CN109852860B - High-strength-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting and preparation method thereof - Google Patents

High-strength-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting and preparation method thereof Download PDF

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CN109852860B
CN109852860B CN201910251425.2A CN201910251425A CN109852860B CN 109852860 B CN109852860 B CN 109852860B CN 201910251425 A CN201910251425 A CN 201910251425A CN 109852860 B CN109852860 B CN 109852860B
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CN109852860A (en
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刘希琴
叶兵
刘子利
刘思雨
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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Abstract

The invention provides a high-strength and high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting and a preparation method thereof, wherein the alloy comprises the following components in stoichiometric ratio: 2.5-5.0% of Y, 1.0-4.0% of Zn, 0.5-1.2% of Al, 0.1-0.3% of Mn, 0.01-0.08% of M and the balance of Mg; wherein M is Ti, and B is one or two elements. The preparation method comprises the following steps: 1) preparing materials according to Mg-Y alloy components; 2) melting an industrial pure magnesium ingot; 3) heating to 700 ℃, adding the industrial pure zinc, Mg-Y and Mg-Mn intermediate alloy, and stirring until the materials are completely melted; 4) heating to 730 ℃, and refining to obtain a magnesium alloy melt after all the industrial pure aluminum ingot, the Al-Ti and the Al-Ti-B, Al-B intermediate alloy which are sequentially added are melted; 5) low-pressure casting; 6) secondary solution treatment and artificial aging treatment. After the alloy is subjected to low-pressure casting, secondary solution treatment and artificial aging heat treatment, the tensile strength at room temperature reaches 305MPa, and the elongation is 19 percent; the tensile strength at high temperature of 200 ℃ reaches 210MPa, the elongation is 26%, and the high-end requirement of aerospace and other industries on light weight is met.

Description

High-strength-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting and preparation method thereof
Technical Field
The invention relates to a high-strength, high-toughness and heat-resistant Mg-Y alloy suitable for low-pressure casting, which meets the high-end requirement on light weight development in the industries of aerospace, automobiles, telecommunication and the like. The invention also relates to a preparation method of the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting, belonging to the field of industrial magnesium alloy and manufacturing thereof.
Background
The magnesium alloy is used as the lightest engineering metal material (the density of magnesium is 2/3 of aluminum and 1/4 of steel), the specific strength of the magnesium alloy is obviously higher than that of aluminum alloy and steel, the specific stiffness of the magnesium alloy is equivalent to that of the aluminum alloy and the steel but far higher than that of engineering plastics, and the magnesium alloy has a series of advantages of good castability, good cutting processability, good thermal conductivity, strong damping property and electromagnetic shielding capability, easy recovery and the like, and has wide application prospects in the fields of aviation, aerospace, automobiles, electronics, national defense war industry and the like. Magnesium alloys have become ideal materials to replace aluminum alloys, steel and engineering plastics to achieve light weight, with the most promising replacement potential being aluminum alloys. The cast aluminum alloy has the necessary toughness and thermal stability, and is widely used for producing parts such as engine cylinder blocks, cylinder covers, wheel hubs and the like at present, and the representative alloys are A354, A356 and A380. If magnesium alloy is substituted for cast aluminum alloy, it must have equivalent toughness and be inexpensive and easy to cast. The low-pressure casting is a casting method in which dry compressed air or inert gas is introduced into a sealed crucible, liquid alloy is smoothly pressed into a metal mold or sand mold cavity from bottom to top through a pouring channel along a riser tube by means of pressure acting on the metal liquid level, and the liquid alloy is solidified under the action of the pressure to obtain a casting. Compared with the alloy die casting process and the like which are generally adopted at present, low-pressure casting is the preferred technology for producing large-scale high-quality high-performance castings with complex shapes.
The Mg-Al magnesium alloy is applied earliest, and the main alloy elements of the Mg-Al magnesium alloy have larger atomic radius difference between aluminum and magnesium and larger solid solubility in magnesium, and play the roles of solid solution strengthening and precipitation strengthening in the alloy. After a small amount of Mn is found in 1925 to remarkably improve the corrosion resistance of Mg-Al-Zn magnesium alloy, AZ (such as AZ91) and AM magnesium alloy (such as AM60 and AM50) are developed into commercial magnesium alloy which is most widely applied at present. However, AZ and AM magnesium alloys have very poor high temperature creep properties, more than an order of magnitude lower than conventional alloys, and rapidly decrease in tensile strength at temperatures above 150 ℃ due to the supersaturated alpha-Mg matrix Mg at grain boundaries during high temperature creep17Al12The phases are separated out discontinuously. The heat resistance of Mg-Al alloy is improved by adding alloy elements to improve the characteristics (crystal structure, form and thermal stability) of precipitated phases, but the normal-temperature and high-temperature mechanical properties of the Mg-Al alloy still can not reach the level of cast aluminum alloy, so that the application development of the Mg-Al alloy is severely limited. For example, patent document CN109136701A (a sand gravity casting magnesium alloy material and a method for producing the same) discloses magnesium alloy with the following components: 3.5-4.5 wt.% of Al, 0.5-4.5 wt.% of one or more of La, Ce and Pr, 0.2-0.5 wt.% of Mn, 0.01-2.5 wt.% of one or more of Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy and Yb, and the balance of Mg; the reported best normal temperature mechanical properties of the alloy: the tensile strength is 231MPa, and the elongation is 11.4%.
