CN114703411A - Mg-Sn series magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention provides an Mg-Sn series magnesium alloy and a preparation method thereof, belonging to the technical field of magnesium alloy materials. The Mg-Sn magnesium alloy provided by the invention comprises the following components in percentage by mass: sn 2-5%, Al 1.5-4.0%, Zn1.0-2.0%, Mn0.3-0.5% and the balance Mg. The Mg-Sn magnesium alloy provided by the invention can effectively promote the cooperative strengthening mechanism of each alloying element by regulating and controlling the variety and the content of each alloying element, thereby effectively improving the mechanical property and the processing efficiency of the Mg-Sn magnesium alloy.

Description

A kind of Mg-Sn magnesium alloy and preparation method thereof

technical field

The invention relates to the technical field of magnesium alloy materials, in particular to a Mg-Sn series magnesium alloy and a preparation method thereof.

Background technique

As the lightest metal structural material, magnesium alloy can meet the lightweight requirements of aerospace, automotive and electronic products due to its high specific strength and good impact resistance, and can reduce energy consumption and environmental pollution. Therefore, it has become a medium and high-end manufacturing industry. One of the fastest growing materials for industrial applications.

In order to improve the comprehensive properties of cast magnesium alloys and wrought magnesium alloys, most of the current research and development ideas of magnesium alloys are similar to those of aluminum alloys, mainly through alloying design to control the microstructure, strengthening and plastic deformation mechanisms. At present, Mg-Al series, Mg-Zn series, and Mg-RE series magnesium alloys have been developed, but Mg-Al series and Mg-Zn series magnesium alloys still have problems such as poor formability. The preparation cost of rare earth elements is high, which limits the further development and application of magnesium alloys. Compared with Mg-Al alloys, the preparation cost of Mg-Sn-based magnesium alloys is similar, but the microscopic strengthening and toughening mechanism of Mg-Sn-based alloys mainly involves the solid solution strengthening of Sn alloy elements and the second phase of intermetallic compounds such as Mg ₂ Sn. Precipitation strengthening, dispersion strengthening and other strengthening mechanisms, the structure is not easy to control, and has a greater impact on the plastic deformation process. There are still problems such as low room temperature strength and slow work hardening response speed.

Therefore, there is an urgent need to provide a Mg-Sn-based magnesium alloy with excellent mechanical properties and high processing efficiency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a Mg-Sn-based magnesium alloy and a preparation method thereof. The Mg-Sn-based magnesium alloy provided by the present invention has excellent mechanical properties and high processing efficiency.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a Mg-Sn magnesium alloy, which comprises the following components by mass percentage: Sn 2-5%, Al 1.5-4.0%, Zn 1.0-2.0%, Mn 0.3-0.5% and the balance Mg.

Preferably, the Mg-Sn-based magnesium alloy includes the following components by mass percentage: Sn 2.2-4.8%, Al 1.8-3.8%, Zn 1.2-1.8%, Mn 0.32-0.48% and the balance Mg.

Preferably, the Mg-Sn-based magnesium alloy comprises the following components by mass percentage: Sn 2.5-4.5%, Al 2-3.5%, Zn 1.4-1.6%, Mn 0.35-0.45% and the balance Mg.

The present invention also provides the preparation method of the Mg-Sn system magnesium alloy described in the above technical solution, comprising the following steps:

(1) smelting and casting the alloy raw material successively to obtain an alloy ingot;

(2) Post-processing the alloy ingot obtained in the step (1) to obtain a Mg-Sn-based magnesium alloy; the post-processing includes one or more of solution treatment, extrusion and aging treatment.

Preferably, the casting temperature in the step (1) is 680-700°C.

Preferably, the solution treatment in the step (2) includes a first-stage solution treatment and a second-stage solution treatment in sequence; the holding temperature of the first-stage solution treatment is 390-410° C., and the first-stage solution treatment The holding time is 10-12 h; the holding temperature of the second-level solution treatment is 440-460° C., and the holding time of the second-level solution treatment is 14-16 h.

