Magnesium alloys with improved castability and cast parts made with such alloys
By adjusting the composition of aluminum, zinc and silicon in the magnesium alloy and using the tweakization process, a magnesium alloy with low CSI was developed, which solved the problem that existing magnesium alloys are prone to hot tear and cold separator defects during casting, significantly improving the quality and production efficiency of the components.
Patent Information
- Application Number
- CN202311459141.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-03
- Publication Date
- 2025-05-06
AI Technical Summary
Existing magnesium alloys such as AZ91D are prone to thermal tearing and cold separating defects during casting, resulting in unstable component quality and reduced yield.
A magnesium alloy was developed, which consisted of approximately 10-15% aluminum, 0.1-0.5% zinc, 0.5-1.5% silicon, and magnesium and impurities as the margin. The alloy is made by a tactile process and has a low crack sensitivity index (CSI), thereby reducing the occurrence of thermal tear and cold septum defects.
The magnesium alloy significantly reduces the incidence of thermal tear and cold-septal defects during casting, and improves the quality stability and production efficiency of the components.
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Figure CN119932384A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to magnesium alloys, and in particular to magnesium alloys having improved castability compared to conventionally used alloys such as AZ91D, and in particular to magnesium alloys having improved castability by thixoforming. Background Art
[0002] The information provided in this section is intended to generally introduce the background of the present disclosure. To the extent that work currently named as inventors is described in this section, and aspects of the specification that may not have been otherwise identified as prior art at the time of filing, are not admitted, either explicitly or implicitly, as prior art to the present disclosure.
[0003] The present disclosure relates to magnesium alloys, and in particular to magnesium alloys having improved castability compared to conventionally used alloys such as AZ91D, and in particular to magnesium alloys having improved castability by thixoforming.
[0004] AZ91D alloy is one of the most widely used magnesium die casting alloys due to its combination of mechanical properties, corrosion resistance and castability. (AZ91D is nominally 8.2-9.7 wt% Al, 0.35-1.0 wt% Zn, <0.1 wt% Si, and the balance is Mg). However, one problem with existing magnesium alloys such as AZ91D is that die cast parts made from the alloy are susceptible to hot tear and cold shut defects.
[0005] Hot tears are discontinuities that occur during the casting operation as the material being cast solidifies. Hot tears occur when the material experiences some force or restraint during the solidification phase of the casting operation, i.e. when the material being cast is part solid and part liquid. Hot tears occur because as the material solidifies it contracts, and the forces or restraints that resist this contraction cause the material to "tear".
[0006] A cold shut is a defect that occurs when two leading edges of liquid metal meet during the casting process and the liquid metal surfaces cool and do not fuse properly in the mold cavity, leaving a weak spot or crack.
[0007] Current strategies to try to control defects such as hot tears and cold shuts include sophisticated control methods to manage heat losses during casting operations, but in many cases defects continue to recur, resulting in reduced yields. In some cases, it may even be necessary to redesign the part to achieve commercially acceptable yields. Summary of the invention
[0008] The present disclosure provides magnesium alloys that are less sensitive to casting defects such as hot tearing and cold shut, and die-cast magnesium alloy parts made from such alloys.
[0009] In general, the magnesium alloy according to the present disclosure is particularly suitable for die casting, and is particularly suitable for thixoforming, and has a low defect rate (compared with widely used commercial magnesium alloys). The alloy generally contains about 9.8% by weight to about 15% by weight of Al, greater than 0 and less than about 1.5% by weight of zinc; and greater than 0 and less than about 1.0% by weight of silicon. The balance of the alloy is magnesium and impurities. Impurities of no more than about 0.15% by weight are optionally present, and no single impurity accounts for more than about 0.05% by weight. Optionally, at least 0.1% by weight of Zn and at least about 0.5% by weight of Si are present.
