Ultra-light high-strength dual-phase magnesium-lithium alloy, preparation method and use thereof

Abstract

The present invention provides an ultra-light high-strength and tough dual-phase magnesium-lithium alloy, a preparation method and use thereof, and the preparation method of the ultra-light high-strength and tough dual-phase magnesium-lithium alloy comprises the following steps: weighing alloy smelting raw materials according to the following ratios: Li: 6-9wt.%; Al: 3-5wt.%; Ca: 0.1-0.5wt.%; Y: 0.1-0.5wt.%; Sn: 0.5-2.0wt.%; the rest is Mg and inevitable impurity elements; smelting the raw materials in a vacuum induction furnace; homogenizing and solution treating the magnesium-lithium alloy ingot; hot extruding the ingot; hot rolling the magnesium-lithium alloy extrusion at medium and low temperature; rolling the hot-rolled sample at room temperature to obtain an ultra-light high-strength and tough dual-phase magnesium-lithium alloy. The method can effectively refine the grains, inhibit the aging softening process of the β phase of the magnesium-lithium alloy, regulate the deformation consistency of the dual phases, effectively improve the mechanical properties of the magnesium-lithium alloy, and improve the synergistic matching of the strength and plasticity of the magnesium-lithium alloy.

Description

Technical Field

[0001] The present invention relates to magnesium-lithium alloy technology, and in particular to an ultra-light high-strength and tough dual-phase magnesium-lithium alloy, a preparation method thereof and uses thereof. Background Art

[0002] As an ultra-light metal material, magnesium-lithium alloy has the advantages of high specific strength, specific stiffness, good electromagnetic shielding, good room temperature processability, etc. The density is 1.35-1.65g / cm 3 , 30% lower than the density of aluminum, is the preferred metal for lightweight application needs. As the lightest metal structural material in the world, magnesium-lithium alloy can meet the needs of lightweight electronic equipment. The thermal conductivity and electrical conductivity of magnesium-lithium alloy are much higher than those of plastics and composite materials, which can achieve better heat dissipation effect and avoid the defects of poor heat dissipation of thin and light notebooks and mobile phone shells. Magnesium-lithium alloy has good shock absorption performance and a large internal friction coefficient. It can consume energy inside the metal, which can effectively improve the stability of the product; and it has high electromagnetic shielding performance, and has a good shielding effect on electromagnetic waves of different bands, which can improve the safety and accuracy of the equipment. Magnesium-lithium alloy has excellent cold processing performance and can be stamped and formed at room temperature to improve production efficiency. These advantages make it a good candidate material for the shells of portable electronic devices such as notebooks and mobile phones. Therefore, magnesium-lithium alloy is widely used in aerospace, military, transportation, 3C electronic equipment and other fields.

[0003] However, magnesium-lithium alloys have low absolute strength, poor corrosion resistance, and aging softening characteristics, which limit the application of magnesium-lithium alloys. The document Materials Science & Engineering A, 2022, 857: 144039 describes the influence of element Y on the structure and properties of dual-phase magnesium-lithium alloys, but it is found that although element Y enhances the mechanical properties of the alloy, its strength improvement is limited. Journal of Rare Earths, 2016, 34 (6) describes the influence of the introduction of element Y on the structure and properties of dual-phase magnesium-lithium alloys, but the single extrusion process has limitations on the improvement of alloy strength. Rare Metal Materials and Engineering, 2013, 42 (10): 1993-1998 mentions that element Y improves the corrosion resistance of dual-phase magnesium-lithium alloys, but the mechanical properties of extruded magnesium-lithium alloys are relatively improved. Patents 201610445399.3 and 201610412731.6 mention that the Y element optimizes the corrosion resistance and mechanical properties of dual-phase magnesium-lithium alloys, but the strength improvement is relatively low, and alloying has certain limitations in improving the corrosion performance of magnesium-lithium alloys. Therefore, improving the mechanical properties of magnesium-lithium alloys is one of the important issues that need to be solved in magnesium-lithium alloys. Summary of the invention

[0004] The purpose of the present invention is to propose a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy in response to the problem that the mechanical properties of traditional magnesium-lithium alloys need to be improved. The method can effectively refine the grains, inhibit the aging softening process of the β phase of the magnesium-lithium alloy, regulate the deformation consistency of the dual phases, effectively improve the mechanical properties of the magnesium-lithium alloy, and improve the synergistic matching of the strength and plasticity of the magnesium-lithium alloy.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, comprising the following steps:

