Synthetic TiC granule intensified titanium aluminum alloy materials of original position and preparation method thereof
Technical field
The present invention relates to the synthetic TiC granule intensified titanium aluminum alloy materials of a kind of original position, belong to powder metallurgical technology.The invention still further relates to the preparation method of above-mentioned alloy material.
Background technology
Titanium is a kind of important structural metal growing up the 1950's, and its fusing point is 1670 ℃.The titanium alloy features such as specific tenacity is high, yield tensile ratio is high because having, solidity to corrosion is good become desirable aerospace engineering structured material and obtain application widely.
Under room temperature, titanium alloy has three kinds of matrix, and titanium alloy is also just divided into following three classes: α alloy, (alpha+beta) alloy and beta alloy.China represents with TA, TC, TB respectively.Can be divided into structural titanium alloy and high-temperature titanium alloy (use temperature is greater than 400 ℃) by purposes.Current most popular titanium alloy is industrially pure titanium (TA1, TA2 and TA3), Ti-5Al-2.5Sn (TA7) and Ti-6Al-4V (TC4), the Ti-6Al-4V alloy that wherein U.S. in 1954 succeeds in developing, because its thermotolerance, intensity, plasticity, toughness, plasticity, weldability, solidity to corrosion and biocompatibility are all better, and becoming the trump alloy in titanium alloy industry, this alloy usage quantity has accounted for 75%~85% of whole titanium alloys.
Along with the great market potential demand in the civilian industry such as develop rapidly and the petroleum and petrochemical industries field of the sophisticated industry technology such as aviation, aerospace, military project, the research and development of Ti alloy with high performance are subject to unprecedented attention and development:
(1) high-temperature titanium alloy: be successfully applied in the IMI829 with the solution strengthening of α phase, IMI834 alloy that 500 ~ 600 ℃ of high-temperature titanium alloys in dual-use aircraft engine have Britain to develop at present, Americanologist is crossed method exploitation Ti-4242S, the Ti-1100 alloy of sacrificing fatigue strength and improve creep strength, Muscovite BT18Y, BT36 alloy etc., China has developed Ti-5.3Al-4sn-2Zr-1Mo-0.25Si-1Nd (Ti55) and Ti-Al-Sn-Zr-Mo-Nb-Si-1Nd (Ti66).
(2) structural titanium alloy is to high-strength, high-ductility, high-strength and high ductility, high-modulus and high damage tolerance future development, for the requirement that adapts to more high strength and toughness is (as intensity is increased to 1275~1373MPa, specific tenacity is increased to 29~33, Young's modulus is increased to 196GPa), in recent years developed the tough performance beta-titanium alloy of many novel high-strengths, as the Ti-10V-2Fe-3Al of the U.S. (Ti1023), Ti-15V-3Cr-3Sn-3Al (Ti153), Ti-15Mo-3Al-2.7Nb-0.2Si (β 21S); The Ti-4Al-4Mo-2Sn-0.5Si (IMI500) of Britain, the BT22 of SPF00, CR800, SP700 and the USSR (Union of Soviet Socialist Republics) of Japan etc.
New type high temperature titanium alloy is mainly alpha titanium alloy and alpha+beta titanium alloys at present, generally under as-annealed condition, use and temperature are no more than 600 ℃, alpha+beta titanium alloys can be heat-treated strengthening, but hardening capacity is lower, after strengthening thermal treatment, fracture toughness property also reduces, and therefore the strength property of new type high temperature titanium alloy is far below the tough performance beta-titanium alloy of novel high-strength.But beta-titanium alloy thermostability is poor, should not at high temperature use.Therefore, adopt at present alloying process to be difficult to take into account high-strong toughness energy and resistance toheat by the new titanium alloy material of solution strengthening and the exploitation of thermal treatment Precipitation strengthening means.
