High-strength magnesium alloy containing long-period structural phase and preparation method of high-strength magnesium alloy

Abstract

The invention provides a high-strength magnesium alloy containing a long-period structural phase and a preparation method of the high-strength magnesium alloy, and belongs to the technical field of metal materials. The high-strength magnesium alloy containing the long-period structural phase, provided by the invention, comprises the following components in percentage by mass: 3-6% of Y, 1.5-3% of Zn and the balance of Mg, in the high-strength magnesium alloy containing the long-period structure phase, according to the mass content of all elements, Y / Zn is larger than or equal to 1.6 and smaller than or equal to 2.5. The long-period structure phase in the high-strength magnesium alloy is in a needle-shaped lamellar morphology, the lamellar spacing is smaller than 100 nm, the volume fraction exceeds 50%, magnesium matrixes between the lamellas have different orientations, the highest yield strength can reach 477 MPa, the highest tensile strength can reach 528 MPa, and the alloy strength is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to a high-strength magnesium alloy containing a long-period structural phase and a preparation method thereof. Background Art

[0002] Long-period structural phase (LPSO) refers to a phase in which the crystal lattice is arranged periodically and the solute atoms also have a long-range orderly stacking characteristic structure. Introducing a long-period structural phase into a magnesium alloy can effectively improve the strength of the magnesium alloy and solve the problem of low strength of the magnesium alloy.

[0003] However, existing studies on magnesium alloys containing long-period structural phases have found that the magnesium matrix between the long-period structural phase layers of magnesium alloys has the same orientation, and the strengthening effect is limited. In addition, the volume fraction of the long-period structural phase in the magnesium alloys containing long-period structural phases in the prior art is small, the spacing between the long-period structural phases is large, and they are not lamellar, and the strengthening potential of the long-period structural phases of magnesium alloys is not fully utilized. The tensile strength of magnesium alloys containing long-period structural phases in the prior art is mostly 200-300MPa, and the yield strength is mostly 100-200MPa, which cannot meet the high-strength requirements.

[0004] Therefore, providing a magnesium alloy with higher strength that can further exert the strengthening effect of the long-period structure relative to magnesium alloy has become a technical problem that needs to be urgently solved in the field. Summary of the invention

[0005] The object of the present invention is to provide a high-strength magnesium alloy containing a long-period structural phase and a preparation method thereof. The high-strength magnesium alloy containing a long-period structural phase provided by the present invention has the characteristic of high strength.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a high-strength magnesium alloy containing a long-period structural phase, which comprises, by mass percentage, 3-6% Y, 1.5-3% Zn and the balance Mg;

[0008] In the high-strength magnesium alloy containing the long-period structural phase, based on the mass content of each element, 1.6≤Y / Zn≤2.5.

[0009] Preferably, the high-strength magnesium alloy containing a long period structural phase comprises, by mass percentage, 3.2-5% Y, 1.9-2.5% Zn and the balance Mg.

[0010] Preferably, the high-strength magnesium alloy containing a long period structural phase comprises, by mass percentage, 4-5% Y, 2-2.2% Zn and the balance Mg.

[0011] Preferably, in the high-strength magnesium alloy containing a long period structural phase, based on the mass content of each element, 2≤Y / Zn≤2.5.

[0012] Preferably, the long-period structural phase has a needle-like lamellar morphology, the magnesium matrix between the lamellar layers has different orientations, the lamellar spacing is less than 100 nm, and the volume fraction of the long-period structural phase is greater than 50%.

[0013] The present invention provides a method for preparing a high-strength magnesium alloy containing a long-period structural phase as described in the above technical solution, comprising: smelting the alloy raw material and casting it to obtain a magnesium alloy casting rod, and then sequentially performing heat treatment and hot extrusion to obtain a high-strength magnesium alloy containing a long-period structural phase.

[0014] Preferably, multiple passes of rotary forging are performed after the hot extrusion is completed.

[0015] Preferably, the temperature of the heat treatment is 500-530° C., and the holding time of the heat treatment is 10-20 hours.

[0016] Preferably, the deformation amount of a single pass of the multi-pass rotary forging is 1-3%.

[0017] Preferably, the total deformation of the multi-pass rotary forging is 15-90%.