[0006] Step (1) Weigh the alloy smelting raw materials according to the following mass percentages:

[0007]

[0008] The rest are Mg and unavoidable impurity elements; unless otherwise specified, % in this article refers to mass percentage;

[0009] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot;

[0010] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot;

[0011] Step (4) hot extruding the ingot after heat treatment (homogenization treatment and solution treatment) to obtain a magnesium-lithium alloy extrusion;

[0012] Step (5) hot rolling the magnesium-lithium alloy extrusion at medium and low temperatures;

[0013] Step (6) rolling the hot-rolled sample at room temperature to obtain an ultra-light and high-strength dual-phase magnesium-lithium alloy product.

[0014] Furthermore, in step (1), the alloy smelting raw materials are weighed according to the following mass percentages:

[0015]

[0016]

[0017] The rest is Mg and inevitable impurity elements.

[0018] Furthermore, the purity of the raw materials magnesium blocks, aluminum particles, tin particles, and lithium particles is greater than or equal to 99.99%, and the Y element and Ca element are Mg-30Y and Mg-20Ca alloys, respectively, with a purity greater than or equal to 99.97%, so as to reduce the impact of impurity elements on the quality of the ingot.

[0019] Furthermore, step (1) pre-treats the raw materials for alloy smelting, and the raw material pre-treatment includes: taking out pure Li from paraffin oil, performing surface ultrasonic degreasing treatment in acetone solution, and then placing it in a vacuum drying oven for drying for standby use; first removing the surface oxide layer of the raw materials except Li particles, and then ultrasonically cleaning and drying with anhydrous ethanol, and after treatment, all raw materials are vacuum sealed for standby use.

[0020] Furthermore, before smelting in step (2), the crucible in the vacuum induction furnace is preheated at 300-500° C. for 30-60 min, and the ingot mold is heated to 150-200° C. and kept warm until the smelting is completed; after the crucible is preheated, when the crucible temperature drops below 100° C., a high-purity magnesium block and a high-purity aluminum block are placed in the crucible, and pure Li particles are placed in a secondary feeding bin for gas washing;

[0021] After the gas washing is completed, the vacuum is evacuated to 0.02-0.05MPa, and argon is filled in. The heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for 5-10 minutes and argon is filled in again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400-600r / min for 1-2 minutes. After stirring, the crucible is kept warm for 3-5 minutes.

[0022] Furthermore, in step (3), homogenization treatment: temperature 250-260° C., heat preservation time 3-4 h, air cooling treatment.

[0023] Furthermore, in step (3), solution treatment is performed at a temperature of 350 to 400° C., a holding time of 0.5 to 3 h, and water quenching.

[0024] Furthermore, in step (4), hot extrusion: temperature 260-300° C., extrusion rate 0.5-2 mm / s, extrusion ratio 25:1-45:1, water quenching.

[0025] Further, in step (5), the medium-low temperature hot rolling comprises the following steps:

[0026] The first stage of hot rolling: temperature 260-300℃, deformation 50-55%, reduction 10-20% per pass;

[0027] Cooling control: Cooling (such as water spray cooling), cooling rate 5 ~ 10 ℃ / min, the final temperature is controlled 5 ~ 10 ℃ above the second stage rolling temperature;

[0028] The second stage of hot rolling: temperature 50-100°C, deformation 15-20%, reduction 5-10% per pass, water quenching.

[0029] Furthermore, in step (6), the room temperature rolling temperature is 25 to 45° C., the deformation amount is 8 to 10%, and the reduction amount per pass is 1 to 5%.

[0030] Furthermore, the total deformation in step (5) and step (6) is 73-85%, and the final thickness is 2-3 mm.

[0031] Another object of the present invention is to disclose an ultra-light and high-strength dual-phase magnesium-lithium alloy prepared by the above method.

[0032] Furthermore, the density of the ultra-light and high-strength dual-phase magnesium-lithium alloy is less than or equal to 1.65 g / cm 3 .

[0033] Furthermore, the ultra-light and high-strength dual-phase magnesium-lithium alloy has a tensile strength of 280 to 310 MPa and an elongation of 7 to 15%.

