CN105543618A - Process for reducing reaction of directional solidification titanium-aluminum alloy castings and casting mold coatings - Google Patents

Process for reducing reaction of directional solidification titanium-aluminum alloy castings and casting mold coatings Download PDF

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CN105543618A
CN105543618A CN201510944647.4A CN201510944647A CN105543618A CN 105543618 A CN105543618 A CN 105543618A CN 201510944647 A CN201510944647 A CN 201510944647A CN 105543618 A CN105543618 A CN 105543618A
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aluminum alloy
directional solidification
casting mold
titanium
alloy
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CN105543618B (en
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隋艳伟
程成
冯坤
戚继球
何业增
委福祥
孟庆坤
孙智
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China University of Mining and Technology CUMT
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/52—Alloys

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Crystallography & Structural Chemistry (AREA)
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Abstract

The invention researches a process for reducing the reaction of directional solidification titanium-aluminum alloy castings and casting mold coatings, and belongs to a directional solidification casting method of a high-temperature structural alloy. The invention aims at providing optimal process parameters during titanium-aluminum alloy preparation achieved through directional solidification, the interface reaction between an alloy melt and casting mold materials is weakened to be minimum when the heat preservation time is 30 minutes and the drawing speed is 60 micrometers per second by means of design of directional solidification parameters of a Ti-48Al-7Nb-2.5V-1.0Cr alloy, the reaction layer thickness is reduced to be less than 10 micrometers, the surfaces of the castings are smooth, and internal contamination is little. The process is characterized in that the time of contact between the melt and casting molds is shortened, and the problems that when the drawing speed is high, the number of crystalline grains is increased and the deviation between the direction of the crystalline grains and the axial direction is large are solved. The process is reasonable and low in cost, can not influence the directional solidification structure orientation of a titanium-aluminum alloy, and can be applied to the directional solidification process of the titanium-aluminum alloy.