In titanium alloy, add the wild phase of high strength, high rigidity can further improve it than Young's modulus, specific rigidity, mechanical property, fatigue and creep resisting ability, and overcome former titanium alloy wear resistance and the shortcoming such as high-temperature behavior is poor, become the candidate material of superelevation velocity of sound aerospace vehicle and advanced aero engine.Compare with metal whisker reinforced composite with fiber, preparation technology is simple for granule intensified titanium alloy material, easily realize, prepared material isotropy, and the susceptibility of the coefficient of thermal expansion mismatch of material property to wild phase and matrix is also lower, the more important thing is and can prepare large-scale part with traditional titanium alloy melting and complete processing, significantly reduce the cost of material.On particulates reinforcements is selected, on the one hand for avoiding hot unrelieved stress, the thermal expansivity of enhanced granule phase and matrix should be close; The chemical compatibility of enhanced granule phase and matrix is good on the other hand, to avoid under hot conditions and titanium alloy substrate generation surface reaction, reduces interface bond strength.Conventional wild phase has at present: TiB and TiC, and rare earth oxide etc.Compared with the material making with the mutually additional method of traditional enhanced granule, original position synthesis particle strengthens titanium alloy material following advantage: preparation technology is simple, easily realize, prepared material isotropy, and the susceptibility of the coefficient of thermal expansion mismatch of material property to wild phase and matrix is low, stable on mechanics, therefore in the time of hot operation, performance is difficult for degenerating; The interface of wild phase and matrix is clean, there is no surface reaction thing; Generated in-situ wild phase is evenly distributed in matrix, shows good mechanical property.For example, Shanghai Communications University's metal-base composites National Key Laboratory adopts fusion casting to prepare TiB and TiC reaction in-situ granule intensified titanium aluminum alloy materials.
Casting and powder metallurgy technology are to prepare the main method of titanium alloy material, and compared with foundry engieering, titanium alloy prepared by powder metallurgy can form shape closely only, and material use efficiency is high, and crystal grain is tiny, homogeneous microstructure, segregation-free.Data shows according to investigations, and the U.S. only aviation accounts for 60 ~ 80% with the titanium part that adopts powder metallurgy process to produce, and titanium casting work in-process only account for 20 ~ 25%.In recent years abroad using the developing direction that adopts rapid solidification/powder metallurgy technology, granule intensified titanium alloy as new titanium alloy, domesticly also adopt powder metallurgy technology to develop original position synthesis particle to strengthen titanium alloy material.A kind of powder metallurgy titanium alloy of Chinese invention patent and preparation method thereof (CN 101962721 A), propose the powder metallurgy titanium alloy of a kind of argentiferous and boride titanium particle, generated boride titanium particle by add lanthanum hexaborane reaction in-situ in vacuum heating-press sintering titanium alloy.Chinese invention patent CN 101696474 B have proposed a kind of method for preparing powder metallurgy of rare-earth containing oxide reinforcing phase titanium alloy, rare earth is to add with the form of the powder of rare earth hydride, and in the deformation process of rare earth oxide strengthening phase after vacuum sintering, reaction generates; Because oxygen is the impurity element in titanium alloy, the existence of oxygen sharply reduces titanium alloy plasticity, its embrittlement effect is 10 times of aluminium, in the time that oxygen level is greater than 0.7%, make titanium lose the ability of viscous deformation completely, but in this patent documentation and the principle that generates of undeclared rare earth oxide strengthening phase, and oxide compound easily increases the oxygen impurities content in alloy while generating.Titanium belongs to a kind of active metal, thereby the preparation of the metallurgical part of titanium alloy powder requires very tight to sintering condition, the required vacuum tightness of traditional vacuum sintering technology is very high, and in the titanium alloy product of institute's sintering, residual porosity is more, causes fatigue property degradation.For obtaining Ti alloy with high performance sintered metal product, develop new shaping and sintering process technology such as () spray up n., powder injection forming, hot isostatic pressings to eliminate the porosity in material or porosity is down to minimum, the tensile property of material meets or exceeds molten level of forging material.But above-mentioned new technology required equipment investment is large, complex process, manufacturing cost is high, has limited its application development.