The maximum solid solubility of Zn in Mg is up to 6.2 wt%, which can play the role of solid solution strengthening and aging strengthening and is an important strengthening element of high-strength magnesium alloy. Typical Mg-Zn-based cast magnesium alloys include ZK51A and ZK60A, and wrought alloys include ZK21A, ZK31, ZK40A, ZK60A, and ZK61, and the like. As the Zn content increases, the tensile strength and yield strength of the alloy increase, the elongation after fracture slightly decreases, but the casting properties, process plasticity and welding properties deteriorate, and the tendency to hot crack is very severe, particularly because of the excessively wide solidification range (for example, the solidification range of ZK60 is as high as 265 ℃, Journal of Materials Science,45(14) (2010) 3797-. The beneficial effect of rare earth element RE (rare earth element) on the strength performance of magnesium alloy and the grain refining effect of zirconium on the magnesium alloy are discovered in the thirties of the twentieth century, and in the Mg-RE-Zr system (EK30, EK31 and EK41), EK31 becomes the highest-developed high-temperature casting magnesium alloy in the Mg-Zr system. Magnesium rare earth alloys based on rare earth RE elements have excellent age hardening effect, and various novel magnesium alloys taking RE as a main element, such as WE54 and WE43 alloys of Mg-Y series, are developed in sequence. Patent document with application publication number CN1676646A (high-strength heat-resistant magnesium alloy and preparation method thereof) discloses a preparation method of high-strength heat-resistant magnesium alloy, and the invented Mg-Gd-Y-Zr (-Ca) rare earth magnesium alloy comprises the following components by weight percent: 6-15% of Gd, 1-6% of Y, 0.35-0.8% of Zr, 0-1.5% of Ca, less than 0.02% of the total amount of impurity elements Si, Fe, Cu and Ni and the balance of Mg. However, when the alloy is used for sand casting, the grain size reaches 90 μm, and the tensile strength, yield strength and elongation of the cast T6 alloy are only 295MPa, 212MPa and 2.2% respectively (the patent document with the application publication number of CN104928548A discloses a high-strength heat-resistant magnesium alloy suitable for sand casting and a preparation method thereof); meanwhile, the addition of Ca increases the yield strength and high-temperature strength of the alloy, also sharply increases the solidification temperature range of the alloy, increases the hot cracking tendency, and reduces the processing performance of the alloy.
Yttrium Y is a rare earth element with large earth crust content and wide application, and the price of yttrium Y is only lower than that of two rare earth elements of cerium Ce and lanthanum La. As a heavy rare earth element having the lowest density except scandium (4.4689 g/cm)3) Y has a solid solubility in magnesium of 12.5 wt%, and is a magnesium alloy solid solution strengthened by YThe GP zone which is difficult to distinguish is generated during decomposition, and the master alloy phase precipitation which is compatible with the matrix can be formed through a certain inoculation time, so that a good heat treatment strengthening effect is generated. The addition of cheap Zn in Mg-Y alloy not only has a remarkable effect on regulating and controlling the aging precipitation structure of the alloy system, but also can form various strengthening phases under different Zn/Y ratio conditions: when the mass ratio of Zn to Y in the alloy is more than or equal to 4.13 (the atomic ratio is more than or equal to 6.0), an icosahedral quasicrystal structure I phase (Mg) is easily formed3Zn6Y); the face centered cubic structure W phase (Mg) is easily formed when the Zn/Y mass ratio in the alloy is between 1.10 and 4.13 (atomic ratio between 1.5 and 6.0)3Zn3Y2) And phase I; the W phase and the LPSO phase (Mg) of the long period stacking ordered structure are easily formed when the Zn/Y mass ratio in the alloy is between 0.69 and 1.10 (the atomic ratio is between 1.0 and 1.5)12ZnY); the LPSO phase is easily formed when the Zn/Y mass ratio in the alloy is less than or equal to 0.69 (atomic ratio less than or equal to 1.0) (Materials Letter,59(29) (2005) 3801-. The room temperature strength and the high temperature performance of the magnesium alloy can be further improved by various Mg-Y-Zn strengthening phases, the elastic modulus and the microhardness of the LPSO phase are much higher than those of pure magnesium except the strengthening phase W, the strength and the plasticity of the magnesium alloy can be obviously improved, and the alloy shows excellent comprehensive mechanical properties. It was found that LPSO structures can be formed only when the rare earth elements are Y, Gd, Er, Dy, Ho, Tb, Tm in the Mg-RE-Zn system (Materials transformations, 48(11) (2007) 2986-. The patent document with application publication number CN101713042A (a quasicrystal reinforced magnesium alloy and a semi-solid preparation method thereof) discloses quasicrystal reinforced magnesium alloy, which comprises the following alloy components in percentage by mass: 4-15% of Zn, 0.5-3.5% of Y, 3-10% of Al and the balance of Mg; the preparation method comprises the steps of extruding the Mg-Zn-Y-Al alloy cast ingot into a bar by a hot extrusion method, heating the extruded bar to be in a semi-solid state by an electromagnetic induction heating device, and carrying out semi-solid die-casting molding. Patent document CN102212727A (authigenic quasicrystal-reinforced Mg-Zn-Y alloy and melting method thereof) discloses that the authigenic quasicrystal-reinforced Mg-Zn-Y alloy comprises the following chemical components in percentage by mass: 3.0-10.0% of Zn, 0.5-3.0% of Y, 0.05-1.0% of Al-Ti-C, and the balance of Mg and inevitable impurities; preparation method bag thereofSmelting and casting, wherein when the temperature of a smelted melt is reduced to 700-720 ℃, Al-Ti-C intermediate alloy is added, ultrasonic waves are introduced into the melt, and the melt is cast after ultrasonic treatment; the tensile strength of the self-generated quasicrystal reinforced Mg-Zn-Y alloy can reach 260MPa, and the elongation is 10.6%. The technology of the invention still has the following problems: the Zn/Y mass ratio content of the alloy is too high, a quasicrystal I phase is formed, and meanwhile, the solidification interval is too large, so that casting defects are easily generated; moreover, the introduction of ultrasonic treatment makes the operation complicated and thus makes it difficult to industrially apply the ultrasonic treatment on a large scale. Under normal solidification conditions, the Mg-Y-Zn alloy has coarse grains, the precipitated phase is often in a coarse network structure, the mechanical property of the Mg-Y-Zn alloy is deteriorated, and the size of the precipitated phase must be adjusted through thermal deformation or heat treatment solid solution and aging so as to play a role of a strengthening phase.
