CN113355576A - High-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency and preparation method thereof - Google Patents
High-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency and a preparation method thereof, wherein the alloy comprises the following components in percentage by mass: 2.5-3.5 wt.% Nd, 2.0-4.5 wt.% Gd, 0.5-2.0 wt.% Yb, 0.1-0.7 wt.% Zn, 0.1-1.0 wt.% Zr, and the balance Mg and inevitable impurity elements. The invention also provides a preparation method of the alloy, which comprises the following steps: smelting and heat treatment. The high-strength high-toughness magnesium alloy provided by the invention greatly reduces the tendency of forming oxidation inclusion defects in the casting process under the condition of ensuring that the room temperature and high temperature performance is equivalent to that of commercial magnesium alloy WE43, is more suitable for producing large thin-wall and complex structures, has structural members with light weight and high strength requirements, and has wide industrial application prospects.
Description
Technical Field
The invention belongs to the field of metal materials and metallurgy, relates to a high-strength and high-toughness cast magnesium alloy and a preparation method thereof, and particularly relates to a high-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency and a preparation method thereof.
Background
The high strength and low density characteristics of magnesium alloys make them central to the application field where "light weight" is the main objective. For example, the magnesium alloy can reduce fuel consumption and improve bearing capacity in the fields of aerospace, ground transportation, military equipment and the like, thereby improving economic benefits. At present, the magnesium alloy has various types, and representative alloys include Mg-Al series, Mg-Zn series and Mg-RE series. Among them, Mg — RE alloys have attracted much attention because of their excellent high-temperature and room-temperature properties.
The WE43 alloy (Mg-4Y-3Nd) has superior age hardening capacity and excellent comprehensive mechanical property, is widely applied in the field of aerospace, and is one of the most successful commercial magnesium rare earth alloys applied at present. However, it has recently been found in practice that Y is highly likely to occur when using WE43 alloy to produce thin-walled complex castings2O3Oxidation of the inclusion defects results in scrap castings. This is mainly because Y element is very easily oxidized. The related thermodynamic analysis shows that the oxide of Y (Y)2O3) Has low standard free energy and is easy to form. Therefore, the method has important production significance for reducing the content of Y and developing the high-strength and high-toughness magnesium rare earth alloy without Y.
The patent of the high-strength high-toughness cast magnesium rare earth alloy without Y element is not disclosed much, and the patent (publication number: CN106591659A) provides a high-strength high-toughness cast rare earth magnesium alloy and a preparation method thereof. The magnesium alloy comprises the following components in percentage by mass: 0.1-3.3% of Yb, 0.2-1.0% of Zn and 0.3-0.8% of Zr. The room temperature ultimate tensile strength of the prepared high-strength high-toughness cast rare earth magnesium alloy can reach 185-205 MPa. The patent (publication number: CN1752251A) discloses a rare earth-containing high-strength cast Mg-Nd-Zn-Zr-Ca magnesium alloy, which consists of the following components in percentage by weight: 2.5-3.6% of Nd, 0.35-0.8% of Zr, less than or equal to 0.4% of Zn, less than or equal to 0.5% of Ca, and the total amount of impurity elements Si, Fe, Cu and Ni is less than 0.02%; the balance being magnesium. The invention obtains the high-strength magnesium alloy by adding alloy elements (Nd, Zr, Zn and Ca) and changing the technological conditions of smelting and heat treatment. The mechanical property of the Y-free casting magnesium rare earth alloy is far lower than that of WE43 alloy due to single type and low content of rare earth elements. The patent (publication number: CN1962914) discloses a rare earth-containing cast magnesium alloy and a preparation method thereof, wherein the magnesium alloy comprises the following components in percentage by weight: 6-15% of Gd, 2-6% of Sm and 0.35-0.8% of Zr, the total amount of impurity elements Si, Fe, Cu and Ni is less than 0.02%, and the balance is Mg. By adding alloy elements Gd and Sm to replace Y, Nd in WE series alloy and through smelting and heat treatment process conditions, high-strength heat-resistant magnesium alloy is obtained, however, although the magnesium alloy has mechanical properties such as room temperature strength, instantaneous high temperature strength and the like superior to those of the traditional WE series commercial magnesium alloy, the plasticity of the magnesium alloy is greatly reduced.