[0034] Another object of the present invention is to disclose an ultra-light and high-strength dual-phase magnesium-lithium alloy for high-end 3C product structural parts: laptop computer shells, tablet computer shells, etc.; military equipment: sights, stocks, smart helmet brackets, etc. in individual intelligent equipment and partial structures of the missile body, inertial navigation structures, guidance systems and other parts; aviation: fighter jets, bombers, helicopters, transport aircraft, airborne radars, inertial navigation equipment and other components; aerospace: gyroscope mounting frame plates, spherical gyroscopes, accelerometer shells, spacecraft frames, brackets and other structural parts on spacecraft.

[0035] The ultra-light and high-strength dual-phase magnesium-lithium alloy of the present invention, its preparation method and use have the following advantages compared with the prior art:

[0036] The present invention adopts vacuum induction melting in an argon protective atmosphere to prepare an ultra-light, high-strength and tough dual-phase magnesium-lithium alloy and provides a processing technology for optimizing the mechanical properties of the magnesium-lithium alloy. The introduction of the Ca element first refines the α-Mg phase in the dual-phase magnesium-lithium alloy, and the Al 2 The Ca precipitation phase improves the corrosion resistance of the magnesium-lithium alloy. The introduction of Y element not only refines the α-Mg phase, but also forms Al 2 Y precipitation phase, Al 2 The introduction of Y phase improves the strength of β phase and reduces MgLi 2 Al and Mg 17 Al 12 phase, inhibiting the formation process of AlLi aging softening phase, regulating the deformation coordination of the two phases, slowing down the occurrence of plastic instability of magnesium-lithium alloy, and 2 Y and Al 2 The improvement of the strength of magnesium-lithium alloy by Ca precipitation is limited. The introduction of Sn element to form Mg 2 Sn is a strengthening phase with good thermal stability, which greatly improves the strength of magnesium-lithium alloys.

[0037] The strength and plasticity of traditional cast magnesium-lithium alloys are far from meeting the application requirements. Large variable hot extrusion is used to improve the recrystallization degree of the dual phase. 2 Y and Al 2 The Ca second phase can pin the grain boundary during hot extrusion, inhibit the growth of recrystallized grains, further refine the α phase and β phase, and then carry out hot rolling combined with medium and low temperature. Medium temperature rolling improves the deformation energy storage of magnesium-lithium alloy and further promotes MgLi 2 The precipitation of Al strengthening phase, low temperature hot rolling improves the dislocation density of the dual-phase magnesium-lithium alloy, and enhances the strength of γ and α fiber texture. Finally, room temperature rolling further increases the dislocation density in the matrix, strengthens the improvement of α and γ fiber texture on the strength of the dual-phase magnesium-lithium alloy, and improves the contribution of work hardening to the strength of the magnesium-lithium alloy. At the same time, the introduction of a large number of micro-nano precipitated phases and subgrain boundaries improves the plasticity of the magnesium-lithium alloy, further improves the synergistic matching of strength and plasticity of the dual-phase magnesium-lithium alloy, and ensures that the density of the dual-phase magnesium-lithium alloy is 1.65g / cm 3 Finally, an ultra-light, high-strength and tough dual-phase magnesium-lithium alloy sheet is obtained.

[0038] In summary, the preparation method of the ultra-light and high-strength dual-phase magnesium-lithium alloy of the present invention can greatly improve the strength of the magnesium-lithium alloy, while continuing the excellent elongation of the magnesium-lithium alloy, inhibiting the aging softening process of the β phase of the magnesium-lithium alloy, and controlling the density of the magnesium-lithium alloy at 1.65g / cm 3 Within the range of 10000~20000, an ultra-light, high-strength and tough dual-phase magnesium-lithium alloy with certain corrosion resistance is finally obtained to meet the application needs in aerospace, military equipment, rail transportation and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the preparation method of ultra-light and high-strength dual-phase magnesium-lithium alloy;

[0040] Figure 2 is the density of magnesium-lithium alloy with different components. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with embodiments:

[0042] Figure 1 This is a schematic diagram of the preparation method of an ultra-light and high-strength dual-phase magnesium-lithium alloy, in which the melting, heat treatment and deformation processing of the ingot are carried out in sequence.

[0043] Example 1

[0044] This embodiment discloses a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, and the specific steps are as follows:

[0045] Step (1) Prepare the raw materials for use.