[0018] The present invention provides a high-strength magnesium alloy containing a long-period structural phase, which comprises, by mass percentage, 3-6% Y, 1.5-3% Zn and the remainder Mg; in the high-strength magnesium alloy containing a long-period structural phase, by mass percentage, 1.6≤Y / Zn≤2.5. The high-strength magnesium alloy containing a long-period structural phase provided by the present invention adjusts the content of the Y element and the Zn element, adjusts the size and content of the long-period structural phase in the magnesium alloy, gives full play to the strengthening effect of the long-period structural phase, and improves the mechanical properties of the magnesium alloy; by limiting the mass ratio of the Y element and the Zn element, the mechanical properties of the magnesium alloy are further improved. The results of the embodiment show that the long-period structural phase in the high-strength magnesium alloy provided by the present invention has a needle-like lamellar morphology, the lamellar spacing is less than 100nm, the volume fraction exceeds 50%, the magnesium matrix between the lamellars has different orientations, the yield strength can reach up to 477MPa, the tensile strength can reach up to 528MPa, and the alloy strength is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A microstructure diagram of a long-period structural phase of a high-strength magnesium alloy containing a long-period structural phase prepared in Example 1 of the present invention under a scanning electron microscope;

[0020] Figure 2 The microstructure diagram of the long period structure phase of the high-strength magnesium alloy containing the long period structure phase prepared in Example 1 of the present invention under a transmission electron microscope;

[0021] Figure 3 is a microstructure diagram of a long period structure phase of a high-strength magnesium alloy containing a long period structure phase prepared in Example 2 of the present invention under a scanning electron microscope;

[0022] Figure 4 is a microstructure diagram of a long period structure phase of a high-strength magnesium alloy containing a long period structure phase prepared in Example 2 of the present invention under a transmission electron microscope;

[0023] Figure 5 is a microstructure diagram of the long period structure phase of the magnesium alloy prepared in Example 3 of the present invention under a scanning electron microscope;

[0024] Figure 6 is a microstructure diagram of the long period structure phase of the magnesium alloy prepared in Example 3 of the present invention under a transmission electron microscope;

[0025] Figure 7 is a microstructure diagram of the long period structure phase of the magnesium alloy prepared in Example 4 of the present invention under a transmission electron microscope;

[0026] Figure 8 This is a microstructure diagram of the long period structure phase of the magnesium alloy prepared in Comparative Example 1 of the present invention under a transmission electron microscope. DETAILED DESCRIPTION

[0027] The present invention provides a high-strength magnesium alloy containing a long-period structural phase, which comprises, by mass percentage, 3-6% Y, 1.5-3% Zn and the balance Mg;

[0028] In the high-strength magnesium alloy containing the long-period structural phase, based on the mass content of each element, 1.6≤Y / Zn≤2.5.

[0029] The high-strength magnesium alloy containing a long-period structural phase provided by the present invention includes Y3-6%, preferably 3.2-5%, and more preferably 4-5%, by mass percentage. In the present invention, Y can react with Zn element to form a long-period ordered phase. The present invention limits the content of Y element to the above range to ensure that the long-period structural phase in the magnesium alloy exerts its strengthening effect and improves the strength of the magnesium alloy.

[0030] The high-strength magnesium alloy containing a long-period structural phase provided by the present invention includes Zn 1.5-3%, preferably 1.9-2.5%, and more preferably 2-2.2%, by mass percentage. In the present invention, Zn can react with the Y element to form a long-period ordered phase. The present invention limits the content of Zn to the above range so that it can work together with Y to ensure that the long-period structural phase in the magnesium alloy has a suitable size and content, thereby improving the strength of the magnesium alloy.

[0031] In the present invention, the mass content of the Y and Zn elements is 1.6≤Y / Zn≤2.5, preferably 2≤Y / Zn≤2.5, based on the mass content of each element. In the present invention, if the mass ratio of the Y / Zn alloy element content is too low, the long period structure phase formed in the magnesium alloy is too small; if the mass ratio of the Y / Zn alloy element content is too high, the long period structure phase formed in the magnesium alloy is too coarse, and the long period structure phase with a needle-like morphology and a lamellar spacing of less than 100nm is too small. The present invention can form a certain number and size of long period structure phases by controlling the addition ratio of Y and Zn within the above range, thereby improving the mechanical properties of the alloy.

