloy comprises Ca intermetallic particles and said particles make up between about 1.0% to 5.0% of said alloy by volume.
- Another optional feature is wherein said alloy has a tensile yield strength of at least 180 MPa and an ultimate tensile strength of at least 270 MPa.
- Yet another optional feature is wherein said forged or drawn alloy has a tensile yield strength of at least 170 MPa, an ultimate tensile strength of at least 280 MPa and an elongation of at least 7% in tube forms.
- According to another preferred embodiment of the invention, it may be considered a method of making a product made from a magnesium-based alloy composition comprising the steps of: providing magnesium-based alloy composition comprising, by weight: 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidable impurities; subjecting said alloy to extrusion to produce an extruded alloy; or subjecting said alloy to rolling to produce a rolled alloy; or subjecting said alloy to forging to produce a forged alloy.
- One optional feature of the method is wherein said extrusion step comprises extruding said alloy into seamless tubes via extrusion of a hollow billet around a mandrel, or into structural tubes via extrusion of solid billets using porthole dies which split metal flow and subsequently merge the metal around a mandrel to form a hollow shape.
- Another optional feature of the method is wherein said extruded alloy has a tensile yield strength of at least 180 MPa and an ultimate tensile strength of at least 270 MPa.
- Yet another optional feature of the method is wherein said extruded alloy has a tensile yield strength of at least 170 MPa, an ultimate tensile strength of at least 280 MPa and an elongation of at least 7% in tube forms.
- According to yet another preferred embodiment of the invention, it may be considered a magnesium-based extrusion alloy composition consisting essentially of, by weight: 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidable impurities.
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FIG. 1 is an electron micrograph of an alloy of the invention showing an 1280 μm by 960 μm area of the alloy in a cast condition; -
FIG. 2 is an electron micrograph of another alloy of the invention showing a 256 μm by 192 μm area of the alloy in an extruded condition; and -
FIG. 3 shows photographs of extruded forms of the alloys. -
FIG. 1 shows an electron micrograph example of thealloy 10 of present invention in an as-cast state.FIG. 1 more specifically shows prominent features of the microstructure including amagnesium matrix phase 12 which makes up most of the microstructure and which contains dissolved aluminum and an aluminum and calciumrich phase 14 that is present in interdendritic spaces left by the magnesium matrix phase. The grain boundaries of the magnesium matrix are not well defined but have sizes well over 100 μm. A 100 μm scale is provided in the figure for size comparison. The aluminum and calcium rich phase is contiguous along some of these boundaries and exists in unbroken linear segments up to 100 μm long. The microstructure also contains blocky Al—Mn—Y particles 16. -
FIG. 2 shows another electron micrograph example of thealloy 10 of the present invention in an as-extruded state. The microstructure consists mainly of relativelyfine Mg grains 18 having an average diameter of 8.9 μm. A 500 μm scale is provided in the figure for size comparison. The microstructure also contains stringers of Ca-rich particles 20, which have been broken up and distributed throughout the microstructure by the extrusion process. The Ca-rich particles 20 make up approximately 3.9% (by area) of the total microstructure and have an average diameter of 0.48 μm. The thorough distribution of these Ca-rich particles helps pin grain boundaries of the matrix phase during and after extrusion, keeping the material's grain size small and contributing to the material's high strength. The small size of the Ca-rich particles makes them less likely to be a failure initiation site, meaning that there should be little detriment to the material's ductility. The microstructure also contains coarse or blocky Al—Mn—Y particles 22 that have not been broken up by the extrusion process and which do not serve to refine the microstructure. -
FIG. 3 shows a photograph of examples of extrusions of the present invention. The present invention is extrudable in bothtube form 24 andbar form 26. Other high strength magnesium alloys with aluminum as the principal alloying element are not typically extrudable in tube forms. - As mentioned, according to one preferred embodiment, the invention includes a magnesium alloy with alloying content, in weight percent, between 7.0% and 11.0% aluminum, between 0.1% and 0.8% zinc, between 0.15% and 0.65% manganese, between 0.6% and 1.5% calcium, and between 0.05% and 0.6% yttrium.
