WO2024129170A1 - Magnesium alloys for thixomolding applications - Google Patents

Magnesium alloys for thixomolding applications Download PDF

Info

Publication number
WO2024129170A1
WO2024129170A1 PCT/US2023/034202 US2023034202W WO2024129170A1 WO 2024129170 A1 WO2024129170 A1 WO 2024129170A1 US 2023034202 W US2023034202 W US 2023034202W WO 2024129170 A1 WO2024129170 A1 WO 2024129170A1
Authority
WO
WIPO (PCT)
Prior art keywords
alloy
less
article
magnesium alloy
thixomolded
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2023/034202
Other languages
French (fr)
Inventor
Govindarajan Muralidharan
Bryan MACEK
Nathan SANKO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leggera Technologies LLC
UT Battelle LLC
FCA US LLC
Original Assignee
Leggera Technologies LLC
UT Battelle LLC
FCA US LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leggera Technologies LLC, UT Battelle LLC, FCA US LLC filed Critical Leggera Technologies LLC
Publication of WO2024129170A1 publication Critical patent/WO2024129170A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002—Castings of light metals
    • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/007—Semi-solid pressure die casting
    • 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
    • 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
    • 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
    • C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent

Definitions

  • the present invention relates generally to thixomolding, and more particularly to alloys for thixomolding applications.
  • Magnesium-alloy die-castings are being increasingly used in the automobile industry as a means of providing cost effective mass reduction, especially in systems where multiple components can be integrated into a single thin-wall die-casting.
  • there is only one die-caster in North America capable of producing die-castings of the size needed for instrument panel structures, liftgate inner panels, swing gate inner panels, and similar components, thus making it difficult to negotiate competitive pricing and creating a supply chain risk.
  • component quality restrictions in thin-walled magnesium die-castings including variability in dimensional accuracy, part-to-part variation in mechanical properties, and porosity in the final part which has limited the continued growth of die-cast components in the automobile industry.
  • An alternative to die-casting is the process of thixomolding.
  • the thixomolding process has begun to make inroads into the automobile industry as a competing process to die-casting for producing complex thin-wall magnesium components. While the thixomolding process is somewhat similar to the die-casting process, it differs in at least one significant aspect. While the die-casting process relies on filling a mold at high speeds with the alloy in the completely molten state, the thixomolding process fills a mold with a thixotropic alloy in a semi-solid slurry state at a temperature between the liquidus and solidus temperatures.
  • the material should be ⁇ 30-65% solid rather than being completely liquid at the beginning of the injection process.
  • Advantages of the thixomolding process include finer grain structure, lower porosity, improved dimensional accuracy, improved part-to-part consistency, improved mechanical properties, particularly ductility in the component, ability to reduce wall thickness for mass savings, and longer tool life due to lower process temperatures.
  • thixomolding offers improved mechanical properties over die-cast Mg components
  • the mechanical properties obtained in the thixomolded parts are still not sufficient to broadly enable application in components where both strength and ductility are key requirements, such as crash critical components exposed to high impact velocities and powertrain or chassis components subjected to high levels of cyclic loading.
  • the mechanical properties are limited by the alloys being used, which are often the same alloys that are used in the die-casting process.
  • new alloys which can achieve high strengths with improved ductilities for use in components fabricated by the thixomolding process.
  • alloy AZ91 D is a very popular die-casting alloy with good processability and has good strength but low ductility.
  • the alloy AM60B is another popular alloy with good strength and ductility but has only a narrow processing range. It would be desirable to provide an alloy with good processability comparable to AZ91 D, strength comparable to AM60B, and with improved ductility.
  • a magnesium alloy comprises on weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium can consist essentially of, in weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy can consist of, in weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy can have a processability index P of 20 to 150.
  • the magnesium alloy can have a Ge content of from 0 - 0.5 wt. % Ge.
  • the magnesium alloy can have a Li content of from 0- 0.5 wt. % Li.
  • the magnesium alloy can have a yield strength of at least 90 MPa.
  • the magnesium alloy can have a yield strength of at least 100 MPa.
  • the magnesium alloy can have a yield strength of at least 120 MPa.
  • the magnesium alloy can have an elongation to failure is at least 16 %.
  • the magnesium alloy can have an elongation to failure is at least 20 %.
  • the magnesium alloy can have a melting range of at least 200 °C.
  • the magnesium alloy can have a melting range of at least 175 °C.
  • the magnesium alloy can have a melting range of at least 150 °C.
  • the magnesium alloy can have a melting range of at least 135 °C.
  • a method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids.
  • the thixotropic alloy is introduced into a mold under a pressure of 50-100 MPa.
  • the thixotropic alloy is allowed to cool to produce a solid thixomolded article.
  • a method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids.
  • the thixotropic alloy is introduced into an open mold under ambient pressure. The mold is closed to compress the thixotropic alloy and thus fill the mold.
  • a thixomolded article includes a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0- 0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the thixomolded article can have a weight of at least 3.6 kg and an average thickness of between 2.0 mm and 4.0 mm.
  • the thixomolded article can have a largest dimension of between 50 cm and 200 cm.
  • the thixomolded article can contain at least 1 molded-in connecting feature, the connecting feature provides a positive location function and structural strength of at least 70% of the base material strength, and the article is joined with other articles to produce an article with a mass of at least 7.2 kg.
  • Figure 1 is a diagram illustrating the strengths and weaknesses of prior art alloys AZ91 D and AM60B for strength, ductility, and ease of processing.
  • Figure 2 is a plot of strength, solidus and melting range for AZ91 D and AM60.
  • Figure 3 shows the calculated equilibrium phase diagram for alloy AM50.
  • Figure 4 shows the calculated equilibrium phase diagram for alloy AM60B.
  • Figure 5 shows the calculated equilibrium phase diagram for alloy AZ91 D.
  • Figure 6 shows the calculated equilibrium phase diagram for alloy A511.
  • Figure 13 shows the calculated equilibrium phase diagram for alloy
  • Figure 16 shows the calculated equilibrium phase diagram for alloy
  • Figure 23 shows the calculated equilibrium phase diagram for alloy
  • Figure 30 shows the calculated equilibrium phase diagram for alloy
  • Figure 32 shows the calculated equilibrium phase diagram for alloy
  • Figure 33 shows the calculated equilibrium phase diagram for alloy
  • Figure 34 shows the calculated equilibrium phase diagram for alloy
  • Figure 37 shows the calculated equilibrium phase diagram for alloy
  • Figure 40 shows the calculated equilibrium phase diagram for alloy
  • Figure 41 shows the calculated equilibrium phase diagram for alloy
  • Figure 42 shows the calculated equilibrium phase diagram for alloy
  • Figure 43 shows the calculated equilibrium phase diagram for alloy
  • Figure 45 shows the calculated equilibrium phase diagram for alloy
  • Figure 46 is a perspective view of a large thixomolded automobile door component.
  • a magnesium alloy comprising, in weight percent:
  • B+Sr 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and,
  • the magnesium alloy can consist essentially of, in weight percent, Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy can consist of, in weight percent, Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0- 1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1
  • the Al in weight percent can be from 4.5 to 6.5 wt. %.
  • the Al in weight percent can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1 , 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1 , 6.2, 6.3, 6.4, or 6.5 wt. % Al.
  • the weight % Al can be within a range of any high value and low value selected from these values.
  • the Zn in weight percent can be from 0.1 -3.0 wt. %.
  • the Zn in weight percent can be 0.10, 0.11 , 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0 wt % Zn.
  • the weight % Zn can be within a range of any high value and low value selected from these values.
  • the Ca in weight percent can be from 0-1 .5 wt. %.
  • the Ca in weight percent can be 0, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4, or 1.5 wt % Ca.
