CN109881065A - High-toughness heat-resistant Mg-Gd-Er alloy and preparation method thereof suitable for low pressure casting - Google Patents

Abstract

The present invention provides the high-toughness heat-resistant Mg-Gd-Er alloys and preparation method thereof for being suitable for low pressure casting, the alloy composition mass percentage content are as follows: 3.0~7.0%RE, 1.2~4.2%Zn, 0.5~1.2%Al, 0.1~0.3%Mn, 0.01~0.08%M, surplus Mg；Wherein M is Ti, one or two kinds of elements in B.Preparation method: 1) by Mg-Gd-Er alloying component ingredient is carried out；2) technical pure magnesium ingot is melted；3) 700 DEG C are warming up to, industrial-purity zinc and Mg-Gd, Mg-Er and Mg-Mn intermediate alloy are melted；4) 730 DEG C are warming up to, after technical pure aluminium ingot, Al-Ti, Al-Ti-B, Al-B intermediate alloy whole fusing is added, refining obtains magnesium alloy fused mass；5) low pressure casting；6) second level solution treatment, artificial aging processing.The present invention is suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting after the heat treatment of low pressure casting, second level solution treatment and artificial aging, and room temperature tensile intensity reaches 305MPa, elongation percentage 18%；Drawing by high temperature tensile strength reaches 214MPa at 200 DEG C, and elongation percentage 22% meets aerospace, the high demand that automobile and other industries develop lightweight.

Description

High-toughness heat-resistant Mg-Gd-Er alloy and preparation method thereof suitable for low pressure casting

Technical field

The present invention relates to the high-toughness heat-resistant Mg-Gd-Er alloys for being suitable for low pressure casting, meet aerospace, automobile, telecommunication Etc. industries high demand that lightweight is developed.The invention further relates to the high-toughness heat-resistant Mg-Gd-Er alloys for being suitable for low pressure casting Preparation method, belong to industrial magnesium alloy and manufacturing field.

Background technique

For magnesium alloy as most light engineering metal material (density of magnesium is 2/3, the 1/4 of steel of aluminium), specific strength is obvious Higher than aluminium alloy and steel, although specific stiffness is suitable with aluminium alloy and steel, it is much higher than engineering plastics, while there is good casting Property, the series of advantages such as machinability is good, thermal conductivity is good, damping and amortization and electromagnetic shielding capability are strong and are easily recycled, navigating The fields such as sky, space flight, automobile, electronics and defence and military have a wide range of applications.Magnesium alloy becomes substitution aluminium alloy, steel With engineering plastics to realize light-weighted ideal material, wherein it is aluminium alloy that it is maximum, which to substitute potentiality,.Cast aluminium alloy gold has must The toughness and tenacity and thermal stability wanted are widely used for production engine cylinder body and the parts such as cylinder cap and wheel hub at present, represent Alloy be A354, A356 and A380.If magnesium alloy replaces cast aluminium alloy gold, it must have equivalent toughness and tenacity, and It is inexpensive, be easy to cast.Low pressure casting is that dry compressed air or inert gas are passed through in the crucible of sealing, by means of effect In the pressure on metal bath surface, liquid alloy is passed through into running channel along stalk from bottom to top and is smoothly pressed into metal mold or sand mold etc. Casting mold type chamber, and solidification obtains the casting method of casting under pressure.With the alloy die cast technique etc. generallyd use at present It compares, low pressure casting is the main method of the large-scale complex-shaped high-quality high-performance casting of production.

Earliest, the Atomic radiuses difference of main alloy element aluminium and magnesium is larger while in magnesium for the application of Mg-Al class magnesium alloy In have biggish solid solubility, play solution strengthening and precipitation strength in the alloy.Find that a small amount of Mn is significant in nineteen twenty-five After the corrosion resistance for improving Mg-Al-Zn system magnesium alloy, AZ (such as AZ91) and AM system magnesium alloy (such as AM60, AM50) develop into mesh Preceding most widely used commercialization magnesium alloy.However the high temperature creep property of AZ and AM magnesium alloy is very poor, it is lower than Aluminium Alloys in Common Use An order of magnitude is more, and the tensile strength when temperature is higher than 150 DEG C reduces rapidly, and reason is during high-temerature creep Mg of the oversaturated α-Mg matrix in grain boundaries₁₇Al₁₂Mutually discontinuous precipitation.By the way that alloying element is added to improve precipitated phase The heat resistance of characteristic (crystal structure, form and thermal stability) Lai Tigao Mg-Al alloy, but its room temperature and mechanical behavior under high temperature It is still unable to reach the level of cast aluminium alloy gold, seriously limits its application development.For example, application publication number is CN109136701A Patent document (a kind of sand mold gravitational casting magnesium alloy materials and preparation method thereof) disclosed in magnesium alloy component content are as follows: 3.5 ~4.5wt.%Al, the mischmetal of one or more of La, Ce, Pr of 0.5~4.5wt.%, 0.2~0.5wt.%Mn, One or more of Gd, Y, Sm, Nd, Er, Eu, Ho, Tm, Lu, Dy, Yb of 0.01~2.5wt.% mischmetal, remaining is Mg；The best ambient temperature mechanical properties for the alloy reported: tensile strength 231MPa, elongation percentage 11.4%.