[0032] In the present invention, the content of impurity elements in the high-strength magnesium alloy containing a long period structural phase is preferably less than 0.06%; in the present invention, the impurity elements preferably include Fe, Si, Cu and Ni; the content of Fe is preferably less than 0.02%; the content of Si is preferably less than 0.05%, the content of Cu is preferably less than 0.02%, and the content of Ni is preferably less than 0.001%. The present invention limits the content of impurity elements to the above range to ensure that the magnesium alloy has good strength.

[0033] In the present invention, the long-period structural phase preferably has a needle-like lamellar morphology, the magnesium matrix between each lamellar has different orientations, the lamellar spacing is less than 100nm, and the volume fraction of the long-period structural phase is greater than 50%. The present invention limits the morphology and content of the long-period structural phase to the above range, which can significantly improve the strength of the magnesium alloy; the present invention limits the morphology of the long-period structural phase and the orientation of the magnesium matrix between each lamellar to the above types, which can further improve the strength of the magnesium alloy.

[0034] The high-strength magnesium alloy containing a long-period structural phase provided by the present invention adjusts the content of the Y element and the Zn element, adjusts the size and content of the long-period structural phase in the magnesium alloy, gives full play to the strengthening effect of the long-period structural phase, and improves the mechanical properties of the magnesium alloy; and further improves the mechanical properties of the magnesium alloy by limiting the mass ratio of the Y element and the Zn element.

[0035] The present invention also provides a method for preparing the high-strength magnesium alloy containing the long-period structural phase described in the above technical solution, comprising: melting the alloy raw material and casting it to obtain a magnesium alloy cast rod, and then performing heat treatment and hot extrusion in sequence to obtain a high-strength magnesium alloy containing the long-period structural phase.

[0036] The invention melts the alloy raw material and then casts it to obtain a magnesium alloy casting rod, and then sequentially performs heat treatment and hot extrusion to obtain a high-strength magnesium alloy containing a long-period structural phase.

[0037] In the present invention, the alloy raw material is a conventional raw material for preparing magnesium alloys that can be obtained by those skilled in the art, and can be added according to the requirements of the alloy composition of the magnesium alloy.

[0038] In the present invention, the smelting and casting is a conventional smelting and casting technology used by those skilled in the art, and any method capable of obtaining magnesium alloy cast rods is sufficient.

[0039] In the present invention, the temperature of the heat treatment is preferably 500-530°C, more preferably 510-525°C; the holding time of the heat treatment is preferably 10-20h, more preferably 15-20h. In the present invention, if the heat treatment temperature is too low and the holding time is too short, the interlamellar spacing of the long-period structural phase will be too large, the needle-like morphology will be discontinuous, and the content will be too little and the holding time will be too long, overburning will easily occur, resulting in decreased mechanical properties. The present invention limits the heat treatment temperature and holding time to the above range to ensure that the long-period structural phase in the magnesium alloy has good morphology, size and content, thereby improving the strength of the magnesium alloy.

[0040] The present invention has no special limitation on the extrusion temperature and extrusion ratio of the hot extrusion. The magnesium alloy can be obtained by hot extruding the heat-treated magnesium alloy using conventional hot extrusion methods in the art.

[0041] After hot extrusion is completed, the present invention preferably performs multiple passes of rotary forging to obtain a high-strength magnesium alloy containing a long-period structural phase.

[0042] In the present invention, the multi-pass rotary forging is preferably carried out at room temperature; the deformation of a single pass of the multi-pass rotary forging is preferably 1-3%, more preferably 2.5-3%; the total deformation of the multi-pass rotary forging is preferably 15-90%, more preferably 25-70%, and further preferably 25-50%. The present invention can ensure the orientation difference of the magnesium matrix between the long-period structural phase layers in the magnesium alloy through multi-pass rotary forging, and further improve the strength of the magnesium alloy. The present invention limits the deformation of a single pass of the multi-pass rotary forging to the above range to avoid the situation where the deformation of the pass is too small, resulting in a small increase in the orientation difference of the magnesium matrix between the layers, or the deformation of the pass is too large, resulting in fracture, thereby improving the strength of the magnesium alloy.

[0043] In the present invention, the feed direction is preferably changed after each pass of rotary forging during the multi-pass rotary forging process. The present invention ensures the straightness of the bar by changing the feed direction after each pass of rotary forging.

[0044] The invention can ensure that the long period structural phase in the magnesium alloy has good morphology, size and quantity through heat treatment and multi-pass rotary forging, and improve the orientation difference of the magnesium matrix between the lamellar layers, thereby further improving the strength of the magnesium alloy.