According to the invention, for the mechanical property of the WE43 alloy, Gd element is matched with Nd element to ensure the age hardening capacity of the alloy, Yb element is added to optimize the plasticity of the alloy, and finally microalloying element Zn is added. Finally, the high-strength and high-toughness cast magnesium rare earth alloy which can replace WE43 and does not contain Y element and has low oxide inclusion tendency is obtained, the oxide inclusion defect in the production process of large-scale complex thin-wall castings is greatly reduced, and the method has important significance for expanding the application of the magnesium rare earth alloy in the aerospace field.
Disclosure of Invention
The invention aims to provide a high-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency and a preparation method thereof aiming at the defects of WE magnesium alloy.
The purpose of the invention is realized by the following technical scheme:
in a first aspect, the invention relates to a high-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency, which comprises the following components in percentage by mass: 2.5-3.5 wt.% Nd, 2.0-4.5 wt.% Gd, 0.5-2.0 wt.% Yb, 0.1-0.7 wt.% Zn, 0.1-1.0 wt.% Zr, and the balance Mg and inevitable impurity elements.
As one embodiment of the invention, the inevitable impurity elements are one or more of Fe, Cu, Si and Ni, and the mass percentages of the impurity elements are as follows: fe is less than or equal to 0.005 wt%, Cu is less than or equal to 0.005 wt%, Si is less than or equal to 0.005 wt%, and Ni is less than or equal to 0.005 wt%.
As an embodiment of the invention, the mass percentage ratio of Nd element to Gd element in the magnesium alloy is controlled to be (0.7-1.3): 1.
according to the invention, Nd is used as a first component, and the solid solubility of the Nd is reduced rapidly along with the change of temperature, so that the aging hardening capacity is strong, and the dispersion of supersaturated Nd atoms in the aging process can enable a plurality of finely dispersed metastable beta' phases and beta 1 phases to be formed in a matrix under the condition of peak aging. The metastable beta' phase as well as the beta 1 phase are the main source of strength in aged Mg-Nd alloys. The Nd atom has high diffusion rate in Mg matrix, so that the ageing hardening rate is high, and the Nd element is selected as the main alloying element to greatly shorten the alloy peak ageing time and realize rapid ageing strengthening. However, since the maximum solid solubility is not higher than 3.6 wt%, too high addition amount will cause a large amount of secondary phases to remain during solution treatment to affect the mechanical properties of the final aged state, and thus the addition amount is adjusted to 2.5 to 3.5 wt%.
The Gd element is used as the second component, the solid solubility of the Gd element in the magnesium alloy is high, and the reduction rate of the solid solubility along with the change of temperature is fast. Therefore, the addition of Gd element can realize additional solid solution strengthening on one hand, and on the other hand, the main strengthening phases in the Mg-Gd alloy are beta 'and beta', so that the addition of Gd element can increase the density of the metastable beta 'phase on the one hand, and can introduce beta', realize the composite strengthening of age hardening capacity, and finally realize the great improvement of strength. However, because the diffusion speed of Gd atoms in Mg is slow, the aging hardening rate of the alloy is slowed down along with the increase of the content of Gd element, so that the aging time required by the alloy is longer, and therefore, the addition amount is adjusted to be 2.0-4.5 wt.%.
In addition, Yb is selected as the third component, and firstly, because the atomic radius (0.19392nm) of Yb atoms is obviously larger than that of Mg (0.1602nm), solid solution in a magnesium matrix can directly cause the reduction of the stacking fault energy to generate stacking fault coordination deformation, thereby improving the plasticity of the magnesium alloy. Secondly, the Yb element can form a fine and dispersed granular Mg2Yb phase in the aging process, and composite reinforcement of a precipitated phase is realized. Thirdly, Yb atoms also easily form atom clusters with Zn atoms (0.153nm) with smaller atomic radius in the magnesium matrix, and the atom clusters can become nucleation sites of age-precipitated phases (beta ', beta' and beta 1), so that the nucleation of the beta ', beta' and beta 1 is further promoted, and the number density is increased. Therefore, the proper addition of Yb can obviously optimize the plasticity of the alloy and also obviously improve the strength. However, the solid solubility of Yb element in Mg is not high, and some insoluble second phases are formed when the addition amount is high, thereby increasing the difficulty of solution treatment, and therefore, the addition amount is adjusted to 0.5 to 2.0 wt.%.