Maximum solid solution degree of the zinc Zn in Mg is up to 6.2wt%, is the important alloy element of high-strength magnesium alloy.It is typical Mg-Zn series cast magnesium alloy include ZK51A and ZK60A, deforming alloy includes ZK21A, ZK31, ZK40A, ZK60A and ZK61 Deng.Increasing with Zn content, the tensile strength and yield strength of alloy improve, and elongation after fracture is declined slightly, but casting character, Process plastic and welding performance deteriorate, especially because freezing range it is wide (such as the freezing range of ZK60 is up to 265 DEG C, Journal of Materials Science 45 (14) (2010) 3797-3803.), cause its hot cracking tendency extremely serious. Rare earth elements RE (rare earth element) is thin to the crystal grain of magnesium alloy to the beneficial effect and zirconium of magnesium alloy strength performance Change effect was found in nineteen thirties, and EK31 becomes Mg-Zr in Mg-RE-Zr system (EK30, EK31, EK41) The high temperature cast magnesium alloy succeeded in developing earliest in class.Magnesium-rare earth alloy based on rare earth RE element has excellent age-hardening Effect, it is a variety of to be successively developed with the novel magnesium alloy that RE is main added elements, such as WE54, WE43 alloy of Mg-Y system. Application publication number is that the patent of the patent document (high-strength heat-resisting magnesium alloy and preparation method thereof) of CN1676646A discloses one The preparation method of kind high-strength heat-resisting magnesium alloy, the component and its weight of the Mg-Gd-Y-Zr (- Ca) magnesium-rare earth invented Percentage are as follows: 6~15%Gd, 1~6%Y, 0.35~0.8%Zr, 0~1.5%Ca, impurity element S i, Fe, Cu and Ni's is total Amount is less than 0.02%, surplus Mg.However, crystallite dimension reaches 90 μm when carrying out sand casting using such alloy, T6 is cast Tensile strength, yield strength and the elongation percentage of state alloy are respectively only 295MPa, 212MPa and 2.2% (application publication number is A kind of high-strength heat-resistant magnesium alloy and preparation method thereof suitable for sand casting disclosed in the patent document of CN104928548A)；Together Although when Ca addition improve the yield strength and elevated temperature strength of alloy, also increased dramatically the solidification temperature range of alloy, Increase hot cracking tendency, reduces the processing performance of alloy.

The solid solubility of heavy rare earth element Gd in the magnesium alloy is up to 25wt%, has strong solution strengthening and ageing strengthening to make With addition Gd can be significantly increased the compactness of magnesium alloy, casting character, three warm (low temperature, room temperature and high temperature) performances, resist Croop property and corrosion resistance.The solid solubility of heavy rare earth element Er in the magnesium alloy is up to 32.7wt.%, significantly larger than its His common rare earth element has strong solution strengthening and ageing strengthening effect.Due to Gd with the performance of Er similar and atomic radius It is close, Er can be added in Mg-Gd system alloy to improve the performance of alloy.Cheap Zn is added in Mg-RE alloy, it is not only right The Precipitation group for regulating and controlling the alloy system is woven with more obvious action, and compares item in different Zn/RE (RE is Gd and Er) A variety of hardening constituents can be formed under part: the icosahedral quasicrystal body structure I easy to form when Zn/RE atomic ratio in alloy >=6.0 Phase (Mg₃Zn₆RE includes Mg₃Zn₆Gd、Mg₃Zn₆Y and Mg₃Zn₆(Gd,Er))；When in alloy Zn/RE atomic ratio between 1.5 and 6.0 When face-centred cubic structure W phase (Mg easy to form₃Zn₃RE₂Including Mg₃Zn₃Gd₂、Mg₃Zn₃Y₂And Mg₃Zn₃(Gd,Er)₂) and I phase； W phase and long period stacking order structure LPSO phase easy to form when Zn/RE atomic ratio is between 1.0 and 1.5 in alloy (Mg₁₂ZnRE includes Mg₁₂ZnGd、Mg₁₂ZnY and Mg₁₂Zn(Gd,Er))；It is easy to form when Zn/RE atomic ratio in alloy≤1.0 LPSO phase (Materials Science and Engineering A, 695 (2017) 135-143；Journal of Alloys and Compounds,602(2014)32-39；Acta Materialia,68(2014)325-338).A variety of Mg-Gd-Y-Zn Hardening constituent can be further improved the room temperature intensity and high-temperature behavior of magnesium alloy, in addition to hardening constituent W, the elasticity modulus of LPSO phase and Microhardness is more much higher than pure magnesium, can significantly improve the intensity and plasticity of magnesium alloy, show alloy excellent Comprehensive mechanical property.The study found that only when rare earth element is that Y, Gd, Er, Dy, Ho, Tb, Tm can be formed in Mg-RE-Zn system LPSO structure (Materials Transactions, 48 (11) (2007) 2986-2992).Application publication number is One kind of patent document (rare earth wrought magnesium alloy containing the trace of Al and preparation method thereof) report of CN104651693A is containing micro The rare earth wrought magnesium alloy of Al element, weight percent composition are as follows: 6.5~15.0%Gd, 3.0~5.5%Y, 2.0~ 4.0%Zn, 0.3~1.5%Nd, 0.3~0.9%Zr, 0.4~1.0%Al, surplus Mg；Preparation method includes raw material standard Standby, alloy melting, alloy semi-solid extruding, Homogenization Treatments, redeformation, cooling and pre-stretching processing and ageing strengthening processing etc. Step.The invention are as follows: in the alloy component range that the invention provides, the Nd rare earth element of addition promotes Formation coarse blocky Mg₅(Gd, Y, Nd) phase, Mg-RE-Zn reinforcing phase amount, which is accordingly reduced, causes performance to decline；Simultaneously Rare earth Gd, Y and Nd content are too high, and expensive rare earth price and complicated preparation process cause the invention to be difficult industrially It is applied on a large scale.Application publication number be CN102212727A patent document (Authigenic quasicrystal-reinforced Mg-Zn-Y alloy and Its method of smelting) report Authigenic quasicrystal-reinforced Mg-Zn-Y alloy chemical component quality percentage composition are as follows: Zn 3.0~ 10.0%, Y 0.5~3.0%, Al-Ti-C 0.05~1.0%, surplus are Mg and inevitable impurity；Preparation method packet Melting and casting are included, Al-Ti-C intermediate alloy is added when being cooled to 700~720 DEG C in the melt after melting, introduces in the melt super Sound wave is cast after ultrasonication and is made；The invention Authigenic quasicrystal-reinforced Mg-Zn-Y alloy tensile strength up to 260MPa, Elongation percentage 10.6%.The inventive technique there are still following problems: the Zn/Y mass of the alloy forms quasi-crystalline substance I than too high levels Phase, while its freezing range is excessive, can only carry out gravitational casting and be not suitable for die casting, and introduce ultrasonication, operate In complexity, it is difficult industrially to be applied on a large scale.Under the conditions of conventional coagulation, Mg-Gd-Er-Zn alloy grain is coarse, Precipitated phase is usually in coarse reticular structure, is degrading its mechanical property, it is necessary to by thermal deformation or heat treatment solid solution and when Effect adjusts precipitate size to play the effect of its hardening constituent.