Mg-Y-Zn alloys usually incorporate Zr as a grain refining element to refine their coarse microstructure. The currently reported Zr adding modes comprise sponge Zr, halogen salt of Zr, Zn-Zr, Mg-Zr intermediate alloy and the like, wherein the Mg-Zr intermediate alloy has the advantages of convenient use, less inclusion, good refining effect and the like, and is the currently main mode for adding Zr. However, the addition of the Mg-Zr intermediate alloy still has a plurality of problems: firstly, the preparation process of the Mg-Zr intermediate alloy is complex and has high energy consumption, so that the price of the Mg-Zr intermediate alloy is high, and the product cost can be increased by refining the crystal grains by using the Mg-Zr intermediate alloy; secondly, Zr has strong chemical activity and is easy to react with atmosphere and furnace gas at high temperature, and when a steel crucible is used and the temperature of a melt is higher than 750 ℃, Zr is easy to react with Fe in the crucible to generate a stable intermetallic compound Fe2Zr, all of which result in high Zr loss; much Zr in Mg-Zr intermediate alloy exists in the form of large-size simple substance particles, the Zr particles are difficult to dissolve in the melt due to the high melting point (1852 ℃) of Zr, and the density of Zr is much higher than that of magnesium melt (the density of Zr is 6.52 g/cm)3The density of the pure magnesium melt was 1.58g/cm3) And is liable to precipitate to the bottom of the crucible, resulting in a low yield of Zr.
Disclosure of Invention
The invention provides a high-strength, high-toughness and heat-resistant Mg-Y alloy suitable for low-pressure casting and a preparation method thereof, aiming at solving the industrial problem that the application of the existing cast magnesium alloy is greatly limited because the performance of the cast aluminum alloy such as A380 and the like cannot be achieved due to insufficient strength, toughness and heat resistance, and the room-temperature tensile strength of the alloy reaches 305MPa and the elongation percentage is 19 percent after the alloy is subjected to low-pressure casting heat treatment; the tensile strength of the high-temperature tensile reaches 210MPa at the temperature of 200 ℃, and the elongation is 26 percent.
In order to solve the technical problems, the invention adopts the following technical scheme:
the high-strength-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting comprises the following elements in percentage by mass: 2.5-5.0% of Y, 1.0-4.0% of Zn, 0.5-1.2% of Al, 0.1-0.3% of Mn, 0.01-0.08% of M, and the balance of Mg and other inevitable impurities, wherein M is one or two of Ti and B.
The invention is suitable for the innovation point of the high-strength-toughness heat-resistant Mg-Y alloy cast at low pressure:
(1) in the alloy design, except common metals of Zn, Al and Mn and a small amount of Ti and B elements, the invention selects cheap Y element (the price of which is only lower than that of Ce and La) in rare earth elements as alloying elements, and the Mg-Y intermediate alloy is easy to prepare because Y has extremely high corrosion resistance. Alloying elements Y and Zn and matrix Mg element form a ternary Mg-Y-Zn strengthening phase, and in the range of the mass ratio of Zn to Y of 0.3-1.0, on the one hand, the alloy mainly forms a long-period stacking ordered structure LPSO phase (Mg/Y mass ratio)12ZnY) and face-centered cubic structure W phase (Mg)3Zn3Y2) All are high melting point phases; compared with binary Mg-Y strengthening, the ternary Mg-RE-Zn strengthening phases LPSO and W have better high-temperature stability in a magnesium matrix, avoid performance reduction caused by dissolution of a precipitation strengthening phase, effectively enhance the room-temperature mechanical property and high-temperature property of high-strength-toughness heat-resistant cast Mg-Y alloy, and particularly improve the high-temperature creep property at 300 ℃ by more than one order of magnitude. On the other hand, the invention solves the technical problem that the toughness and the casting process performance of the traditional Mg-Zn-Y alloy are reduced due to the fact that the solidification interval is too large and the hot cracking defect is easily generated due to too high Zn content.
(2) The precipitated phase of the Mg-Y-Zn alloy is often in a coarse network structure under the conventional solidification condition, the mechanical property of the Mg-Y-Zn alloy is deteriorated, and the Mg-Y-Zn alloy is generally required to be in a coarse network structureThe size of the precipitated phase is adjusted by overheating deformation or heat treatment solid solution and aging to play a role of the strengthening phase. Zr is usually added into the alloy as a grain refining element, the alloy element of the invention contains Al, Mn and rare earth Y alloy elements, and the elements are combined with Zr to form Al3Zr and the like are precipitated on the bottom of the crucible to prevent the crystal grain refinement of zirconium. On the other hand, researches show that the Mg-Y-Zn alloy refined by adding Zr has poor structure thermal stability, and crystal grains are rapidly coarsened when the temperature is kept at 550 ℃, so that the high-temperature performance is greatly reduced. In order to solve the problems, 0.5-1.2% of Al is added to the alloy of the invention to replace Zr to form dispersed high-melting-point Al2The Y phase not only refines the structure of the alloy, but also ensures the high-temperature stability of the magnesium alloy structure with high-temperature phases such as LPSO and the like. Meanwhile, Al and a small amount of Ti and B play a role in composite grain refinement, the alloy structure is further refined, and the toughness of the alloy is improved. The alloy element of the invention is added with a small amount of Mn, which not only can promote the formation of LPSO phase, improve the high-temperature stability of the alloy, but also can improve the corrosion resistance of the magnesium alloy.
(3) In order to reduce the hot cracking tendency in the casting process of the Mg-Y-Zn alloy, the mass ratio of Zn to Y is limited to be 0.3-1.0, and the mass ratio of Zn + Al to Y is 0.5-1.2. Under the condition of the mass ratio, the alloy of the invention obtains a narrower solidification interval, thereby overcoming the hot cracking tendency in the casting process of the Mg-Y-Zn alloy and improving the casting process performance of the alloy.