Preferably, in the step (2), the extrusion temperature is 390-400° C., and the extrusion speed is 0.3-3 m/min.

Preferably, the extrusion pressure in the step (2) is 130-180 MPa.

Preferably, the extrusion ratio during extrusion in the step (2) is 8-22.

Preferably, the holding temperature of the aging treatment in the step (2) is 170-200° C., and the holding time of the aging treatment is 0-900 h.

The invention provides a Mg-Sn magnesium alloy, which comprises the following components by mass percentage: Sn 2-5%, Al 1.5-4.0%, Zn 1.0-2.0%, Mn 0.3-0.5% and the balance Mg. In the present invention, Sn element is added and its content is controlled, and the quantity and distribution of Mg ₂ Sn strengthening phase in the alloy of the invention are regulated. During the solidification process, part of Sn element is solid-dissolved in Mg matrix, and the other part is nucleated and grown by Mg ₂ Sn phase, showing dissociation The eutectic morphology, during the extrusion deformation process, a large amount of Mg ₂ Sn strengthening phase is dynamically precipitated, and the nano-phase Mg ₂ Sn at the grain boundary is dispersed, which can effectively hinder the movement of dislocations and pin the grain boundaries. Refining the grains can effectively improve the mechanical properties and processing efficiency of the magnesium alloy; the present invention also forms a B2-AlMnFe intermetallic compound to extract Fe impurities by adding Mn elements, and at the same time adding Al elements and regulating the content ratio of the two elements, it can be During the aging process, fine AlMn phase particles are formed, and the synergistic precipitation of AlMn phase and Mg ₂ Sn phase further improves the comprehensive mechanical properties of magnesium alloys; The strengthening mechanism improves the mechanical properties of magnesium alloys; the addition of Zn element can effectively improve the response efficiency of ageing hardening of magnesium alloys, it is easy to segregate near the precipitation strengthening phase, refine the size of the precipitation phase, and enable various precipitation strengthening phases to uniformly disperse Distributed in the magnesium alloy matrix, greatly improving the mechanical properties and processing efficiency of magnesium alloys.

The experimental results show that the Mg-Sn-based magnesium alloy provided by the present invention has a tensile strength of 294 MPa, a yield strength of 201 MPa, and an elongation of 18% after solid solution and extrusion of the as-extruded Mg-Sn-based magnesium alloy. The room temperature mechanical properties are excellent; the hardness after aging of the solid solution alloy can reach 69HV, and the hardness is nearly 38% higher than that of the initial solid solution alloy; the Mg-Sn magnesium alloy provided by the present invention is compared with AZ31 and AZ31. Mg-Al-Ca alloy has the highest power dissipation factor, up to 36%, showing more excellent hot working performance; and during hot working, compared with traditional commercial magnesium alloy AZ31, the recrystallization rate is increased by nearly 20% , the work hardening and dynamic recovery are faster, and the processing efficiency is significantly better than that of traditional Mg-Al alloys.

Description of drawings

1 is a photo of the as-cast alloy sample obtained in step (1) of Example 1 of the present invention;

Fig. 2 is the low magnification scanning electron microscope image of the as-cast alloy obtained in step (1) of Example 1 of the present invention;

Fig. 3 is the high magnification scanning electron microscope image of dissociated eutectic phase in the as-cast alloy of Example 1;

Fig. 4 is the high magnification scanning electron microscope image of τ-AlMn phase in the as-cast alloy of Example 1;

Fig. 5 is the high magnification scanning electron microscope image of Al ₈ Mn ₅ phase in the as-cast alloy of Example 1;

Fig. 6 is the high magnification scanning electron microscope image of β-Mn phase in the as-cast alloy of Example 1;

Fig. 7 is the rheological curve diagram of the magnesium alloy in the embodiment 1 of the present invention carrying out the hot compression experiment at different temperatures;

Fig. 8 is the thermal processing diagram obtained after the thermal compression experiment of Example 1 of the present invention is completed;

9 is a scanning electron microscope image of the as-extruded alloy in Example 2 of the present invention;