The Zn element is selected as the fourth component in order to introduce a Zn-Zr phase in the process of solution treatment so as to further optimize the alloy performance. However, when the addition amount of the Zn element is too large, a large amount of rare earth elements are consumed, and a basal plane phase with weak strengthening effect is formed in the aging process, so that the strength of the alloy is greatly reduced, and therefore, the addition amount is adjusted to 0.1-0.7 wt.%.
In addition, the alloy of the present invention does not contain Y.
In a second aspect, the invention also relates to a method for preparing a high-strength and high-toughness cast magnesium alloy with low tendency of oxide inclusion, which comprises the following steps:
A. carrying out preheating and drying treatment on pure Mg, pure Zn, Mg-Nd intermediate alloy, Mg-Zr intermediate alloy, Mg-Gd intermediate alloy and Mg-Yb intermediate alloy;
B. melting pure Mg; adding pure Zn, and melting the pure Zn; then adding Mg-Gd intermediate alloy, Mg-Zr intermediate alloy, Mg-Nd intermediate alloy and Mg-Yb intermediate alloy; after all the alloys are completely melted, the temperature of the melt is raised again and the melt is stirred; then heating and standing, cooling and refining, and preserving heat and standing; then, carrying out secondary cooling on the melt, skimming the surface scum and casting the melt into an alloy ingot;
C. and carrying out solution treatment and aging heat treatment on the alloy ingot.
In one embodiment of the invention, in the step a, the content of Gd in the Mg-Gd intermediate alloy is 20 to 40 wt.%. Because rare earth elements are more active, the intermediate alloy with excessively high rare earth content inevitably has more inclusions, which can affect the quality of the melt. And the addition amount of the intermediate alloy is too large due to the fact that the content of the rare earth in the intermediate alloy is too low, so that the smelting step is complex and tedious.
As an embodiment of the present invention, in step a, the content of Gd in the Mg-Gd master alloy is 30 wt.%.
In one embodiment of the present invention, in the step a, the content of Nd in the Mg — Nd master alloy is 20 to 40 wt.%. Because rare earth elements are more active, the intermediate alloy with excessively high rare earth content inevitably has more inclusions, which can affect the quality of the melt. And the addition amount of the intermediate alloy is too large due to the fact that the content of the rare earth in the intermediate alloy is too low, so that the smelting step is complex and tedious.
As an embodiment of the present invention, in step a, the content of Nd in the Mg — Nd master alloy is 30 wt.%.
In an embodiment of the present invention, in the step a, the content of Zr in the Mg — Zr intermediate alloy is 20 to 40 wt.%. Because rare earth elements are more active, the intermediate alloy with excessively high rare earth content inevitably has more inclusions, which can affect the quality of the melt. And the addition amount of the intermediate alloy is too large due to the fact that the content of the rare earth in the intermediate alloy is too low, so that the smelting step is complex and tedious.
As an embodiment of the present invention, in step a, the content of Zr in the Mg — Zr master alloy is 30 wt.%.
In one embodiment of the invention, in the step a, the content of Yb in the Mg-Yb master alloy is 20 to 30 wt.%. Because rare earth elements are more active, the intermediate alloy with excessively high rare earth content inevitably has more inclusions, which can affect the quality of the melt. And the addition amount of the intermediate alloy is too large due to the fact that the content of the rare earth in the intermediate alloy is too low, so that the smelting step is complex and tedious.
As an embodiment of the invention, in the step A, the content of Yb in the Mg-Yb master alloy is 20 wt%.
In the step B, the adding temperature of the pure Zn is 700-730 ℃; the adding temperature of the master alloy is 740-760 ℃; the temperature of the melt is raised to 740-760 ℃; and the temperature of the second cooling is 710-740 ℃.