- According to another feature of the invention, it includes an alloying addition of Mn between about 0.15% and 0.65% by weight. Furthermore, it is preferable that the alloy contain between 0.15% and 0.3% Mn by weight. Manganese is added to Mg—Al alloys to increase corrosion resistance by reducing the Fe impurity levels in the melt during primary processing; dissolved Fe content is very detrimental to Mg alloys' corrosion properties. In the present invention, this preferred range results in low Fe impurity levels and also low amounts of Al—Mn precipitates in the metal, contributing to the invention's superior workability.
- According to yet another feature of the invention, it may include an alloying addition of Zn between about 0.1% and 0.8% by weight. In one embodiment, it is preferable that the alloy contain about 0.4% to 0.6% Zn. Zinc is added to the alloy for solid solution strengthening. In this preferred Zn content range, there is some effect of strengthening, but the Zn content is low enough to allow extrusion at moderate speeds and temperatures. In another embodiment of the present invention, it is instead preferable for the Zn content to be between 0.1% and 0.35% of the alloy by weight. This amount of Zn will allow some solid solution strengthening but will allow a slightly higher extrusion temperature, allowing the invention to be extruded at higher speeds.
- According to yet another feature of the invention, it may include a Ca addition of between about 0.6 wt. % and 1.5 wt. % and a Y addition of between 0.05 wt. % and 0.6 wt. %. This combined Ca and Y addition imparts flammability resistance to the invention. The most obvious benefit is imparting flammability resistance in the final product, but equally important is the effect of flammability resistance during processing. For the present invention, billets of raw material can be safely preheated to higher temperatures than conventional alloys and can subsequently be extruded at higher temperatures. Higher working temperatures increase the workability of the present invention and allow it to be extruded into tubes and complicated shapes; similar tubes and shapes would be impossible to extrude in conventional high strength Mg—Al alloys.
- According to yet another aspect of the invention, it may include a Ca addition resulting in the formation of Mg—Al—Ca intermetallic compounds which are broken up and finely dispersed by a wrought process. These particles contribute to grain refinement during extrusion and help mitigate grain growth immediately after extrusion or during subsequent heat treatment. It is preferred that the invention contain approximately 1.0% to 5.0% (by volume) of such particles and that such particles have an average diameter of less than 1μm. Furthermore, it is preferred that the Mg matrix grains of the invention have an average diameter of less than about 10 μm resulting from the finely distributed intermetallic compound content of the invention.
- According to another aspect of the invention, it is preferred that components of the present invention are produced via extrusion. Any other wrought process which subjects a material to significant shear deformation, and which is capable of breaking up the aforementioned Ca-containing intermetallic particles of the present invention, may also be used, including forging or rolling. The extrusion process accomplishes this by using a hydraulic ram to force a billet through an orifice in the desired shape. The rolling process accomplishes this by using a set of flat rollers to impose successive thickness reduction of a plate or sheet or by using a set of shaped rollers to do the same for simple shapes. The forging process accomplishes this by slowly compressing or rapidly impacting a material one or more times with a hammer, die, or set of progressive dies.
- According to yet another aspect of the invention, it may include a total amount of Ca and Y alloying addition be between about 0.75% and 1.5% of the alloy by weight. This amount of Ca and Y alloying addition has been found to give the present invention a favorable volume fraction of Ca-containing and Y-containing precipitates. This is sufficient for grain refinement purposes but will not contribute too much to brittleness. Further, it is preferred that the alloying content of Y be at the low end of the above prescribed 0.05 wt %-0.5 wt. % range, in order to minimize costs associated with rare earth alloying additions.
- As set forth, a preferred embodiment of the invention provides an Al alloying addition of about 7.0 wt. % to 11.0 wt. %. This alloying addition may be more preferably an Al content of between about 8.3% and 10% of the alloy by weight. Such an amount of Al content has been found to give the present invention good mechanical properties from solid solution strengthening, while still remaining low enough in total alloying content so that the alloy can be easily extruded. Such an amount of Al content also gives the present invention a Mg17Al12 solvus very similar to conventional high strength Mg—Al alloys, meaning that the present invention has a potential for age hardening in a similar manner as conventional high strength Mg—Al alloys.