Mg-Gd-Er-Zn alloy is usually added into Zr as grain refining element, to refine its coarse microstructure.At present Reported plus Zr mode has halogen, Zn-Zr intermediate alloy and Mg-Zr intermediate alloy of sponge Zr, Zr etc., wherein in Mg-Zr Between alloy have the advantages that it is easy to use, be mingled with less and good in refining effect, be the major way for being currently fed Zr.Application publication number is The patent document (a kind of the anti-flaming Mg-Gd-Y-Zn-Zr alloy of high-strength anticorrosion and preparation method thereof) of CN106756370A is disclosed A kind of anti-flaming Mg-Gd-Y-Zn-Zr alloy of high-strength anticorrosion and preparation method thereof, the Mg-Gd-Y-Zn-Zr alloy includes each Component and its mass percent are as follows: 3.0%≤Gd≤9.0%, 1.0%≤Y≤6.0%, 0.5%≤Zn≤3.0%, 0.2% ≤ Zr≤1.5%, surplus are Mg and inevitable impurity.The inventive technique there are still following problems: firstly, in Mg-Zr Between alloy preparation process is complicated, energy consumption is high, lead to that it is expensive, production can be improved using Mg-Zr intermediate alloy refinement crystal grain Product cost；Secondly, the chemical activity of Zr is strong, it is easy at high temperature and atmosphere, furnace gas reacts, when using steel crucibles, molten When temperature is higher than 750 DEG C, Zr is easy to react with the Fe in crucible, generates stable intermetallic compound Fe₂Zr, these are all led Cause the loss of Zr high；Many Zr in Mg-Zr intermediate alloy are existed in the form of large scale simple substance Zr particle, due to melting for Zr Point is high (1852 DEG C), and Zr particle is difficult to dissolve in melt, in addition the density of Zr is much larger than the density of Serum Magnesium, (density of Zr is 6.52g/cm³, the density of pure Serum Magnesium is 1.58g/cm³), it is easy to be deposited to crucible bottom, causes Zr recovery rate low.

Summary of the invention

The present invention is unable to reach the casting aluminium such as A380 to solve existing cast magnesium alloy because of obdurability, heat resistance deficiency The performance of alloy, the professional problem for causing its application to be extremely restricted, provides the high-toughness heat-resistant Mg- suitable for low pressure casting Gd-Y alloy and preparation method thereof, for the alloy after low pressure casting is heat-treated, the room temperature tensile intensity of alloy reaches 307MPa, prolongs Stretch rate 17%；Drawing by high temperature tensile strength reaches 216MPa, elongation percentage 23% at 200 DEG C.

In order to solve the above-mentioned technical problem, the present invention adopts the following technical solutions:

High-toughness heat-resistant Mg-Gd-Er alloy of the present invention suitable for low pressure casting, including following mass percent Element: 3.0~7.0%RE, 1.2~4.2%Zn, 0.5~1.2%Al, 0.1~0.3%Mn, 0.01~0.08%M, surplus are Mg and other inevitable impurity, wherein RE is the composite component of Gd and Er, one or both of M Ti, B.

The present invention is suitable for the innovative point of the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting:

(1) in alloy design in addition to common metal Zn, Al, Mn and a small amount of Ti and B element, the present invention selects heavy rare earth Element Gd and Er is as its alloy element.Alloy element RE element (RE is Gd and Er) and Zn and matrix Mg element form three First Mg-RE-Zn hardening constituent, especially Zn/RE mass ratio are 0.2~0.6, and wherein the mass ratio of Gd/Er is in the composition of RE In 0.25~4 range, on the one hand, alloy of the present invention primarily forms long period stacking order structure LPSO phase (Mg₁₂ZnRE includes Mg₁₂ZnGd、Mg₁₂ZnEr and Mg₁₂Zn (Gd, Er)) and face-centred cubic structure W phase (Mg₃Zn₃RE₂Including Mg₃Zn₃Gd₂、 Mg₃Zn₃Er₂And Mg₃Zn₃(Gd,Er)₂), it is high-melting-point phase；With binary Mg-Y hardening constituent ratio, ternary Mg-RE-Zn hardening constituent High-temperature stable of the LPSO and W in magnesium matrix is more preferable, avoids the reduced performance as caused by precipitation strength phased soln, effectively increases The room-temperature mechanical property and high-temperature behavior of the strong high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting, especially 300 DEG C when high temperature creep property improve an order of magnitude or more.On the other hand, the present invention solves traditional Mg-Zn-RE alloy Because excessively high Zn content causes to be also easy to produce thermal fragmentation defect, the toughness and tenacity of alloy and Production Practice of Casting Technologies drop due to freezing range is excessive Low technical problem.

It (2) is the mixed of Gd and Er suitable for rare earth RE element added by the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting Rare earth is closed, without the mischmetal using Gd or Er and common Ce, La, Nd, Pr, reason is: on the one hand, if alloy Middle addition often uses rare earth element containing Ce, La, Nd, Pr, with the raising of the common rare earth element content such as Ce, the solidification temperature of alloy Degree range, which becomes larger, causes segregation and Production Practice of Casting Technologies to be deteriorated, casting flaw easy to form；On the other hand, as Ce etc. is normal With the raising of rare earth element content, main hardening constituent W, LPSO phase that alloy is precipitated is gradually converted into (Mg, Zn)₁₂RE phase, causes W, LPSO of stable components strengthen phase amount and sharply reduce in alloy, so as to cause precipitating reinforcing effect reduction.In addition, Er is being mentioned Plasticity is influenced less while rising alloy strength, Gd, which mixes the promotion being added to alloy property with Er, to be had than being individually added into more Good composite effect.

(3) Mg-Gd-Er-Zn alloy precipitated phase under the conditions of conventional coagulation is usually in coarse reticular structure, is degrading it Mechanical property, it is often necessary to which precipitate size is adjusted to play its hardening constituent by thermal deformation or heat treatment solid solution and timeliness Effect.Such alloy is usually added into Zr as grain refining element, closes in alloying element of the invention containing Al, Mn and Rare Earth Y Gold element, these elements form Al in conjunction with Zr₃The compounds such as Zr and being deposited to crucible bottom makes zirconium not play Grain Refinement Effect. On the other hand, studies have shown that the thermal structure stability of the Mg-Gd-Er-Zn alloy of addition Zr refinement is poor, in 550 DEG C of heat preservations Crystal grain is sharply roughened, and high-temperature behavior is caused to be greatly lowered.To solve the above-mentioned problems, low melt is added in alloy of the invention 0.5-1.2%Al substitute Zr, form the high-melting-point Al of disperse₃Er、Al₂Gd and Al₄GdY phase has not only refined the group of alloy It knits, and ensures the high-temperature stability of Magnesium Alloy with high-temperature-phases such as LPSO.Al rises multiple together with a small amount of Ti and B simultaneously Grain Refinement Effect is closed, alloy structure has further been refined, has improved the obdurability of alloy.It is added in alloying element of the invention A small amount of Mn can not only promote the formation of LPSO phase, improve the high-temperature stability of alloy, and improve the corrosion-resistant of magnesium alloy Performance.