According to the invention, the addition temperature of the intermediate alloy is 740-760 ℃, if the addition temperature is higher than 760 ℃, the burning loss of the rare earth elements is easily caused in the addition process, so that the actual components of the alloy obtained by smelting are difficult to control. If the adding temperature is lower than 740 ℃, the intermediate alloy is not easy to melt, and the smelting process is difficult to control.
In step C, as an embodiment of the present invention, the solution treatment process comprises: and (3) carrying out solid solution on the alloy ingot obtained by smelting at the temperature of 490-550 ℃ for 5-10 hours, and carrying out water quenching to room temperature.
The solid solution temperature is limited to 490-550 ℃, and if the solid solution temperature is higher than 550 ℃, the overburning phenomenon occurs at the grain boundary, so that the alloy performance is greatly reduced; if the solution temperature is less than 490, it is difficult to completely dissolve the intergranular second phase, which affects the age-hardening ability of the alloy and the plasticity of the alloy in the aged state.
The solid solution time is limited to 5-10 hours, and if the solid solution time exceeds 10 hours, crystal grains excessively grow, so that the performance of the alloy is reduced; if the solution time is less than 5 hours, the intergranular second phase is difficult to completely dissolve, and the age-hardening ability of the alloy and the plasticity of the alloy in an aged state are affected.
In step C, as an embodiment of the present invention, the aging heat treatment process comprises: aging for 4-8 hours at 200-250 ℃.
The temperature of the aging treatment is limited to 200-250 ℃, and if the aging temperature is higher than 250 ℃, the density of the alloy precipitated phase is too low, and the alloy strength is reduced; if the solid solution temperature is lower than 200, the aging time is greatly prolonged, and the plasticity of the aged alloy is reduced.
The aging treatment time is limited to 4-8 hours, if the aging treatment time exceeds 8 hours, the density of alloy precipitated phases is too low, and the alloy strength is reduced; if the aging time is less than 4 hours, the alloy precipitated phase coarsens, and the alloy strength and plasticity decrease.
Compared with the prior art, the invention has the following beneficial effects:
1. the Gd element is used for replacing an easily-oxidized Y element in the Mg-Y-Nd alloy, so that the oxide inclusion tendency of the alloy is reduced.
2. The Gd element and the Nd element are compounded and strengthened, so that the strength of the alloy is ensured. Meanwhile, the Yb element is added to optimize the plasticity of the alloy. The excellent comprehensive mechanical property of the Mg-Y-Nd alloy is maintained while the casting process property of the alloy is improved. The compound addition of Gd element and Nd element can simultaneously obtain strong precipitation strengthening and solid solution strengthening effects, and the alloy still has good mechanical properties under the condition of removing Y element. In addition, the Yb element can reduce the stacking fault energy in the magnesium matrix, coordinate deformation and optimize the plasticity of the alloy. The composite addition of the elements ensures that the alloy has excellent comprehensive mechanical properties equivalent to commercial WE43 alloy while not easily generating oxidation inclusion defects.
3. The magnesium alloy has low tendency of oxide inclusion in the casting process, and simultaneously maintains good room-temperature and high-temperature mechanical properties. Compared with WE43 alloy castings, the alloy has the advantage that the defects of oxide inclusions are obviously reduced when the alloy is used for producing large sand casting complex thin-walled parts. In addition, the room-temperature tensile strength, yield strength and elongation of the alloy in a T6 heat treatment state are respectively more than 340MPa, 220MPa and 10 percent. The high-temperature tensile strength, the yield strength and the elongation are respectively more than 190MPa, 150MPa and 16 percent, and are equivalent to WE43 alloy under the same conditions.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a metallographic microstructure of a Mg-Nd-Gd-Yb-Zn-Zr alloy with a low tendency of oxide inclusions obtained in example 1;
FIG. 2 is a metallographic microstructure of a conventional WE43 magnesium rare earth alloy obtained in comparative example 3.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The following examples, which are set forth to provide a detailed description of the invention and a detailed description of the operation, will help those skilled in the art to further understand the present invention. It should be noted that the scope of the present invention is not limited to the following embodiments, and that several modifications and improvements made on the premise of the idea of the present invention belong to the scope of the present invention.