Fig. 10 is the IPF Z inverse pole figure and its (0001) pole figure of the extruded magnesium alloy in Example 2 of the present invention;

11 is the scanning electron microscope image of the solid solution alloy in Example 3 of the present invention and the SEM image of the aged alloy in Examples 3 to 5; wherein, FIG. 11(a) is the SEM image of the solid solution alloy in Example 3. , Figure 11(b) is the SEM image of the aged alloy of Example 3, Figure 11(c) is the SEM image of the aged alloy of Example 4, and Figure 11(d) is the SEM of the aged alloy of Example 5 picture;

Figure 12 shows the as-cast alloy obtained in step (1) of Example 2 of the present invention, the as-extruded alloy obtained in step (2), the solid-solution alloy obtained in step (1) in Example 3, and the aging obtained in step (2) Stress-strain curves of the as-state alloys and the aged-state alloys obtained in Examples 4-5;

FIG. 13 is a graph showing the hardness change of the sample in Example 5 of the present invention at an aging treatment temperature of 180° C. as the aging incubation time is prolonged.

Detailed ways

The invention provides a Mg-Sn magnesium alloy, which comprises the following components by mass percentage: Sn 2-5%, Al 1.5-4.0%, Zn 1.0-2.0%, Mn 0.3-0.5% and the balance Mg.

In terms of mass percentage, the Mg-Sn magnesium alloy provided by the present invention includes 2-5% Sn, preferably 2.2-4.8%, more preferably 2.5-4.5%, and most preferably 3-4%. In the present invention, Sn element is added and its content is controlled, and the quantity and distribution of Mg ₂ Sn strengthening phase in the alloy of the invention are regulated. During the solidification process, part of Sn element is solid-dissolved in Mg matrix, and the other part is nucleated and grown by Mg ₂ Sn phase, showing dissociation The eutectic morphology, during the extrusion deformation process, a large number of Mg ₂ Sn strengthening phases are dynamically precipitated, and the nano-phase Mg ₂ Sn at the grain boundary is dispersed, which can effectively hinder the movement of dislocations and pin the grain boundaries. Refine grains, effectively improve the mechanical properties and processing efficiency of magnesium alloys.

In terms of mass percentage, the Mg-Sn-based magnesium alloy provided by the present invention includes Al 1.5-4.0%, preferably 1.8-3.8%, more preferably 1.4-1.6%, most preferably 1.5%. In the present invention, by adding Al element and adjusting its content, fine AlMn phase particles can be formed with Mn element, and the mechanical properties and processing efficiency of magnesium alloy can be further improved through the synergistic precipitation of AlMn phase and Mg ₂ Sn phase; Part of it exists in the matrix in the form of solid solution, and the mechanical properties of magnesium alloys are improved by the solid solution strengthening mechanism.

In terms of mass percentage, the Mg-Sn-based magnesium alloy provided by the present invention includes 1.0-2.0% of Zn, preferably 1.2-1.8%, more preferably 1.4-1.6%. The present invention can effectively improve the age-hardening response efficiency of the magnesium alloy by adding Zn element and regulating its content.

In terms of mass percentage, the Mg-Sn-based magnesium alloy provided by the present invention includes 0.3-0.5% of Mn, preferably 0.32-0.48%, more preferably 0.35-0.45%. By adding Mn element and regulating its content, the present invention can not only extract Fe impurities by forming B2-AlMnFe intermetallic compound, but also introduce various Al-Mn phases, such as Al ₈ Mn ₅ and τ-AlMn are equal, which can be uniformly dispersed and distributed In the magnesium alloy matrix, the mechanical properties and processing efficiency of the magnesium alloy can be effectively improved.

In terms of mass percentage, the Mg-Sn-based magnesium alloy provided by the present invention includes the balance of Mg.

The Mg-Sn series magnesium alloy provided by the invention can effectively control the strengthening mechanism of each alloy element by regulating the types and contents of each alloy element, thereby effectively improving the mechanical properties and processing efficiency of the Mg-Sn series magnesium alloy.