  • the weight % Ca can be within a range of any high value and low value selected from these values.
  • the Sn in weight percent can be from 0-4.0 wt. %.
  • the Sn in weight percent can be 0, 0.25, 0.5, 0.75, 1 .0, 1 .25, 1 .5, 1 .75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75 or 4.0 wt % Sn.
  • the weight % Sn can be within a range of any high value and low value selected from these values.
  • the Mn in weight percent can be from 0.1 -0.5 wt. %.
  • the Mn in weight percent can be 0.1 , 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5 wt. % Mn.
  • the weight % Mn can be within a range of any high value and low value selected from these values.
  • the Si in weight percent can be from 0-0.5 wt. %.
  • the Si weight percent can be 0, 0.05, 0.1 , 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5 wt. % Si.
  • the weight % Si can be within a range of any high value and low value selected from these values.
  • the B+Sr in weight percent can be from 0-0.5 wt. %.
  • the B weight percent can be 0, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.17, 0.20, 0.22, 0.25, 0.27, 0.30, 0.32, 0.35, 0.37, 0.40, 0.42, 0.45, 0.47, or 0.50 wt. % B+Sr.
  • the weight % B+Sr can be within a range of any high value and low value selected from these values.
  • the alloy can have Fe less than 0.1 wt. % Fe.
  • the alloy can have 0, 0.0001 , 0.0002, 0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.0125, 0.015, 0.0175, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 wt. % Fe.
  • the weight % Fe can be within a range of any high value and low value selected from these values.
  • the alloy can have less than 0.1 wt. % Cu;
  • the alloy can have 0, 0.0001 , 0.0002, 0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.0125, 0.015, 0.0175, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 wt. % Cu.
  • the weight % Cu can be within a range of any high value and low value selected from these values.
  • the alloy can have less than 0.01 wt. % Ni.
  • the wt. % Ni can be 0, 0.0001 , 0.0002, 0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, or 0.01 wt. % Ni.
  • the weight % Ni can be within a range of any high value and low value selected from these values.
  • the alloy can have Ge in weight percent can be from 0-0.5 wt. % Ge.
  • the Ge weight percent can be 0, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.17, 0.20, 0.22, 0.25, 0.27, 0.30, 0.32, 0.35, 0.37, 0.40, 0.42, 0.45, 0.47, or 0.50 wt. % Ge.
  • the weight % Ge can be within a range of any high value and low value selected from these values.
  • the alloy can have Li in weight percent can be from 0-0.5 wt. % Li.
  • the Li weight percent can be 0, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.17, 0.20, 0.22, 0.25, 0.27, 0.30, 0.32, 0.35, 0.37, 0.40, 0.42, 0.45, 0.47, or 0.50 wt. % Li.
  • the weight % Li can be within a range of any high value and low value selected from these values.
  • a method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy is heated to a temperature of 500-600 °C (a temperature between the liquidus and solidus), producing a thixotropic alloy comprising 30-65 weight % solids.
  • the thixotropic alloy is transported into a mold.
  • the thixotropic alloy is then allowed to cool to produce a solid thixomolded article.
  • a thixomolded article can comprise a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the article can have a weight of at least 3.6 kg.
  • the thixomolded article can have a largest dimension of at least 50 cm.
  • Figure 2 shows that alloy AZ91 D which has good processability has a lower solidus and a larger melting range, which is the difference between the liquidus and the solidus.
  • the magnesium alloys of the invention have solidus and melting ranges greater than that of AM50 and AM60B and closer to that of AZ91 D and ductility comparable to AM60B and better than that of AZ91 D.
  • a number of alloys were computationally evaluated for their solidus, liquidus, and solidification range. Table 2 shows nominal compositions of AM50, AM60B, and AZ91 D along with the invention alloys.
  • Table 3 shows the calculated liquidus, solidus, and melting ranges of
  • the invention alloys A511 - A545 have a solidus lower than and a melting range larger than that of AM50. Also, several alloys have achieved a melting range comparable to or greater than that of AZ91 D.
  • the invention alloys A611 - A645 have a solidus lower than and a melting range larger than that of AM60B. Also, several alloys have achieved a melting range comparable to or greater than that of AZ91 D.
  • A511 to A516 have increasing levels only of Zn.
  • A521 to A523 have increasing levels only of Ca, and A531 to A536 have increasing levels only of Sn.
  • A541 to A545 have increasing levels of Zn, Sn and Ca, where two or three of these elements have increasing values. These levels of elements decrease the solidus and increase the melting range when compared to that of AM50.
  • A611 to A616 have increasing levels only of Zn.
  • A621 to A623 have increasing levels only of Ca
  • A631 to A636 have increasing levels only of Sn.
  • A641 to A645 have increasing levels of Zn, Sn and Ca, where two or three of these elements have increasing values. These levels of elements decrease the solidus and increase the melting range when compared to that of AM60B.
  • Table 4 shows some compositions of invention alloys selected for testing. These alloys were fabricated in laboratory scale heats and tested for their solidus, liquidus and melting range. Table 5 shows the measured compositions of these example invention alloys.
  • Table 6 shows the effect of additions of Zn (AI2M), Sn (AI3M), and both Zn and Sn (AI4M) on the measured solidus of these alloys when compared to that of AM60B (AI1 M) without these additions. Additions of Zn and Sn reduce the solidus much more effectively than the addition of Zn only or Sn only.
  • Zn+Sn+B (AI14M) are also effective in reducing the solidus when compared to
  • AM60B with Zn+B (501) (AI12M) and Zn+Sn+B (501) (AI14M) as compared to
  • P (32 x wt.% Zn) + (9 x wt. % Ca) + (4 x wt. % Sn) + 28 when wt. % of Sn > 2
  • P is the processability index, and P is from 20 to 150.
  • P can be 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 , 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 , 42, 43,
  • the corrosion resistance of magnesium alloys can be improved by keeping impurity levels such as Fe, Cu, and Ni low. Additions of Li and Ge also can improve the corrosion resistance. These alloys are designed to be compatible with standard anticorrosion coating used in the industry.
  • Table 7 shows the measured yield strength and ductility of the invention alloys compared to the baseline alloy AM60B and AZ91 D.
  • the targeted values of the yield strengths (comparable that of AM60B) were achieved along with ductilities that are comparable to AM60B and better than AZ91 D.
  • AI15M resulted in an improved yield strength ( ⁇ 20-43% increase) and increased elongation to failure ( ⁇ 6-30%) when compared to the alloys without the addition of B (AI1 M, AI2M, AI3M, AI4M, and AI5M) due to grain refinement. Addition of B improves strength and ductility without compromising the processibility.
  • the ease of processing these alloys is characterized by the difference between the liquidus and solidus of these alloys and by the P values quantified in Equations 1 and 2.
  • the alloys possess a liquid + solid range which provides good control on solid fraction at injection temperature.
  • the alloys possess a fine grain size microstructure which provides good ductility while maintaining or improving strength over existing alloys used in thixomolding.
  • the alloys further possess or improve on corrosion resistance relative to existing thixomolding alloys.
  • the alloys with a good combination of processability as indicated by the P values and with good strength and ductility, as shown in Table 7, are ideally suited for larger thixomolding operations such as for parts have largest dimensions of between 50 cm to 100 cm, thicknesses of between 2-4 mm, and weights of at least 3.6 kg.
  • FIG. 46 a door component 10 that can be cast by the alloys of the invention.
  • a method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids.
  • the thixotropic alloy is introduced into a mold under a pressure of 50-100 MPa.
  • the thixotropic alloy is allowed to cool to produce a solid thixomolded article.
  • a method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids.
  • the thixotropic alloy is introduced into an open mold under ambient pressure. The mold is closed to compress the thixotropic alloy and thus fill the mold.
  • the thixotropic alloy is allowed to cool to produce a solid thixomolded article.
  • a thixomolded article includes a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0- 0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
  • the thixomolded article can have a weight of at least 3.6 kg and an average thickness of between 2.0 mm and 4.0 mm.
  • the thixomolded article can have a largest dimension of between 50 cm and 200 cm.
  • the thixomolded article can contain at least 1 molded-in connecting feature, the connecting feature provides a positive location function and structural strength of at least 70% of the base material strength, and the article is joined with other articles to produce an article with a mass of at least 7.2 kg.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Forging (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