The preparation method of the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting comprises the following steps:
(1) properly considering the burning loss, calculating the consumption of required raw materials (industrial pure magnesium ingot, industrial pure zinc, industrial pure aluminum ingot, Mg-Y intermediate alloy, Mg-Mn intermediate alloy, Al-Ti-B intermediate alloy and Al-B intermediate alloy) according to the Mg-Y alloy components and the stoichiometric ratio; removing oxide layers from industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and Mg-Y and Mg-Mn intermediate alloys, drying and preheating to 200 ℃.
(2) Melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas, and adding the rest magnesium ingot. The securityThe shielding gas is argon or SF with volume fraction of 0.2%6And CO2Mixed gas (i.e. SF)6Volume fraction of 0.2%, CO299.8% by volume).
(3) After the magnesium ingot is completely melted, heating to 700 ℃, adding industrial pure zinc and Mg-Y and Mg-Mn intermediate alloy for 2-4 times, keeping the temperature constant at 700 ℃, stirring until the industrial pure zinc and the Mg-Y and Mg-Mn intermediate alloy are completely melted, and keeping the temperature for 30 min. Preferably, the Mg-Y master alloy is MgY25 or MgY30, and the Mg-Mn master alloy is MgMn 10.
(4) And heating to 730 ℃ before low-pressure casting for 40-60 min, adding a refining agent for refining after all the industrial pure aluminum ingot, the Al-Ti intermediate alloy, the Al-Ti-B intermediate alloy and the Al-B intermediate alloy which are sequentially added are melted, heating the furnace to 750 ℃, keeping the temperature and standing for 10-20 min, and promoting the settlement of impurities to obtain the magnesium alloy melt. The Al-Ti-B intermediate alloy is AlTi5B1, the Al-B intermediate alloy is AlB3 or AlB8, and the Al-Ti intermediate alloy is AlTi5 or AlTi 10. The refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. The addition amount of the refining agent is 1.0-3.5% of the total weight of the raw materials, the refining temperature when the refining agent is added for refining is 720-730 ℃, and the stirring time of refining treatment is 10-15 min.
(5) And cooling the magnesium alloy melt to 720-740 ℃, removing slag, and preheating the sand mold casting temperature to 25-150 ℃ or the metal mold temperature to 180-250 ℃. The low pressure casting process is controlled and pressurized in stages through a proportional valve, and comprises the following steps: the method comprises the steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.02-0.05MPa, and the pressurization time is controlled to be 5-8 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; uniformly raising the pressure of the pressurization stage to 0.1MPa, and controlling the pressurization time to be 10-15 s; the pressure maintaining time in the pressure maintaining stage is controlled within 200-300 s. And taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief.
(6) And sequentially carrying out secondary solid solution treatment and artificial aging treatment on the as-cast alloy obtained by low-pressure casting to obtain the required high-strength-toughness heat-resistant Mg-Y alloy.
The secondary solution treatment process of the high-strength and high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting comprises the following steps: putting the as-cast alloy into a solid solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, and introducing protective gas (the protective gas is argon or SF with the volume fraction of 0.2 percent)6And CO2Mixed gas (i.e. SF)6Volume fraction of 0.2%, CO2The volume fraction is 99.8 percent), continuously heating to the first-stage solid solution temperature of 480-490 ℃ at the speed of 5 ℃/min, and keeping the temperature for 36-48 hours; and then slowly raising the temperature to 535-545 ℃ of the second-stage solution treatment at a speed of 10 ℃/h, preserving the temperature for 1-2 h, and then quickly transferring to a quenching device for water-cooling quenching.
The artificial aging treatment process of the high-strength and high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting comprises the following steps: and (3) putting the quenched alloy into an aging furnace, heating to 185-215 ℃ at the temperature of artificial aging treatment at the speed of 5 ℃/min, keeping the temperature for 12-36 h, discharging from the furnace, and air cooling to room temperature.
The secondary solution treatment process parameters are as follows: the primary solid solution temperature is 480-490 ℃, and the heat preservation time is 36-48 h; the temperature of the second-stage solid solution is 535-545 ℃, and the heat preservation time is 1-2 h;
the technological parameters of the artificial aging treatment are as follows: the aging temperature is 185-215 ℃, and the heat preservation time is 12-36 h.
The preparation method of the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting has the following innovation points: (1) Mg-Y intermediate alloy which is easy to burn is added at 700 ℃, and is melted in the low-temperature melt in a heat preservation way, so that the yield of the rare earth Y is improved; (2) the refining treatment adopts MgCl-free2The special refining agent further reduces the burning loss of the rare earth Y in the refining process; (3) the heat treatment of the high-strength high-toughness heat-resistant cast Mg-Y alloy comprises two procedures of solution treatment and aging treatment. The first-stage temperature of the secondary solution treatment is 480-490 ℃, the time is 36-48 h, the solubility of Y and Zn in a magnesium matrix is fully promoted, and coarse precipitated phases such as LPSO and the like are eliminated; the temperature of the first stage of the secondary solution treatment is 535-545 ℃ for 1-2 h, the heat preservation is carried out for a short time, coarse phases such as undissolved LPSO (Long period of time) are further eliminated, and the deviation of areas existing in the casting is eliminatedAnd the segregation in the crystal lead the components of the alloy to be homogenized, thereby improving the performance of the alloy and preventing the phenomenon of overburning in heat treatment. Keeping the furnace temperature at 185-215 ℃, preserving the temperature for 12-36 h, carrying out aging treatment, and finally precipitating a nano-grade and finely dispersed strengthening phase in alloy crystal after long-time aging, so that the alloy has excellent room temperature and high temperature performances. The heat treatment of the invention has the advantages of stable alloy components, no obvious growth of crystal grains, obvious improvement of alloy performance, simple method, safety, reliability and convenient operation.