[0046] The raw materials are as follows by mass percentage: Li: 9wt.%, Al: 3wt.%, Ca: 0.5wt.%, Y: 0.5wt.%, Sn: 1.5wt.%, and the rest are Mg and unremovable impurity elements, wherein the purity of magnesium blocks, aluminum particles, tin particles, and lithium particles all reach 99.99%, and the Y element and Ca element are Mg-30Y and Mg-20Ca alloys respectively, and the purity both reach 99.97%. Among them, all raw materials except Li particles need to be treated to remove the surface oxide layer, and then ultrasonically cleaned with anhydrous ethanol and blown dry. After treatment, all raw materials are vacuum sealed for standby use.

[0047] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot.

[0048] Before smelting, the crucible in the vacuum induction furnace is preheated at 300°C for 60 minutes. After the preheating is completed, when the crucible temperature drops below 100°C, high-purity magnesium blocks and high-purity aluminum blocks are placed in the crucible, and pure lithium particles are placed in the secondary feeding box for gas washing;

[0049] After the gas washing is completed, the crucible is evacuated to 0.02MPa, filled with argon, and the heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for a period of time, and argon is filled again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400r / min for 1min. After the stirring is completed, it is kept warm for a period of time, and the insulation time is 3min.

[0050] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot.

[0051] Homogenization treatment: temperature 250℃, holding time 4h, air cooling treatment;

[0052] Solution treatment temperature is 400℃, holding time is 0.5h, and water quenching is performed.

[0053] Step (4) hot extruding the heat-treated ingot.

[0054] Hot extrusion process: temperature 260℃, extrusion rate 1mm / s, extrusion ratio 45:1, water quenching.

[0055] Step (5) performs medium and low temperature combined hot rolling on the magnesium-lithium alloy extrusions.

[0056] Medium and low temperature combined with hot rolling, including the following steps:

[0057] The first stage of hot rolling: temperature 260℃, deformation 50%, and reduction of 20% per pass;

[0058] Cooling control: water spray cooling, cooling rate 5℃ / min, the final temperature is controlled to be about 10℃ above the second stage rolling temperature;

[0059] The second stage of hot rolling: temperature 100°C, deformation 20%, reduction of 10% per pass, water quenching.

[0060] Step (6) rolling the hot-rolled sample at room temperature to obtain a finished dual-phase magnesium-lithium alloy.

[0061] Room temperature rolling: temperature 25℃, deformation 10%, reduction 1% per pass, final deformation 80%, thickness 2mm.

[0062] The mechanical properties of this ultra-light and high-strength magnesium-lithium alloy are: tensile strength 303.8MPa, elongation 13.6%, density 1.53g / cm 3 .

[0063] Example 2

[0064] This embodiment discloses a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, and the specific steps are as follows:

[0065] Step (1) Prepare the raw materials for use.

[0066] The raw materials are as follows by mass percentage: Li: 9wt.%, Al: 3wt.%, Ca: 0.5wt.%, Y: 0.5wt.%, Sn: 1.5wt.%, and the rest are Mg and irremovable impurity elements, among which the purity of magnesium blocks, aluminum particles, tin particles, and lithium particles all reach 99.99%, and the Y element and Ca element are Mg-30Y and Mg-20Ca alloys respectively, with a purity of 99.97%. Among them, all raw materials except Li particles need to be treated to remove the surface oxide layer, and then ultrasonically cleaned with anhydrous ethanol and blown dry. After treatment, all raw materials are vacuum sealed for standby use.

[0067] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot.

[0068] Before smelting, the crucible in the vacuum induction furnace is preheated at 300°C for 60 minutes. After the preheating is completed, when the crucible temperature drops below 100°C, high-purity magnesium blocks and high-purity aluminum blocks are placed in the crucible, and pure lithium particles are placed in the secondary feeding bin for gas washing.

[0069] After the gas washing is completed, the crucible is evacuated to 0.02MPa, filled with argon, and the heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for a period of time, and argon is filled again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400r / min for 1min. After the stirring is completed, it is kept warm for a period of time, and the insulation time is 3min.

[0070] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot.

[0071] Homogenization treatment: temperature 250℃, holding time 4h, air cooling treatment;

[0072] Solution treatment temperature is 400℃, holding time is 0.5h, and water quenching is performed.