A magnesium alloy includes, in weight percent Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: Balance. A process for thixomolding, and a large dimension magnesium alloy article are also disclosed.

Description

MAGNESIUM ALLOYS FOR THIXOMOLDING APPLICATIONS
CROSS-REFERENCE TO RELATED APPLICATIONS.
[0001] This application claims priority to US 63/433,077 filed on December 16, 2022, entitled “Magnesium Alloys for Thixomolding Applications”, the entire disclosure of which incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED
RESEARCH AND DEVELOPMENT
[0002] This invention was made with government support under Contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in this invention.
FIELD OF THE INVENTION
[0003] The present invention relates generally to thixomolding, and more particularly to alloys for thixomolding applications.
BACKGROUND OF THE INVENTION
[0004] Magnesium-alloy die-castings are being increasingly used in the automobile industry as a means of providing cost effective mass reduction, especially in systems where multiple components can be integrated into a single thin-wall die-casting. However, there is only one die-caster in North America capable of producing die-castings of the size needed for instrument panel structures, liftgate inner panels, swing gate inner panels, and similar components, thus making it difficult to negotiate competitive pricing and creating a supply chain risk. Furthermore, there are several component quality restrictions in thin-walled magnesium die-castings including variability in dimensional accuracy, part-to-part variation in mechanical properties, and porosity in the final part which has limited the continued growth of die-cast components in the automobile industry.
[0005] An alternative to die-casting is the process of thixomolding. Widely used in the electronics industry, the thixomolding process has begun to make inroads into the automobile industry as a competing process to die-casting for producing complex thin-wall magnesium components. While the thixomolding process is somewhat similar to the die-casting process, it differs in at least one significant aspect. While the die-casting process relies on filling a mold at high speeds with the alloy in the completely molten state, the thixomolding process fills a mold with a thixotropic alloy in a semi-solid slurry state at a temperature between the liquidus and solidus temperatures. Ideally, the material should be ~30-65% solid rather than being completely liquid at the beginning of the injection process. Advantages of the thixomolding process include finer grain structure, lower porosity, improved dimensional accuracy, improved part-to-part consistency, improved mechanical properties, particularly ductility in the component, ability to reduce wall thickness for mass savings, and longer tool life due to lower process temperatures.
[0006] Although thixomolding offers improved mechanical properties over die-cast Mg components, the mechanical properties obtained in the thixomolded parts are still not sufficient to broadly enable application in components where both strength and ductility are key requirements, such as crash critical components exposed to high impact velocities and powertrain or chassis components subjected to high levels of cyclic loading. Currently, the mechanical properties are limited by the alloys being used, which are often the same alloys that are used in the die-casting process. Thus there is a need for the development of new alloys which can achieve high strengths with improved ductilities for use in components fabricated by the thixomolding process.
[0007] Alloys currently used have one or more drawbacks. The alloy AZ91 D is a very popular die-casting alloy with good processability and has good strength but low ductility. The alloy AM60B is another popular alloy with good strength and ductility but has only a narrow processing range. It would be desirable to provide an alloy with good processability comparable to AZ91 D, strength comparable to AM60B, and with improved ductility.
[0008] Table 1 . Currently used alloys and their properties.
Figure imgf000006_0001
[0009] These existing alloys have been primarily designed for injection molding in liquid state for die casting. Components thixomolded with die casting alloys do not have balanced properties. As seen in Table 1 , AZ91 D has good processing characteristics, high strength, but poor ductility, while AM60B has good ductility but needs improvement in strength and processing characteristics. This is illustrated in Figure 1 . Figure 2 illustrates that AZ91 D has high strength, lower solidus and wider melting range than AM60 (F. Czerwinski, Die Casting Engineer, Nov. 2004).
SUMMARY OF THE INVENTION
[0010] A magnesium alloy comprises on weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium can consist essentially of, in weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy can consist of, in weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy can have a processability index P of 20 to 150.
[0011] The magnesium alloy can have a Ge content of from 0 - 0.5 wt. % Ge. The magnesium alloy can have a Li content of from 0- 0.5 wt. % Li.
[0012] The magnesium alloy can have a yield strength of at least 90 MPa. The magnesium alloy can have a yield strength of at least 100 MPa. The magnesium alloy can have a yield strength of at least 120 MPa.
[0013] The magnesium alloy can have an elongation to failure is at least 16 %. The magnesium alloy can have an elongation to failure is at least 20 %.
[0014] The magnesium alloy can have a melting range of at least 200 °C. The magnesium alloy can have a melting range of at least 175 °C. The magnesium alloy can have a melting range of at least 150 °C. The magnesium alloy can have a melting range of at least 135 °C.
[0015] A method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids. The thixotropic alloy is introduced into a mold under a pressure of 50-100 MPa. The thixotropic alloy is allowed to cool to produce a solid thixomolded article.