The invention has the following beneficial effects:
after the high-strength high-toughness heat-resistant cast Mg-Y alloy is subjected to low-pressure casting, secondary solution treatment and artificial aging heat treatment, the room-temperature tensile strength reaches 305MPa, and the elongation is 19%; the tensile strength at high temperature of 200 ℃ reaches 210MPa, the elongation is 26 percent, and the comprehensive performance reaches the performance of cast aluminum alloy such as A380; the preparation method has the advantages of simple process, high efficiency, suitability for large-scale production and the like, and meets the high-end requirements of the industries of aerospace, war industry, automobiles and the like on light weight development.
Drawings
FIG. 1 is an as-cast metallographic structure chart of a magnesium alloy obtained in example 3.
Detailed Description
Example 1
The high-strength and high-toughness heat-resistant cast Mg-Y alloy comprises the following components in percentage by weight: 2.5 percent of Y, 1.0 percent of Zn, 0.5 percent of Al, 0.3 percent of Mn, 0.01 percent of Ti, 0.01 percent of B, and the balance of Mg and other inevitable impurities according to the theoretical proportion. The preparation method comprises the following steps:
(1) properly considering the burning loss, calculating the consumption of the required raw materials according to the components of the Mg-Y alloy and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY25 and MgMn10, drying and preheating to 200 ℃.
(2) Melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas argon, and adding the rest magnesium ingot.
(3) After the magnesium ingot is completely melted, heating to 700 ℃, adding the industrial pure zinc, the MgY25 and the MgMn10 intermediate alloy for 2-4 times, keeping the temperature constant at 700 ℃, stirring until the magnesium ingot is completely melted, and keeping the temperature for 30 min.
(4) Heating to 730 ℃ after 40-60 min before low-pressure casting, adding a refining agent accounting for 1% of the weight of the raw materials for refining after all the intermediate alloys of the industrial pure aluminum ingot, the AlTi5B1 and the AlB3 which are sequentially added are melted, wherein the refining temperature is 730 ℃, the stirring time of refining treatment is 10min, and the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. And (4) heating the furnace to 750 ℃, preserving heat and standing for 10min to promote the settlement of impurities, thereby obtaining the magnesium alloy melt.
(5) And cooling the magnesium alloy melt to 720 ℃ for deslagging, wherein the temperature of a sand mold is 25 ℃. The low pressure casting process is controlled and staged pressurized by a proportional valve comprising: the method comprises the following steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.02MPa, and the pressurization time is 5 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; the pressure in the pressurizing stage is uniformly increased to 0.1MPa, and the pressurizing time is 10 s; the dwell time of the dwell phase was 200 s. And taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief.
(6) Sequentially carrying out secondary solution treatment on the as-cast alloy obtained by low-pressure casting, putting the cast alloy into a solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, and introducing SF containing 0.2% of volume fraction6And CO2The mixed gas is continuously heated to 480 ℃ of the first-stage solid solution temperature at the speed of 5 ℃/min, the temperature is kept for 36h, then the mixed gas is slowly heated to 535 ℃ of the second-stage solid solution temperature at the speed of 10 ℃/h, and the mixed gas is quickly transferred to a quenching device for water cooling quenching after the temperature is kept for 1 h.
(7) And (3) carrying out artificial aging treatment on the cast alloy after the solution treatment, putting the quenched alloy into an aging furnace, heating to 185 ℃ of the artificial aging treatment at the speed of 5 ℃/min, keeping the temperature for 12h, discharging from the furnace, and carrying out air cooling to room temperature to obtain the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting.
Respectively carrying out a-room temperature tensile test on the prepared high-strength high-toughness heat-resistant Mg-Y alloy; b, performing high-temperature tensile property test at 200 ℃ after 200h of heat exposure treatment at 200 ℃. The solidification interval of the high-strength high-toughness heat-resistant Mg-Y alloy obtained in the embodiment is 80 ℃, the room-temperature tensile strength is 280MPa, and the elongation is 23%; the tensile strength at high temperature of 200 ℃ is 185MPa, and the elongation is 32%.
Example 2
The high-strength and high-toughness heat-resistant cast Mg-Y alloy comprises the following components in percentage by weight: according to the theoretical mixture ratio, 5.0 percent of Y, 4.0 percent of Zn, 1.2 percent of Al, 0.1 percent of Mn, 0.08 percent of Ti, and the balance of Mg and other inevitable impurities. The preparation method comprises the following steps:
(1) properly considering the burning loss, calculating the consumption of the required raw materials according to the components of the Mg-Y alloy and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY30 and MgMn10, drying and preheating to 200 ℃.
(2) Melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, and introducing protective gas containing 0.2% of SF by volume fraction6And CO2The remaining magnesium ingot is added to the mixed gas of (1).
(3) After the magnesium ingot is completely melted, heating to 700 ℃, adding the industrial pure zinc, the MgY30 and the MgMn10 intermediate alloy for 2-4 times, keeping the temperature constant at 700 ℃, stirring until the magnesium ingot is completely melted, and keeping the temperature for 30 min.
(4) Heating to 730 ℃ after 40-60 min before low-pressure casting, adding a refining agent accounting for 3.5% of the weight of the raw materials for refining after all the industrial pure aluminum ingot and the AlTi5 intermediate alloy which are sequentially added are melted, wherein the refining temperature is 730 ℃, the stirring time of the refining treatment is 10min, and the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. And (4) heating the furnace to 750 ℃, preserving heat and standing for 20min to promote the settlement of impurities, thereby obtaining the magnesium alloy melt.
(5) And cooling the magnesium alloy melt to 720 ℃, removing slag, and preheating the sand mold to 150 ℃. The low pressure casting process is controlled and staged pressurized by a proportional valve comprising: the method comprises the following steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.05MPa, and the pressurization time is 8 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; the pressure in the pressurizing stage is uniformly increased to 0.1MPa, and the pressurizing time is 15 s; the dwell time of the dwell phase was 300 s. And taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief.