[0073] Step (4) subjecting the heat-treated ingots to medium-low temperature combined hot rolling.

[0074] Medium and low temperature combined with hot rolling, including the following steps:

[0075] The first stage of hot rolling: temperature 260℃, deformation 50%, and reduction of 20% per pass;

[0076] Cooling control: water spray cooling, cooling rate 5℃ / min, the final temperature is controlled to be 10℃ above the second stage rolling temperature;

[0077] The second stage of hot rolling: temperature 100°C, deformation 20%, reduction of 10% per pass, water quenching.

[0078] Step (5) rolling the hot-rolled sample at room temperature to obtain a finished dual-phase magnesium-lithium alloy.

[0079] Room temperature rolling: temperature 25℃, deformation 10%, reduction 1% per pass, final deformation 80%, thickness 2mm.

[0080] The mechanical properties of this ultra-light and high-strength magnesium-lithium alloy are: tensile strength 310.3MPa, elongation 7.2%, density 1.53g / cm 3 .

[0081] Example 3

[0082] This embodiment discloses a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, and the specific steps are as follows:

[0083] Step (1) Prepare the raw materials for use.

[0084] The raw materials are as follows by mass percentage: Li: 9wt.%, Al: 3wt.%, Ca: 0.5wt.%, Y: 0.5wt.%, Sn: 1.5wt.%, and the rest are Mg and unremovable impurity elements, wherein the purity of magnesium blocks, aluminum particles, tin particles, and lithium particles all reach 99.99%, and the Y element and Ca element are Mg-30Y and Mg-20Ca alloys respectively, and the purity both reach 99.97%. Among them, all raw materials except Li particles need to be treated to remove the surface oxide layer, and then ultrasonically cleaned with anhydrous ethanol and blown dry. After treatment, all raw materials are vacuum sealed for standby use.

[0085] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot.

[0086] Before smelting, the crucible in the vacuum induction furnace is preheated at 300°C for 60 minutes. After the preheating is completed, when the crucible temperature drops below 100°C, high-purity magnesium blocks and high-purity aluminum blocks are placed in the crucible, and pure lithium particles are placed in the secondary feeding bin for gas washing;

[0087] After the gas washing is completed, the crucible is evacuated to 0.02MPa, filled with argon, and the heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for a period of time, and argon is filled again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400r / min for 1min. After the stirring is completed, it is kept warm for a period of time, and the insulation time is 3min.

[0088] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot.

[0089] Homogenization treatment: temperature 250℃, holding time 4h, air cooling treatment;

[0090] Solution treatment temperature is 400℃, holding time is 0.5h, and water quenching is performed.

[0091] Step (4) hot extruding the heat-treated ingot.

[0092] Hot extrusion process: temperature 260℃, extrusion rate 1mm / s, extrusion ratio 45:1, water quenching.

[0093] Step (5) hot rolling the magnesium-lithium alloy extrusions at medium temperature.

[0094] Hot rolling: temperature 260℃, deformation 70%, reduction per pass 20%;

[0095] Step (6) rolling the hot-rolled sample at room temperature to obtain a finished dual-phase magnesium-lithium alloy.

[0096] Room temperature rolling: temperature 25℃, deformation 10%, reduction 1% per pass, final deformation 80%, thickness 2mm.

[0097] The mechanical properties of this ultra-light and high-strength magnesium-lithium alloy are: tensile strength 296.6MPa, elongation 10.4%, density 1.53g / cm 3 .

[0098] Comparative Example 1

[0099] This embodiment discloses a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, and the specific steps are as follows:

[0100] Step (1) Prepare the raw materials for use.

[0101] The raw materials are as follows by mass percentage: Li: 9wt.%, Al: 3wt.%, Y: 0.5wt.%, Sn: 1.5wt.%, and the rest are Mg and unremovable impurity elements, among which the purity of magnesium blocks, aluminum particles, tin particles, and lithium particles all reach 99.99%. The source of Y element is Mg-30Y alloy with a purity of 99.97%. Among them, all raw materials except Li particles need to be treated to remove the surface oxide layer, and then ultrasonically cleaned with anhydrous ethanol and blown dry. After treatment, all raw materials are vacuum sealed for standby use.

[0102] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot.