(4) in order to reduce the hot cracking tendency in Mg-Gd-Er-Zn alloy casting process, Gd/Er is limited in alloy of the present invention Mass ratio be that 0.25~4, Zn/RE mass ratio is 0.2~0.6 and (Zn+Al)/RE mass ratio is 0.3~0.8.In this matter Under amount ratio, alloy of the invention obtains relatively narrow freezing range, to overcome in Mg-Gd-Er-Zn alloy casting process Hot cracking tendency improves the Production Practice of Casting Technologies of alloy.

The preparation method of the above-mentioned high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting, includes the following steps:

(1) with due regard to after scaling loss, by above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, raw material (work needed for calculating Industry pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot, Mg-Gd intermediate alloy, Mg-Er intermediate alloy, Mg-Mn intermediate alloy, Al-Ti Intermediate alloy, Al-Ti-B intermediate alloy and Al-B intermediate alloy) dosage；By technical pure magnesium ingot, industrial-purity zinc, commercial-purity aluminium Ingot and Mg-Gd, Mg-Er and Mg-Mn intermediate alloy remove removing oxide layer and dry to be preheated to 200 DEG C.

(2) after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath at 680 DEG C, it is passed through protective gas, is added Enter remaining magnesium ingot.The protective gas is argon gas, or the SF for being 0.2% containing volume fraction₆And CO₂Mixed gas (i.e. SF₆Body Fraction is 0.2%, CO₂Volume fraction be 99.8%).

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, will be closed among industrial-purity zinc and Mg-Gd, Mg-Er and Mg-Mn More (2~4) the secondary additions of gold point, and keep temperature constant at 700 DEG C, it is stirred until all melting, and keep the temperature 30min.Make To be preferred, the Mg-Gd intermediate alloy is MgGd25 or MgGd30, and the intermediate alloy of the Mg-Er is MgEr25 or MgEr30, The intermediate alloy of the Mg-Mn is MgMn10.

(4) 40~60min before low pressure casting is warming up to 730 DEG C, closes among technical pure aluminium ingot to be sequentially added, Al-Ti Gold, Al-Ti-B intermediate alloy, Al-B intermediate alloy all after fusing, are added refining agent and are refined, furnace temperature is risen to 750 DEG C Heat preservation stands 10~20min, and promotion is mingled with sedimentation, obtains magnesium alloy fused mass.The Al-Ti-B intermediate alloy is AlTi5B1, institute Stating Al-B intermediate alloy is that perhaps the AlB8 Al-Ti intermediate alloy is AlTi5 or AlTi10 to AlB3.The refining agent Mass percent component are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂, 15%BaCl₂.The refining agent additive amount is that raw material is total The 1.0~3.5% of weight, refining temperature when refining agent refining is added are 720~730 DEG C, the mixing time 10 of refining treatment ~15min.

(5) magnesium alloy fused mass is cooled between 720~740 DEG C and is removed the gred, preheating sand mold type molds temperature is extremely 25~150 DEG C or preheated metallic type mold temperature are to 180~250 DEG C.Low pressure casting process is controlled and is divided by proportioning valve Grade pressurization, comprising: rise liquid, fill type, pressurization, pressure maintaining, release stage, wherein the pressure for rising the liquid stage is uniformly increased to 0.02- 0.05MPa, pressing time control in 5~8s；The pressure for filling the type stage is uniformly increased to 0.08MPa, and molten metal fills under stress Full casting mold type chamber；The pressure of pressurization stages is uniformly increased to 0.1MPa, and pressing time controls in 10~15s；The guarantor of packing stage Press time control in 200~300s.Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release.

(6) the resulting cast alloy of low pressure casting is successively carried out needed for second level solution treatment, artificial aging processing acquisition High-toughness heat-resistant Mg-Y alloy.

The step of second level solid solution treatment process suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting are as follows: will Cast alloy is put into solid solution furnace, is warming up to 200 DEG C with 5 DEG C/min, is passed through protective gas (i.e. SF₆Volume fraction is 0.2%, CO₂Volume fraction be 99.8%)), continue to be warming up to 480~490 DEG C of first order solid solubility temperature with 5 DEG C/min, heat preservation 36~ 48h；Then 535~545 DEG C of second level solid solution temperature are warming up at a slow speed with 10 DEG C/h, fast transfer is extremely after keeping the temperature 1~2h Water hardening is carried out on quenching unit.

The step of artificial aging treatment process suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting are as follows: will Quenched alloy is put into aging furnace, is warming up to 185~215 DEG C of artificial aging treatment temperature with 5 DEG C/min, and heat preservation 12~ It comes out of the stove after 36h and is air-cooled to room temperature.

The second level solid solution treatment process parameter are as follows: 480~490 DEG C of first order solid solubility temperature, 36~48h of soaking time； 535~545 DEG C of second level solid solubility temperature, 1~2h of soaking time；

The artificial aging treatment process parameter: 185~215 DEG C of aging temp, 12~36h of soaking time.