The present invention also provides the preparation method of the Mg-Sn system magnesium alloy described in the above technical solution, comprising the following steps:

(1) smelting and casting the alloy raw material successively to obtain an alloy ingot;

(2) Post-processing the alloy ingot obtained in the step (1) to obtain a Mg-Sn-based magnesium alloy; the post-processing includes one or more of solution treatment, extrusion and aging treatment.

In the present invention, the alloy raw materials are sequentially smelted and cast to obtain an alloy ingot.

In the present invention, the kinds of alloy raw materials preferably include pure Mg ingots, pure Sn ingots, pure Al ingots, pure Zn ingots and Al-20%Mn master alloys. The present invention has no special requirements on the source of the alloy raw materials, and the raw material sources of magnesium alloys well-known to those skilled in the art or commercially available products can be used.

In the present invention, the temperature of the melting is preferably 710 to 740°C. The present invention has no special requirements on the smelting time, and the smelting time well known to those skilled in the art can ensure that the alloy raw material is completely melted.

In the present invention, after the smelting is completed, it also preferably includes successively feeding argon gas for refining and feeding a mixed protective gas of CO ₂ and SF 6 for slag removal; the refining temperature is preferably 715-725 ° C, so The refining time is preferably 9-11 min. The present invention can effectively remove impurities in the melt through refining and slag removal, improve the purity of the melt, reduce ingot defects and improve the uniformity of the alloy structure, and is more conducive to improving the mechanical properties and processing efficiency of the alloy.

In the present invention, the casting temperature is preferably 680 to 700°C. In the present invention, by controlling the casting temperature within the above-mentioned range, casting defects can be reduced and the uniformity of the alloy structure can be improved.

After the alloy ingot is obtained, the present invention performs post-treatment on the alloy ingot to obtain a Mg-Sn-based magnesium alloy.

In the present invention, the post-treatment includes one or more of solution treatment, extrusion and aging treatment; preferably solution treatment, or sequential solution treatment and extrusion, or sequential solution treatment processing and aging.

In the present invention, when the post-treatment is preferably a solution treatment, the uniformity of the ingot structure can be effectively improved, more intermetallic compounds are redissolved in the matrix, and the alloy is mainly improved by solid solution strengthening. performance and processing efficiency.

In the present invention, when the post-treatment is preferably sequentially performed solution treatment and extrusion, the coarse dendrites can be effectively broken through extrusion deformation, and the grain size can be further refined through dynamic recrystallization of deformation, that is, by Grain refinement strengthening effectively improves the mechanical properties and processing efficiency of the alloy. At the same time, the dispersed dynamic precipitation phase during extrusion can promote the formation of dynamic recrystallization and further improve the microstructure of grains, so that the mechanical properties and processing efficiency of the alloy can be jointly improved by precipitation strengthening and grain refinement strengthening.

In the present invention, when the post-treatment is preferably sequentially performed solution treatment and aging treatment, the coarse intermetallic compound is redissolved by the solution treatment to prepare the structure for the subsequent aging, and then the aging treatment effectively promotes The uniform precipitation of each precipitation phase can effectively improve the mechanical properties and processing efficiency of the alloy.

In the present invention, the solution treatment preferably includes a first-stage solution treatment and a second-stage solution treatment performed in sequence.

In the present invention, the holding temperature of the first-stage solution treatment is preferably 390-410°C, more preferably 400°C; the holding time of the first-stage solution treatment is preferably 10-12h, more preferably 11h.

In the present invention, after the first-stage solution treatment is completed, the temperature is preferably continued to be raised to the holding temperature of the second-stage solution treatment.

In the present invention, the holding temperature of the secondary solid solution treatment is preferably 440-460°C, more preferably 450°C; the holding time of the secondary solid solution treatment is preferably 14-16 h, more preferably 15 h. The invention can ensure that more coarse precipitates are redissolved in the matrix by controlling the holding temperature and holding time of the first-stage solid solution treatment, which is more conducive to realizing solid solution strengthening and improving the performance of the alloy.