- According to yet another aspect of the invention, it may include a total amount of Al, Ca, and Y alloying additions to not exceed about 11 wt % of the total alloy. This maximum ensures that the material will not become brittle and will maintain workability at safe working temperatures.
- Several examples of the present invention demonstrate improved properties over existing commercial alloys. The material examples were produced by casting ingots and subsequent extrusion. Casting consisted of a fluxed process in a steel crucible, using high purity magnesium, aluminum, and zinc metals, manganese chloride, and magnesium-calcium and magnesium-yttrium master alloys as input materials. Molten alloys were gravity cast into permanent steel molds. The chemistry of each example alloy was verified via optical emission spectroscopy (OES). Alloy examples are listed in Table 1. Comparative Example 1 and Comparative Example 2 are commercial alloys AZ61 and AZ80 respectively. For these materials, the compositions listed in Table 1 are the nominal compositions for those alloys instead (not verified by OES), and they were produced using a larger scale direct chill casting process.
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TABLE 1 Alloy Chemistries Composition, wt. % Alloy Al Ca Mn Y Zn Example 1 7.45 1.34 0.15 0.13 0.52 Example 2 8.34 1.41 0.17 0.14 0.62 Example 3 8.56 0.79 0.22 0.07 0.63 Example 4 9.42 0.71 0.23 0.09 0.65 Example 5 9.98 0.66 0.18 0.08 0.64 Example 6 8.69 0.82 0.15 0.41 0.6 Example 7 9.2 0.8 0.16 0.36 0.62 Example 8 9.97 0.83 0.24 0.56 0.6 Example 9 9.23 1.01 0.19 0.11 0.65 Example 10 9.54 0.63 0.15 0.42 0.65 Comparative 6.5 0 0.33 0 0.95 Example 1 Comparative 8.5 0 0.33 0 0.50 Example 2 - Billets were scalped to two final diameters and sectioned to length for extrusion. Billets were preheated in a furnace for up to two hours prior to extrusion. Extrusion was carried out on a 500-ton extrusion press with three die geometries, which correlated to two extrusion profiles. Combinations of billet and die configurations are listed in Table 2. Often, a flat die for a round rod with an extrusion ratio of 25 is used to benchmark extrusion speeds. More complicated shapes and higher reduction ratios are more difficult to extrude, especially for porthole dies and hollow shapes, where higher pressure is required to overcome friction with greater surface area in the die. The choice of dies provided in this example is closer to an industrial setting, and it allows for demonstration of the present invention's superior extrudability in both bar and tube form.
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TABLE 2 Extrusion geometries. Reduction ratio Billet Extrudate (extrusion diameter Die type geometry ratio) Alloys used 3.18″ Porthole tube 30 mm outer 29.28 Examples 3 - die. diameter, 2 mm 10 wall thickness. 4.16″ Porthole tube 30 mm outer 49.86 Examples 1 - die. diameter, 2 mm 2, Comp. wall thickness. Example 1 4.16″ Flat die. 1.5″ by 0.25″ cross 36.25 All alloys section rectangular bar. - During extrusion, temperatures of the billet, die, and container varied. Temperatures were continually adjusted during experimentation in order to maximize extrusion speed for all example alloys. All temperatures were between 275° C. and 480° C. (527° F.-896° F.), but process temperatures were generally between 370° C. and 480° C. (698° F.-896° F.). Using these conditions and the die geometries in Table 2, the extrusion speeds and mechanical properties of extrudates are listed for bar form in Table 3 and are listed for tube form in Table 4.