Summary of the invention
Technical problem to be solved by this invention is for above-mentioned deficiency of the prior art, and synthetic TiC granule intensified titanium aluminum alloy materials of a kind of original position and preparation method thereof is provided, and prepares high-strong toughness low cost granule intensified titanium aluminum alloy materials.
The technological thought of the synthetic TiC granule intensified titanium aluminum alloy materials of original position of the present invention is: aluminium is most widely used α stable element in titanium alloy, aluminium in titanium alloy with substitutional atom mode be present in α mutually in, adding of aluminium can reduce fusing point and improve beta transus temperature, all plays strengthening effect in room temperature and high temperature.Al has promoted the phase mutual diffusion of Ti with C in sintering process, is conducive to formation and the refinement of TiC Particle Phase.In addition, add aluminium and also can reduce the proportion of alloy.But too high addition there will be with Ti
3al is the α of base
2ordered solid solution, becomes fragile alloy, and thermostability reduces.
Carbon is the clearance type α phase stable element in titanium alloy, the equivalent thickness of aluminium calculation formula according to titanium alloy: the equivalent thickness of aluminium=%Al+%Sn/3+%Zr/6+%Si*4+ (O, C, N) %*10, and its effect is 10 times of aluminium.With interstitial atom mode be present in α mutually in carbon there is the solid solution strengthening effect far above aluminium, in the present invention, carbon is incorporated in alloy as alloy element, carbon has reduced the content of Al in alloy to the metalepsy of Al, guarantees the plasticity and toughness that alloy has had; Solution strengthening and hollow cathode sintering reaction in-situ by carbon are introduced the means acquisition high strength of high-melting-point disperse TiC Particle Phase strengthening matrix and the granule intensified titanium aluminum alloy materials of wear resisting property.
The feasibility of the technology of the present invention thought is:
(1) obdurability of titanium-based alloy material is replaced part aluminium, is controlled reaction in-situ and generate TiC particle strengthening and realize mutually by carbon: in alloy of the present invention, replace part aluminium by carbon and fall low-aluminum-content, guaranteed that alloy has good plasticity and toughness, this is the relatively low major reason of Al content in alloy material of the present invention; Intensity, the wear resisting property of alloy are realized by the solution strengthening effect of carbon, quantity, size and the distribution that changes interpolation quantity of graphite and regulate hollow cathode sintering process parameter control reaction in-situ to generate TiC particle strengthening phase.According to Ti-C binary phase diagram, at 920 ℃, there is Peritectic Reaction: β-Ti
0.6at%.C+ TiC
38at%.Cα-Ti
1.6 at%.C, carbon atom percentage composition when Peritectic Reaction in α-Ti is 1.6, its mass percent is 0.4%.
(2) select the advantage of TiC particle as material reinforcement phase of the present invention: compared with TiB, TiC particle fusing point high (3433 ℃), approach the most with density, the thermal expansivity of titanium and there is identical Poisson's ratio, tensile strength and Young's modulus are 4 times of titanium, good again with the affinity of titanium, and can increase the wear resistance of titanium.