[0103] Before smelting, the crucible in the vacuum induction furnace is preheated at 300°C for 60 minutes. After the preheating is completed, when the crucible temperature drops below 100°C, high-purity magnesium blocks and high-purity aluminum blocks are placed in the crucible, and pure lithium particles are placed in the secondary feeding bin for gas washing;

[0104] After the gas washing is completed, the crucible is evacuated to 0.02MPa, filled with argon, and the heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for a period of time, and argon is filled again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400r / min for 1min. After the stirring is completed, it is kept warm for a period of time, and the insulation time is 3min.

[0105] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot.

[0106] Homogenization treatment: temperature 250℃, holding time 4h, air cooling treatment;

[0107] Solution treatment temperature is 350℃, holding time is 3h, and water quenching is performed.

[0108] Step (4) hot extruding the heat-treated ingot.

[0109] Hot extrusion process: temperature 260℃, extrusion rate 0.5mm / s, extrusion ratio 25:1, water quenching.

[0110] Step (5) performs medium and low temperature combined hot rolling on the magnesium-lithium alloy extrusions.

[0111] Medium and low temperature combined with hot rolling, including the following steps:

[0112] The first stage of hot rolling: temperature 260℃, deformation 50%, and reduction of 20% per pass;

[0113] Cooling control: water spray cooling, cooling rate 5℃ / min, the final temperature is controlled to be 10℃ above the second stage rolling temperature;

[0114] The second stage of hot rolling: temperature 100°C, deformation 20%, reduction of 10% per pass, water quenching.

[0115] Step (6) rolling the hot-rolled sample at room temperature to obtain a finished dual-phase magnesium-lithium alloy.

[0116] Room temperature rolling: temperature 25℃, deformation 10%, reduction 1% per pass, final deformation 80%, thickness 2mm.

[0117] The mechanical properties of this ultra-light and high-strength magnesium-lithium alloy are as follows: tensile strength is 252.2MPa, elongation is 15.3%, and density is 1.51g / cm 3 .

[0118] Comparative Example 2

[0119] This embodiment discloses a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, and the specific steps are as follows:

[0120] Step (1) Prepare the raw materials for use.

[0121] The raw materials are as follows by mass percentage: Li: 9wt.%, Al: 3wt.%, Ca: 0.5wt.%, Sn: 1.5wt.%, and the rest are Mg and unremovable impurity elements, among which the purity of magnesium blocks, aluminum particles, tin particles, and lithium particles all reach 99.99%, and the source of Ca element is Mg-20Ca alloy with a purity of 99.97%. Among them, all raw materials except Li particles need to be treated to remove the surface oxide layer, and then ultrasonically cleaned with anhydrous ethanol and blown dry. After treatment, all raw materials are vacuum sealed for standby use.

[0122] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot.

[0123] Before smelting, the crucible in the vacuum induction furnace is preheated at 300°C for 60 minutes. After the preheating is completed, when the crucible temperature drops below 100°C, high-purity magnesium blocks and high-purity aluminum blocks are placed in the crucible, and pure lithium particles are placed in the secondary feeding bin for gas washing;

[0124] After the gas washing is completed, the crucible is evacuated to 0.02MPa, filled with argon, and the heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for a period of time, and argon is filled again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400r / min for 1min. After the stirring is completed, it is kept warm for a period of time, and the insulation time is 3min.

[0125] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot.

[0126] Homogenization treatment: temperature 250℃, holding time 4h, air cooling treatment;

[0127] Solution treatment temperature is 350℃, holding time is 3h, and water quenching is performed.

[0128] Step (4) hot extruding the heat-treated ingot.

[0129] Hot extrusion process: temperature 260℃, extrusion rate 1mm / s, extrusion ratio 35:1, water quenching.

[0130] Step (5) performs medium and low temperature combined hot rolling on the magnesium-lithium alloy extrusions.

[0131] Medium and low temperature combined with hot rolling, including the following steps:

[0132] The first stage of hot rolling: temperature 260℃, deformation 50%, and reduction of 20% per pass;

[0133] Cooling control: water spray cooling, cooling rate 5℃ / min, the final temperature is controlled to be 10℃ above the second stage rolling temperature;

[0134] The second stage of hot rolling: temperature 100°C, deformation 20%, reduction of 10% per pass, water quenching.

[0135] Step (6) rolling the hot-rolled sample at room temperature to obtain a finished dual-phase magnesium-lithium alloy.