[0045] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Example 1

[0047] A high-strength magnesium alloy containing a long period structural phase, the composition of which is, by mass percentage, 3.2% Y, 1.9% Zn, 0.003% Fe, 0.01% Si, 0.009% Cu, 0.0005% Ni and the balance Mg; wherein Y / Zn=1.68;

[0048] The method for preparing the high-strength magnesium alloy containing a long period structural phase comprises the following steps:

[0049] The alloy raw materials are melted and then cast to obtain magnesium alloy cast rods (Mg-Y-Zn alloy cast rods), which are kept at 525°C in a heat treatment furnace for 20 hours, and then hot extruded at an extrusion temperature of 420°C and an extrusion ratio of 25. After hot extrusion, multiple rotary forgings are performed at room temperature, and the deformation of a single rotary forging is 3%. The feeding direction is changed after each rotary forging to ensure the straightness of the rod. The total deformation is 30%, and a high-strength magnesium alloy containing a long-period structural phase is obtained.

[0050] The alloy microstructure of the high-strength magnesium alloy containing a long period structural phase obtained in Example 1 is as follows: Figure 1 and Figure 2 As shown, from Figure 1 and Figure 2 It can be seen that the long-period structural phase presents a needle-like lamellar morphology, with an interlamellar spacing of 89nm and a volume fraction of 63%. The magnesium matrix between each lamellar has different orientations.

[0051] The tensile properties of the obtained high-strength magnesium alloy containing a long period structural phase were tested according to GB / T 16865-2013, and the yield strength was 458 MPa and the tensile strength was 510 MPa.

[0052] Example 2

[0053] A high-strength magnesium alloy containing a long period structural phase, the composition of which is, by mass percentage, 4.7% Y, 2.2% Zn, 0.006% Fe, 0.01% Si, 0.008% Cu, 0.0005% Ni and the balance Mg; wherein Y / Zn=2.14;

[0054] The method for preparing the high-strength magnesium alloy containing a long period structural phase comprises the following steps:

[0055] The alloy raw materials are melted and then cast to obtain magnesium alloy cast rods (Mg-Y-Zn alloy cast rods), which are kept at 520°C in a heat treatment furnace for 18 hours, and then hot extruded at an extrusion temperature of 420°C and an extrusion ratio of 25. After hot extrusion, multiple rotary forgings are performed at room temperature, and the deformation of a single rotary forging is 2.5%. The feeding direction is changed after each rotary forging to ensure the straightness of the rod. The total deformation is 25%, and a high-strength magnesium alloy containing a long-period structural phase is obtained.

[0056] The alloy microstructure of the high-strength magnesium alloy containing a long period structural phase obtained in Example 2 is as follows: Figure 3 and Figure 4 As shown, from Figure 3 and Figure 4 It can be seen that the long-period structural phase presents a needle-like lamellar morphology, with an interlamellar spacing of 93nm and a volume fraction of 56%. The magnesium matrix between each lamellar has different orientations.

[0057] The tensile properties of the obtained high-strength magnesium alloy containing a long period structural phase were tested according to GB / T 16865-2013, and the yield strength was 477 MPa and the tensile strength was 528 MPa.

[0058] Example 3

[0059] The only difference between Example 3 and Example 1 is that the heat treatment temperature is 450° C., and the rest is the same as Example 1.

[0060] The alloy microstructure of the magnesium alloy containing the long period structural phase obtained in Example 3 is as follows: Figure 5 and Figure 6 As shown, from Figure 5 and Figure 6 It can be seen that the interlamellar spacing of the long period structure phase in the magnesium alloy is relatively large, the interlamellar spacing is 153nm, the needle-like morphology is discontinuous, and the content is too small, with a volume fraction of only 14%.

[0061] The tensile properties of the obtained magnesium alloy were tested according to GB / T 16865-2013, and the yield strength was 401 MPa and the tensile strength was 472 MPa.

[0062] Example 4

[0063] The difference between Example 4 and Example 1 is that the multi-pass rotary forging at room temperature is not performed, and the other conditions are the same as Example 1.

[0064] The alloy microstructure of the magnesium alloy containing the long period structural phase obtained in Example 4 is as follows: Figure 7 As shown, from Figure 7It can be seen that the long-period structural phase presents a needle-like lamellar morphology, with an interlamellar spacing of 89nm and a volume fraction of 63%, and the magnesium matrix between each lamellar has the same orientation.