In the present invention, the cooling method after the solution treatment is completed is preferably air cooling to room temperature or water cooling to room temperature.

In the present invention, the extrusion temperature is preferably 390-400°C; the extrusion speed is preferably 0.3-3 m/min, more preferably 0.5-2.5 m/min, most preferably 1-2 m/min . By controlling the extrusion temperature and extrusion speed within the above ranges, the invention can reduce the deformation resistance of the alloy, reduce the problem of cracking or cracking in the alloy, and is more conducive to crushing the coarse dendrites in the alloy matrix by extrusion.

In the present invention, the pressure of the extrusion is preferably 130-180 MPa, more preferably 140-160 MPa, and most preferably 150 MPa.

In the present invention, the extrusion ratio during the extrusion is preferably 8-22, more preferably 10-20, and most preferably 12-18. By controlling the extrusion pressure and extrusion ratio within the above-mentioned ranges, the present invention is more favorable for refining the grain size.

In the present invention, the holding temperature of the aging treatment is preferably 170-200°C, more preferably 180-190°C; the holding time of the aging treatment is preferably 0-900h, more preferably 80-700h, and most preferably 100～500h. The present invention can effectively promote the precipitation of each precipitation phase by controlling the holding temperature and holding time of the aging treatment within the above-mentioned ranges, and achieve precipitation strengthening to improve the mechanical properties and processing efficiency of the alloy.

In the present invention, the cooling method after the aging treatment is completed is preferably air cooling to room temperature.

The preparation method provided by the invention has a variety of optional post-treatment combination modes, all of which can obtain magnesium alloys with excellent mechanical properties and processing efficiency, the process is simple, the parameters are easy to control, and the cost is low.

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

The Mg-Sn magnesium alloy provided in this embodiment is composed of the following components by mass percentage: Sn 3.8%, Al 2.82%, Zn 1.39%, Mn 0.61% and the balance Mg.

The preparation method of above-mentioned Mg-Sn series magnesium alloy, concrete steps are as follows:

(1) smelting and casting the alloy raw materials in turn to obtain an alloy ingot; Concrete: take pure Mg ingot, pure Sn, Al, Zn block, Al-20%Mn master alloy as raw material, add in the melting furnace and carry out at 740 ℃ Smelting, after the smelting is completed, the melt is kept at 720 °C and argon gas is introduced for refining for 10 minutes, and then a mixed protective gas of CO ₂ and SF6 is introduced for 1 hour to remove slag; finally, the temperature is lowered to 690 ° C for semi-continuous casting to obtain alloy castings. ingot.

(2) post-processing the alloy ingot obtained in the step (1) to obtain a Mg-Sn-based magnesium alloy; wherein, the post-processing is a solution treatment, specifically a first-level solution treatment and a second-level solution treatment sequentially performed. Solution treatment; more specifically: the alloy ingot is subjected to first-level solution treatment at 400°C for 10 hours, then continues to heat up to 450°C for second-level solution treatment for 16 hours, and finally air-cooled to room temperature.

The photo of the as-cast alloy sample obtained in step (1) of Example 1 of the present invention is shown in FIG. 1 .

It can be seen from Figure 1 that the as-cast alloy obtained by casting has a smooth appearance and no defects.

The microstructure of the as-cast alloy obtained in step (1) of Example 1 was observed with a scanning electron microscope, and the observation results are shown in Figures 2-6. Wherein, Fig. 2 is a low-magnification SEM image of the as-cast alloy obtained in Example 1; Fig. 3 is a high-magnification SEM image of the as-cast alloy in Example 1; High magnification scanning electron microscope images of various AlMn phases in as-stated alloys

It can be seen from Figures 2 to 6 that during the solidification process of the alloy of the present invention, the primary AlMn phase takes the lead in nucleation and growth, and as the temperature decreases, the primary Mg dendrite nucleation growth and eutectic reaction occur in sequence, and the final as-cast microstructure presents a coarse microstructure. α-Mg matrix dendrites and interdendritic dissociated eutectic phases.