The innovative point of the preparation method of high-toughness heat-resistant Mg-Gd-Er alloy provided by the invention suitable for low pressure casting: (1) Mg-Gd, Mg-Er intermediate alloy of easy scaling loss are added at 700 DEG C, and keeps the temperature fusing in this low-temperature melt, improves rare earth The recovery rate of Gd and Er；(2) refining treatment, which uses, is free of MgCl₂Dedicated refining agent, further reduced dilute in refining process The scaling loss of native Gd and Er.(3) heat treatment of high-toughness heat-resistant casting Mg-Gd-Er alloy of the present invention includes solution treatment With two processes of ageing treatment.480~490 DEG C, 36~48h of time of the first order temperature of second level solution treatment, sufficiently promote Gd, Solubility of the Er and Zn in magnesium matrix eliminates the coarse precipitated phases such as LPSO；The first order temperature 535 of second level solution treatment~ 545 DEG C, 1~2h of time, the coarse phase such as undissolved LPSO is further eliminated in short time heat preservation, eliminates existing region in casting Segregation, microsegregation, so that the homogenization of composition of alloy, to improve the performance of alloy, and prevents that heat treatment burning is existing As.Furnace temperature is maintained at 185~215 DEG C, 12~36h of heat preservation carries out ageing treatment, and long period timeliness finally makes alloy transgranular Nano grade, dispersed and tiny hardening constituent is precipitated, so that alloy be made to have both excellent room temperature and high-temperature behavior.Through the invention Heat treatment, alloying component are stablized, and crystal grain is not obviously grown up, and the performance of alloy is significantly improved, and method is simple, peace It is complete reliable, it is easy to operate.

The present invention have it is following the utility model has the advantages that

High-toughness heat-resistant casting Mg-Gd-Er alloy of the invention is through low pressure casting, second level solution treatment and artificial aging warm After processing, room temperature tensile intensity reaches 305MPa, elongation percentage 18%；Drawing by high temperature tensile strength reaches 214MPa at 200 DEG C, prolongs Rate 22% is stretched, comprehensive performance reaches the performance of the cast aluminium alloy golds such as A380；Provided preparation method has simple process, efficiency The advantages that high, suitable large-scale production, meet the high demand that aerospace, military project, automobile and other industries develop lightweight.

Detailed description of the invention

Fig. 1 is the low pressure casting magnesium alloy cast metallographic structure figure prepared in embodiment 3.

Specific embodiment

Embodiment 1

The weight percent of high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting are as follows: press stoichiometric, 0.6% Er, 2.4%Gd, 1.2%Zn, 1.2%Al, 0.3%Mn, 0.01%Ti, 0.01%B, surplus is Mg and other are inevitable Impurity.

Preparation method: (1) with due regard to scaling loss after, by above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, institute is calculated Need the dosage of raw material；By technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot and MgGd30, MgEr30 and MgMn10 intermediate alloy It removes removing oxide layer and dries to be preheated to 200 DEG C.

(2) after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath at 680 DEG C, it is passed through protective gas argon Remaining magnesium ingot is added in gas.

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, among industrial-purity zinc and MgGd30, MgEr30 and MgMn10 2~4 additions of alloy point, and keep temperature constant at 700 DEG C, it is stirred until all melting, and keep the temperature 30min.

(4) 40~60min before low pressure casting, is warming up to 730 DEG C, closes among technical pure aluminium ingot to be sequentially added, AlTi10 Gold, AlB8 intermediate alloy are all after fusing, and the refining agent that raw material weight 1% is added is refined, 730 DEG C of the temperature of refining, essence The mixing time 10min of processing is refined, refining agent component is by mass percentage are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂, 15% BaCl₂.Furnace temperature is risen into 750 DEG C of heat preservations and stands 10min, promotion is mingled with sedimentation, obtains magnesium alloy fused mass.

(5) magnesium alloy fused mass is cooled to 720 DEG C to remove the gred, sand mold mould temperature is 25 DEG C.Low pressure casting mistake Journey is controlled and is classified pressurization by proportioning valve, comprising: is risen liquid, is filled type, pressurization, pressure maintaining, release stage, wherein rises liquid rank The pressure of section is uniformly increased to 0.02MPa, pressing time 5s；The pressure for filling the type stage is uniformly increased to 0.08MPa, molten metal It is full of casting mold type chamber under stress；The pressure of pressurization stages is uniformly increased to 0.1MPa, pressing time 10s；Packing stage Dwell time is 200s.Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release.

(6) second level solution treatment is successively carried out to the resulting cast alloy of low pressure casting, casting alloy is put into solid solution furnace It is interior, 200 DEG C are warming up to 5 DEG C/min, is passed through the SF containing 0.2% volume fraction₆And CO₂Mixed gas, continue with 5 DEG C/min 480 DEG C of first order solid solubility temperature are warming up to, 36h is kept the temperature, is then warming up to 535 DEG C of second level solid solubility temperature at a slow speed with 10 DEG C/h, Water hardening is carried out on fast transfer to quenching unit after heat preservation 1h.

(7) artificial aging processing is carried out to the casting alloy after solution treatment, quenched alloy is put into aging furnace, Be warming up to 185 DEG C of artificial aging treatment temperature with 5 DEG C/min, keep the temperature to come out of the stove after 12h and be air-cooled to room temperature, obtain it is described be suitable for it is low The high-toughness heat-resistant Mg-Gd-Er alloy that die casting is made.

High-toughness heat-resistant Mg-Gd-Er alloy obtained is subjected to a. room temperature tensile test respectively；B.200 DEG C, 200h heat is sudden and violent In 200 DEG C of progress high temperature tensile properties tests after dew processing.The room temperature tensile for the high-toughness heat-resistant magnesium alloy that this example obtains is strong Degree is 278MPa, elongation percentage 23%；Drawing by high temperature tensile strength is 188MPa, elongation percentage 28% at 200 DEG C.

Embodiment 2

The weight percent of high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting are as follows: press stoichiometric, 2.0% Er, 4.0%Gd, 3.6%Zn, 0.6%Al, 0.1%Mn, 0.08%Ti, surplus are Mg and other inevitable impurity.

Preparation method: (1) with due regard to scaling loss after, by above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, institute is calculated Need the dosage of raw material；By technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot and MgGd30, MgEr30 and MgMn10 intermediate alloy It removes removing oxide layer and dries to be preheated to 200 DEG C.

(2) it after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath at 680 DEG C, is passed through protective gas and contains The SF of 0.2% volume fraction₆And CO₂Mixed gas, remaining magnesium ingot is added.

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, among industrial-purity zinc and MgGd30, MgEr30 and MgMn10 2~4 additions of alloy point, and keep temperature constant at 700 DEG C, it is stirred until all melting, and keep the temperature 30min.