All examples and comparative examples of the present application were tested according to the following test standards:
room temperature mechanical properties: GB/T228.1-2010;
high temperature mechanical properties (mechanical properties at 300 ℃): GB/T4338-2006.
Example 1
The embodiment relates to a high-strength and high-toughness cast magnesium rare earth alloy, which comprises the following alloy components in percentage by weight: 2.5 wt.% Nd,2.0 wt.% Gd,0.5 wt.% Zn, 0.5 wt.% Yb; 0.5 wt.% Zr, balance Mg. Preparing raw materials according to the components and the stoichiometric ratio of the alloy; carrying out preheating and drying treatment on pure Mg, pure Zn, Mg-Nd intermediate alloy, Mg-Zr intermediate alloy, Mg-Gd intermediate alloy and Mg-Yb intermediate alloy; melting pure Mg, adding pure Zn at 700 ℃, adding Mg-Gd intermediate alloy, Mg-Zr intermediate alloy, Mg-Nd intermediate alloy and Mg-Yb intermediate alloy at 740 ℃ after the pure Zn is melted; after all the alloys are completely melted, the temperature of the melt is raised to 750 ℃ again, the melt is stirred, then the temperature is raised to 780 ℃, and the mixture is kept stand for 10 min; cooling to 730 deg.C, and refining; then keeping the temperature and standing for 20 min; and after standing, cooling the melt to 730 ℃, skimming the surface scum, and casting to obtain an alloy ingot.
The casting is sampled and observed, and figure 1 is a metallographic microstructure diagram of the Mg-Nd-Gd-Yb-Zn-Zr alloy with low tendency of oxide inclusion obtained in example 1; it can be seen that the metallographic structure has few oxide inclusions, the content of the oxide inclusions is only 0.007%, and the inclusions are identified to be mainly Gd2O3。
The alloy ingot obtained by smelting is firstly subjected to solid solution for 10 hours at the temperature of 525 ℃, water quenching is carried out to the room temperature, and finally, the aging is carried out for 4 hours at the temperature of 200 ℃.
The room temperature mechanical properties of the alloy prepared in example 1 are: yield strength: 220MPa, tensile strength: 345MPa, elongation: 10 percent.
The mechanical properties at 300 ℃ are: yield strength: 179MPa, tensile strength: 225MPa, elongation: 19 percent. The strength and plasticity at room temperature and high temperature are better than those of WE43 alloy.
Example 2
The embodiment relates to a high-strength and high-toughness cast magnesium rare earth alloy which comprises the following components in percentage by weight: 3.5 wt.% Nd, 4.5 wt.% Gd,0.5 wt.% Zn, 2 wt.% Yb; 0.5 wt.% Zr, balance Mg. Preparing raw materials according to the components and the stoichiometric ratio of the alloy; carrying out preheating and drying treatment on pure Mg, pure Zn, Mg-Nd intermediate alloy, Mg-Zr intermediate alloy, Mg-Gd intermediate alloy and Mg-Yb intermediate alloy; melting pure Mg, adding pure Zn at 700 ℃, adding Mg-Gd intermediate alloy, Mg-Zr intermediate alloy, Mg-Nd intermediate alloy and Mg-Yb intermediate alloy at 740 ℃ after the pure Zn is melted; after all the alloys are completely melted, the temperature of the melt is raised to 750 ℃ again, the melt is stirred, then the temperature is raised to 780 ℃, and the mixture is kept stand for 10 min; cooling to 730 deg.C, and refining; then keeping the temperature and standing for 20 min; and after standing, cooling the melt to 730 ℃, skimming the surface scum, and casting to obtain an alloy ingot.
The sampling observation is carried out on the casting, and the inclusion content in the metallographic structure is only 0.005%. The inclusion is identified and found to be mainly Gd2O3。
The alloy ingot obtained by smelting is firstly subjected to solid solution for 10 hours at the temperature of 525 ℃, water quenching is carried out to the room temperature, and finally, the aging is carried out for 4 hours at the temperature of 200 ℃.
The room temperature mechanical properties of the alloy prepared in example 2 are: yield strength: 240MPa, tensile strength: 346MPa, elongation: 11 percent.