(6) And sequentially carrying out secondary solution treatment on the cast alloy obtained by low-pressure casting, putting the cast alloy into a solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, introducing protective gas argon, continuously heating to 490 ℃ of the first-stage solution temperature at the speed of 5 ℃/min, preserving heat for 48h, slowly heating to 545 ℃ of the second-stage solution temperature at the speed of 10 ℃/h, preserving heat for 2h, and quickly transferring to a quenching device for water-cooling quenching.
(7) And (3) carrying out artificial aging treatment on the cast alloy after the solution treatment, putting the quenched alloy into an aging furnace, heating to the artificial aging treatment temperature of 215 ℃ at the speed of 5 ℃/min, keeping the temperature for 36h, discharging from the furnace, and carrying out air cooling to room temperature to obtain the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting.
Respectively carrying out a-room temperature tensile test on the prepared high-strength high-toughness heat-resistant Mg-Y alloy; b, performing high-temperature tensile property test at 200 ℃ after 200h of heat exposure treatment at 200 ℃. In the example, the solidification interval of the high-strength high-toughness heat-resistant Mg-Y alloy is 40 ℃, the room-temperature tensile strength is 305MPa, and the elongation is 19 percent; the tensile strength at high temperature of 200 ℃ is 210MPa, and the elongation is 26%.
Example 3
The high-strength and high-toughness heat-resistant cast Mg-Y alloy comprises the following components in percentage by weight: 3.0% of Y, 2.0% of Zn, 1.0% of Al, 0.2% of Mn, 0.05% of Ti, 0.03% of B and the balance of Mg and other inevitable impurities according to the theoretical proportion. The preparation method comprises the following steps:
(1) properly considering the burning loss, calculating the consumption of the required raw materials according to the components of the Mg-Y alloy and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY30 and MgMn10, drying and preheating to 200 ℃.
(2) Melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas argon, and adding the rest magnesium ingot.
(3) After the magnesium ingot is completely melted, heating to 700 ℃, adding the industrial pure zinc, the MgY30 and the MgMn10 intermediate alloy for 2-4 times, keeping the temperature constant at 700 ℃, stirring until the magnesium ingot is completely melted, and keeping the temperature for 30 min.
(4) Heating to 730 ℃ after 40-60 min before low-pressure casting, adding a refining agent accounting for 2.5 percent of the weight of the raw materials for refining after all the intermediate alloys of the industrial pure aluminum ingot, the AlTi10 and the AlB8 which are sequentially added are melted, wherein the refining temperature is 720 ℃, the stirring time of refining treatment is 15min, and the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. And (4) heating the furnace to 750 ℃, preserving heat and standing for 15min to promote the settlement of impurities, thereby obtaining the magnesium alloy melt.
(5) And cooling the magnesium alloy melt to 730 ℃ for deslagging, wherein the temperature of the preheated metal mold is 180 ℃. The low pressure casting process is controlled and staged pressurized by a proportional valve comprising: the method comprises the following steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.03MPa, and the pressurization time is 6 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; the pressure in the pressurizing stage is uniformly increased to 0.1MPa, and the pressurizing time is 12 s; the dwell time of the dwell phase was 250 s. And taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief.
(6) And sequentially carrying out secondary solution treatment on the cast alloy obtained by low-pressure casting, putting the cast alloy into a solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, introducing protective gas argon, continuously heating to the first-stage solution temperature of 485 ℃ at the speed of 5 ℃/min, keeping the temperature for 42h, slowly heating to the second-stage solution temperature of 540 ℃ at the speed of 10 ℃/h, keeping the temperature for 1.5h, and then quickly transferring to a quenching device for water-cooling quenching.
(7) And (3) carrying out artificial aging treatment on the cast alloy after the solution treatment, putting the quenched alloy into an aging furnace, heating to the artificial aging treatment temperature of 200 ℃ at the speed of 5 ℃/min, keeping the temperature for 24h, discharging from the furnace, and carrying out air cooling to room temperature to obtain the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting.
Respectively carrying out a-room temperature tensile test on the prepared high-strength high-toughness heat-resistant Mg-Y alloy; b, performing high-temperature tensile property test at 200 ℃ after 200h of heat exposure treatment at 200 ℃. The solidification range of the high-strength high-toughness heat-resistant Mg-Y alloy obtained in the embodiment is 50 ℃, the room-temperature tensile strength is 295MPa, and the elongation is 17%; the tensile strength at high temperature of 200 ℃ is 193MPa, and the elongation is 25%. The as-cast metallographic structure of the magnesium alloy obtained in the example is shown in fig. 1.
Example 4
The high-strength and high-toughness heat-resistant cast Mg-Y alloy comprises the following components in percentage by weight: according to the theoretical mixture ratio, 4.0% of Y, 4.0% of Zn, 1.0% of Al, 0.2% of Mn and 0.08% of B, and the balance of Mg and other inevitable impurities. The preparation method comprises the following steps:
(1) properly considering the burning loss, calculating the consumption of the required raw materials according to the components of the Mg-Y alloy and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY30 and MgMn10, drying and preheating to 200 ℃.
(2) Melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, and introducing SF containing 0.2% of volume fraction6And CO2The remaining magnesium ingot is added to the mixed protective gas of (1).
(3) After the magnesium ingot is completely melted, heating to 700 ℃, adding the industrial pure zinc, the MgY30 and the MgMn10 intermediate alloy for 2-4 times, keeping the temperature constant at 700 ℃, stirring until the magnesium ingot is completely melted, and keeping the temperature for 30 min.
(4) Heating to 730 ℃ after 40-60 min before low-pressure casting, adding a refining agent accounting for 3.0 percent of the weight of the raw materials for refining after all the industrial pure aluminum ingot and the AlB8 intermediate alloy which are sequentially added are melted, wherein the refining temperature is 720 ℃, the stirring time of the refining treatment is 15min, and the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. And (4) heating the furnace to 750 ℃, preserving heat and standing for 10min to promote the settlement of impurities, thereby obtaining the magnesium alloy melt.