(4) 40~60min before low pressure casting is warming up to 730 DEG C, closes among technical pure aluminium ingot to be sequentially added, AlTi5 After golden all fusings, the refining agent that raw material weight 3.5% is added is refined, 730 DEG C of the temperature of refining, the stirring of refining treatment Time 10min, refining agent component is by mass percentage are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂, 15%BaCl₂.By furnace temperature It rises to 750 DEG C of heat preservations and stands 20min, promotion is mingled with sedimentation, obtains magnesium alloy fused mass.

(5) magnesium alloy fused mass is cooled to 720 DEG C to remove the gred, preheats sand mold mould temperature to 150 DEG C.Low pressure casting It makes process and is controlled and be classified pressurization by proportioning valve, comprising: rise liquid, fill type, pressurization, pressure maintaining, release stage, wherein rise The pressure in liquid stage is uniformly increased to 0.05MPa, pressing time 8s；The pressure for filling the type stage is uniformly increased to 0.08MPa, gold Belong to liquid and is full of casting mold type chamber under stress；The pressure of pressurization stages is uniformly increased to 0.1MPa, pressing time 15s；Pressure maintaining rank The dwell time of section is 300s.Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release.

(6) second level solution treatment is successively carried out to the resulting cast alloy of low pressure casting, casting alloy is put into solid solution furnace It is interior, 200 DEG C are warming up to 5 DEG C/min, is passed through protective gas argon gas, continues to be warming up to first order solid solubility temperature 490 with 5 DEG C/min DEG C, 48h is kept the temperature, is then warming up to 545 DEG C of second level solid solubility temperature at a slow speed with 10 DEG C/h, keeps the temperature after 2h fast transfer to quenching dress Set carry out water hardening.

(7) artificial aging processing is carried out to the casting alloy after solution treatment, quenched alloy is put into aging furnace, Be warming up to 215 DEG C of artificial aging treatment temperature with 5 DEG C/min, keep the temperature to come out of the stove after 36h and be air-cooled to room temperature, obtain it is described be suitable for it is low The high-toughness heat-resistant Mg-Gd-Er alloy that die casting is made.

High-toughness heat-resistant Mg-Gd-Er alloy obtained is subjected to a. room temperature tensile test respectively；B.200 DEG C, at 200h heat exposure In 200 DEG C of progress high temperature tensile properties tests after reason.The room temperature tensile intensity of high-toughness heat-resistant magnesium alloy that this example obtains is 305MPa, elongation percentage 18%；Drawing by high temperature tensile strength is 211MPa, elongation percentage 16% at 200 DEG C.

Embodiment 3

The weight percent of high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting are as follows: press stoichiometric, 3.0% Gd, 3.0%Er, 1.2%Zn, 0.6%Al, 0.2%Mn, 0.05%Ti, 0.03%B, surplus is Mg and other are inevitable Impurity.

Preparation method: (1) with due regard to scaling loss after, by above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, institute is calculated Need the dosage of raw material；By technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot and MgGd30, MgEr30 and MgMn10 intermediate alloy It removes removing oxide layer and dries to be preheated to 200 DEG C.

(2) after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath at 680 DEG C, it is passed through protective gas argon Remaining magnesium ingot is added in gas.

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, among industrial-purity zinc and MgGd30, MgEr30 and MgMn10 2~4 additions of alloy point, and keep temperature constant at 700 DEG C, it is stirred until all melting, and keep the temperature 30min.

(4) 40~60min before low pressure casting, is warming up to 730 DEG C, among technical pure aluminium ingot to be sequentially added, AlTi10 Alloy, AlB3 intermediate alloy are all after fusing, and the refining agent that raw material weight 2.5% is added is refined, the temperature 720 of refining DEG C, the mixing time 15min of refining treatment, refining agent component is by mass percentage are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂、 15%BaCl₂.Furnace temperature is risen into 750 DEG C of heat preservations and stands 15min, promotion is mingled with sedimentation, obtains magnesium alloy fused mass.

(5) magnesium alloy fused mass is cooled to 730 DEG C to remove the gred, preheated metallic type mold temperature is 180 DEG C.Low pressure Casting process is controlled and is classified pressurization by proportioning valve, comprising: is risen liquid, is filled type, pressurization, pressure maintaining, release stage, wherein The pressure for rising the liquid stage is uniformly increased to 0.03MPa, pressing time 6s；The pressure for filling the type stage is uniformly increased to 0.08MPa, Molten metal is full of casting mold type chamber under stress；The pressure of pressurization stages is uniformly increased to 0.1MPa, pressing time 12s；Pressure maintaining The dwell time in stage is 250s.Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release.

(6) the resulting cast alloy of low pressure casting successively carries out second level solution treatment, and casting alloy is put into solid solution furnace, 200 DEG C are warming up to 5 DEG C/min, is passed through protective gas argon gas, continues to be warming up to 485 DEG C of first order solid solubility temperature with 5 DEG C/min, 42h is kept the temperature, is then warming up to 540 DEG C of second level solid solubility temperature at a slow speed with 10 DEG C/h, keeps the temperature after 1.5h fast transfer to quenching dress Set carry out water hardening.

(7) artificial aging processing is carried out to the casting alloy after solution treatment, quenched alloy is put into aging furnace, Be warming up to 200 DEG C of artificial aging treatment temperature with 5 DEG C/min, heat preservation is come out of the stove afterwards for 24 hours is air-cooled to room temperature, obtain it is described be suitable for it is low The high-toughness heat-resistant Mg-Gd-Er alloy that die casting is made.

High-toughness heat-resistant Mg-Gd-Er alloy obtained is subjected to a. room temperature tensile test respectively；B.200 DEG C, 200h heat is sudden and violent In 200 DEG C of progress high temperature tensile properties tests after dew processing.The room temperature tensile for the high-toughness heat-resistant magnesium alloy that this example obtains is strong Degree is 294MPa, elongation percentage 20%；Drawing by high temperature tensile strength is 202MPa, elongation percentage 21% at 200 DEG C.The present embodiment obtains Magnesium alloy cast metallographic structure figure it is as shown in Figure 1.

Embodiment 4

The weight percent of high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting are as follows: press stoichiometric, 4.0% Er, 2.0%Gd, 2.0%Zn, 1.2%Al, 0.2%Mn, 0.08%B, surplus are Mg and other inevitable impurity.