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TABLE 3 Extrusion and mechanical properties of example alloys in bar form. Maximum defect- Tensile Ultimate Elongation free extrusion Yield Tensile after speed (feet per Strength Strength fracture Alloy minute) (MPa) (MPa) (%) Example 1 11.1 188 298 12.72 Example 2 8.2 194 274 5.58 Example 3 8.2 190 301 12.05 Example 4 8.2 203 307 10.29 Example 5 5.7 217 290 4.16 Example 6 7.3 187 290 7.88 Example 7 6.9 197 276 5.81 Example 8 6.9 208 306 9.46 Example 9 5.4 201 300 8.66 Example 10 5.1 203 299 8.47 Comparative 6 165 275 9 Example 1 Comparative 7 195 295 8 Example 2 -
TABLE 4 Extrusion and mechanical properties of example alloys in tube form. Maximum defect- Tensile Ultimate Elongation free extrusion Yield Tensile after speed (feet per Strength Strength fracture Alloy minute) (MPa) (MPa) (%) Example 1 7 199 280 7.79 Example 2 5.6 194 319 9.94 Example 3 6.1 187 306 9.16 Example 4 5.8 188 308 7.44 Example 5 5.1 170 280 6.06 Example 6 6.1 171 295 9.21 Example 7 5.6 173 298 8.56 Example 8 5.3 192 295 6.15 Example 9 5.6 191 302 8.34 Example 10 5.6 183 296 7.36 Comparative 6 110 250 7 Example 1 Comparative N/A N/A N/A N/A Example 2 - For all Examples of the present invention, strengths in Tables 3 and 4 were measured using the testing procedures described in ASTM B557-15. Tensile properties were measured in the extrusion direction of the material using samples that had 2″ gage lengths, 0.50″ widths, and nominal thicknesses of the material (listed in Table 2). Tensile Yield Strength was determined via the offset method detailed in ASTM B557-15 section 7.1.6, and it generally refers to the tensile stress that can be imposed on the material before it will permanently deform. Ultimate Tensile Strength is calculated as the maximum force the specimen will withstand, divided by its initial cross-sectional area. Elongation after fracture was determined per the method listed in ASTM B557-15 section 7.8.1, and it generally refers to the percent increase in the specimen's gage length after tension testing. For the commercial alloys AZ61 and AZ80 (Comparative Example 1 and Comparative Example 2, respectively), reference mechanical properties are taken from the relevant alloy specifications in ASTM B107.
- Values for mechanical properties listed in Tables 3 and 4 are averages of test sets of up to 12 samples, with any sample discarded which had measurements at least 3 scaled median absolute deviations (MAD) lower than the median (about 2 standard deviations lower than the median), in order to prevent skewing the results due to a defect in the sample. Commercial alloy AZ80 (Comparative Example 2) is widely known to not be extrudable in tube or other hollow forms; as such, properties are not given for Comparative Example 2 in Table 4.
- Tables 3 and 4 demonstrate that the present invention has excellent as-fabricated mechanical properties relative to commercial alloys. All Examples well exceed the yield strength of AZ61 (Comparative Example 1) in both tube and bar form. All Examples are also on par with AZ80 (Comparative Example 2) yield strength in bar form, with most Examples exceeding it. With the exception of Example 2, all Examples exceed the ultimate tensile strength (UTS) of AZ61 in bar form, with most Examples on par with or exceeding the UTS of AZ80. All Examples well exceed the UTS of AZ61 in tube form. In bar form, most Examples have elongation on par with or exceeding AZ80, with some examples exceeding the elongation of AZ61. In tube form, most Examples exceed the elongation of AZ61.
- Tables 3 and 4 also demonstrate that the present alloys have excellent workability relative to commercial alloys. Most Examples have extrusion speeds on par with that of AZ61 (Comparative Example 1) or AZ80 (Comparative Example 2) in bar form. Some Examples significantly exceed these reference speeds, with Example 1 having an extrusion speed nearly double that of AZ61 in bar form. Unlike AZ80, all Examples are extrudable in tube form. In tube form, most Examples are on par with the extrusion speed of AZ61, with some Examples exceeding AZ61 speeds. In addition to simply being extrudable in tube form, it is especially significant that the present invention is able to maintain mechanical properties on par with AZ80, while being extrudable in tube form.
- Selected alloys were tested for flammability by a third party, pursuant to the FAA Aircraft Materials Fire Test Handbook, Chapter 25 (Oil Burner Flammability Test for Magnesium Alloy Seat Structure). Test results are summarized in Table 5.