(5) And cooling the magnesium alloy melt to 740 ℃, removing slag, and preheating the metal mold to 250 ℃. The low pressure casting process is controlled and staged pressurized by a proportional valve comprising: the method comprises the following steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.04MPa, and the pressurization time is 8 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; the pressure in the pressurizing stage is uniformly increased to 0.1MPa, and the pressurizing time is 12 s; the dwell time of the dwell phase was 220 s. And taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief.
(6) Sequentially carrying out secondary solution treatment on the as-cast alloy obtained by low-pressure casting, putting the cast alloy into a solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, and introducing SF containing 0.2% of volume fraction6And CO2The mixed protective gas is continuously heated to 480 ℃ of the first-stage solid solution temperature at the speed of 5 ℃/min, the temperature is kept for 48 hours, then the temperature is slowly heated to 535 ℃ of the second-stage solid solution temperature at the speed of 10 ℃/h, and the temperature is kept for 2 hours and then the steel plate is quickly transferred to a quenching device for water cooling quenching.
(7) And (3) carrying out artificial aging treatment on the cast alloy after the solution treatment, putting the quenched alloy into an aging furnace, heating to the temperature of 185 ℃ of the artificial aging treatment at the speed of 5 ℃/min, keeping the temperature for 36h, discharging from the furnace, and carrying out air cooling to room temperature to obtain the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting.
Respectively carrying out a-room temperature tensile test on the prepared high-strength high-toughness heat-resistant Mg-Y alloy; b, performing high-temperature tensile property test at 200 ℃ after 200h of heat exposure treatment at 200 ℃. The solidification interval of the high-strength high-toughness heat-resistant Mg-Y alloy obtained in the embodiment is 43 ℃, the room-temperature tensile strength is 300MPa, and the elongation is 18%; the tensile strength at high temperature of 200 ℃ is 207MPa, and the elongation is 23%.
Example 5
The high-strength and high-toughness heat-resistant cast Mg-Y alloy comprises the following components in percentage by weight: 4.0% of Y, 1.2% of Zn, 0.8% of Al, 0.3% of Mn, 0.04% of Ti, 0.04% of B and the balance of Mg and other inevitable impurities according to the theoretical proportion. The preparation method comprises the following steps:
(1) properly considering the burning loss, calculating the consumption of the required raw materials according to the components of the Mg-Y alloy and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and intermediate alloys of MgY30 and MgMn10, and drying and preheating to 200 ℃; and calculating the consumption of the required raw materials according to the components and the stoichiometric ratio of the alloy.
(2) Melting industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool at 680 ℃, introducing protective gas argon, and adding the rest magnesium ingot.
(3) After the magnesium ingot is completely melted, heating to 700 ℃, adding the industrial pure zinc, the MgY30 and the MgMn10 intermediate alloy for 2-4 times, keeping the temperature constant at 700 ℃, stirring until the magnesium ingot is completely melted, and keeping the temperature for 30 min.
(4) Heating to 730 ℃ after 40-60 min before low-pressure casting, sequentially adding and completely melting industrial pure aluminum ingots, AlTi5 and AlB3 intermediate alloys to be sequentially added, and then adding a refining agent accounting for 2.0 percent of the weight of the raw materials for refining, wherein the refining temperature is 730 ℃, the stirring time of refining treatment is 10min, and the refining agent comprises the following components in percentage by mass: 55% KCl and 25% CaCl2、5%CaF2、15%BaCl2. And (4) heating the furnace to 750 ℃, preserving heat and standing for 15min to promote the settlement of impurities, thereby obtaining the magnesium alloy melt.
(5) And cooling the magnesium alloy melt to 720 ℃, removing slag, and preheating the sand mold to 100 ℃. The low pressure casting process is controlled and staged pressurized by a proportional valve comprising: the method comprises the following steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.05MPa, and the pressurization time is 5 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; the pressure in the pressurizing stage is uniformly increased to 0.1MPa, and the pressurizing time is 15 s; the dwell time of the dwell phase was 300 s. And taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief.
(6) Sequentially carrying out secondary solution treatment on the as-cast alloy obtained by low-pressure casting, putting the cast alloy into a solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, and introducing SF containing 0.2% of volume fraction6And CO2The mixed protective gas is continuously heated to the first-stage solid solution temperature of 490 ℃ at the speed of 5 ℃/min, the temperature is kept for 36h, then the temperature is slowly heated to the second-stage solid solution temperature of 545 ℃ at the speed of 10 ℃/h, and the temperature is kept for 1h and then the steel plate is quickly transferred to a quenching device for water-cooling quenching.
(7) And (3) carrying out artificial aging treatment on the cast alloy after the solution treatment, putting the quenched alloy into an aging furnace, heating to the artificial aging treatment temperature of 215 ℃ at the speed of 5 ℃/min, keeping the temperature for 12h, discharging from the furnace, and carrying out air cooling to room temperature to obtain the high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting.
Respectively carrying out a-room temperature tensile test on the prepared high-strength high-toughness heat-resistant Mg-Y alloy; b, performing high-temperature tensile property test at 200 ℃ after 200h of heat exposure treatment at 200 ℃. In the example, the solidification interval of the high-strength high-toughness heat-resistant Mg-Y alloy is 74 ℃, the room-temperature tensile strength is 285MPa, and the elongation is 16 percent; the tensile strength at high temperature of 200 ℃ is 200MPa, and the elongation is 28%.