Preparation method: (1) with due regard to scaling loss after, by above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, institute is calculated Need the dosage of raw material；By technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot and MgGd30, MgEr30 and MgMn10 intermediate alloy It removes removing oxide layer and dries to be preheated to 200 DEG C.

(2) it after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath at 680 DEG C, is passed through containing 0.2% volume The SF of score₆And CO₂Hybrid protection gas, remaining magnesium ingot is added.

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, among industrial-purity zinc and MgGd30, MgEr30 and MgMn10 2~4 additions of alloy point, and keep temperature constant at 700 DEG C, it is stirred until all melting, and keep the temperature 30min.

(4) 40~60min before low pressure casting, is warming up to 730 DEG C, technical pure aluminium ingot to be sequentially added, AlB8 intermediate alloy All after fusing, the refining agent that raw material weight 3.0% is added is refined, 720 DEG C of the temperature of refining, when the stirring of refining treatment Between 15min, refining agent component is by mass percentage are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂, 15%BaCl₂.By furnace temperature liter 10min is stood to 750 DEG C of heat preservations, promotion is mingled with sedimentation, obtains magnesium alloy fused mass.

(5) magnesium alloy fused mass is cooled to 740 DEG C to remove the gred, preheated metallic type mold temperature is to 250 DEG C.Low pressure Casting process is controlled and is classified pressurization by proportioning valve, comprising: is risen liquid, is filled type, pressurization, pressure maintaining, release stage, wherein The pressure for rising the liquid stage is uniformly increased to 0.04MPa, pressing time 8s；The pressure for filling the type stage is uniformly increased to 0.08MPa, Molten metal is full of casting mold type chamber under stress；The pressure of pressurization stages is uniformly increased to 0.1MPa, pressing time 12s；Pressure maintaining The dwell time in stage is 220s.Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release.

(6) second level solution treatment is successively carried out to the resulting cast alloy of low pressure casting, casting alloy is put into solid solution furnace It is interior, 200 DEG C are warming up to 5 DEG C/min, is passed through the SF containing 0.2% volume fraction₆And CO₂Hybrid protection gas, continue with 5 DEG C/ Min is warming up to 480 DEG C of first order solid solubility temperature, keeps the temperature 48h, is then warming up to second level solid solubility temperature 535 at a slow speed with 10 DEG C/h DEG C, water hardening is carried out on fast transfer to quenching unit after heat preservation 2h.

(7) artificial aging processing is carried out to the casting alloy after solution treatment, quenched alloy is put into aging furnace, Be warming up to 185 DEG C of artificial aging treatment temperature with 5 DEG C/min, keep the temperature to come out of the stove after 36h and be air-cooled to room temperature, obtain it is described be suitable for it is low The high-toughness heat-resistant Mg-Gd-Er alloy that die casting is made.

High-toughness heat-resistant Mg-Gd-Er alloy obtained is subjected to a. room temperature tensile test respectively；B.200 DEG C, 200h heat is sudden and violent In 200 DEG C of progress high temperature tensile properties tests after dew processing.The room temperature tensile for the high-toughness heat-resistant magnesium alloy that this example obtains is strong Degree is 300MPa, elongation percentage 18%；Drawing by high temperature tensile strength is 207MPa, elongation percentage 19% at 200 DEG C.

Embodiment 5

The weight percent of high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting are as follows: press stoichiometric, 1.7% Gd, 6.8%Er, 4.8%Zn, 0.9%Al, 0.3%Mn, 0.04%Ti, 0.04%B, surplus is Mg and other are inevitable Impurity.

Preparation method: (1) with due regard to scaling loss after, by above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, institute is calculated Need the dosage of raw material；By technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot and MgGd30, MgEr30 and MgMn10 intermediate alloy It removes removing oxide layer and dries to be preheated to 200 DEG C.

(2) after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath at 680 DEG C, it is passed through protective gas argon Remaining magnesium ingot is added in gas.

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, among industrial-purity zinc and MgGd30, MgEr30 and MgMn10 2~4 additions of alloy point, and keep temperature constant at 700 DEG C, it is stirred until all melting, and keep the temperature 30min.

(4) 40~60min before low pressure casting, is warming up to 730 DEG C, among technical pure aluminium ingot to be sequentially added, AlTi5B1 Alloy, AlB8 intermediate alloy are all after fusing, and the refining agent that raw material weight 2.0% is added is refined, the temperature 730 of refining DEG C, the mixing time 10min of refining treatment, refining agent component is by mass percentage are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂、 15%BaCl₂.Furnace temperature is risen into 750 DEG C of heat preservations and stands 20min, promotion is mingled with sedimentation, obtains magnesium alloy fused mass.

(5) magnesium alloy fused mass is cooled to 720 DEG C to remove the gred, preheats sand mold mould temperature to 100 DEG C.Low pressure casting It makes process and is controlled and be classified pressurization by proportioning valve, comprising: rise liquid, fill type, pressurization, pressure maintaining, release stage, wherein rise The pressure in liquid stage is uniformly increased to 0.05MPa, pressing time 5s；The pressure for filling the type stage is uniformly increased to 0.08MPa, gold Belong to liquid and is full of casting mold type chamber under stress；The pressure of pressurization stages is uniformly increased to 0.1MPa, pressing time 15s；Pressure maintaining rank The dwell time of section is 300s.Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release.

(6) second level solution treatment is successively carried out to the resulting cast alloy of low pressure casting, casting alloy is put into solid solution furnace It is interior, 200 DEG C are warming up to 5 DEG C/min, is passed through the SF containing 0.2% volume fraction₆And CO₂Hybrid protection gas, continue with 5 DEG C/ Min is warming up to 490 DEG C of first order solid solubility temperature, keeps the temperature 36h, is then warming up to second level solid solubility temperature 545 at a slow speed with 10 DEG C/h DEG C, water hardening is carried out on fast transfer to quenching unit after heat preservation 1h.

(7) artificial aging processing is carried out to the casting alloy after solution treatment, quenched alloy is put into aging furnace, Be warming up to 215 DEG C of artificial aging treatment temperature with 5 DEG C/min, keep the temperature to come out of the stove after 12h and be air-cooled to room temperature, obtain it is described be suitable for it is low The high-toughness heat-resistant Mg-Gd-Er alloy that die casting is made.

