JP2011162805A - Method for producing functionally gradient material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a functionally gradient material without producing the molten metal of a part of stock composing the same. <P>SOLUTION: Using a slurry containing two or more kinds of particles composed of high speed moving particles having a high specific gravity and/or a large particle diameter and low speed moving particles having a low specific gravity and/or a small particle diameter, this slurry is settled in a centrifugal force field; thereafter, a liquid phase part is removed to produce a green body having a compositional gradient, and this green body is sintered so as to be solidified; thus the functionally gradient material is obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a functionally gradient material.

  The functionally gradient material is a material in which a plurality of materials having different compositions and structures are inclined and integrally combined. In order to manufacture a functionally gradient material, a technique capable of freely controlling the composition distribution and structure inside the material according to the material design is required. The manufacturing technology of functionally gradient materials varies widely depending on the combination of materials and sizes. As a specific example, there is a powder metallurgy method in which metal powder and ceramic powder are mixed at a predetermined ratio, the mixed powder is laminated while changing the composition in accordance with a predetermined composition distribution, and sintered. However, in this method, the composition gradient is stepwise, and it is difficult to manufacture a material having a continuously gradient composition.

  In the manufacturing methods using centrifugal force described in Patent Document 1, Patent Document 2 and Patent Document 3, continuous composition gradient is possible. Conventional manufacturing technology of functionally gradient materials using centrifugal force can be roughly divided into two methods. One of them is the centrifugal force method using centrifugal casting (Fig. 1). When the molten metal containing the second phase particles is subjected to centrifugal casting, the second phase particles move in the metal matrix due to the difference in density between the molten metal and the second phase particles. If the movement is terminated in a state where the particles are distributed in the metal melt, a functionally gradient material manufacturing method can be manufactured, which is called a centrifugal solid phase method.

  The moving speed of particles in the molten metal is governed by the following Stokes equation.

Here, dx / dt, r _p , r _m , g, D _p and h are the moving speed of the particle, the density of the particle, the density of the molten mother phase, the gravity, the particle diameter and the apparent viscosity, respectively. As can be seen from this equation, the moving speed of the particles is proportional to the density difference between the molten mother phase and the solid phase particles, the multiple of gravity, and the square of the solid phase particle diameter. It has also been reported that functionally gradient materials are produced by adding particles to molten metal and using sedimentation in a gravitational field without applying centrifugal force. This is in principle equal to the centrifugal force method. In some cases, the second phase particles in the molten metal dissolve and crystallize in a centrifugal force application field, which is referred to as a centrifugal force crystallization method (Patent Documents 4 and 5). In any case, the movement of the particles is completed by solidification of the molten metal, and the solidified metal portion becomes the parent phase of the functionally gradient material. Therefore, this technique using centrifugal force has a drawback that it is necessary to produce a molten metal. Moreover, this technique cannot produce a functionally gradient material having a composition gradient of 0% to 100% inside the material.

  Another manufacturing technique using centrifugal force is a centrifugal force pressurizing method that uses the centrifugal force as a pressurizing method (FIG. 1). The composition gradient is usually applied before the centrifugal force is applied, and the composition gradient in the centrifugal force field is not expected. As an application example of this technique, there is a centrifugal powder mixing method (Patent Document 6). However, this technique using centrifugal force also has a drawback that it is necessary to produce a molten metal of one material, and it is impossible to produce a functionally gradient material having a composition gradient of 0% to 100% inside the material. .

JP 2001-80972 A JP 2001-115224 A JP 2001-112263 A JP 2001-252753 A Japanese Patent Laid-Open No. 2003-166028 Japanese Patent Application No. 2008-284589

  In view of the above points, an object of the present invention is to produce a functionally gradient material without producing a part of molten material constituting the functionally gradient material.