The mechanical properties at 300 ℃ are: yield strength: 178MPa, tensile strength: 220MPa, elongation: 18 percent. The strength and plasticity at room temperature and high temperature are better than those of WE43 alloy.
Example 3
This example is identical to example 2 except that the magnesium rare earth alloy has the composition of 3.5 wt.% Nd, 2.3 wt.% Gd,0.5 wt.% Zn, 2 wt.% Yb; 0.5 wt.% Zr, balance Mg, i.e. the ratio of the mass percent of Nd element to Gd element in this comparative example is 1.52: 1.
the room temperature mechanical properties of the alloy obtained in this example are: yield strength: 217MPa, tensile strength: 325MPa, elongation: 6 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 161MPa, tensile strength: 215MPa, elongation: 15 percent.
Example 4
This example is identical to example 1 except that the magnesium rare earth alloy has the composition of 2.5 wt.% Nd, 4.0 wt.% Gd,0.5 wt.% Zn, 0.5 wt.% Yb; 0.5 wt.% Zr, balance Mg. That is, the ratio of the mass percent of the Nd element to the mass percent of the Gd element in this comparative example is 0.625: 1.
the room temperature mechanical properties of the alloy obtained in the comparative example are as follows: yield strength: 212MPa, tensile strength: 315MPa, elongation: 6.5 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 160MPa, tensile strength: 201MPa, elongation: 15.5 percent.
Comparative example 1
The comparative example relates to a high-strength and high-toughness cast magnesium rare earth alloy which comprises the following components in percentage by weight: 3.5 wt.% Nd, 4.5 wt.% Gd,0.5 wt.% Zn,0 wt.% Yb; 0.5 wt.% Zr, balance Mg. Preparing raw materials according to the components and the stoichiometric ratio of the alloy; carrying out preheating and drying treatment on pure Mg, pure Zn, Mg-Nd intermediate alloy, Mg-Zr intermediate alloy, Mg-Gd intermediate alloy and Mg-Yb intermediate alloy; melting pure Mg, adding pure Zn at 700 ℃, adding Mg-Gd intermediate alloy, Mg-Zr intermediate alloy, Mg-Nd intermediate alloy and Mg-Yb intermediate alloy at 740 ℃ after the pure Zn is melted; after all the alloys are completely melted, the temperature of the melt is raised to 750 ℃ again, the melt is stirred, then the temperature is raised to 780 ℃, and the mixture is kept stand for 10 min; cooling to 730 deg.C, and refining; and then preserving heat and standing for 20min, cooling the melt to 730 ℃ after standing, skimming the surface scum, and casting into alloy ingots.
And sampling and observing the casting. The inclusion content in the metallographic structure is only 0.008%. The inclusion is identified and found to be mainly Gd2O3。
The alloy ingot obtained by smelting is firstly subjected to solid solution for 10 hours at the temperature of 525 ℃, water quenching is carried out to the room temperature, and finally, the aging is carried out for 4 hours at the temperature of 200 ℃.
The room temperature mechanical properties of the alloy prepared by the comparative example are as follows: yield strength: 210MPa, tensile strength: 312MPa, elongation: 3 percent.
The mechanical properties at 300 ℃ are: yield strength: 152MPa, tensile strength: 200MPa, elongation: 10 percent. Comparative example 2 the main difference is that the preparation process is completely identical without addition of Yb element, in which case the elongation of the alloy is significantly lower than in the alloys prepared in examples 1 and 2.
Comparative example 2
The comparative example relates to a high-strength and high-toughness cast magnesium rare earth alloy which comprises the following components in percentage by weight: 3.5 wt.% Nd, 4.5 wt.% Gd,0.5 wt.% Zn, 3 wt.% Yb; 0.5 wt.% Zr, balance Mg. Preparing raw materials according to the components and the stoichiometric ratio of the alloy; carrying out preheating and drying treatment on pure Mg, pure Zn, Mg-Nd intermediate alloy, Mg-Zr intermediate alloy, Mg-Gd intermediate alloy and Mg-Yb intermediate alloy; melting pure Mg, adding pure Zn at 700 ℃, adding Mg-Gd intermediate alloy, Mg-Zr intermediate alloy, Mg-Nd intermediate alloy and Mg-Yb intermediate alloy at 740 ℃ after the pure Zn is melted; after all the alloys are completely melted, the temperature of the melt is raised to 750 ℃ again, the melt is stirred, then the temperature is raised to 780 ℃, and the mixture is kept stand for 10 min; cooling to 730 deg.C, and refining; and then preserving heat and standing for 20min, cooling the melt to 730 ℃ after standing, skimming the surface scum, and casting into alloy ingots.