[0016] A method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids. The thixotropic alloy is introduced into an open mold under ambient pressure. The mold is closed to compress the thixotropic alloy and thus fill the mold. The thixotropic alloy is allowed to cool to produce a solid thixomolded article. [0017] A thixomolded article includes a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0- 0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The thixomolded article can have a weight of at least 3.6 kg and an average thickness of between 2.0 mm and 4.0 mm. The thixomolded article can have a largest dimension of between 50 cm and 200 cm. The thixomolded article can contain at least 1 molded-in connecting feature, the connecting feature provides a positive location function and structural strength of at least 70% of the base material strength, and the article is joined with other articles to produce an article with a mass of at least 7.2 kg.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] There are shown in the drawings embodiments that are presently preferred it being understood that the invention is not limited to the arrangements and instrumentalities shown, wherein:
[0019] Figure 1 is a diagram illustrating the strengths and weaknesses of prior art alloys AZ91 D and AM60B for strength, ductility, and ease of processing.
[0020] Figure 2 is a plot of strength, solidus and melting range for AZ91 D and AM60.
[0021] Figure 3 shows the calculated equilibrium phase diagram for alloy AM50.
[0022] Figure 4 shows the calculated equilibrium phase diagram for alloy AM60B.
[0023] Figure 5 shows the calculated equilibrium phase diagram for alloy AZ91 D.
[0024] Figure 6 shows the calculated equilibrium phase diagram for alloy A511.
[0025] Figure 7 shows the calculated equilibrium phase diagram for alloy
A512. [0026] Figure 8 shows the calculated equilibrium phase diagram for alloy
A513.
[0027] Figure 9 shows the calculated equilibrium phase diagram for alloy
A514.
[0028] Figure 10 shows the calculated equilibrium phase diagram for alloy
A515.
[0029] Figure 11 shows the calculated equilibrium phase diagram for alloy
A516.
[0030] Figure 12 shows the calculated equilibrium phase diagram for alloy
A521.
[0031] Figure 13 shows the calculated equilibrium phase diagram for alloy
A522.
[0032] Figure 14 shows the calculated equilibrium phase diagram for alloy
A523.
[0033] Figure 15 shows the calculated equilibrium phase diagram for alloy
A531.
[0034] Figure 16 shows the calculated equilibrium phase diagram for alloy
A532. [0035] Figure 17 shows the calculated equilibrium phase diagram for alloy
A533.
[0036] Figure 18 shows the calculated equilibrium phase diagram for alloy
A534.
[0037] Figure 19 shows the calculated equilibrium phase diagram for alloy
A535.
[0038] Figure 20 shows the calculated equilibrium phase diagram for alloy
A536.
[0039] Figure 21 shows the calculated equilibrium phase diagram for alloy
A541.
[0040] Figure 22 shows the calculated equilibrium phase diagram for alloy
A542.
[0041] Figure 23 shows the calculated equilibrium phase diagram for alloy
A543.
[0042] Figure 24 shows the calculated equilibrium phase diagram for alloy
A544.
[0043] Figure 25 shows the calculated equilibrium phase diagram for alloy
A545. [0044] Figure 26 shows the calculated equilibrium phase diagram for alloy
A611.
[0045] Figure 27 shows the calculated equilibrium phase diagram for alloy
A612.
[0046] Figure 28 shows the calculated equilibrium phase diagram for alloy
A613.
[0047] Figure 29 shows the calculated equilibrium phase diagram for alloy
A614.
[0048] Figure 30 shows the calculated equilibrium phase diagram for alloy
A615.
[0049] Figure 31 shows the calculated equilibrium phase diagram for alloy
A616.
[0050] Figure 32 shows the calculated equilibrium phase diagram for alloy
A621.
[0051] Figure 33 shows the calculated equilibrium phase diagram for alloy
A622.
[0052] Figure 34 shows the calculated equilibrium phase diagram for alloy
A623. [0053] Figure 35 shows the calculated equilibrium phase diagram for alloy
A631.
[0054] Figure 36 shows the calculated equilibrium phase diagram for alloy
A632.
[0055] Figure 37 shows the calculated equilibrium phase diagram for alloy
A633.
[0056] Figure 38 shows the calculated equilibrium phase diagram for alloy
A634.
[0057] Figure 39 shows the calculated equilibrium phase diagram for alloy
A635.
[0058] Figure 40 shows the calculated equilibrium phase diagram for alloy
A636.
[0059] Figure 41 shows the calculated equilibrium phase diagram for alloy
A641.
[0060] Figure 42 shows the calculated equilibrium phase diagram for alloy
A642.
[0061] Figure 43 shows the calculated equilibrium phase diagram for alloy
A643. [0062] Figure 44 shows the calculated equilibrium phase diagram for alloy
A644.
[0063] Figure 45 shows the calculated equilibrium phase diagram for alloy
A645.
[0064] Figure 46 is a perspective view of a large thixomolded automobile door component.
DETAILED DESCRIPTION OF THE INVENTION
[0065] A magnesium alloy comprising, in weight percent:
Al: 4.5-6.5;
Zn: 0.1-3.0;
Ca: 0-1.5;
Sn: 0-4.0;
Mn: 0.1-0.5;
Si: 0-0.5;
B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and,
Mg: balance.
[0066] The magnesium alloy can consist essentially of, in weight percent, Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy can consist of, in weight percent, Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0- 1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1
Cu; less than 0.01 Ni; and Mg: balance. [0067] The Al in weight percent can be from 4.5 to 6.5 wt. %. The Al in weight percent can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1 , 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1 , 6.2, 6.3, 6.4, or 6.5 wt. % Al. The weight % Al can be within a range of any high value and low value selected from these values.
[0068] The Zn in weight percent can be from 0.1 -3.0 wt. %. The Zn in weight percent can be 0.10, 0.11 , 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0 wt % Zn. The weight % Zn can be within a range of any high value and low value selected from these values.
[0069] The Ca in weight percent can be from 0-1 .5 wt. %. The Ca in weight percent can be 0, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4, or 1.5 wt % Ca. The weight % Ca can be within a range of any high value and low value selected from these values.
[0070] The Sn in weight percent can be from 0-4.0 wt. %. The Sn in weight percent can be 0, 0.25, 0.5, 0.75, 1 .0, 1 .25, 1 .5, 1 .75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75 or 4.0 wt % Sn. The weight % Sn can be within a range of any high value and low value selected from these values.