  In the invention according to claim 1, in order to produce a functionally gradient material without producing a part of molten material constituting the functionally gradient material, a slurry containing a plurality of types of particles having a difference in moving speed is used. This is characterized in that a functionally gradient material is manufactured by utilizing a difference in moving speed by applying a centrifugal force thereto. Further, in the invention according to claim 2, a slurry containing a plurality of types of particles having a difference in moving speed is used, and after pouring the slurry onto the liquid phase, a centrifugal force is applied to move the difference in moving speed of the particles in the liquid. A functionally gradient material is manufactured using

  In the invention according to claim 3, in order to make it possible to produce a functionally gradient material having a composition gradient of 0% to 100% inside the material without producing a part of the raw material melt constituting the functionally gradient material. Using a slurry containing multiple types of particles with different moving speeds, pouring them onto a solid that can be melted, and then melting the solids, and then applying a centrifugal force, the difference in moving speed of the particles in the liquid A functionally gradient material is manufactured using In the invention according to claim 4, a slurry containing a plurality of types of particles having different moving speeds is used, which is poured onto a solid that can be melted or vaporized, and a liquid is placed under the solid. Then, after the solid is melted, a centrifugal force is applied, and the functionally gradient material is manufactured using the difference in the moving speed of the particles in the liquid.

It is a schematic diagram which shows the principle of functionally gradient material manufacture by centrifugal force. Ti particles (density of 4.5 mg / ^{m 3)} is a diagram showing the moving speed of the slurry of ZrO ₂ particles (density of 5.95Mg / ^{m 3).} It is a figure which shows the particle distribution (composition gradient) of the functionally gradient material manufactured in the centrifugal force slurry method using Ti particles with a particle size of 90 to 150 μm and ZrO ₂ particles with a particle size of 38 to 75 μm. It is determined by simulation. It is a figure which shows the influence of the solvent zone | band width which acts on the particle distribution (composition gradient) in the functionally gradient material manufactured by the centrifugal force slurry injection method. The solvent band widths are 40 mm, 60 mm and 100 mm. It is determined by simulation. It is a figure which shows the composition inclination of a functionally gradient material when the width | variety of a solvent zone is 0 mm and 100 mm. The particle size of Ti particles is a diagram showing 63～90Myuemu, the composition gradient of FGM the particle size of the ZrO ₂ particles were produced by using a system of 75～106Myuemu. The upper graph is the simulation result, and the lower graph is the experimental result. It is a figure which shows the Example of a slurry injection method. It is a figure which shows the Example of the slurry injection method using the solid which can be melt | dissolved as a solvent zone.

  In this embodiment, a centrifugal force is applied to a slurry in which a plurality of types of particles having different moving speeds are mixed, thereby creating a composition gradient using the moving speed difference between the particles, and all particles are in the direction of the centrifugal force. The functionally graded material is produced without using the molten metal by removing the liquid phase portion of the slurry after solidification and solidifying.

The functionally gradient material according to the present embodiment is manufactured according to the following procedure.
(1) As a slurry, as shown in FIG. 1, high-speed moving particles (first particles) having a large specific gravity and / or large particle size, and low-speed moving particles (first particles) having a small specific gravity and / or small particle size A slurry containing two or more types of particles having a specific gravity smaller than that of the second particle and / or a second particle having a smaller particle diameter) is used.
(2) The slurry is allowed to settle in a centrifugal force field, and then the liquid phase portion is removed to produce a green body having a composition gradient.
(3) The green body is solidified by sintering to obtain a functionally gradient material.

In this embodiment, Ti particles (density 4.5 Mg / m ³ ) and ZrO ₂ particles (density 5.95 Mg / m ³ ) are used as a plurality of types of particles having a difference in moving speed, which determines the material system. It is not a thing. These sedimentation rates are obtained by calculation and are shown in FIG. As shown in the figure, when the particle diameter is the same, the sedimentation rate of the ZrO ₂ particles having a high density is fast. On the other hand, when the particle size of the Ti particles is large and that of the ZrO ₂ particles is small, the direction may be reversed. The slurry is allowed to settle in a centrifugal field, and then the liquid phase portion is removed to produce a green body having a composition gradient. This method is called a centrifugal slurry method. A functionally gradient material is obtained by sintering the green body.

First, the motion of particles in the centrifugal slurry method was analyzed by simulation. The particle size of Ti particles used in the simulation is 90-150, the particle size of the ZrO ₂ particles is 38～75Myuemu, in this condition, settling velocity of the Ti particles as can be seen from Figure 2 is that of the ZrO ₂ particles Exceed. The obtained results are shown in FIG. Here, the horizontal axis is a normalized position, and 1.0 and 0.0 are the lower part of the sediment (the lowest side in the centrifugal force direction) and vice versa. As shown in the figure, the volume fraction of Ti particles increases and the composition gradient can be confirmed as it goes to the lower part of the sediment, but the composition gradient does not change from 0% to 100%. This is because low-speed moving particles (in this case, ZrO ₂ particles) are present from the beginning even in the bottom of the slurry in the centrifugal force direction.

