JP3350710B2 - Alumina-based superplastic ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina-based superplastic ceramic. More specifically, the invention of this application does not require a special powder process for synthesis, and the possible strain rate is 10 to 100
This is a new type of alumina-based superplastic ceramics that is twice as large.

[0002]

2. Description of the Related Art Alumina-based ceramics have been widely used as high-temperature materials, high-rigidity materials and the like because of their excellent heat resistance, corrosion resistance, wear resistance, and hardness. However, these conventional alumina-based ceramics are brittle and do not exhibit ductility even at a high temperature, so that plastic working like a metal material cannot be performed. Further, the material has a high hardness and is difficult to cut or grind, so that the material is very expensive to process. Recently, by dispersing zirconia particles in alumina to reduce the particle size,
Alumina ceramics having a tensile ductility of about 200 to 500% can be obtained. In general, in order to produce ceramics having a fine grain structure, it is necessary to use fine particles for adjusting raw material powders such as alumina and zirconia, and to further suppress grain growth occurring during high-temperature tensile deformation. You. However, the finer the particles, the more likely they are to agglomerate. Therefore, it is very difficult to reduce the particle size of the alumina matrix of the alumina-based ceramics or to disperse zirconia as fine particles. for that reason,
In order to obtain such ductility, a high level of control is required to disperse the fine powder of the raw material during the synthesis of ceramics, and the strain rate during plastic working is 1 × 10-4 to 2 ×
It was necessary to be extremely small, 10-3 / sec or less.

On the other hand, in the case of ceramics using zirconia doped with yttria as a substrate, ceramics having a relatively high strain rate and high ductility can be obtained by adding a large amount of a SiO2 glass phase to alleviate stress concentration. be able to. However, coexistence of a glass phase in ceramics has reduced toughness and repeatedly deteriorated fatigue properties. Even for other existing ceramics other than zirconia-based ceramics, even if superplasticity was exhibited, the strain rate was extremely low at 10-4 / sec or less.

At such a low strain rate, it is impossible to actually apply the ceramic material to industrial plastic working. For this reason, it is strongly required to increase the speed at which the processing of alumina-based ceramics is possible, that is, the strain speed. Therefore, the invention of this application has been made in view of the circumstances described above, and solves the problems of the prior art, and does not require a special powder process for synthesis, and can easily perform the distortion. Speed is 10 ~ 100
It is an object to provide a new alumina-based superplastic ceramic that is twice as large.

[0005]

Means for Solving the Problems The invention of this application provides the following inventions to solve the above problems. That is, first of all, the invention of this application relates to an alumina-based superplastic ceramic containing zirconia and magnesia-alumina-based spinel, wherein a total of three phases of a zirconia phase, a magnesia-alumina-based spinel phase and an alumina phase is provided. Is 90 vol% or more, and the average crystal grain size of each phase after sintering is 2.5 μm or less for each of the magnesia-alumina-based spinel phase and the alumina phase, 1.0 μm or less for the zirconia phase, and 1300 ° C. or more. Tensile ductility at a strain rate of 1.0 × 10-4 / sec or more at a temperature of 20
An alumina-based superplastic ceramic characterized by being at least 0%. Secondly, the invention of the present application discloses that the zirconia phase is 20 to 40 vol%, the magnesia-alumina spinel phase is 20 to 40 vol%, and the alumina phase is 20 to 40 vol%.
60 vol%, 1.0 × 10-4 at a temperature of 1300 ° C or higher
The alumina-based superplastic ceramic according to the first aspect of the present invention is characterized in that the tensile ductility at a strain rate of 1.0 to 10-2 / sec is 500% or more.

