Based on Ti-B
4In-situ self-generated TiB+TiC/Ti matrix material of C-C system and preparation method thereof
Technical field
The present invention relates to a kind of matrix material and preparation technology thereof, be specifically related to a kind of in-situ authigenic and strengthen titanium matrix composite and preparation technology thereof.
Background technology
Titanium matrix composite (TMCs, wherein the content of titanium surpasses 50%) have high specific tenacity, specific rigidity, than Young's modulus and good creep property, therefore in the aerospace field very attractive, become this field ideal Material Used, be widely used in blade of aviation engine, frame, rise and fall set a roof beam in place, on the member such as rocket engine case.Particularly (research of TMCs shows the flourish new situation for Discontinuouslyreinforced titanium matrix composites, DRTMCs) carrying out of research along with discontinuous enhancing titanium matrix composite.In recent years, such material has also shown good prospects for application aspect civilian industry, becomes one extremely active in metal-base composites (MMCs) research.Compare with aluminium base, magnesium base composite material, TMCs not only has higher intensity, rigidity, Young's modulus, also has better resistance to elevated temperatures, can be 450~650 ℃ of uses, and be expected to 600~800 ℃ of uses, be the middle adiabator that development potentiality is arranged very much.Strengthen TMCs with continuous fiber and compare, DRTMCs has the many advantages of self: the production cost of DRTMCs is low, and the preparation method is simple, has isotropic behavior preferably, and the interface is also reduced greatly to effect of material performance simultaneously.The in-situ authigenic technology of preparing of development in recent years has attracted the attention of Many researchers owing to having very outstanding advantage, is just more and more paid close attention to, and development potentiality is widely arranged.In the technology of preparing of discontinuous enhancing titanium matrix composite, the in-situ authigenic enhancement techniques obtains extensive studies owing to having very outstanding advantage, as: strengthen body and matrix and have good thermodynamic stability, survivable when in hot environment, being on active service; Strengthening body and matrix has direct atom bonded interface structure, and the interface is straight, in conjunction with firm, and the existence of reactionless thing or precipitated phase; The interface is very clean, strengthens the enhancing body that exists in produced pollution problem and the fusion-casting process and the wettability problem between matrix thereby solved the conventional particle that adds; It is more tiny to strengthen the body size, is evenly distributed, and has good mechanical property.
The method for preparing titanium matrix composite has: fusion casting, combustion synthesis method, burning be synthetic-and fusion casting, mechanical alloying method and powder metallurgic method.The reaction heat platen press is a kind of of powder metallurgic method, be meant in hot pressing, by in the mix powder between each element or the chemical reaction between element and the compound generate the compounding technology that ceramic particle strengthens body, it combines thermopositive reaction and densification process subsequently, has finished the preparation of fine and close product in an operation.The blank that this method prepares can secondary processing, reinforce content is not subjected to process technology limit, the granular size of selecting for use can be selected in the larger context, and made full use of that various powder are easy to this advantage of mixing in the powder metallurgic method, can prepare and strengthen the matrix material that body distributes very evenly.Because this method has made full use of the thermopositive reaction of respectively reacting between the constituent element when synthesizing wild phase, can carry out under relatively low temperature, thereby save the energy, has reduced production cost.
Prepare in the system at present in-situ autogenic titanium base composite material, by Ti-B
4C is that in-situ authigenic prepares TiB and TiC ceramic particle and mixes that to strengthen titanium matrix composite be a kind of method of simple possible, obtains extensive studies.But immutable by TiB and two kinds of mol ratios that strengthen between the body of TiC that this system reaction generates, promptly perseverance is 4: 1, and this means that also the volume ratio of the two is unmodifiable.This has limited their reinforced effects for matrix probably, thereby influences the further optimization of such composite property.Therefore, whether research TiB and TiC exists aspect the reinforced effects optimum volume ratio will be highly significant mixing between the two.Existing in this respect scholar uses fusion casting and add B in the titanium matrix
4C powder and Graphite Powder 99 prepare (TiB+TiC)/Ti6242 matrix material that TiB and TiC mol ratio are respectively 4: 1 and 1: 1, and point out to add intensity and the hardness that has improved material behind the graphite, the further systematize but this research awaits, do not provide the relation that exists between mole and the volume ratio yet, be not easy to analysis and research.At present, the research of applied powder metallurgy method is not also reported in this respect.
Summary of the invention
In order to have solved Ti-B
4TiB and the unmodifiable problem of TiC volume ratio in the C system preparation titanium base the invention provides a kind of based on Ti-B
4In-situ self-generated TiB+TiC/Ti matrix material of C-C system and preparation method thereof.Of the present invention based on Ti-B
4In-situ self-generated TiB+TiC/Ti the matrix material of C-C system is made up of Ti matrix, TiB and TiC wild phase, and the tensile strength 〉=900MPa of described matrix material, unit elongation are 0.4~5.0%, and the volume ratio of TiB and TiC is for being not equal to any ratio of 4: 1.