[0010] In a first embodiment of the alloy of the present disclosure, the aluminum content is about 10 wt % to about 13 wt % Al, and the other ingredients are about 0.1 wt % to 1.5 wt % Zn; and about 0.5 wt % to 1.0 wt % Si. The alloy of the first embodiment may have a crack sensitivity index (CSI) as defined below, which is similar to that of common aluminum casting alloys such as a356, or about 250 or less.
[0011] In a second embodiment of the alloy of the present disclosure, the aluminum content is about 13 wt % to 15 wt % Al, and the other ingredients are about 0.1 wt % to 1.5 wt % zinc; and about 0.5 wt % to 1.0 wt % silicon. The alloy of the second embodiment preferably has a CSI similar to that of common aluminum casting alloys such as a356, or about 250 or less.
[0012] Some embodiments of the present disclosure provide a magnesium die-cast component, and in particular a magnesium component made by thixoforming. The component is made of an alloy comprising about 10 wt % to about 15 wt % Al; about 0.1 wt % to 1.5 wt % Zn; and about 0.5 wt % to 1.0 wt % Si, and the balance Mg and impurities. Preferably, there is no more than about 0.15 wt % impurities, and no single impurity accounts for more than about 0.05 wt %.
[0013] The present invention discloses the following scheme:
[0014] Solution 1. A magnesium alloy for die casting with reduced defects, the alloy comprising:
[0015] Aluminum in an amount greater than or equal to about 10 wt % and less than or equal to about 15 wt %
[0016] Zinc in an amount greater than 0 and less than or equal to about 0.5 weight percent;
[0017] Silicon in an amount greater than 0 and less than or equal to about 1.5 weight percent;
[0018] The balance is magnesium and unavoidable impurities.
[0019] Option 2. The magnesium alloy according to Option 1, wherein the magnesium alloy contains aluminum in an amount greater than or equal to about 10 wt. % and less than or equal to about 13 wt. %.
[0020] Option 3. The magnesium alloy according to Option 1, wherein the magnesium alloy contains aluminum in an amount greater than or equal to about 13 weight % and less than or equal to about 15 weight %.
[0021] Option 4. The magnesium alloy according to Option 1, wherein the magnesium alloy has a total of up to about 0.15 weight % of additional elements, each additional element accounting for no more than about 0.05 weight %.
[0022] Option 5. The magnesium alloy of Option 1, wherein the magnesium alloy has a CSI of less than about 250.
[0023] Option 6. The magnesium alloy of Option 1, wherein the magnesium alloy comprises zinc in an amount of at least about 0.1 wt. %.
[0024] Option 7. The magnesium alloy of Option 1, wherein the magnesium alloy comprises silicon in an amount less than or equal to about 1.0 wt. %.
[0025] Option 8. A magnesium alloy according to Option 7, wherein the magnesium alloy contains silicon in an amount greater than or equal to about 0.5 weight percent.
[0026] Aspect 9. A cast magnesium component produced by thixoforming the magnesium alloy according to aspect 1.
[0027] Option 10. A cast magnesium component according to Option 9, wherein the magnesium alloy has a total of up to about 0.15 weight percent of additional elements, each additional element accounting for no more than about 0.05 weight percent.
[0028] Embodiment 11. The cast magnesium component of Embodiment 10, wherein the magnesium alloy has a CSI of less than about 250.
[0029] Embodiment 12. The cast magnesium component of Embodiment 11, wherein the magnesium alloy comprises zinc in an amount of at least about 0.1 weight percent.
[0030] Embodiment 13. A cast magnesium component according to Embodiment 12, wherein the magnesium alloy contains silicon in an amount less than or equal to about 1.0 weight percent.
[0031] Embodiment 14. The cast magnesium component of Embodiment 13, wherein the magnesium alloy comprises silicon in an amount greater than or equal to about 0.5 weight percent.
[0032] Embodiment 15. A magnesium alloy for die casting with reduced defects, the alloy comprising:
[0033] aluminum in an amount greater than or equal to about 10 wt % and less than or equal to about 15 wt %;
[0034] zinc in an amount greater than or equal to about 0.1 wt % and less than or equal to about 0.5 wt %;
[0035] Silicon in an amount greater than about 0.5 wt. % and less than or equal to about 1.0 wt. %; and
[0036] The balance is magnesium and unavoidable impurities.