Thirdly, the invention of the present application discloses that one or more of a zirconia phase, a magnesia-alumina-based spinel phase and an alumina phase contain Y, C
e, containing at least one element of Ca, Ti, Cr, Mn, and Fe up to a total of 10 wt% or less; and fourth, other than zirconia phase, magnesia-alumina spinel phase and alumina phase. Is less than 10 vol%, and those compounds are Zr, Mg, Al, Y, Ce, Ca, Ti, Cr, Mn,
The present invention provides the alumina-based superplastic ceramic according to the first or second invention, which is an oxide composed of one or more elements of Fe. Fifth, according to the invention of this application, the zirconia phase is tetragonal or cubic, and the magnesia-alumina spinel phase has a molar ratio of magnesia to alumina in the range of 1: 1 to 1: 1.5. The present invention provides any one of the above alumina-based superplastic ceramics, wherein the alumina phase has a rhombohedral structure.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the features as described above, and the embodiments will be described in detail below. The alumina-based superplastic ceramics of the first invention of the present application is obtained by mixing fine powder of alumina, magnesia, and zirconia, which are raw materials, with a total of three phases of a zirconia phase, a magnesia-alumina-based spinel phase, and an alumina phase of 90 vol% or more. It is prepared by subjecting the raw material powder obtained by mixing and mixing with a ball mill to ordinary CIP molding (hydrostatic molding) and sintering. As a preferable particle size range of the raw material fine powder, alumina is 0.03 to 0.
5 μm, magnesia 0.017-0.3 μm, and zirconia 0.025-0.1 μm. Further, the sintering treatment is preferably performed at a temperature of 1350 to 1500 ° C. under normal pressure and atmospheric atmosphere.

The obtained alumina-based superplastic ceramics has a structure in which zirconia particles and magnesia-alumina-based spinel particles are simultaneously and largely dispersed in an alumina matrix, and the average crystal grain size of the magnesia-alumina-based spinel phase and the alumina phase is respectively The average crystal grain size of the zirconia phase is refined to 2.5 μm or less and 1.0 μm or less. With this structure, it is possible to suppress grain growth that inhibits superplasticity generated during high-temperature tensile deformation and damage caused by stress concentration at grain boundaries.

[0009] Thereby, at a temperature of 1300 ° C or more,
At a strain rate of 1.0 × 10−4 / sec or more, an alumina-based superplastic ceramic exhibiting a tensile ductility of 200% or more is realized. Further, the alumina-based superplastic ceramics of the second invention of this application is the same as the first invention, wherein the fine powder of alumina, magnesia, and zirconia as raw materials is mixed with a zirconia phase and a magnesia-alumina-based spinel phase each having a particle size of 20 to 50%. The alumina phase is adjusted to 20 to 60 vol% to 40 vol%, and then molded and sintered in the same manner.

[0010] Thereby, at a temperature of 1300 ° C or more,
At a strain rate of 1.0 × 10−4 to 1.0 × 10−2 / sec, an alumina-based superplastic ceramic exhibiting a tensile ductility of 500% or more is realized. Further, in the alumina-based superplastic ceramic of the first or second invention, according to the third invention of this application, one or more of a zirconia phase, a magnesia-alumina-based spinel phase and an alumina phase are provided. The phase may contain one or more of Y, Ce, Ca, Ti, Cr, Mn, and Fe elements up to a total of 10 wt% or less. And, the total of the compounds other than the zirconia phase, the magnesia-alumina-based spinel phase and the alumina phase is less than 10 vol%, and those compounds are Zr, Mg, Al, Y, Ce, Ca, Ti, Cr, Mn, Fe May be made to be an oxide composed of one or more of the above elements. Cr and Fe are converted to alumina phase, Y and
Ce, Ca, and Ti are dissolved in the zirconia phase and Y, Cr, Mn, and Fe are dissolved in the magnesia-alumina-based spinel phase, thereby promoting the diffusion of particles. Also, Y3Al5O12, ZrTi
When oxides such as O4, AlFeO4, Al2TO5, CaZrO3, MgCr2O4, and MgMn2O4 are formed, there is an effect of suppressing grain growth.

According to this, the alumina-based superplastic ceramics having the same tensile ductility as the first or second invention is realized. In the alumina-based superplastic ceramics according to the fifth invention of this application, the zirconia phase is tetragonal or cubic, and the magnesia-alumina-based spinel phase has a molar ratio of magnesia to alumina in the range of 1: 1 to 1.5. The alumina-based superplastic ceramic according to any one of the above inventions, characterized in that the alumina phase has the most stable structure having a rhombohedral structure.