And sampling and observing the casting. The inclusion content in the metallographic structure is only 0.006%. Butt clampImpurities are identified to find that the impurities are mainly Gd2O3。
The alloy ingot obtained by smelting is firstly subjected to solid solution for 10 hours at the temperature of 525 ℃, water quenching is carried out to the room temperature, and finally, the aging is carried out for 4 hours at the temperature of 200 ℃.
The room temperature mechanical properties of the alloy prepared by the comparative example are as follows: yield strength: 180MPa, tensile strength: 260MPa, elongation: 4 percent.
The mechanical properties at 300 ℃ are: yield strength: 140MPa, tensile strength: 186MPa, elongation: 8 percent. Comparative example 2 the main difference is that with the addition of the higher Yb element, the process is completely consistent, in which case the strength elongation of the alloy is significantly lower than in the alloy prepared in example 2.
Comparative example 3
The comparative example relates to a cast magnesium alloy, the mass percent content of each component of the alloy is basically consistent with WE43, namely the alloy comprises the following components: 4 wt.% Y, 3 wt.% Nd, 0.5 wt.% Zn, 0.5 wt.% Zr, the balance Mg. The preparation method of the magnesium alloy comprises two process procedures of smelting and subsequent heat treatment, and the specific steps are consistent with those of the embodiment 1 and the embodiment 2.
And sampling and observing the casting. FIG. 2 is a metallographic microstructure of a conventional WE43 magnesium rare earth alloy obtained in comparative example 3, and it can be seen that the inclusion content in the metallographic structure is high and is 0.4%. The inclusion is identified to find that the inclusion is mainly Y2O3。
The room temperature mechanical properties of the alloy prepared by the comparative example are as follows: yield strength: 190MPa, tensile strength: 299MPa, elongation: 4.5 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 130MPa, tensile strength: 178MPa, elongation: 10 percent.
Comparative example 4
The preparation method and the heat treatment process of the comparative example are completely the same as those of the example 2, and the difference is only that the alloy components (weight percentage) are as follows: 2.5 wt.% Nd,2.0 wt.% Gd, 0.9 wt.% Zn, 0.5 wt.% Yb; 0.5 wt.% Zr, balance Mg.
The room temperature mechanical properties of the alloy obtained in the comparative example are as follows: yield strength: 191MPa, tensile strength: 289MPa, elongation: 5.0 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 125MPa, tensile strength: 176MPa, elongation: 12.5 percent. In this case, the strength and elongation of the alloy were significantly lower than those of the alloy prepared in example 2.
Comparative example 5
The compositions and preparation methods of the components of the magnesium alloy of the comparative example and the magnesium alloy of the example 2 are completely the same, and the difference is that the temperature of the solution treatment is 480 ℃, and the solution time is 10 h.
The room temperature mechanical properties of the alloy obtained in the comparative example are as follows: yield strength: 186MPa, tensile strength: 289MPa, elongation: 3.5 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 145MPa, tensile strength: 176MPa, elongation: 12 percent. In this case, the strength and elongation of the alloy were significantly lower than those of the alloy prepared in example 2.
Comparative example 6
The magnesium alloy of this comparative example and example 2 had the same composition and preparation method, except that the aging temperature was 175 ℃ and the aging time was 4 hours.
The room temperature mechanical properties of the alloy obtained in the comparative example are as follows: yield strength: 189MPa, tensile strength: 288MPa, elongation: 4.5 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 144MPa, tensile strength: 179MPa, elongation: 13% in this case, the strength and elongation of the alloy are significantly lower than those of the alloy prepared in example 2.
Comparative example 7
The magnesium alloy of this comparative example was prepared identically to the magnesium alloy of example 2, except that the alloy had a composition of 3.5 wt.% Nd, 8.1 wt.% Gd,0.5 wt.% Zn, 2 wt.% Yb; 0.5 wt.% Zr, balance Mg.