[0037] Option 16. A magnesium alloy according to Option 15, wherein the magnesium alloy has a total of up to about 0.15 weight % of additional elements, each additional element accounting for no more than about 0.05 weight %.
[0038] Option 17. A magnesium alloy according to Option 15, wherein the magnesium alloy has a CSI of less than about 250.
[0039] Option 18. A magnesium alloy according to Option 15, wherein the magnesium alloy contains aluminum in an amount greater than or equal to about 10 weight % and less than or equal to about 13 weight %.
[0040] Option 19. A magnesium alloy according to Option 15, wherein the magnesium alloy contains aluminum in an amount greater than or equal to about 13 weight % and less than or equal to about 15 weight %.
[0041] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended to be illustrative only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The present disclosure will be more fully understood through the detailed description and accompanying drawings, in which:
[0043] Figure 1 is a graph of temperature versus solid fraction (fs) for three alloys Mg-9%Al, Mg-9%Al-0.5%Zn and Mg-9%Al-1.0%Zn (wt%), showing the effect of zinc content on solidification behavior;
[0044] Figure 2 is a graph of temperature versus solid fraction (fs) for eight binary Mg-Al alloys with 8, 9, 10, 11, 12, 13, 14 and 15 weight percent aluminum, showing the effect of aluminum content on solidification behavior; and
[0045] Figure 3is a plot of temperature versus solid fraction (fs) for four Mg-9%Al-0.5%Zn (wt %) alloys with 0, 0.5, 1.0 and 1.5 wt % silicon, showing the effect of silicon content on solidification behavior.
[0046] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION
[0047] The present disclosure provides magnesium alloys that are less susceptible to casting defects such as hot tearing and cold shut than currently commercially used magnesium alloys such as AZ91D, and provides die-cast magnesium alloy parts made from these alloys.
[0048] In general, magnesium alloys according to the present disclosure are particularly suitable for die casting, and are particularly (but not exclusively) suitable for thixoforming, where the incidence of defects such as hot tearing and cold shut is low. Thixoforming or magnesium injection molding is a single-step semi-solid molding process in which magnesium alloy chips are fed into a heated screw and barrel, then heat treated and machined into a semi-solid state and injected directly into a tool cavity.
[0049] The alloys disclosed herein generally include greater than or equal to about 10 wt % and less than or equal to about 15 wt % aluminum, greater than 0 and less than or equal to about 0.5 wt % zinc; greater than 0 and less than or equal to about 1.5 wt % silicon, and the balance being magnesium and impurities. Additional elements up to about 0.15 wt % may be present, with no single additional element accounting for more than about 0.05 wt %. Optionally, at least 0.1 wt % Zn and at least about 0.5 wt % Si are present.
[0050] Crack Sensitivity Index (CSI)
[0051] The crack sensitivity index (CSI) has been proposed as an indicator of when cracking, such as hot tearing, occurs in magnesium alloys. See Lie and SIndo, "Susceptibility of Magnesium Alloys to Solidification Cracking," Science and Technology of Welding and Joining 25.3 (2020): 251-257, the entire disclosure of which is incorporated herein by reference. The CSI is the maximum slope of temperature relative to the square root of the solid fraction (fs) over the relevant range. Figures 1 to 3T vs. (fs)1 / 2 for various alloys are shown. These curves can be generated by standard thermodynamic software (e.g., Pandat from CompuTherm LLC, Madison, WI) using metallurgical data from a standard reference database (e.g., PanMagnesium, also from CompuTherm LLC). The CSI cited in this disclosure is the maximum slope of the curve within the range 0.87≤fs≤0.99 indicated on each graph. CSI = maximum value of |dT / d(fs)1 / 2| for 0.87≤fs≤0.99. The CSI for AZ91D is about 506, while the CSI for standard aluminum alloy A356 is about 250. Embodiments of the alloys disclosed herein have a CSI of 0 to about 250, which means that they are more resistant to cracking than AZ91D and are generally at least as resistant to cracking defects as popular aluminum alloys.