[0136] Room temperature rolling: temperature 25℃, deformation 10%, reduction 1% per pass, final deformation 80%, thickness 2mm.

[0137] The mechanical properties of this ultra-light and high-strength magnesium-lithium alloy are: tensile strength 279.3MPa, elongation 18.7%, density 1.52g / cm 3 .

[0138] Comparative Example 3

[0139] This embodiment discloses a method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy, and the specific steps are as follows:

[0140] Step (1) Prepare the raw materials for use.

[0141] The raw materials are as follows by mass percentage: Li: 9wt.%, and the rest are Mg and unremovable impurity elements, wherein the purity of magnesium blocks reaches 99.99%. Among them, all raw materials except Li particles need to be treated to remove the surface oxide layer, and then ultrasonically cleaned with anhydrous ethanol and blown dry. After treatment, all raw materials are vacuum sealed for standby use.

[0142] Step (2) smelting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot.

[0143] Before smelting, the crucible in the vacuum induction furnace is preheated at 300°C for 60 minutes. After the preheating is completed, when the crucible temperature drops below 100°C, high-purity magnesium blocks and high-purity aluminum blocks are placed in the crucible, and pure lithium particles are placed in the secondary feeding bin for gas washing;

[0144] After the gas washing is completed, the crucible is evacuated to 0.02MPa, filled with argon, and the heating power is increased until the raw materials in the crucible are completely melted. The crucible is kept warm for a period of time, and argon is filled again. Pure Li particles are added through the secondary feeding port and mechanically stirred at a rate of 400r / min for 1min. After the stirring is completed, it is kept warm for a period of time, and the insulation time is 3min.

[0145] Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot.

[0146] Homogenization treatment: temperature 250℃, holding time 4h, air cooling treatment;

[0147] Solution treatment temperature is 400℃, holding time is 0.5h, and water quenching is performed.

[0148] Step (4) hot extruding the heat-treated ingot.

[0149] Hot extrusion process: temperature 260℃, extrusion rate 1mm / s, extrusion ratio 45:1, water quenching.

[0150] Step (5) performs medium and low temperature combined hot rolling on the magnesium-lithium alloy extrusions.

[0151] Medium and low temperature combined with hot rolling, including the following steps:

[0152] The first stage of hot rolling: temperature 260℃, deformation 50%, and reduction of 20% per pass;

[0153] Cooling control: water spray cooling, cooling rate 5℃ / min, the final temperature is controlled to be 10℃ above the second stage rolling temperature;

[0154] The second stage of hot rolling: temperature 100°C, deformation 20%, reduction of 10% per pass, water quenching.

[0155] Step (6) rolling the hot-rolled sample at room temperature to obtain a finished dual-phase magnesium-lithium alloy.

[0156] Room temperature rolling: temperature 25℃, deformation 10%, reduction 1% per pass, final deformation 80%, thickness 2mm.

[0157] The mechanical properties of this ultra-light and high-strength magnesium-lithium alloy are as follows: tensile strength is 187.1MPa, elongation is 15.7%, and density is 1.48g / cm 3 .

[0158] Example 1 After extrusion, the alloy dual phase recrystallization degree is improved, the dual phase grain size is refined, and then the extruded part is subjected to medium and low temperature mixed rolling to further refine the α-Mg phase and promote MgLi 2 The precipitation of Al strengthening phase, room temperature rolling further improves the dislocation density in the matrix on the basis of rolling, and the strength of the α and γ fiber texture is further improved by enhancing the strength of the alloy. The precipitation of a large number of micro-nano phases and the introduction of subgrain boundaries in a series of deformation processes further improve the plasticity of the alloy. Example 2 does not perform hot extrusion, and the grain recrystallization and refinement effect after rolling is relatively poor, which leads to little change in strength compared with Example 1, and a serious decrease in elongation. Example 3 performs single temperature hot rolling on the basis of extrusion, which leads to a low dislocation density in the alloy matrix, and the fiber texture strengthening effect is not obvious, resulting in a decrease in strength and a small change in elongation.