Thus, for example, at a strain rate of 8.times.10.sup.-4 to 2.times.10.sup.-2 / sec at a temperature of 1300.degree.
Alumina-based superplastic ceramics with the highest tensile ductility of 1000% are realized. As described above, the alumina-based superplastic ceramics of the present invention is a new component system that has not been conventionally reported as alumina-based superplastic ceramics, and can be synthesized without requiring a special powder process.
And the possible strain rate is about 10 to 100 times that of existing alumina ceramics. In the alumina-based superplastic ceramics of the present invention, for example, the strain rate when a high ductility of 500% or more is obtained is about 5 to 60 times that of the existing alumina-based ceramics. In addition, superplasticity itself is difficult to obtain in alumina-based ceramics, which has achieved tensile ductility of up to 1000% for the first time. Even when tensile ductility as high as 1000% can be obtained, existing alumina-based ceramics have the highest performance. It is realized at a strain rate about 20 times faster than the condition showing ductility.

Further, the alumina-based superplastic ceramic of the present invention suppresses grain growth by a dispersed phase such as zirconia fine particles dispersed in an alumina matrix, and at the same time, reduces stress concentration at grain boundaries by plastic deformation thereof. Has achieved ductility. Relaxation of stress concentration by the dispersed phase is a new method that has not been known before. In addition, in order to obtain a strain rate and tensile ductility close to those of the alumina-based superplastic ceramics of the present invention, it was necessary to use zirconia with yttria as a substrate and to add a large amount of a SiO2-based glass phase to alleviate stress concentration. Due to the coexistence of the glass phase, toughness and repeated fatigue properties were deteriorated. In contrast, the alumina-based superplastic ceramics of the present invention
It does not contain a glass phase and does not include these negative factors.

According to the invention of the present application, alumina-based superplastic ceramics can be synthesized without requiring any special method, and therefore, the production cost can be reduced. Further, the present invention applies superplasticity of ceramics to plastic working in actual industry, thereby enabling high-speed net-shaping of alumina-based ceramics. Conventionally, ceramic members have required a lot of cost for processing, and therefore, the processing cost can be reduced by the net shape processing, and it is hoped that the use thereof can be widely expanded. For example, by net shape processing,
If dimensional accuracy that does not require finishing cutting can be achieved, the problem of toughness degradation due to surface scratches caused by cutting can be avoided, so that the mechanical properties of the member can be improved or the finishing cost of the member can be reduced. It becomes possible. In addition, by forming a member of a complex shape consisting of multiple parts integrally by net shape processing,
It is possible to reduce the number of steps and the number of parts. They can be widely used for precision plastic working of ceramic members, such as automobile engines, aerospace engines, chemical plants, and cutting material chips, which require heat resistance, wear resistance, or high toughness.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0016]

EXAMPLES Example 1 Al2O3 particles having a particle size of 0.2 μm, Zr2O particles having a particle size of 0.07 μm, and MgO particles having a particle size of 17 nm were weighed so that the weight ratios became 83.5%, 14.7% and 1.8%, respectively. And
The mixture was mixed by a ball mill. The mixed powder was preformed at 20 MPa, subjected to CIP treatment at 200 MPa, and further heated at 1450 ° C. for 1 hour to obtain a sintered body.