(3) reaction in-situ generates the realization condition of TiC particle strengthening phase: it is to utilize the hollow cathode sintering between Ti and graphite (C) synthetic that the original position of TiC wild phase is synthesized, and its reaction formula is: Ti+C → TiC.In the time selecting the strengthening phase of in-situ composite, conventionally first judge wild phase by thermomechanical analysis, whether can be by adding material automatically to generate in matrix, the standard of judgement is whether the variation of the Gibbs free energy of reaction is less than zero.The condition that another one need to be considered is enthalpy produced in chemical reaction, the heat effect of its representative reaction.Utilize the data of document to calculate enthalpy produced in chemical reaction △ H and the reaction Gibbs free energy △ G of this reaction formula, in the time of temperature of reaction T < 1939K, its formula △ H and △ G can be expressed as follows:
ΔH=-184571.8+5.024T-2.425×10
-3T
2-1.958×10
6/T (1)
ΔG=-184571.8+41.382T-5.024TlnT+2.425×10
-3T
2-9.79×10
5/T (2)
Calculation result shows in sintering range of the present invention (1250 ~ 1500 ℃), the standard Gibbs free energy change value (Δ G) of reaction and enthalpy produced in chemical reaction (Δ H) are always much smaller than zero, the adiabatic temperature of this reaction is 3210K, and exceeding reaction can the spontaneous experience criterion Tad > 2500K maintaining.This illustrates that this thermopositive reaction can make reaction maintain automatically and carry out, and self propagating high temperature building-up reactions occurs, and saves the energy.
(4) advantage of the synthetic TiC particle strengthening phase of hollow cathode sintering reaction in-situ.Powder metallurgy sintered temperature is most important to the structure property of sintered article.It is generally acknowledged, the sintering effect of the higher sintered article of temperature is better.Be in particular in: sintered compact is densification more, powder particle combining site increases, pore shape rounding.But high temperature action has also been accompanied by the side effects such as grain-size is grown up, sintered part contraction increase for a long time.Hollow cathode discharge plasma sintering is as a kind of emerging powder metallurgy sintered technology, hollow cathode effect when it utilizes and produces glow discharge under vacuum condition, produce very highdensity macro-energy ion bombardment at cathode surface, the heat effect of ion bombardment can make cathode material be rapidly heated to very high temperature, its sintering temperature can reach 3000 ℃, and temperature rise rate can reach 100 ℃/s.Quickly heating up to high temperature is conducive to activate crystal boundary and lattice diffusion and suppresses surface diffusion, thereby be conducive to the densification process of material, suppress the growth of inner crystal grain simultaneously, reduce porosity, make material obtain higher sintered density, the effect of the Fast Sintering that reaches a high temperature.In addition, hollow cathode sintering utilizes the bombardment of high energy particle to pulverulent product and direct heating and do not need special heating unit, and its equipment volume is little, and temperature control is convenient, energy consumption is few, and there is the feature of vacuum sintering, can obtain the sintered article of high-quality.Therefore, hollow cathode sintering technology is the synthetic TiC granule intensified titanium aluminum alloy materials sintering method of a kind of well original position.
Based on the technological thought of foregoing invention, technical scheme of the present invention is: a kind of original position is synthesized TiC granule intensified titanium aluminum alloy materials, described Ti-Al alloy material is made up of the component of following quality percentage: 0.2%≤Al≤2.5%, and 0.5%≤C≤1.5%, surplus is Ti and inevitable impurity.
Described inevitable foreign matter content is controlled at below 0.5%.And described Al, C are provided by aluminium powder, Graphite Powder 99 respectively.
Preparation method's (hollow cathode sintering method) of the synthetic TiC granule intensified titanium aluminum alloy materials of above-mentioned original position, comprises the following steps:
1) batching: the aluminium powder, Graphite Powder 99 and the titanium valve that take respective amount by following mass percent: 0.2%≤Al≤2.5%, 0.5%≤C≤1.5%, surplus is Ti; The powder size of above-mentioned each component is: aluminium powder: 300 ~ 500 orders, Graphite Powder 99: 800 ~ 2000 orders, titanium valve: 300 ~ 500 orders;
2) ball milling mixes: above-mentioned powder is packed in ball grinder by ratio of grinding media to material 5:1, and at rotating speed 250 ~ 350r/min, ball grinder is ball milling 1 ~ 2h under argon shield atmosphere, then compound after ball milling is crossed to 100 mesh sieves of GB/T6005 regulation;
3) by step 2) in the compound of ball milling after sieving by the pressed compact of two-way mold pressing, described molding pressure is 400 ~ 600Mpa;
4) anode and hollow cathode are set in vacuum chamber, anode is vacuum vessel housing, and hollow cathode is by the above-mentioned pressed compact material of making and can play heat-blocking action graphite cake and form, and being placed on blank on negative electrode distance is each other 10 ~ 20mm;
5) choosing technical pure argon gas is sputter gas, and vacuum tightness in stove is evacuated to the limit, is then filled with shielding gas high-purity argon gas, regulates argon flow amount to make operating air pressure in stove reach 10 ~ 50Pa;
6) after argon gas reaches operating air pressure, open workpiece power supply, blank and negative electrode are carried out to particle bombardment, sintering 2 ~ 6 hours at 1350 ~ 1550 ℃ of temperature.