[0071] The Mn in weight percent can be from 0.1 -0.5 wt. %. The Mn in weight percent can be 0.1 , 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5 wt. % Mn. The weight % Mn can be within a range of any high value and low value selected from these values.
[0072] The Si in weight percent can be from 0-0.5 wt. %. The Si weight percent can be 0, 0.05, 0.1 , 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5 wt. % Si. The weight % Si can be within a range of any high value and low value selected from these values.
[0073] The B+Sr in weight percent can be from 0-0.5 wt. %. The B weight percent can be 0, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.17, 0.20, 0.22, 0.25, 0.27, 0.30, 0.32, 0.35, 0.37, 0.40, 0.42, 0.45, 0.47, or 0.50 wt. % B+Sr. The weight % B+Sr can be within a range of any high value and low value selected from these values.
[0074] The alloy can have Fe less than 0.1 wt. % Fe. The alloy can have 0, 0.0001 , 0.0002, 0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.0125, 0.015, 0.0175, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 wt. % Fe. The weight % Fe can be within a range of any high value and low value selected from these values.
[0075] The alloy can have less than 0.1 wt. % Cu; The alloy can have 0, 0.0001 , 0.0002, 0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.0125, 0.015, 0.0175, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 wt. % Cu. The weight % Cu can be within a range of any high value and low value selected from these values.
[0076] The alloy can have less than 0.01 wt. % Ni. The wt. % Ni can be 0, 0.0001 , 0.0002, 0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, or 0.01 wt. % Ni. The weight % Ni can be within a range of any high value and low value selected from these values.
[0077] The alloy can have Ge in weight percent can be from 0-0.5 wt. % Ge. The Ge weight percent can be 0, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.17, 0.20, 0.22, 0.25, 0.27, 0.30, 0.32, 0.35, 0.37, 0.40, 0.42, 0.45, 0.47, or 0.50 wt. % Ge. The weight % Ge can be within a range of any high value and low value selected from these values.
[0078] The alloy can have Li in weight percent can be from 0-0.5 wt. % Li. The Li weight percent can be 0, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 , 0.02, 0.03, 0.04, 0.05, 0.06 0.07, 0.08, 0.09, 0.10, 0.12, 0.15, 0.17, 0.20, 0.22, 0.25, 0.27, 0.30, 0.32, 0.35, 0.37, 0.40, 0.42, 0.45, 0.47, or 0.50 wt. % Li. The weight % Li can be within a range of any high value and low value selected from these values. [0079] In another aspect, the magnesium alloys described herein are used in thixomolding applications. A method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy is heated to a temperature of 500-600 °C (a temperature between the liquidus and solidus), producing a thixotropic alloy comprising 30-65 weight % solids. The thixotropic alloy is transported into a mold. The thixotropic alloy is then allowed to cool to produce a solid thixomolded article.
[0080] Articles made from the magnesium alloys of the invention are designed to be used in the as-cast condition. They can be cast with typical procedures for magnesium alloys to protect them from oxidation. A thixomolded article can comprise a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.1-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The article can have a weight of at least 3.6 kg. The thixomolded article can have a largest dimension of at least 50 cm.
[0081] Figure 2 shows that alloy AZ91 D which has good processability has a lower solidus and a larger melting range, which is the difference between the liquidus and the solidus. The magnesium alloys of the invention have solidus and melting ranges greater than that of AM50 and AM60B and closer to that of AZ91 D and ductility comparable to AM60B and better than that of AZ91 D. [0082] A number of alloys were computationally evaluated for their solidus, liquidus, and solidification range. Table 2 shows nominal compositions of AM50, AM60B, and AZ91 D along with the invention alloys.
[0083] Table 2. Nominal compositions of baseline and computationally designed invention alloys.
Figure imgf000021_0001
Figure imgf000022_0001
Figure imgf000023_0001
[0084] Table 3 shows the calculated liquidus, solidus, and melting ranges of
AZ91 D, AM50, and AM60B and those of the invention alloys.
Table 3. Calculated Liquidus, Solidus, Melting Range, and Decrease in Solidus for
Invention Alloys
Figure imgf000023_0002
Figure imgf000024_0001
[0085] As shown in Table 3, the invention alloys A511 - A545 have a solidus lower than and a melting range larger than that of AM50. Also, several alloys have achieved a melting range comparable to or greater than that of AZ91 D.
[0086] Also as shown in Table 3, the invention alloys A611 - A645 have a solidus lower than and a melting range larger than that of AM60B. Also, several alloys have achieved a melting range comparable to or greater than that of AZ91 D.
[0087] A511 to A516 have increasing levels only of Zn. A521 to A523 have increasing levels only of Ca, and A531 to A536 have increasing levels only of Sn. A541 to A545 have increasing levels of Zn, Sn and Ca, where two or three of these elements have increasing values. These levels of elements decrease the solidus and increase the melting range when compared to that of AM50. [0088] A611 to A616 have increasing levels only of Zn. A621 to A623 have increasing levels only of Ca, and A631 to A636 have increasing levels only of Sn. A641 to A645 have increasing levels of Zn, Sn and Ca, where two or three of these elements have increasing values. These levels of elements decrease the solidus and increase the melting range when compared to that of AM60B.
[0089] Table 4 shows some compositions of invention alloys selected for testing. These alloys were fabricated in laboratory scale heats and tested for their solidus, liquidus and melting range. Table 5 shows the measured compositions of these example invention alloys.
[0090] Table 4. Nominal compositions of example invention alloys.
Figure imgf000025_0001
[0091] Table 5. Measured compositions of example invention alloys.
Figure imgf000026_0001
[0092] Table 6 shows the effect of additions of Zn (AI2M), Sn (AI3M), and both Zn and Sn (AI4M) on the measured solidus of these alloys when compared to that of AM60B (AI1 M) without these additions. Additions of Zn and Sn reduce the solidus much more effectively than the addition of Zn only or Sn only.