FIG. 1 shows the microstructure of the obtained sintered body, and FIG. 2 shows the result of X-ray identification. In the obtained sintered body, the volume ratio of the alumina phase, the zirconia phase, and the magnesia-alumina-based spinel phase was 78.5%: 9.5%: 12%, and the average particle diameters were 0.8 μm, 0.15 μm, and 0.42 μm, respectively. Met.
Also, a test piece was cut out from the obtained sintered body and
A tensile test was performed at a strain rate of 8.3 × 10−4 / sec. As a result, a 560% elongation was obtained. (Example 2) Al2O3 particles having a particle size of 0.2 μm, particle size 0.07 μm
Of Zr2O particles and MgO particles having a particle size of 17 nm, each having a weight ratio of
It was weighed so as to be 54.4%, 40.6% and 5.0% and mixed by a ball mill. The mixed powder is preformed at 20MPa,
The sintered body was subjected to a CIP treatment at 0 MPa and a heating process at 1400 ° C. for 1 hour. A test piece was cut out from the obtained sintered body and subjected to a tensile test at 1500 ° C. at a strain rate of 1.0 × 10 −2 / sec. As a result, an elongation of 500% was obtained. Also, at 1500 ° C
When a tensile test was performed at a strain rate of 2.8 × 10 −3 / sec, an elongation of 900% was obtained. (Example 3) Al2O3 particles with a particle size of 0.2 μm, particle size 0.07 μm
Zr2O particles, 17 nm MgO particles and 0.02 μm particle size
Y2O3 particles, the weight ratio of each is 76.3%, 14.5%, 1.8%, 7.
It was weighed to 4% and mixed by a ball mill. The mixed powder is preformed at 20 MPa, CIP treated at 200 MPa,
Further, a sintered body was obtained through a heating process at 1400 ° C. for 2 hours.
A test piece was cut out from the obtained sintered body, and 1.4 × at 1500 ° C.
Tensile tests were performed at a strain rate of 10-3 / sec. as a result,
A 380% growth was obtained.

[0018]

As described in detail above, according to the present invention, it is possible to synthesize without a special powder process, and the possible strain rate is 10 to 100 times that of the conventional one.
An alumina-based superplastic ceramic containing zirconia and magnesia-alumina-based spinel is provided.

[Brief description of the drawings]

FIG. 1 is a photograph showing a microstructure of an alumina-based superplastic ceramic according to the invention of this application. (The alphabets in the figure are A: alumina, Z: zirconia,
S: Magnesia-alumina spinel. )

FIG. 2 shows the results of X-ray identification of each phase of the alumina-based superplastic ceramics of the present invention. (The alphabets in the figure indicate A: alumina phase, Z: zirconia phase, and S: magnesia-alumina spinel phase, respectively.)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-11-71166 (JP, A) JP-A-1-242462 (JP, A) JP-A-1-242461 (JP, A) JP-A 64-64 83566 (JP, A) JP-A-9-194257 (JP, A) JP-A-3-237059 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/10

Claims (5)

(57) [Claims] An alumina-based superplastic ceramic containing zirconia and magnesia-alumina-based spinel, wherein a total of three phases of a zirconia phase, a magnesia-alumina-based spinel phase and an alumina phase is 90 vol% or more, and The average crystal grain size of each of the subsequent phases is 2.5 μm or less in each of the magnesia-alumina spinel phase and the alumina phase, and is 1.0 μm or less in the zirconia phase.
Alumina-based superplastic ceramics having a tensile ductility of 200% or more at a strain rate of 1.0 × 10 −4 / sec or more at a temperature of 00 ° C. or more. 2. A zirconia phase of 20 to 40 vol%, a magnesia-alumina spinel phase of 20 to 40 vol%, and an alumina phase of 20 to 60 vol% at a temperature of 1300 ° C. or more.
The alumina-based superplastic ceramic according to claim 1, wherein the tensile ductility at a strain rate of 1.0 x 10-4 to 1.0 x 10-2 / sec is 500% or more. 3. One or more of a zirconia phase, a magnesia-alumina-based spinel phase, and an alumina phase, one or more of Y, Ce, Ca, Ti, Cr, Mn, and Fe. 3. The alumina-based superplastic ceramic according to claim 1, wherein the total amount of the elements is at least 15 mol% or less. 4. The total of compounds other than the zirconia phase, the magnesia / alumina spinel phase and the alumina phase is 10 vol.
less than 1% and the compounds are Zr, Mg, Al, Y, C
4. The alumina-based superplastic ceramic according to claim 1, wherein the oxide is an oxide composed of one or more of e, Ca, Ti, Cr, Mn, and Fe. 5. The zirconia phase is tetragonal or cubic, the magnesia-alumina spinel phase has a molar ratio of magnesia to alumina in the range of 1: 1 to 1: 1.5, and the alumina phase has a rhombohedral structure. Characterized by the fact that
The alumina-based superplastic ceramic according to any one of claims 1 to 4.