The room temperature mechanical properties of the alloy obtained in the comparative example are as follows: yield strength: 188MPa, tensile strength: 287MPa, elongation: 3.0 percent.
The mechanical properties at 300 ℃ are as follows: yield strength: 142MPa, tensile strength: 175MPa, elongation: 12 percent.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. A high-strength and high-toughness cast magnesium alloy with low oxide inclusion tendency is characterized by comprising the following components in percentage by mass: 2.5-3.5 wt.% Nd, 2.0-4.5 wt.% Gd, 0.5-2.0 wt.% Yb, 0.1-0.7 wt.% Zn, 0.1-1.0 wt.% Zr, and the balance Mg and inevitable impurity elements.
2. The high-toughness cast magnesium alloy with low tendency of oxide inclusion according to claim 1, wherein the mass percentage ratio of Nd element to Gd element in the magnesium alloy is (0.7-1.3): 1.
3. a method of making a high toughness cast magnesium alloy with low inclusion tendency to oxidation according to claim 1, comprising the steps of:
A. carrying out preheating and drying treatment on pure Mg, pure Zn, Mg-Nd intermediate alloy, Mg-Zr intermediate alloy, Mg-Gd intermediate alloy and Mg-Yb intermediate alloy;
B. melting pure Mg; adding pure Zn, and melting the pure Zn; then adding Mg-Gd intermediate alloy, Mg-Zr intermediate alloy, Mg-Nd intermediate alloy and Mg-Yb intermediate alloy; after all the alloys are completely melted, the temperature of the melt is raised again and the melt is stirred; then heating and standing, cooling and refining, and preserving heat and standing; then, carrying out secondary cooling on the melt, skimming the surface scum and casting the melt into an alloy ingot;
C. and carrying out solution treatment and aging heat treatment on the alloy ingot.
4. The method for preparing the high-strength and high-toughness cast magnesium alloy with low inclusion tendency of oxide according to claim 3, wherein in the step A, the mass percent content of Gd in the Mg-Gd intermediate alloy is 20-40 wt.%.
5. The method for preparing the high-strength and high-toughness cast magnesium alloy with low tendency of oxide inclusion according to claim 3, wherein in the step A, the mass percent content of Nd in the Mg-Nd intermediate alloy is 20-40 wt.%.
6. The method for preparing the high-strength and high-toughness cast magnesium alloy with low inclusion tendency of oxide according to claim 3, wherein in the step A, the mass percent content of Zr in the Mg-Zr intermediate alloy is 20-40 wt.%.
7. The method for preparing the high-strength and high-toughness cast magnesium alloy with low inclusion tendency of oxide according to claim 3, wherein in the step A, the mass percent of Yb in the Mg-Yb intermediate alloy is 20-30 wt.%.
8. The preparation method of the high-strength and high-toughness cast magnesium alloy with low inclusion tendency according to claim 3, wherein in the step B, the adding temperature of the pure Zn is 700-730 ℃; the adding temperature of the master alloy is 740-760 ℃; the temperature of the melt is raised to 740-760 ℃; and the temperature of the second cooling is 710-740 ℃.
9. The method for preparing the high-strength and high-toughness cast magnesium alloy with low inclusion tendency in the claim 3 is characterized in that in the step C, the solution treatment process comprises the following steps: and (3) carrying out solid solution on the alloy ingot obtained by smelting at the temperature of 490-550 ℃ for 5-10 hours, and carrying out water quenching to room temperature.
10. The method for preparing the high-toughness cast magnesium alloy with low inclusion tendency of oxide according to claim 3, wherein in the step C, the aging heat treatment process comprises the following steps: aging for 4-16 hours at 200-250 ℃.
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| CN117144218A (en) * | 2023-09-15 | 2023-12-01 | 株洲宜安精密制造有限公司 | High-strength magnesium alloy and preparation method and application thereof |
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| CN109666832A (en) * | 2019-02-22 | 2019-04-23 | 中国科学院长春应用化学研究所 | High-intensity thermal deformation resistant magnesium alloy and preparation method thereof |
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