In order to get rid of impurity in stove, between described step 5) and step 6), also comprise step:
(1) blank and negative electrode are carried out to particle bombardment, and lasting 20min;
(2) by air pressure adjustment to final vacuum, discharge due to particle bombardment produce impurity;
(3), if still remain impurity in furnace chamber, continue execution step (1), (2), until fully meet the sintering of titanium alloy.
In described step 5) stove, operating air pressure is realized by following methods:
(1) open first successively mechanical pump, molecular pump, vacuum tightness in stove is evacuated to the limit;
(2) be then filled with shielding gas high-purity argon gas, regulate argon flow amount to make stove internal gas pressure reach the operating air pressure needing;
(3) after stable, be again pumped to final vacuum, repeat above-mentioned steps, until the foreign gas content such as the interior oxygen of stove reach minimum.
Effect of the present invention is: the present invention breaks through the thought binding of tradition using carbon as titanium alloy impurity element, propose carbon to be incorporated into the new approaches in alloy as useful alloy element, carbon has reduced the content of Al in alloy to the metalepsy of Al, guarantees the plasticity and toughness that alloy has had; By the solution strengthening of carbon and the means of hollow cathode sintering reaction in-situ introducing high-melting-point disperse TiC Particle Phase strengthening matrix, obtain the low cost granule intensified titanium aluminum alloy materials of high strength and wear resisting property.
The present invention proposes hollow cathode sintering method and realize the high temperature Fast Sintering of In-situ Synthesis TiC Particle enhancing Ti-Al alloy material, the density of agglomerated material reaches 97%, and overcome the shortcomings such as titanium alloy wears no resistance, Young's modulus is low, to expanding titanium alloy material, in the field such as aerospace and civilian industry, application will have huge pushing effect.
Embodiment
Embodiment 1
Preparation method's (hollow cathode sintering method) of the synthetic TiC granule intensified titanium aluminum alloy materials of original position of the present invention, comprises the following steps:
1) batching: Ti-Al alloy material is Ti-0.2%Al-0.5%C.Take 300 object aluminium powders, 800 object Graphite Powder 99s and 300 object titanium valves according to the proportioning of alloy.
2) ball milling mixes: above-mentioned powder is packed in ball grinder by ratio of grinding media to material 5:1, and at rotating speed 350r/min, Ball-milling Time 1h.For preventing powder oxidation in mechanical milling process, ball grinder passes into argon shield.Then compound after ball milling is crossed to 100 mesh sieves of GB/T6005 regulation.
3) by step 2) in the compound of ball milling after sieving by the pressed compact of two-way mold pressing, described molding pressure is 400Mpa.
4) anode and hollow cathode are set in vacuum chamber, hollow cathode is by the above-mentioned pressed compact material of making and can play heat-blocking action graphite cake and form, and being placed on blank on negative electrode distance is each other 10mm.