[0052] Zinc content
[0053] The inventors have found that zinc increases CSI and may be detrimental to hot tear resistance. Figure 1 It is shown that for a given composition, the CSI increases with increasing zinc content. Specifically, the CSI for Mg-9%Al is about 0, the CSI for Mg-9%AL-0.5%Zn is about 223, and the CSI for Mg-9%AL-1%Zn is about 506. However, zinc can lower the liquidus temperature of a given composition. Therefore, zinc can be present, but keeping zinc ≤ 1 wt % can be advantageous, and keeping zinc ≤ 0.5 wt % is more advantageous.
[0054] Aluminum content
[0055] The inventors have found that aluminum contents of 9 wt % or higher have no significant effect on CSI or tear resistance. Figure 2 As shown in , increasing the aluminum content from 10 wt % to 15 wt % does reduce the liquidus temperature, thereby improving the fluidity of the alloy. Therefore, aluminum ≥ 10 to at least aluminum ≤ 15 wt % may be advantageous.
[0056] Silicon content
[0057] The inventors have found that silicon has no significant effect on CSI or tear resistance. Figure 3 As shown in , silicon can lower the liquidus temperature, thereby improving the fluidity of the alloy. Figure 3 It is shown that for a given composition, for Mg-9%Al-0.5%Zn, the Si content is 0≤Si wt%≤1.5 and the CSI remains the same. Figure 3It is further shown that increasing the silicon content from 0 wt % to about 1 wt % reduces the liquidus temperature, which improves the fluidity of the alloy. Further increases in silicon beyond about 1 wt % do not reduce the liquidus temperature and may actually increase the liquidus temperature at low solid fractions (fs). Figure 3 As shown in , the liquidus temperature of Mg-9%AL-0.5%Zn-1%Si is lower than the liquidus temperature of Mg-9%AL-0.5%Zn-0.5%Si, which in turn has a lower liquidus temperature than the liquidus temperature of Mg-9%AL-0.5%Zn-0.5%Si. Thus, 0.1 ≤ Silicon ≤ 1.5 wt % may be advantageous, and 0.1 wt % ≤ Silicon ≤ 1.0 wt % may be more advantageous. As noted, at least some silicon, e.g., Silicon ≥ 0.1 to Si ≤ 0.5 wt %, may provide a lower liquidus temperature.
[0058] A first embodiment of the alloy of the present disclosure comprises aluminum in an amount greater than or equal to about 10 wt % and less than or equal to about 13 wt %; zinc in an amount greater than 0 and less than or equal to about 0.5 wt %; and silicon in an amount greater than 0 and less than or equal to about 1.5 wt %, with the balance being magnesium and impurities. In some forms of the first embodiment, the zinc content is greater than or equal to about 0.1 wt % and less than or equal to about 0.5 wt %. In some forms of the first embodiment, the silicon content is greater than or equal to about 0.5 wt % and less than or equal to about 1.0 wt %. The alloy of the first embodiment typically has a CSI of less than 250.
[0059] In a second embodiment of the alloy of the present disclosure, the aluminum content is greater than or equal to about 13 wt% and less than or equal to 15 wt%, the amount of zinc is greater than 0 and less than or equal to about 0.5 wt%; and the amount of silicon is greater than 0 and less than or equal to about 1.5 wt%, and the balance is magnesium and impurities. In some forms of the first embodiment, the zinc content is greater than or equal to about 0.1 wt% and less than or equal to about 0.5 wt%. In some forms of the first embodiment, the silicon content is greater than or equal to about 0.5 wt% and less than or equal to about 1.0 wt%. The alloys of this second embodiment generally have a CSI of less than 250 and have a lower liquidus temperature because they have a greater aluminum content than the first embodiment.