[0093] The solidus of AI5M which contains additions of Zn and Sn (516) is significantly lower than that of AM50 (as shown in Table 3, 547.93) without these additions. Additions of Zn and Sn are effective in reducing the solidus and increasing the melting range. [0094] Table 6. Measured melting range of invention alloys compared with calculated melting range of AZ91 D
Figure imgf000027_0001
[0095] Table 6 also shows that additions of Zn+B together (AI12M) and
Zn+Sn+B (AI14M) are also effective in reducing the solidus when compared to
AM60B, with Zn+B (501) (AI12M) and Zn+Sn+B (501) (AI14M) as compared to
AM60B (537) without these additions.
[0096] The solidus of Al 15M which contains additions of Zn+Sn+B (506.5) is significantly lower than that of AM50 (as shown in Table 3, 547.93) without these additions. Additions of Zn+Sn+B are effective in reducing the solidus and increasing the melting range.
[0097] The amounts of Zn, Ca, and Sn can have relative concentrations as shown in Equations 1 and 2:
Eq. 1) P = (32 x wt.% Zn) + (9 x wt. % Ca) + (18 x wt. % Sn) when wt. % of Sn < 2
Eq. 2) P = (32 x wt.% Zn) + (9 x wt. % Ca) + (4 x wt. % Sn) + 28 when wt. % of Sn > 2 where P is the processability index, and P is from 20 to 150. P can be 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 , 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 , 42, 43,
44, 45, 46, 47, 48, 49, 50, 51 , 52, 53, 54, 55, 56, 57, 58, 59, 60, 61 , 62, 63, 64,
65, 66, 67, 68, 69, 70, 71 , 72, 73, 74, 75, 76, 77, 78, 79, 80,81 , 82, 83, 84, 85, 86,
87, 88, 89, 90, 91 , 92, 93, 94, 95, 96, 97, 98, 99, 100, 101 , 102, 103, 104, 105,
106, 107, 108, 109, 110, 11 1 , 112, 113, 114, 115, 116, 117, 118, 119, 120, 121 , 122, 123, 124, 125, 126, 127, 128, 129, 130, 131 , 132, 133, 134, 134, 136, 137, 138, 139, 140, 141', 142, 143, 144, 145, 146, 147, 148, 149 or 150 and can be within a range of any high value and low value selected from these values. For example, in Table 6, alloy AI5M with 2.10 wt. % Zn, and Sn level of 1.5 wt. % has a processability index P according to Equation 1 that is P= (32 x 2.10) + (9 x 0) + (18 x 1.5) = 94.2. [0098] The corrosion resistance of magnesium alloys can be improved by keeping impurity levels such as Fe, Cu, and Ni low. Additions of Li and Ge also can improve the corrosion resistance. These alloys are designed to be compatible with standard anticorrosion coating used in the industry.
[0099] Table 7 shows the measured yield strength and ductility of the invention alloys compared to the baseline alloy AM60B and AZ91 D. The targeted values of the yield strengths (comparable that of AM60B) were achieved along with ductilities that are comparable to AM60B and better than AZ91 D.
[0100] Table 7. Yield strength and elongation of invention alloys
Figure imgf000029_0001
[0101] The addition of 0.15 wt. % B (AI11 M, AI12M, AI13M, AI14M, and
AI15M) resulted in an improved yield strength (~20-43% increase) and increased elongation to failure (~6-30%) when compared to the alloys without the addition of B (AI1 M, AI2M, AI3M, AI4M, and AI5M) due to grain refinement. Addition of B improves strength and ductility without compromising the processibility.
[0102] The ease of processing these alloys is characterized by the difference between the liquidus and solidus of these alloys and by the P values quantified in Equations 1 and 2. The alloys possess a liquid + solid range which provides good control on solid fraction at injection temperature. The alloys possess a fine grain size microstructure which provides good ductility while maintaining or improving strength over existing alloys used in thixomolding. The alloys further possess or improve on corrosion resistance relative to existing thixomolding alloys.
[0103] The alloys with a good combination of processability as indicated by the P values and with good strength and ductility, as shown in Table 7, are ideally suited for larger thixomolding operations such as for parts have largest dimensions of between 50 cm to 100 cm, thicknesses of between 2-4 mm, and weights of at least 3.6 kg. There is shown in FIG. 46 a door component 10 that can be cast by the alloys of the invention.
[0104] A method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids. The thixotropic alloy is introduced into a mold under a pressure of 50-100 MPa. The thixotropic alloy is allowed to cool to produce a solid thixomolded article.
[0105] A method of preparing a thixomolded article can include the step of providing a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05- 3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The magnesium alloy is heated to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids. The thixotropic alloy is introduced into an open mold under ambient pressure. The mold is closed to compress the thixotropic alloy and thus fill the mold. The thixotropic alloy is allowed to cool to produce a solid thixomolded article.
[0106] A thixomolded article includes a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0- 0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance. The thixomolded article can have a weight of at least 3.6 kg and an average thickness of between 2.0 mm and 4.0 mm. The thixomolded article can have a largest dimension of between 50 cm and 200 cm. The thixomolded article can contain at least 1 molded-in connecting feature, the connecting feature provides a positive location function and structural strength of at least 70% of the base material strength, and the article is joined with other articles to produce an article with a mass of at least 7.2 kg.
[0107] The invention as shown in the drawings and described in detail herein disclose arrangements of elements of particular construction and configuration for illustrating preferred embodiments of structure and method of operation of the present invention. It is to be understood however, that elements of different construction and configuration and other arrangements thereof, other than those illustrated and described may be employed in accordance with the spirit of the invention, and such changes, alternations and modifications as would occur to those skilled in the art are considered to be within the scope of this invention as broadly defined in the appended claims. In addition, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