[0065] The tensile properties of the obtained magnesium alloy were tested according to GB / T 16865-2013, and the yield strength was 228 MPa and the tensile strength was 312 MPa.

[0066] Comparative Example 1

[0067] A magnesium alloy, the composition of which is, by mass percentage, 8.1% Y, 1.9% Zn, 0.009% Fe, 0.01% Si, 0.01% Cu, 0.0006% Ni and the balance Mg; wherein Y / Zn=4.26;

[0068] The preparation method of Comparative Example 1 is the same as that of Example 1.

[0069] The alloy microstructure of the magnesium alloy obtained in Comparative Example 1 is as follows Figure 8 As shown, from Figure 8 It can be seen that the long-period structural phase is mainly in the form of large blocks and coarse flakes, and the volume fraction of needle-shaped flakes is very small.

[0070] The tensile properties of the obtained magnesium alloy were tested according to GB / T 16865-2013, and the yield strength was 398 MPa and the tensile strength was 469 MPa.

[0071] The high-strength magnesium alloy containing a long-period structural phase prepared in Examples 1 and 2 of the present invention adjusts the content of the Y element and the Zn element, adjusts the size and content of the long-period structural phase in the magnesium alloy, gives full play to the strengthening effect of the long-period structural phase, and improves the mechanical properties of the magnesium alloy; the mechanical properties of the magnesium alloy are further improved by heat treatment and multi-pass rotary forging, and adjusting the process parameters. The long-period structural phase in the high-strength magnesium alloy containing a long-period structural phase prepared in Examples 1 and 2 has a needle-like lamellar morphology, the lamellar spacing is less than 100nm, the volume fraction exceeds 50%, and the magnesium matrix between each lamellar has different orientations. The yield strength can reach up to 477MPa, and the tensile strength can reach up to 528MPa. The yield strength and tensile strength are increased by 15-20% and 9-13% respectively compared with Comparative Example 1; compared with Example 3, they are increased by 14-19% and 8-12%, respectively, and compared with Example 4, they are increased by 101-109% and 63-69%, respectively. It shows that the high-strength magnesium alloy containing a long-period structural phase prepared in Examples 1 and 2 has higher strength.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high-strength magnesium alloy containing a long period structural phase, comprising, by mass percentage: Y3-6%, Zn 1.5-3% and the balance Mg; In the high-strength magnesium alloy containing the long-period structural phase, based on the mass content of each element, 1.6≤Y / Zn≤2.

5.

2. The high-strength magnesium alloy containing a long period structural phase according to claim 1, characterized in that: The high-strength magnesium alloy containing a long-period structural phase comprises, by mass percentage, 3.2-5% Y, 1.9-2.5% Zn and the balance Mg.

3. The high-strength magnesium alloy containing a long period structural phase according to claim 2, characterized in that: The high-strength magnesium alloy containing a long-period structural phase comprises, by mass percentage, 4-5% Y, 2-2.2% Zn and the balance Mg.

4. The high-strength magnesium alloy containing a long period structural phase according to any one of claims 1 to 3, characterized in that: In the high-strength magnesium alloy containing the long-period structural phase, based on the mass content of each element, 2≤Y / Zn≤2.

5.

5. The high-strength magnesium alloy containing a long period structural phase according to claim 1, characterized in that: The long-period structural phase has a needle-like lamellar morphology, the magnesium matrix between the lamellar layers has different orientations, the lamellar spacing is less than 100nm, and the volume fraction of the long-period structural phase is greater than 50%.

6. A method for preparing a high-strength magnesium alloy containing a long period structural phase according to any one of claims 1 to 5, comprising: The alloy raw materials are melted and then cast to obtain magnesium alloy casting rods, which are then subjected to heat treatment and hot extrusion in sequence to obtain a high-strength magnesium alloy containing a long-period structural phase.

7. The preparation method according to claim 6, characterized in that: After the hot extrusion is completed, multiple rotary forgings are performed.

8. The preparation method according to claim 6, characterized in that: The temperature of the heat treatment is 500-530° C., and the heat preservation time of the heat treatment is 10-20 hours.

9. The preparation method according to claim 7, characterized in that: The deformation amount of a single pass of the multi-pass rotary forging is 1-3%.

10. The preparation method according to claim 7, characterized in that: The total deformation amount of the multi-pass rotary forging is 15-90%.

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