Based on Ti-B
4The preparation method of the in-situ self-generated TiB+TiC/Ti matrix material of C-C system is prepared according to following step: one, batch mixing: take by weighing titanium valve, boron carbide powder, Graphite Powder 99 according to following reaction equation,
, in the formula: x is the molar weight of the C powder that added, y is finally as the molar weight of the titanium of matrix, is being that 300~500r/min, ratio of grinding media to material are under 1: 1 the condition mixed 6~10 hours at rotating speed on the planetary ball mill then; Two, vacuum heating-press sintering: with the powder vacuum stripping under 200~400 ℃ temperature that mixes, the graphite jig of packing into then cold pressing to density be 60~80% of theoretical value, carry out vacuum heating-press sintering again, sintering condition is: heat-up rate is 10~30 ℃/h, sintering time is 10~20 hours, finish until sintering since 600~700 ℃ of 10~30Mpa that pressurize, and respectively 600~700 ℃ of insulations 0.5~2 hour, 1100~1300 ℃ are incubated 0.5~2 hour; Three, hot extrusion: earlier matrix material and extrusion mould are separately heated simultaneously during extruding, the holding temperature of mould is 600~700 ℃, matrix material was 1100~1300 ℃ of insulations 0.5~1 hour, then matrix material being put into mould pushes, the control extrusion ratio is 16: 1 or 25: 1, obtains the TiB+TiC/Ti matrix material.
The present invention has confirmed in theory at Ti-B
4Add the feasibility of Graphite Powder 99 in the C two component system with wild phase TiB and TiC volume ratio in the change matrix material.The application response pressure sintering is by Ti-B
4C-C three component system in-situ authigenic synthetic population integration number is 10% and TiB and TiC have in-situ authigenic (the TiBw+TiCp)/Ti matrix material of different volumes ratio.
At a certain temperature, Ti and B
4May there be two reactions between the C:
Analyze as can be known to the Gibbs free energy Δ G of above-mentioned two reaction formula that the two is a negative value all, on thermodynamics, can both react.And because in 1200~2200K scope, the free energy value Δ G of formula (1) is lower than (2), so (1) easier generation.If reaction is undertaken by (2), promptly generate TiB
2, then owing to there is the existence of a large amount of superfluous Ti will continue to take place following reaction:
Like this, still can obtain reaction formula (1) by formula (2) and (3).Therefore the reaction of (1) formula will finally take place under the situation of Ti surplus, promptly when Ti is excessive, will finally generate two kinds of wild phases of TiB and TiC.But be not difficult to find that enhancing body TiB that generates in this reaction and the mol ratio of TiC immobilize from formula (1), perseverance is 4: 1, and and B
4The add-on of C is irrelevant, and this also illustrates and utilizes Ti-B
4The TiB and the TiC of in-situ authigenic preparation mix in the enhanced titanium matrix composite in the C system, and the volume ratio of the two also is constant.If can change the wherein mol ratio of TiB and TiC, then can change the volume ratio of the two.
By calculating as can be known, TiB with the molecular volume ratio of TiC is:
In the formula: A
TiB, A
TiCThe molecular mass of difference TiB and TiC, A
TiB=58.69, A
TiC=59.89;
ρ
TiB, ρ
TiCBe respectively the density of TiB and TiC, ρ
TiB=4.51, ρ
TiC=4.99;
As seen, mol ratio of the two and volume ratio have proximate 1: 1 relation.If at Ti-B
4Thereby add the C powder in the C system and constitute Ti-B
4The C-C three component system, utilize:
Reaction in generation TiC particle then can be realized the regulation and control to whisker shape TiB in (TiB+TiC)/Ti matrix material and particulate state TiC volume ratio.This reaction Gibbs free energy Δ G is that negative value and reaction Enthalpies of Formation Δ H are very big, and this explanation this reaction on thermodynamics is feasible, and has the possibility that self-propagating reaction takes place.
From being reflected at of above analysis visible (1) and formula (5) all is feasible on the thermodynamics, can generate stable TiB and TiC and strengthen body.Thereby can draw following reaction formula by (1) and (5):
X wherein is the molar weight of the C powder that added, and y is finally as the molar weight of the titanium of matrix.Like this, in prepared titanium matrix composite, the volume ratio of TiB and TiC is approximately 4: (1+x), as long as change the value of x, the C content that is promptly added has just changed the two volume ratio.