Claims

CLAIMS We claim:
1 . A magnesium alloy comprising, in weight percent:
Al: 4.5-6.5;
Zn: 0.1-3.0;
Ca: 0-1.5;
Sn: 0-4.0;
Mn: 0.1-0.5;
Si: 0-0.5;
B+Sr: 0-0.5 less than 0.1 Fe less than 0.1 Cu less than 0.01 Ni; and,
Mg: balance.
2. The magnesium alloy of claim 1 , wherein the alloy consists essentially of, in weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0- 0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
3. The magnesium alloy of claim 1 , wherein the alloy consists of, in weight percent, Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
4. The magnesium alloy of claim 1 , wherein the alloy has a processability index P of 20 to 150.
5. The magnesium alloy of claim 1 , wherein the alloy has a Ge content of from 0 - 0.5 wt. % Ge.
6. The magnesium alloy of claim 1 , wherein the alloy has a Li content of from 0- 0.5 wt. % Li.
7. The magnesium alloy of claim 1 , wherein the alloy has a yield strength of at least 90 MPa.
8. The magnesium alloy of claim 1 , wherein the alloy has a yield strength of at least 100 MPa.
9. The magnesium alloy of claim 1 , wherein the alloy has a yield strength of at least 120 MPa.
10. The magnesium alloy of claim 1 , wherein the elongation to failure is at least
11 . The magnesium alloy of claim 1 , wherein the elongation to failure is at least 20 %.
12. The magnesium alloy of claim 1 , wherein the alloy has a melting range of at least 200 °C.
13. The magnesium alloy of claim 1 , wherein the alloy has a melting range of at least 175 °C.
14. The magnesium alloy of claim 1 , wherein the alloy has a melting range of at least 150 °C.
15. The magnesium alloy of claim 1 , wherein the alloy has a melting range of at least 135 °C.
16. A method of preparing a thixomolded article, comprising the steps of: providing a magnesium alloy comprising, in weight percent Al: 4.5- 6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance; heating the magnesium alloy to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids; introducing the thixotropic alloy into a mold under a pressure of 50-
100 MPa; and, allowing the thixotropic alloy to cool to produce a solid thixomolded article.
17. A method of preparing a thixomolded article, comprising the steps of: providing a magnesium alloy comprising, in weight percent Al: 4.5- 6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5; B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance; heating the magnesium alloy to a temperature of 500-600 °C, producing a thixotropic alloy comprising 30-65 weight % solids; introducing the thixotropic alloy into an open mold under ambient pressure; closing the mold to compress the thixotropic alloy and thus fill the mold; and, allowing the thixotropic alloy to cool to produce a solid thixomolded article.
18. A thixomolded article, comprising a magnesium alloy comprising, in weight percent Al: 4.5-6.5; Zn: 0.05-3.0; Ca: 0-1.5; Sn: 0-4.0; Mn: 0.1-0.5; Si: 0-0.5;
B+Sr: 0-0.5; less than 0.1 Fe; less than 0.1 Cu; less than 0.01 Ni; and Mg: balance.
19. The thixomolded article of claim 18, wherein the article has a weight of at least 3.6 kg and an average thickness of between 2.0 mm and 4.0 mm.
20. The thixomolded article of claim 18, wherein the article has a largest dimension of between 50 cm and 200 cm.
21 . The thixomolded article of claim 18, wherein the article contains at least 1 molded-in connecting feature, the connecting feature provides a positive location function and structural strength of at least 70% of the base material strength, and the article is joined with other articles to produce an article with a mass of at least 7.2 kg.
PCT/US2023/034202 2022-12-16 2023-09-29 Magnesium alloys for thixomolding applications Ceased WO2024129170A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US202263433077P 2022-12-16 2022-12-16
US63/433,077 2022-12-16