[0159] Comparative Example 1-2: Based on Example 1, Ca or Y element is removed, and it can be found that the strength of the alloy decreases sharply. 2 Ca or Al 2 The reduction of Y phase also leads to a decrease in the effect of inhibiting the growth trend of recrystallized grains during extrusion. The grain refinement effect in the subsequent deformation process is somewhat different from that in Example 1. The lack of Ca element leads to the introduction of oxidation phase or the lack of Y element leads to the insignificant effect of cast grain refinement. The β phase aging softening process is inhibited, resulting in a decrease in alloy strength. Comparative analysis of Example 1 and Comparative Example 3 shows that the Al element has a significant strengthening effect on the magnesium-lithium alloy, but the Al element has certain limitations in improving the alloy strength. Therefore, adding Ca, Y and Sn elements can further improve the synergy between alloy strength and plasticity. Figure 2 This means that the density of the alloy system designed in this patent is between 1.35 and 1.65 g / cm 3 It meets the application requirements of lightweight fields such as aerospace, military equipment, etc.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ultra-light and high-strength dual-phase magnesium-lithium alloy. It is characterized in that The following steps are involved: Step (1) Weigh the alloy smelting raw materials according to the following mass percentages: Li 6~9wt.%; Al 3~5wt.%; Ca 0.1~0.5wt.%; Y 0.1~0.5wt.%; Sn 0.5~2.0wt.%; The rest is Mg and unavoidable impurity elements; Step (2) melting the alloy smelting raw materials in a vacuum induction furnace to obtain a magnesium-lithium alloy ingot; Step (3) homogenizing and solution treating the magnesium-lithium alloy ingot; Step (4) hot extruding the heat-treated ingot to obtain a magnesium-lithium alloy extrusion; Step (5) hot rolling the magnesium-lithium alloy extrusion at medium and low temperature; Medium and low temperature hot rolling includes the following steps: The first stage of hot rolling: temperature 260~300℃, deformation 50%~55%, and reduction of 10~20% per pass; Cooling control: Cooling, cooling rate 5~10℃ / min, the final temperature is controlled 5~10℃ above the second rolling temperature; The second stage of hot rolling: temperature 50~100℃, deformation 15%~20%, reduction 5~10% per pass, water quenching; Step (6) rolling the hot-rolled sample at room temperature to obtain an ultra-light and high-strength dual-phase magnesium-lithium alloy product.

2. The method for preparing the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 1, It is characterized in that Step (1) pre-treating the raw materials for alloy smelting, the raw material pre-treatment comprising: taking out pure Li from paraffin oil, performing surface ultrasonic degreasing treatment in acetone solution, and then placing in a vacuum drying oven for drying for standby use; first performing surface oxide layer removal treatment on the raw materials except Li particles, and then performing ultrasonic cleaning with anhydrous ethanol and drying, and after treatment, all raw materials are vacuum sealed for standby use.

3. The method for preparing the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 1, It is characterized in that Step (2) Before smelting, preheat the crucible in the vacuum induction furnace at 300-500°C for 30-60 minutes, and heat the ingot mold to 150-200°C and keep it warm until the smelting is completed; after the crucible is preheated, wait for the crucible temperature to drop below 100°C, put the high-purity magnesium block and the high-purity aluminum block into the crucible, and put the pure Li particles into the secondary feeding bin for gas washing; After the gas washing is completed, evacuate to 0.02~0.05MPa, fill with argon, increase the heating power until the raw materials in the crucible are completely melted, keep warm for 5~10min, fill with argon again, add pure Li particles through the secondary feeding port and mechanically stir at a rate of 400~600r / min for 1~2min. After stirring, keep warm for 3~5min.

4. The method for preparing the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 1, It is characterized in that In step (3), homogenization treatment: temperature 250-260°C, heat preservation time 3-4h, air cooling treatment.

5. The method for preparing the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 1, It is characterized in that In step (3), solution treatment: temperature 350~400°C, holding time 0.5~3h, water quenching.

6. The method for preparing the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 1, It is characterized in that In step (4), hot extrusion: temperature 260~300°C, extrusion rate 0.5~2mm / s, extrusion ratio 25:1~45:1, water quenching.

7. The method for preparing the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 1, It is characterized in that In step (6), the room temperature rolling temperature is 25-45°C, the deformation is 8%-10%, and the reduction per pass is 1-5%.

8. An ultra-light, high-strength and tough dual-phase magnesium-lithium alloy. It is characterized in that Prepared by any one of the methods of claims 1 to 7.

9. Use of the ultra-light and high-strength dual-phase magnesium-lithium alloy according to claim 8 in the fields of military equipment, aviation or aerospace.

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