-
TABLE 5 Flammability Test Results Alloy Test Result Example 1 Pass - no burning Example 2 Not tested Example 3 Pass - no burning Example 4 Pass - no burning Example 5 Not tested Example 6 Not tested Example 7 Not tested Example 8 Pass - no burning Example 9 Pass - no burning Example 10 Pass - no burning - Comparative Example alloys 1 and 2 were not tested in this manner because they are known to be flammable and are known not to be self-extinguishing. The Example materials which were tested all pass the flammability test requirements and demonstrate clear superiority over conventional alloys, especially for applications which require flammability resistance. Referring to Table 1, the alloys which were tested reflect alloys with a combination of the highest and lowest Ca and Y content, which gives good confidence that all combinations of the present invention have significant flammability resistance.
- The alloys described herein are robust and may be produced via many production methods. The preferred production method for Mg alloys according to the present work is direct chill (DC) casting followed by extrusion, but it is not intended that the present invention be limited to a specific process. Rather the process may be designed for several other casting and wrought processes not mentioned in detail. Such casting methods include but are not limited to sand casting, gravity die casting, tilt casting, low pressure die casting, high pressure die casting, strip casting, continuous casting, squeeze casting, centrifugal casting, thixomolding, and rheocasting. Such wrought processing methods include but are not limited to extrusion, rolling, and forging.
Claims (23)
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US16/555,919 US20210062306A1 (en) | 2019-08-29 | 2019-08-29 | High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy |
CN201980099501.0A CN114651077A (en) | 2019-08-29 | 2019-08-30 | High-strength, flame-retardant and extrudable pipe-made aviation-grade magnesium alloy |
EP19943070.3A EP3987070A4 (en) | 2019-08-29 | 2019-08-30 | High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy |
PCT/US2019/049045 WO2021040731A1 (en) | 2019-08-29 | 2019-08-30 | High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy |
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US16/555,919 US20210062306A1 (en) | 2019-08-29 | 2019-08-29 | High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy |
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US5078962A (en) * | 1989-08-24 | 1992-01-07 | Pechiney Electrometallurgie | High mechanical strength magnesium alloys and process for obtaining these by rapid solidification |
CN101037753A (en) * | 2007-04-19 | 2007-09-19 | 沈阳工业大学 | High-strength heat-proof compression casting magnesium alloy and preparation method thereof |
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US3826122A (en) * | 1970-06-16 | 1974-07-30 | K Braeuninger | Mandrel for extruding tubing |
DE102007061236A1 (en) * | 2007-12-19 | 2009-07-09 | Ecka Granulate Gmbh & Co. Kg | Transport form for base metal particles and use of the same |
CN102310295B (en) * | 2010-06-30 | 2013-05-29 | 比亚迪股份有限公司 | Magnesium alloy welding wire and preparation method thereof |
KR101080164B1 (en) * | 2011-01-11 | 2011-11-07 | 한국기계연구원 | Ignition-proof magnesium alloy with excellent mechanical properties and method for manufacturing the ignition-proof magnesium alloy |
KR101931672B1 (en) * | 2014-12-19 | 2018-12-21 | 한국기계연구원 | High speed extrudable non-flammability magnesium alloys and method for manufacturing magnesium alloy extrusion using the same |
KR20160011136A (en) * | 2015-03-25 | 2016-01-29 | 한국기계연구원 | Magnesium alloy having improved corrosion resistance and method for manufacturing magnesium alloy member using the same |
CN105256206A (en) * | 2015-10-30 | 2016-01-20 | 无棣向上机械设计服务有限公司 | Thermal-deformation-resistant magnesium alloy |
CN105385917B (en) * | 2015-12-07 | 2017-06-20 | 赣州有色冶金研究所 | High-strength high-plasticity magnesium alloy and preparation method thereof |
CN108555477B (en) * | 2018-07-11 | 2020-10-30 | 河南维可托镁合金科技有限公司 | Magnesium alloy welding wire and preparation method thereof |
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- 2019-08-29 US US16/555,919 patent/US20210062306A1/en not_active Abandoned
- 2019-08-30 CN CN201980099501.0A patent/CN114651077A/en active Pending
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US5078962A (en) * | 1989-08-24 | 1992-01-07 | Pechiney Electrometallurgie | High mechanical strength magnesium alloys and process for obtaining these by rapid solidification |
CN101037753A (en) * | 2007-04-19 | 2007-09-19 | 沈阳工业大学 | High-strength heat-proof compression casting magnesium alloy and preparation method thereof |
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CN114651077A (en) | 2022-06-21 |
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