Hot compression experiment: The solid solution Mg-Sn-based magnesium alloy finally obtained in Example 1 was machined to obtain 5 groups of cylindrical samples with a size of Φ10mm×12mm. Before thermal compression, the 5 groups of samples were heated to 300°C, 340°C, 380°C, 420°C and 460°C respectively at a rate of 5°C/s, and then stayed for 120s after reaching the above target temperatures to ensure that the samples The whole is uniformly heated to the target temperature. Subsequently, the above-mentioned 5 groups of heated samples were all compressed at the rates of 0.001s ^-1 , 0.01s ^-1 , 0.1s ^-1 , 1s ^-1 and 10s ^-1 to produce -0.8 The amount of strain is then water-cooled and quenched to obtain the sample to be tested. The rheological curve obtained after the hot compression experiment is completed is shown in Figure 7, and the thermal processing diagram obtained after the hot compression experiment is completed is shown in Figure 8.

According to FIGS. 7-8 , the Mg-Sn magnesium alloy prepared in Example 1 of the present invention exhibits good machinability. By calculating the instability criterion, the alloy has a larger machinability range than the AZ31 alloy. . In addition, the alloy of the present invention has a higher power dissipation factor under a high strain rate, which effectively improves the processing efficiency.

Example 2

Take two groups of solid solution state Mg-Sn system magnesium alloy samples prepared in Example 1 and carry out extrusion treatment to obtain the extruded state Mg-Sn system magnesium alloy of Example 2, wherein the parameters of Example 2 when extruding are as shown in the table 1 shown.

Table 1 Parameters of Example 2 when extruding

Billet temperature/℃ Extrusion barrel temperature/℃ Mold temperature/℃ Equipment pressure/MPa Extrusion speed/m/min squeeze ratio Example 2 400 400 400 140 1.0 22:1

The microstructure of the as-extruded Mg-Sn-based magnesium alloy in Example 2 was observed by scanning electron microscope, and the observed microstructure was shown in FIG. 9 .

According to Fig. 9, during the extrusion process, the alloy undergoes dynamic recrystallization process grain refinement, and there are a large number of dynamic precipitation phases distributed in the grain and grain boundaries. Phase dispersion strengthening effectively improves the mechanical properties of Mg-Sn magnesium alloys.

Backscattered electron diffraction (EBSD) was used to characterize the grain orientation distribution of the as-extruded Mg-Sn-based magnesium alloy of Example 2, and its IPF-Z inverse pole figure and (0001) pole figure are shown in Figure 10.

According to Fig. 10, it can be seen that the extruded Mg-Sn alloy has a typical magnesium alloy extruded wire texture, which plays a role in texture strengthening of the alloy, and further improves the mechanical properties of the alloy by combining fine-grain strengthening and dispersion strengthening.

Example 3

The post-processing of step (2) in Example 1 is replaced by the following post-processing process: the alloy ingot obtained in step (1) is successively subjected to solution treatment and aging treatment, more specifically: the alloy ingot is carried out at 400 ° C. First-level solution treatment for 10 hours, then continue to heat up to 450 °C for second-level solution treatment for 16 hours, and finally water-cooled to room temperature;

Example 4

The holding time of the aging treatment in step (2) of Example 3 was replaced by 100h.

Example 5

The holding time of the aging treatment in step (2) of Example 3 was replaced by 300h.

Scanning electron microscope was used to observe the microstructure of the solid solution alloy in Example 3 and the aged alloy finally obtained in Examples 3 to 5. The observed results are shown in FIG. 11 . Among them, Fig. 11(a) is the scanning electron microscope image of the solid solution alloy of Example 3, Fig. 11(b) is the scanning electron microscope image of the aged alloy of Example 3, and Fig. 11(c) is the SEM image of the aged alloy of Example 4 SEM image, FIG. 11(d) is the SEM image of the aged alloy in Example 5.