5) choosing technical pure argon gas is sputter gas, and vacuum tightness in stove is evacuated to the limit, is then filled with shielding gas high-purity argon gas, regulates argon flow amount to make stove internal gas pressure reach 10Pa.Hollow cathode discharge plasma sintering and vacuum sintering furnace, sintering process need could realize under certain operating air pressure.In stove, operating air pressure is realized by following methods:
(1) open first successively mechanical pump, molecular pump, vacuum tightness in stove is evacuated to the limit;
(2) be then filled with shielding gas high-purity argon gas, regulate argon flow amount to make stove internal gas pressure reach the operating air pressure needing;
(3) after stable, be again pumped to final vacuum, repeat above-mentioned steps, until the foreign gas content such as the interior oxygen of stove reach minimum.
6) after argon gas reaches operating air pressure, open workpiece power supply, blank and negative electrode are carried out to particle bombardment, sintering 2 hours at 1550 ℃ of temperature.
In above-mentioned steps 5) and step 6) between, also comprise step:
(1) blank and negative electrode are carried out to particle bombardment, and lasting 20min;
(2) by air pressure adjustment to final vacuum, discharge due to particle bombardment produce impurity;
(3), if still remain impurity in furnace chamber, continue execution step (1), step (2), until fully meet the sintering of titanium alloy.
The bending strength of Ti-0.2%Al-0.5%C alloy prepared by employing aforesaid method is 670Mpa, and relative density is 94%.
Embodiment 2
The present embodiment is identical with embodiment 1, and different is that the prepared Ti-Al alloy material of step 1) is Ti-0.6%Al-1.5%C.Take 500 object aluminium powders, 1500 object Graphite Powder 99s and 500 object titanium valves according to the proportioning of alloy; From step 2) different be at rotating speed 300r/min, Ball-milling Time 1.5h; Different from step 3) is that molding pressure used is 600Mpa; Different from step 4) is, and to be placed on blank on negative electrode distance be each other 20mm; Different from step 5) is to regulate argon flow amount to make operating air pressure in stove reach 30Pa; Different from step 6) is at 1350 ℃ of temperature sintering 6 hours, all the other are all with to implement 1 identical.The bending strength of Ti-Al alloy material Ti-0.6%Al-1.5%C prepared by employing aforesaid method is 850Mpa, and relative density is 97%.
Embodiment 3
The present embodiment is identical with embodiment 1, and different is that the prepared Ti-Al alloy material of step 1) is Ti-1.5%Al-1.0%C.Take 400 object aluminium powders, 2000 object Graphite Powder 99s and 400 object titanium valves according to the proportioning of alloy; From step 2) different be at rotating speed 250r/min, Ball-milling Time 2h; Different from step 3) is that molding pressure used is 500Mpa; Different from step 4) is, and to be placed on blank on negative electrode distance be each other 15mm; Different from step 5) is to regulate argon flow amount to make operating air pressure in stove reach 50Pa; Different from step 6) is at 1450 ℃ of temperature sintering 4 hours, all the other are all with to implement 1 identical.The bending strength of Ti-Al alloy material Ti-1.5%Al-1.0%C prepared by employing aforesaid method is 780Mpa, and relative density is 95%.
Embodiment 4
The present embodiment is identical with embodiment 1, and different is that the prepared Ti-Al alloy material of step 1) is Ti-2.5%Al-1.5%C.Take 500 object aluminium powders, 2000 object Graphite Powder 99s and 400 object titanium valves according to the proportioning of alloy; From step 2) different be at rotating speed 300r/min, Ball-milling Time 2h; Different from step 3) is that molding pressure used is 450Mpa; Different from step 4) is, and to be placed on blank on negative electrode distance be each other 15mm; Different from step 5) is to regulate argon flow amount to make operating air pressure in stove reach 35Pa; Different from step 6) is at 1480 ℃ of temperature sintering 4 hours, all the other are all with to implement 1 identical.The bending strength of Ti-Al alloy material Ti-2.5%Al-1.5%C prepared by employing aforesaid method is 920Mpa, and relative density is 95%.