The above embodiments do not limit the present invention in any way, and all technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims (8)

1. The high-strength high-toughness heat-resistant Mg-Y alloy suitable for low-pressure casting is characterized by comprising the following elements in percentage by mass: 2.5-5.0% of Y, 1.0-4.0% of Zn, 0.5-1.2% of Al, 0.1-0.3% of Mn, 0.01-0.08% of M, and the balance of Mg and other inevitable impurities; wherein M is one or two of Ti and B; the mass ratio of Zn to Y is 0.3-1.0; the mass ratio of (Zn + Al)/Y is 0.5-1.2;
the preparation method of the high-strength, high-toughness and heat-resistant Mg-Y alloy suitable for low-pressure casting is characterized by comprising the following steps of:
(1) calculating the use amounts of an industrial pure magnesium ingot, an industrial pure zinc ingot, an industrial pure aluminum ingot, an Mg-Y intermediate alloy, an Mg-Mn intermediate alloy, an Al-Ti-B intermediate alloy and an Al-B intermediate alloy according to the components of the Mg-Y alloy and the stoichiometric ratio; removing oxide layers of industrial pure magnesium ingots, industrial pure zinc, industrial pure aluminum ingots and Mg-Y and Mg-Mn intermediate alloys, and drying and preheating to 200 ℃;
(2) melting an industrial pure magnesium ingot accounting for 25% of the height of the crucible into a molten pool, introducing protective gas, and adding the rest magnesium ingot;
(3) after the magnesium ingot is completely melted, heating to 700 ℃, adding industrial pure zinc, Mg-Y intermediate alloy and Mg-Mn intermediate alloy for multiple times, keeping the temperature constant at 700 ℃, stirring until the industrial pure zinc, the Mg-Y intermediate alloy and the Mg-Mn intermediate alloy are completely melted, and keeping the temperature for 30 min;
(4) heating to 730 ℃ after 40-60 min before low-pressure casting, adding a refining agent for refining after all the industrial pure aluminum ingot, the Al-Ti intermediate alloy, the Al-Ti-B intermediate alloy and the Al-B intermediate alloy which are sequentially added are melted, heating the furnace to 750 ℃, keeping the temperature and standing for 10-20 min, and promoting the settlement of impurities to obtain a magnesium alloy melt;
(5) cooling the magnesium alloy melt to 720-740 ℃, removing slag, and preheating a sand mold casting temperature to 25-150 ℃ or a metal mold temperature to 180-250 ℃; the low pressure casting process is controlled and pressurized in stages through a proportional valve, and comprises the following steps: the method comprises the steps of liquid lifting, mold filling, pressurization, pressure maintaining and pressure relief, wherein the pressure in the liquid lifting stage is uniformly increased to 0.02-0.05MPa, and the pressurization time is controlled to be 5-8 s; the pressure in the mold filling stage is uniformly increased to 0.08MPa, and the metal liquid is filled in the mold cavity of the casting mold under the pressure; uniformly raising the pressure of the pressurization stage to 0.1MPa, and controlling the pressurization time to be 10-15 s; the pressure maintaining time in the pressure maintaining stage is controlled to be 200-300 s; taking out the prepared as-cast high-strength-toughness heat-resistant cast Mg-Y alloy after pressure relief;
(6) sequentially carrying out secondary solution treatment and artificial aging treatment on the as-cast alloy obtained by low-pressure casting to obtain the required high-strength high-toughness heat-resistant Mg-Y alloy;
the secondary solution treatment process parameters are as follows: the primary solid solution temperature is 480-490 ℃, and the heat preservation time is 36-48 h; the temperature of the second-stage solid solution is 535-545 ℃, and the heat preservation time is 1-2 h;
the technological parameters of the artificial aging treatment are as follows: the aging temperature is 185-215 ℃, and the heat preservation time is 12-36 h.
2. The high toughness, heat resistant Mg-Y alloy suitable for low pressure casting of claim 1, wherein: the Mg-Y intermediate alloy is MgY25 or MgY 30; the Mg-Mn intermediate alloy is MgMn 10; the Al-Ti-B intermediate alloy is AlTi5B 1; the Al-B intermediate alloy is AlB3 or AlB 8; the Al-Ti intermediate alloy is AlTi5 or AlTi 10.
3. The high toughness, heat resistant Mg-Y alloy suitable for low pressure casting of claim 1, wherein: the mass percent of the refining agentThe components are as follows: 55% KCl and 25% CaCl2、5% CaF2、15% BaCl2
4. The high toughness, heat resistant Mg-Y alloy suitable for low pressure casting of claim 1, wherein: the addition amount of the refining agent is 1.0-3.5% of the total weight of the raw materials.
5. The high toughness, heat resistant Mg-Y alloy suitable for low pressure casting of claim 1, wherein: the refining temperature when the refining agent is added for refining is 720-730 ℃, and the stirring time of the refining treatment is 10-15 min.
6. The high toughness, heat resistant Mg-Y alloy suitable for low pressure casting of claim 1, wherein: the secondary solution treatment process comprises the following steps: putting the as-cast alloy into a solid solution furnace, heating to 200 ℃ at the speed of 5 ℃/min, introducing protective gas, continuously heating to 480-490 ℃ at the speed of 5 ℃/min for the first-stage solid solution temperature, and keeping the temperature for 36-48 h; and then slowly raising the temperature to 535-545 ℃ of the second-stage solution treatment at a speed of 10 ℃/h, preserving the temperature for 1-2 h, and then quickly transferring to a quenching device for water-cooling quenching.
7. The high-toughness, heat-resistant Mg-Y alloy suitable for low-pressure casting according to claim 1 or 6, wherein: the protective gas is argon or SF with the volume fraction of 0.2 percent6And CO2The mixed gas of (1).
8. The high toughness, heat resistant Mg-Y alloy suitable for low pressure casting of claim 1, wherein: the artificial aging treatment process comprises the following steps: and (3) putting the quenched alloy into an aging furnace, heating to 185-215 ℃ at the temperature of artificial aging treatment at the speed of 5 ℃/min, keeping the temperature for 12-36 h, discharging from the furnace, and air cooling to room temperature.
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