According to Fig. 11, it can be seen that after the solution treatment of Mg-Sn alloys, there are still a small amount of residual AlMn and Mg ₂ Sn phases that are not completely dissolved. A semi-continuous distribution of precipitates appeared at the grain boundaries, and with the prolongation of aging time, the number density of the precipitates increased continuously, and the size of the precipitates also gradually coarsened.

According to the standard of the national standard GBT228-2002, the as-cast alloy obtained in step (1) in Example 2, the extruded alloy obtained in step (2), the solid solution alloy obtained in step (1) in Example 3 and the alloy in step (2) ) and the aging alloys obtained in Examples 4 to 5 were processed into standard tensile specimens by wire cutting for tensile testing. The tensile specimens were in the shape of round rods, and their axial directions were parallel to the extrusion direction to obtain The tensile test results of each sample are shown in Figure 12.

According to FIG. 12 , the extruded Mg-Sn magnesium alloy obtained in Example 2 of the present invention has a tensile strength of 294 MPa, a yield strength of 201 MPa, an elongation of 18%, and excellent mechanical properties at room temperature.

Hardness test: Using the HV-1000TPTA digital micro-Vickers hardness tester, the aging hardness test was carried out on the samples of Example 5 aged at 180 °C for different time periods. When the sample is completed in the previous time period, the sample is taken out of the heat treatment furnace for testing and then placed in the heat treatment furnace for aging. The aging time at each aging time point is the cumulative aging time).

It can be seen from Fig. 13 that the aging strengthening effect of the Mg-Sn magnesium alloy finally prepared by the present invention is remarkable. The hardness of the alloy increases from ~50HV in the solid solution state with the aging time, and the hardness increases continuously, reaching a peak hardness of ~69HV at 300h, and the hardness is increased by nearly ~ 38%, the hardness did not decrease after the aging time was further extended.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A Mg-Sn-based magnesium alloy, comprising the following components by mass percentage: Sn 2-5%, Al 1.5-4.0%, Zn 1.0-2.0%, Mn 0.3-0.5% and the balance Mg. 2. The Mg-Sn-based magnesium alloy according to claim 1, wherein the Mg-Sn-based magnesium alloy comprises the following components by mass percentage: Sn 2.2-4.8%, Al 1.8-3.8%, Zn 1.2% ~1.8%, Mn 0.32~0.48% and balance Mg. 3. The Mg-Sn-based magnesium alloy according to claim 2, wherein the Mg-Sn-based magnesium alloy comprises the following components by mass percentage: Sn 2.5-4.5%, Al 2-3.5%, Zn 1.4% ~1.6%, Mn 0.35~0.45% and balance Mg. 4. A preparation method of the Mg-Sn system magnesium alloy according to any one of claims 1 to 3, comprising the steps of: (1) smelting and casting the alloy raw material successively to obtain an alloy ingot; (2) Post-processing the alloy ingot obtained in the step (1) to obtain a Mg-Sn-based magnesium alloy; the post-processing includes one or more of solution treatment, extrusion and aging treatment. 5 . The preparation method according to claim 4 , wherein the casting temperature in the step (1) is 680-700° C. 6 . 6. The preparation method according to claim 4, characterized in that, in the step (2), the solution treatment comprises a first-level solution treatment and a second-level solution treatment in sequence; The holding temperature is 390-410°C, the holding time of the first-level solution treatment is 10-12h; the holding temperature of the second-level solution treatment is 440-460°C, and the holding time of the second-level solution treatment is 14-16h. 7 . The preparation method according to claim 4 , wherein in the step (2), the extrusion temperature is 390-400° C., and the extrusion speed is 0.3-3 m/min. 8 . 8. The preparation method according to claim 4 or 7, wherein the extrusion pressure in the step (2) is 130-180 MPa. 9 . The preparation method according to claim 4 or 7 , wherein the extrusion ratio during extrusion in the step (2) is 8-22. 10 . 10 . The preparation method according to claim 4 , wherein in the step (2), the holding temperature of the aging treatment is 170-200° C., and the holding time of the aging treatment is 0-900 h. 11 .

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