High-toughness heat-resistant Mg-Gd-Er alloy obtained is subjected to a. room temperature tensile test respectively；B.200 DEG C, 200h heat is sudden and violent In 200 DEG C of progress high temperature tensile properties tests after dew processing.The room temperature tensile for the high-toughness heat-resistant magnesium alloy that this example obtains is strong Degree is 301MPa, elongation percentage 15%；Drawing by high temperature tensile strength is 214MPa, elongation percentage 24% at 200 DEG C.

Above-described embodiment is not limit the invention in any way, all to be obtained by the way of equivalent substitution or equivalent transformation Technical solution fall within the scope of protection of the present invention.

Claims (13)

1. being suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting, it is characterised in that the member including following mass percent Element: 3.0~7.0%RE, 1.2~4.2%Zn, 0.5~1.2%Al, 0.1~0.3%Mn, 0.01~0.08%M, surplus Mg With other inevitable impurity；Wherein, RE is the combination of Gd and Er, one or both of M Ti, B.

2. being suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as described in claim 1, it is characterised in that: Zn/RE Mass ratio is 0.2~0.6, wherein the mass ratio of Gd/Er is 0.25~4.

3. being suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as described in claim 1, it is characterised in that: (Zn+ Al)/RE mass ratio is 0.3~0.8.

4. the preparation side of the high-toughness heat-resistant Mg-Gd-Er alloy as claimed in any one of claims 1 to 3 suitable for low pressure casting Method, it is characterised in that include the following steps:

(1) press above-mentioned Mg-Gd-Er alloying component and stoichiometric ratio, calculate technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot, Mg-Gd intermediate alloy, Mg-Er intermediate alloy, Mg-Mn intermediate alloy, Al-Ti intermediate alloy, Al-Ti-B intermediate alloy and Al-B The dosage of intermediate alloy；By technical pure magnesium ingot, industrial-purity zinc, technical pure aluminium ingot, Mg-Gd intermediate alloy, Mg-Er intermediate alloy and Mg-Mn intermediate alloy removes removing oxide layer and dries to be preheated to 200 DEG C；

(2) after the technical pure magnesium ingot for accounting for crucible height 25% being fused into molten bath, it is passed through protective gas, remaining magnesium ingot is added；

(3) after magnesium ingot all fusing, 700 DEG C are warming up to, by industrial-purity zinc and Mg-Gd, Mg-Er and Mg-Mn intermediate alloy point It is repeatedly added, and keeps temperature constant at 700 DEG C, be stirred until all melting, and keep the temperature 30min；

(4) 40~60min before low pressure casting, is warming up to 730 DEG C, technical pure aluminium ingot to be sequentially added, Al-Ti intermediate alloy, Al-Ti-B intermediate alloy, Al-B intermediate alloy all after fusing, are added refining agent and are refined, furnace temperature is risen to 750 DEG C of heat preservations 10~20min is stood, promotion is mingled with sedimentation, obtains magnesium alloy fused mass；

(5) magnesium alloy fused mass is cooled between 720~740 DEG C and is removed the gred, preheating sand mold type molds temperature to 25~ 150 DEG C or preheated metallic type mold temperature are to 180~250 DEG C；Low pressure casting process, which is controlled and is classified by proportioning valve, to be added Pressure, low pressure casting process include: a liter liquid, fill type, pressurization, pressure maintaining, release stage, wherein the pressure for rising the liquid stage uniformly increases To 0.02-0.05MPa, pressing time is controlled in 5~8s；The pressure for filling the type stage is uniformly increased to 0.08MPa, and molten metal is being pressed Casting mold type chamber is full of under power；The pressure of pressurization stages is uniformly increased to 0.1MPa, and pressing time controls in 10~15s；Pressure maintaining rank The dwell time of section controls in 200~300s；Prepared As-cast High Strength Toughness heat-resistant cast Mg-Gd-Er alloy is taken out after release；

(6) second level solution treatment is successively carried out to the resulting cast alloy of low pressure casting, artificial aging processing obtains required height Tough heat-resisting Mg-Y alloy.

5. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 4, feature Be: the Mg-Gd intermediate alloy is MgGd25 or MgGd30, and the Mg-Er intermediate alloy is MgEr25 or MgEr30, described Mg-Mn intermediate alloy be MgMn10, the Al-Ti-B intermediate alloy be AlTi5B1, the Al-B intermediate alloy be AlB3 or AlB8, the Al-Ti intermediate alloy are AlTi5 or AlTi10.

6. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 4, feature It is: the mass percent component of the refining agent are as follows: 55%KCl, 25%CaCl₂, 5%CaF₂, 15%BaCl₂。

7. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 4, feature Be: the refining agent additive amount is the 1.0~3.5% of raw material gross weight.

8. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 4, feature Be: refining temperature when refining agent refining is added is 720~730 DEG C, 10~15min of mixing time of refining treatment.

9. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 4, feature It is: the second level solid solution treatment process parameter are as follows: 480~490 DEG C of first order solid solubility temperature, 36~48h of soaking time；Second 535~545 DEG C of solid solubility temperature of grade, 1~2h of soaking time.

10. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 9, feature It is: the step of the second level solid solution treatment process are as follows: cast alloy is put into solid solution furnace, is warming up to 200 with 5 DEG C/min DEG C, it is passed through protective gas, continues to be warming up to 480~490 DEG C of first order solid solubility temperature with 5 DEG C/min, keeps the temperature 36~48h；Then 535~545 DEG C of second level solid solution temperature are warming up at a slow speed with 10 DEG C/h, keep the temperature after 1~2h fast transfer to quenching unit Upper carry out water hardening.

11. the preparation method of the high-toughness heat-resistant Mg-Gd-Er alloy suitable for low pressure casting as described in claim 4 or 10, It is characterized in that: the SF that the protective gas is argon gas or volume fraction is 0.2%₆And CO₂Mixed gas.

12. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 4, feature It is: the artificial aging treatment process parameter: 185~215 DEG C of aging temp, 12~36h of soaking time.

13. the preparation method suitable for the high-toughness heat-resistant Mg-Gd-Er alloy of low pressure casting as claimed in claim 12, special Sign is: the step of the artificial aging treatment process are as follows: quenched alloy is put into aging furnace, with 5 DEG C/min heating To 185~215 DEG C of artificial aging treatment temperature, comes out of the stove after 12~36h of heat preservation and be air-cooled to room temperature.