Through Theoretical Calculation, thereby in the Ti powder, add boron carbide powder and Graphite Powder 99 formation Ti-B
4The C-C three component system is utilized Ti-B
4The C reaction generates TiB whisker and TiC particle, thereby the Ti-C reaction generates the regulation and control of two self-propagating reaction in-situ formation of TiC of TiC particle realization to whisker shape TiB in (TiB+TiC)/Ti matrix material and particulate state TiC volume ratio.By optimum sintering process, utilize Ti powder and B in the system
4C powder self-formed from reaction TiB whisker and TiC ceramic particle strengthen body; Ti powder and Graphite Powder 99 reaction have generated the TiC ceramic particle and have strengthened sintered state (TiB+TiC)/Ti matrix material that these two thermopositive reaction of body obtain certain size.By the optimal heat extrusion process, to the titanium matrix composite hot extrusion molding, make the further densification of matrix material, obtain high performance section bar.
After high temperature crimp, obvious variation is taking place along the direction of extrusion (vertically) with perpendicular to the direction of extrusion (laterally) in the weave construction of extruding attitude matrix material, and evident characteristic is that whisker aligns along the direction of extrusion.The matrix material of sintered state is behind hot extrusion deformation, and material is fine and close more, strengthens body and is evenly distributed, thereby can obtain better tissue, thereby improved its use properties as structured material.For prepared enhancing body total volume fraction is 10% matrix material, and the matrix material density of extruding attitude is very high, reaches 99.87% of theoretical value.Matrix material has best tensile strength and unit elongation when two kinds of volume ratios that strengthen body TiB and TiC are 1: 1, is to mix the enhanced best ratio, its tensile strength than the raising of pure matrix 62.89%.
The preparation method that the present invention adopts is the in-situ authigenic enhancement techniques, it is that a kind of material internal material chemical reaction that relies on generates the method that strengthens body, enhancing body and matrix have good thermodynamic stability in the gained material, and be survivable when being on active service in hot environment; Strengthening body and matrix has direct atom bonded interface structure, and the interface is straight, in conjunction with firm, and the existence of reactionless thing or precipitated phase; The interface is very clean, strengthens the enhancing body that exists in produced pollution problem and the fusion-casting process and the wettability problem between matrix thereby solved the conventional particle that adds; It is more tiny to strengthen the body size, is evenly distributed, and has good mechanical property etc.
Preparation system of the present invention forms in the titanium matrix and is evenly distributed, tiny stable TiB whisker and TiC particle, has solved Ti-B
4TiB and the unmodifiable problem of TiC volume ratio in the C system preparation titanium base, optimized the weave construction of matrix material, and make full use of the plurality of advantages of powder metallurgical technique, and further improved the mechanical property and the processability of material, prepare (TiB+TiC)/Ti matrix material of excellent performance.
Embodiment
Embodiment one: present embodiment based on Ti-B
4In-situ self-generated TiB+TiC/Ti the matrix material of C-C system is made up of Ti matrix, TiB and TiC wild phase, tensile strength 〉=the 900MPa of described matrix material, unit elongation is 0.4~5.0%, the volume ratio of TiB and TiC is for being not equal to any ratio of 4: 1, the volume ratio that is TiB and TiC is 4: 1+x, x>0.
TiB described in the present embodiment and TiC account for 10% of total composite volume, and it also can adjust TiB and the volume content of TiC in the Ti based composites according to different needs.
The particle size range of Ti described in the present embodiment is 1~20 μ m, B
4C average particle size particle size 1 μ m.
Embodiment two: different with embodiment one is that the value of x is got respectively in the present embodiment: 1,3,7,15.The TiB of so final acquisition and the volume ratio of TiC are respectively: 2: 1, and 1: 1,1: 2,1: 4.The concrete proportioning of raw material is as shown in table 1:
The proportioning content of the volume ratio of TiB and TiC and various powder in table 1 matrix material
Design strengthens the body total content | The material sequence number | TiB/TiC (Volume) | The proportioning content (1000g) of various powder |
Ti | B
4C
| C |
10vol%(TiB+TiC)/Ti | 1 2 3 4 5 | 4∶1 2∶1 1∶1 1∶2 1∶4 | 980.87 980.38 979.82 977.62 978.75 | 19.13 16.12 12.21 8.88 4.99 | - 3.30 7.97 13.51 16.26 |
Embodiment three: present embodiment prepares based on Ti-B according to following step
4In-situ self-generated TiB+TiC/Ti the matrix material of C-C system:
One, batch mixing:
Take by weighing titanium valve, boron carbide powder, Graphite Powder 99 according to following reaction equation during batch mixing,
, in the formula: x is the molar weight of the C powder that added, y is finally as the molar weight of the titanium of matrix, being that 300~500r/min, ratio of grinding media to material are mixed 6~10h under 1: 1 the condition at rotating speed on the planetary ball mill, reaches the best powder effect of mixing then.Because graphite itself is a kind of well behaved process control agent, therefore, it not only participates in the effect of reacting the constituent element that reacts when reaction, participate in reaction and generate the TiC particle, and in the batch mixing process, play the effect of process control agent, powder makes material be easy to mixing for the level of adhesion of abrading-ball in the reduction batch mixing process.