Description

A kind of technique reducing directionally solidifying titanium aluminum alloy foundry goods and casting mold coating reaction
Technical field
The present invention relates to a kind of optimization reducing directionally solidifying titanium aluminum alloy foundry goods and casting mold coating reaction, belong to the surface reaction Optimization Technology of thermal structure alloy.
Background technology
Titanium aluminum alloy is as a kind of lightweight high-temperature structural material, not only density is low, specific tenacity is high, Young's modulus is high, and have good high-temperature oxidation resistant and creep resisting ability, be one of study hotspot of engine material, be widely used in fields such as aerospace, biologic medical and automobile makings.By TiAl (γ phase) and a small amount of Ti 3al (α 2phase) complete lamellar structure that forms has better mechanical property than other forms of tissue, significantly present anisotropy, when plus load is consistent with lamella direction, the yield strength of material, unit elongation, fracture toughness property and creep property are all significantly improved, and can effectively carry heavy alloyed comprehensive mechanical property.Therefore, the lamellar orientation of control solidi fication alloy greatly can widen the use range of TiAl alloy.
Directional solidification technique adopts compulsive means in process of setting, the thermograde of specific direction is set up in frozen metal and non-solidified melt, thus melt is solidified along the direction contrary with hot-fluid, obtain and there is the column crystal of specific orientation or a kind of casting technique of monocrystalline.Directional solidification technique can obtain and be parallel to axial column crystal, eliminate transverse grain boundaries vertical with stress axis in conventional cast, the main source cracked under avoiding high temperature stress, put forward heavy alloyed creep rupture strength and plasticity, improve thermal shocking drag and creep strength, thus increase substantially the service ability of titanium aluminum alloy component.
There is scholar to adopt directional solidification technique, utilize the adductive crystallization of seed crystal in ceramic-mould, control the lamellar orientation of TiAl alloy, prepared the completely parallel directed complete lamellar structure with the direction of growth.But titanium aluminum alloy fusing point is high, have very high chemically reactive, can and mold material there is in various degree surface reaction, cause, at cast(ing) surface formation pollution layer, deteriorating inside and the surface quality of Ti-Al alloy cast, affecting the dimensional precision of foundry goods.
Also have research to attempt adopting the generation of reacting to avoid directional freeze process median surface without casting mold melting, but practical application is restricted.Such as Electromagnetic shaping and directional solidification and suspension magnetostrictive properties, the former depends merely on electromagnetic force constraint alloy melt and there is the problem being difficult to shaping complex component, and the latter relies on surface tension to keep the stable micro-member that can only be shaped in melting zone, be difficult to prepare larger foundry goods.Effective Regulation has the surface reaction in casting mold directional freeze process between titanium aluminum alloy melt and mold material to be problem demanding prompt solution.
Directionally solidifying titanium aluminum alloy has special requirement to casting mold: high-temperature stability is good, shaking property of heat resistanceheat resistant, resistance to chemical attack, also will easily process, low price simultaneously.The mold material be applied at present in directional freeze has graphite, ZrO 2, Al 2o 3and Y 2o 3deng.But the C element in graphite casting mould enters into the solidification path that alloy melt changes original composition alloy; ZrO 2fragility is comparatively large and thicker with specimen reaction layer; High temperature Al 2o 3particle can come off and enter melt in solidified structure, form a large amount of inclusiones; Fine and close Y 2o 3heat-shock resistance is poor, easily cracked and expensive during directional freeze.Therefore, bilayer structure casting mold is greatly improved on saving cost.What the present invention adopted is that inwall scribbles Y 2o 3the Al of coating 2o 3casting mold.
Research shows, surface reaction is relevant with duration of contact and temperature, in order to weaken the surface reaction of mold material and melt, obtain good oriented freezing organization, the duration of contact of melt and casting mold should be reduced as far as possible, therefore when directional freeze process, withdrawing rate should be large as much as possible, with Reaction time shorten.But along with the increase of withdrawing rate, number of die quantitative change is many, grain orientation and axial deviation larger, for obtaining few crystal grain quantity and little angle, lower withdrawing rate must be adopted.Therefore, how the processing parameter of conservative control directional freeze, turns to industrialization to be very necessary to directionally solidifying titanium aluminum alloy.
Summary of the invention
Technical problem: when the present invention is directed to titanium aluminum alloy directional freeze and the surface reaction problem of casting mold, optimizing directional solidification processes, Solidification Parameters reasonable in design, to weakening surface reaction, obtaining the better directional solidification castings of surface quality.
For reaching above technical problem, the present invention is achieved through the following technical solutions:
That the present invention adopts is Al 2o 3(inside cover the Y that thickness is 0.5mm 2o 3coating) casting mold, it is characterized in that affordable, easily process, find all more weak than the surface reaction under other casting molds in research in the past.Raw material of the present invention is Ti-48Al-7Nb-2.5V-1.0Cr, belongs to high Nb titanium aluminum alloy.
The directed solidification step of described titanium aluminum alloy is as follows:
(1) melting: the sponge Ti after optimized proportion, Al powder, Cr powder, AlV and AlNb particle (granular 325 orders) are put batch mixing in vertical centrifugal type vacuum induction casting furnace with suitable orientation, be convenient to each raw material in fusion process to react to each other heat release, make it melt sooner.In stove, vacuum tightness passes into Ar gas shielded after remaining on about 0.5Pa.After fusion cast process, ingot casting back-off is put into founding again, repeatedly make for three times ingot casting Elemental redistribution even, get an inspection composition profiles, last ingot casting is as female ingot of directional freeze;
(2) directional freeze: cut from the alloy pig (1) pole that diameter is 6mm, grind off oxide skin, loads in crucible after cleaning, oven dry.Five times are repeatedly vacuumized, when furnace chamber vacuum tightness reaches 5 × 10 before beginning -3start heating during Pa, passing into argon gas to pressure when being heated to 500 DEG C is 0.05MPa.Carry out zone heating to casting mold, first paragraph is room temperature to 1300 DEG C, heat-up time 3h, second segment is 1300 DEG C to 1600 DEG C, be then incubated 30 minutes.Under 60 μm/s, carry out pull, pull length is 100mm.Melt is quick solidification under gallium indium liquid metal cooling fluid.
Beneficial effect: by this experiment, directional freeze parameter adopts insulation 30 minutes, withdrawing rate 60 μm/s, and in strict accordance with experimental procedure and requirement of experiment, the directional freeze sample interface responding layer obtained is the thinnest, internal contamination thing is minimum, achieves the optimization of the directional solidification processes to titanium aluminum alloy.Processing parameter directional setting interface reaction layer thickness through design has dropped within 10 μm, and surface quality of continuous castings and dimensional precision are greatly enhanced, and internal contamination thing also obviously reduces, and surface reaction obtains reasonable control.
To be that Ti-48Al-7Nb-2.5V-1.0Cr is alloy directionally solidified provide effective processing parameter in the present invention, and provide reference to the directional freeze process of high niobium containing titanium aluminium alloy.
Accompanying drawing explanation
Fig. 1 is matrix pattern and the surface reaction layer thickness of titanium aluminum alloy.
Fig. 2 is the thing phase collection of illustrative plates of surface reaction place powder.
Embodiment
A kind of technique reducing directionally solidifying titanium aluminum alloy foundry goods and casting mold coating reaction.
(1) sample melting, in vacuum induction casting furnace, prepare female ingot of test, alloying constituent is as shown in table 1.Insulation 1 hour after graphite jig being preheated to 200 DEG C before heating, has heated the sampling of rear rapid cooling as cast condition;
(2) on above-mentioned alloy pig, cutting diameter is 6mm, and length is that the pole of 100mm is as directional freeze sample.Polishing surface scale, dries one hour at 120 DEG C with after acetone ultrasonic cleaning;
(3) sample is put into Al 2o 3in (internal diameter is 6mm, external diameter 8mm) casting mold, be fixed in directional solidification furnace, the equipment of shutting starts to vacuumize, and requires that furnace chamber vacuum tightness reaches 5 × 10 -3pa, passes into argon gas to 0.05MPa when being heated to 500 DEG C, to reduce evaporation loss in experimentation;
(4) induction heating process is divided into 2 sections: first paragraph is 500 DEG C to 1300 DEG C, heat-up time 3h, second segment is 1300 DEG C to 1600 DEG C, conservative control induced current, voltage, is incubated 30 minutes;
(5) withdrawing rate during directional freeze is 60 μm/s, and pull length is 100mm;
(6) take out directional freeze sample, cleaning surface after longitudinally cutting, require to carry out to polish according to metallographic, mechanical polishing, corrosion, observe oriented freezing organization, surface reaction thickness, pollutent and composition thereof.
Concrete test is as follows: the tissue topography and the surface reaction layer thickness that adopt U.S. FEIQuantaTM250 type sem observation foundry goods matrix, result as shown in Figure 1.Matrix is typical titanium aluminum alloy oriented freezing organization, a small amount of pollutent that matrix is adhered, and responding layer is thin and discontinuous, illustrates that surface reaction is more weak.Polished by specimen surface thin layer, carry out material phase analysis after mortar refinement, material phase analysis adopts German Brooker D8AdanceX x ray diffractometer x, and result as shown in Figure 2, solidifies rear crucible complete, cuts in powder containing Al 2o 3, illustrate that surface reaction occurs over just melt and Y 2o 3between coating, effectively reduce surface reaction severe degree.
Finally illustrate: these are only example of the present invention; and by example to invention has been detailed description; for those skilled in the art person, all the present invention is made to simple modification, equivalent replace and improve, all should within protection scope of the present invention.