Publications (1)

Publication Number Publication Date
WO2024129170A1 true WO2024129170A1 (en) 2024-06-20

Family

ID=91474541

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2023/034202 Ceased WO2024129170A1 (en) 2022-12-16 2023-09-29 Magnesium alloys for thixomolding applications

Country Status (2)

Country Link
US (1) US20240200173A1 (en)
WO (1) WO2024129170A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5223347A (en) * 1989-02-23 1993-06-29 Composites Technology International, Inc. Creep resistant composite alloys
US20080193322A1 (en) * 2005-05-26 2008-08-14 Cast Centre Pty Ltd Hpdc Magnesium Alloy
US8333924B2 (en) * 2006-03-20 2012-12-18 National University Corporation Kumamoto University High-strength and high-toughness magnesium alloy and method for manufacturing same
US20170129006A1 (en) * 2015-05-07 2017-05-11 Dead Sea Magnesium Ltd. Creep resistant, ductile magnesium alloys for die casting
KR101744432B1 (en) * 2013-03-28 2017-06-08 닛폰 스틸 앤드 스미킨 스테인레스 스틸 코포레이션 Heat-resistant austenitic stainless steel sheet

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090196787A1 (en) * 2008-01-31 2009-08-06 Beals Randy S Magnesium alloy

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5223347A (en) * 1989-02-23 1993-06-29 Composites Technology International, Inc. Creep resistant composite alloys
US20080193322A1 (en) * 2005-05-26 2008-08-14 Cast Centre Pty Ltd Hpdc Magnesium Alloy
US8333924B2 (en) * 2006-03-20 2012-12-18 National University Corporation Kumamoto University High-strength and high-toughness magnesium alloy and method for manufacturing same
KR101744432B1 (en) * 2013-03-28 2017-06-08 닛폰 스틸 앤드 스미킨 스테인레스 스틸 코포레이션 Heat-resistant austenitic stainless steel sheet
US20170129006A1 (en) * 2015-05-07 2017-05-11 Dead Sea Magnesium Ltd. Creep resistant, ductile magnesium alloys for die casting

Also Published As

Publication number Publication date
US20240200173A1 (en) 2024-06-20

Similar Documents

Publication Publication Date Title
AU2005269483B2 (en) An Al-Si-Mg-Zn-Cu alloy for aerospace and automotive castings
US20030173005A1 (en) Method of manufacturing magnesium alloy products
Das et al. Studies on die filling of A356 Al alloy and development of a steering knuckle component using rheo pressure die casting system
US11306374B2 (en) High-strength aluminum alloy and high- strength aluminum alloy casting
US20020088512A1 (en) Aluminum die casting alloy, aluminum die cast product and production process
WO2006014948A2 (en) An al-si-mg-zn-cu alloy for aerospace and automotive castings
KR20140148489A (en) Aluminium alloy
WO2010007484A1 (en) Aluminum alloy, method of casting aluminum alloy, and method of producing aluminum alloy product
CN105283571A (en) Spheroidal graphite cast iron
US20120087826A1 (en) High strength aluminum casting alloy
JP6229130B2 (en) Cast aluminum alloy and casting using the same
JP2003517098A (en) Magnesium based casting alloy with excellent high temperature properties
US5186234A (en) Cast compsoite material with high silicon aluminum matrix alloy and its applications
WO2024129170A1 (en) Magnesium alloys for thixomolding applications
JP2021021138A (en) Aluminum alloy for die casting, and method for producing cast product using the same
JP7096690B2 (en) Aluminum alloys for die casting and aluminum alloy castings
US20050167011A1 (en) Casting of aluminum based wrought alloys and aluminum based casting alloys
JPH09296245A (en) Aluminum alloy for casting
JP2002129271A (en) Aluminum alloy and method for producing aluminum alloy casting
EP3550046A1 (en) Semisolid die-casting aluminum alloy and method for preparing semisolid die-casting aluminum alloy castings
JP2004292885A (en) Aluminum alloy casting material having excellent mechanical property
Guo et al. Microstructure evolution and mechanical properties of rheo-squeeze cast Mg-9Al-1Zn alloy by experiments and thermodynamic calculation
JP6932737B2 (en) Manufacturing method of spheroidal graphite cast iron and spheroidal graphite cast iron, and parts for automobile suspension
JP5862406B2 (en) Aluminum alloy member and manufacturing method thereof
Xu et al. Solidification behavior and mechanical properties of Al-Si-Mg alloy with Ti addition

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23904200

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 23904200

Country of ref document: EP

Kind code of ref document: A1