Two, vacuum heating-press sintering:
With the powder vacuum stripping under 200~400 ℃ temperature that mixes, the graphite jig of packing into then cold pressing to density be 70% of theoretical value, carry out vacuum heating-press sintering again, sintering condition is: heat-up rate is 10~30 ℃/h, sintering time is 10~20 hours, finish until sintering since 600~700 ℃ of 10~30Mpa that pressurize, and respectively at 600~700 ℃ of insulation 0.5~2h, 1100~1300 ℃ of insulation 0.5~2h.In the vacuum heating-press sintering process two violent thermopositive reaction can take place: Ti powder and B
4C powder self-formed from reaction TiB whisker and TiC ceramic particle strengthen body; Ti powder and Graphite Powder 99 reaction have generated TiC.Have two kinds and strengthen body in the matrix material of sintered state, a kind of is bar-shaped TiB whisker, about 0.075~0.3 μ m of diameter, length-to-diameter ratio is about about 20: 1, a kind of median size is about 3.5 in order to be similar to equiaxial TiC particulate state, and the two is evenly distributed on the Ti matrix.
Three, hot extrusion:
Because adopt powder metallurgic method, the pressure during sintering is very low,, so there is a certain amount of hole in the agglomerating titanium matrix composite, need to adopt secondary processing method to make material further fine and close.And the titanium matrix is a close-packed hexagonal structure at normal temperatures, and slip system is fewer, and deformation ratio is difficulty, and plasticity is relatively poor, fragility is big, is not easy to carry out plastic working.But when temperature was higher than 885 ℃, titanium was in body-centered cubic structure, and slip system is many, and the viscous deformation ratio is easier to carry out, so thermal distortion is one of main mode of texturing of discontinuous enhancing titanium matrix composite.The hot extrusion condition is: earlier matrix material and extrusion mould are separately heated simultaneously during extruding, the holding temperature of mould is 600~700 ℃, matrix material was 1100~1300 ℃ of insulations 0.5~1 hour, then matrix material being put into mould pushes, the control extrusion ratio is 16: 1 or 25: 1, obtains the TiB+TiC/Ti matrix material.This technology makes the further densification of the matrix material of sintered state, obtains high performance section bar.
The particle size range of Ti described in the present embodiment is 1~20 μ m, B
4C average particle size particle size 1 μ m, graphite powder particle is of a size of nano level.
Embodiment four: present embodiment prepares based on Ti-B according to following step
4In-situ self-generated TiB+TiC/Ti the matrix material of C-C system:
One, batch mixing:
Taking by weighing titanium valve, boron carbide powder, Graphite Powder 99 by the stoichiometric ratio in the table 2 during batch mixing, is 400r/min at rotating speed on planetary ball mill, and ratio of grinding media to material is mixed 8h under 1: 1 the condition.
Two, vacuum heating-press sintering:
With the powder vacuum stripping under 300 ℃ temperature that mixes, the graphite jig of packing into then cold pressing to density be 70% of theoretical value, carried out vacuum heating-press sintering again 10 hours, optimum sintering condition is: heat-up rate is 20 ℃/h, finish until sintering since 650 ℃ of 20Mpa that pressurize, and respectively at 650 ℃ of insulation 0.5h, 1200 ℃ of insulation 0.5h.
Three, hot extrusion:
Matrix material is pushed after 0.5 hour 1200 ℃ of insulations, earlier matrix material and extrusion mould are separately heated simultaneously during extruding, then matrix material being put into mould pushes, the control extrusion ratio is 16: 1 or 25: 1, the holding temperature of mould is 650 ℃, obtain the TiB+TiC/Ti matrix material, the density of this material and room temperature mechanical strength are as shown in table 2.
The density of table 2 matrix material and room temperature mechanical strength
Design strengthens the body total content | The material sequence number | TiB/TiC (Volume) | Density (%) | Room-temperature mechanical property |
Tensile strength (MPa) | Unit elongation (%) |
The pure Ti matrix of 10vol% (TiB+TiC)/Ti | 1 2 3 4 5 6 | 4∶1 2∶1 1∶1 1∶2 1∶4 - | 99.76 99.78 99.87 99.84 99.88 99.78 | 920 926.77 1192.91 957.61 1045.51 732.34 | 1.1 0.43 1.25 0.65 0.88 9.04 |