Claims (3)

1. reduce a technique for directionally solidifying titanium aluminum alloy foundry goods and casting mold coating reaction, it is characterized in that: the composition by weight of described alloying constituent is: 48%Al, 7%Nb, 2.5%V, 1.0%Cr, all the other are Ti.
2. reduce a technique for directionally solidifying titanium aluminum alloy foundry goods and casting mold coating reaction, it is characterized in that comprising the steps:
(1) sample melting, in vacuum induction casting furnace, prepare female ingot of test, alloying constituent is as shown in table 1, and insulation 1 hour after graphite jig being preheated to 200 DEG C before heating, has heated the sampling of rear rapid cooling as cast condition;
(2) on above-mentioned alloy pig, cutting diameter is 6mm, length be the pole of 100mm as directional freeze sample, polishing surface scale, with after acetone ultrasonic cleaning 120 DEG C dry one hour;
(3) sample is put into inwall and be coated with the thick Y of 0.5mm 2o 3al 2o 3in (internal diameter is 6mm, external diameter 8mm) casting mold, be fixed in directional solidification furnace, the equipment of shutting starts to vacuumize, and requires that furnace chamber vacuum tightness reaches 5 × 10 -3pa, passes into argon gas to 0.05MPa when being heated to 500 DEG C, to reduce evaporation loss in experimentation;
(4) induction heating process is divided into 2 sections: first paragraph is 500 DEG C to 1300 DEG C, heat-up time 3h, second segment is 1300 DEG C to 1600 DEG C, conservative control induced current, voltage, is incubated 30 minutes;
(5) withdrawing rate during directional freeze is 60 μm/s, and pull length is 100mm.
3. the purposes of a kind of directionally solidifying titanium aluminum alloy as claimed in claim 2, is characterized in that: surface reaction is weak, and specimen surface pollutes few, and dimensional precision is high.
CN201510944647.4A 2015-12-17 2015-12-17 It is a kind of to reduce directionally solidifying titanium aluminum alloy casting and the optimize technique of casting mold coating reaction Active CN105543618B (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105603533A (en) * 2015-12-17 2016-05-25 中国矿业大学 Alloy design method for reducing directionally-solidified titanium aluminum alloy interface reaction
CN109226666A (en) * 2018-11-16 2019-01-18 哈尔滨工业大学 It is a kind of for the composite cold crucible directional solidification method of high activity TiAl-base alloy and its TiAl-base alloy component of preparation
CN109226667A (en) * 2018-11-16 2019-01-18 哈尔滨工业大学 A kind of directional freeze method of electromagnetic cold crucible composite ceramics casting mold
CN112048605A (en) * 2020-08-03 2020-12-08 西北工业大学 Directional annealing device and method for preparing metal columnar crystals

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000017360A (en) * 1998-06-30 2000-01-18 Univ Kyoto PRODUCTION OF Ti-Al ALLOY
CN103789598A (en) * 2014-02-28 2014-05-14 南京理工大学 Directional TiAl-based alloy and preparation method thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000017360A (en) * 1998-06-30 2000-01-18 Univ Kyoto PRODUCTION OF Ti-Al ALLOY
CN103789598A (en) * 2014-02-28 2014-05-14 南京理工大学 Directional TiAl-based alloy and preparation method thereof

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105603533A (en) * 2015-12-17 2016-05-25 中国矿业大学 Alloy design method for reducing directionally-solidified titanium aluminum alloy interface reaction
CN109226666A (en) * 2018-11-16 2019-01-18 哈尔滨工业大学 It is a kind of for the composite cold crucible directional solidification method of high activity TiAl-base alloy and its TiAl-base alloy component of preparation
CN109226667A (en) * 2018-11-16 2019-01-18 哈尔滨工业大学 A kind of directional freeze method of electromagnetic cold crucible composite ceramics casting mold
CN112048605A (en) * 2020-08-03 2020-12-08 西北工业大学 Directional annealing device and method for preparing metal columnar crystals

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