[0060] Some embodiments of the present disclosure provide a die-cast component, and in particular a component made by thixoforming. The component is made of an alloy comprising greater than or equal to about 10 wt% and less than or equal to about 15 wt% aluminum, an amount greater than 0 and less than or equal to about 0.5 wt% zinc; and an amount greater than 0 and less than or equal to about 1.5 wt% silicon, with the balance being magnesium and impurities. Preferably, no more than 0.15 wt% of additional elements are present, and no single additional element accounts for more than 0.05 wt%.
[0061] In a first embodiment of the component of the present disclosure, there is about 10 wt% to about 13 wt% Al, an amount greater than 0 and less than or equal to about 0.5 wt% zinc; and an amount greater than 0 and less than or equal to about 1.5 wt% silicon, with the balance being magnesium and impurities. In some forms of the first embodiment, the zinc content is greater than or equal to about 0.1 wt% and less than or equal to about 0.5 wt%. In some forms of the first embodiment, the silicon content is greater than or equal to about 0.5 wt% and less than or equal to about 1.0 wt%. The alloy of this first embodiment typically has a CSI of less than 250.
[0062] In a second embodiment of the alloy of the present disclosure, the aluminum content is greater than or equal to about 13 wt% and less than or equal to 15 wt%, the amount of zinc is greater than 0 and less than or equal to about 0.5 wt%; and the amount of silicon is greater than 0 and less than or equal to about 1.5 wt%, and the balance is magnesium and impurities. In some forms of the first embodiment, the zinc content is greater than or equal to about 0.1 wt% and less than or equal to about 0.5 wt%. In some forms of the first embodiment, the silicon content is greater than or equal to about 0.5 wt% and less than or equal to about 1.0 wt%. The alloys of this second embodiment generally have a CSI of less than 250 and have a lower liquidus temperature because they have a greater aluminum content than the first embodiment.
[0063] The foregoing description is essentially only exemplary and is absolutely not intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in various forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be limited thereto, because after studying the drawings, the specification and the following claims, other modifications will become apparent. It should be understood that one or more steps in the method may be implemented in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more features described with respect to any embodiment of the present disclosure may be implemented in any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the embodiments are not mutually exclusive, and the mutual replacement of one or more embodiments is still within the scope of the present disclosure.
Claims
1. A magnesium alloy for die casting with reduced defects, the alloy comprising: Aluminum in an amount greater than or equal to about 10 wt % and less than or equal to about 15 wt % Zinc in an amount greater than 0 and less than or equal to about 0.5 weight percent; Silicon in an amount greater than 0 and less than or equal to about 1.5 weight percent; The balance is magnesium and unavoidable impurities. 2 . The magnesium alloy of claim 1 , wherein the magnesium alloy comprises aluminum in an amount greater than or equal to about 10 wt % and less than or equal to about 13 wt %. 3 . The magnesium alloy of claim 1 , wherein the magnesium alloy comprises aluminum in an amount greater than or equal to about 13 wt % and less than or equal to about 15 wt %.
4. The magnesium alloy of claim 1, wherein the magnesium alloy has a total of up to about 0.15 wt% of additional elements, with each additional element accounting for no more than about 0.05 wt%. 5 . The magnesium alloy of claim 1 , wherein the magnesium alloy has a CSI of less than about 250.
6. The magnesium alloy of claim 1, wherein the magnesium alloy comprises zinc in an amount of at least about 0.1 wt. %.
7. The magnesium alloy of claim 1, wherein the magnesium alloy comprises silicon in an amount less than or equal to about 1.0 wt. %.
8. The magnesium alloy of claim 7, wherein the magnesium alloy comprises silicon in an amount greater than or equal to about 0.5 wt. %.
9. A cast magnesium part produced by thixoforming the magnesium alloy according to claim 1.
10. The cast magnesium component of claim 9, wherein the magnesium alloy has a total of up to about 0.15 wt. % of additional elements, each additional element comprising no more than about 0.05 wt. %.