  Therefore, in order to obtain a material whose composition is inclined from 0% to 100%, it is effective to prepare a solvent zone having only a liquid phase and add the above slurry thereto. FIG. 4 shows the investigation of the influence of the solvent bandwidth in this centrifugal slurry injection method. The solvent zone widths in FIG. 4 are 40 mm, 60 mm, and 100 mm, and the conditions other than the provision of the solvent zone are the same as in the simulation of FIG. As shown in the figure, a large composition gradient is obtained as the width of the solvent zone increases. As shown in FIG. 4, when the width of the solvent zone is 100 mm, the composition gradient is 0% to 100%.

  This has been confirmed by experiments. Experiments with actual materials were performed with the width of the solvent zone being 0 mm and 100 mm. However, centrifugal force was not applied, and sedimentation was performed in a gravitational field. After settling, the liquid phase was removed, dried, and sintered by a discharge plasma sintering method. Here, the spark plasma sintering method is a new sintering method that is attracting attention in the field of advanced material synthesis. Pulsed electric energy is directly injected into the green compact particle gap, and the high energy of the discharge plasma generated instantaneously by the spark discharge phenomenon is used effectively. FIG. 5 shows the composition gradient of the resulting material. In the sample with the solvent zone of 0 mm, the Ti particle gradient is 0% to 70%, whereas with the sample with the solvent zone of 100 mm, the composition gradient of 0% to 100% can be achieved. This result shows good agreement with the simulation.

Similarly, simulations and experiments were performed in a system in which the particle size of Ti particles was 63 to 90 μm and the particle size of ZrO ₂ particles was 75 to 106 μm. In this system, the fast moving particles become ZrO ₂ particles. FIG. 6 shows simulation results and experimental results when the solvent zone is 100 mm. This time, the volume fraction of ZrO ₂ particles increases as it goes to the bottom of the sediment. It can be seen that even in this system, a wide composition gradient from 0% to 100% can be obtained by providing a solvent zone.

  Care should be taken when introducing the slurry into this solvent zone, as no special flow should occur in the liquid phase. For example, it is possible to use an apparatus as shown in FIG. Here, the slurry is put in the upper part. The lower part is a liquid-only solvent zone. By opening the valve, the slurry can be charged without causing a special flow in the liquid phase of the solvent zone. However, this method is difficult to work in a rotating field and is not suitable for manufacturing in a centrifugal field.

  A solid that can be melted is used as the solvent zone. FIG. 8 is a diagram showing an example of a slurry charging method using a solid that can be melted as a solvent zone. First, a meltable solid is placed in a rotating mold. Here, the shape of the mold is not limited to a cylindrical shape, and it is not necessary to rotate in the case of a gravitational field. The slurry is then poured onto this. Thereafter, if a centrifugal force is applied after the solid is melted or dissolved, it is possible to control the composition gradient in the production of the functionally gradient material using the difference in the moving speed of the particles in the liquid. Here, it may be poured onto a solid that can be melted or vaporized, and a liquid may be placed under the solid. In that case, after the solid is melted, a centrifugal force is applied to control the composition gradient in the functionally gradient material manufacturing utilizing the difference in the moving speed of the particles in the liquid.

  The present invention is not limited to the above-described embodiments, and can be applied with appropriate modifications without departing from the spirit thereof. For example, a slurry having no liquid phase portion may be used. In that case, a functionally gradient material can be produced by producing a composition gradient by applying centrifugal force to the slurry and then solidifying the composition gradient.

Claims (4)

  A method for producing a functionally gradient material, comprising using a slurry containing a plurality of types of particles having a difference in moving speed, and applying a centrifugal force to the slurry to produce a functionally gradient material using the moving speed difference.   Using a slurry containing multiple types of particles with different moving speeds, pouring the slurry onto the liquid phase and then applying centrifugal force to produce functionally gradient materials using the moving speed difference of the particles in the liquid A method for producing a functionally gradient material.   Using a slurry containing multiple types of particles with different moving speeds, pouring them onto a solid that can be melted, and then melting the solids, and then applying a centrifugal force to reduce the moving speed difference of the particles in the liquid. A method for producing a functionally gradient material, characterized by producing a functionally gradient material.   After using a slurry containing multiple types of particles with different moving speeds, pouring it onto a solid that can be melted or vaporized, placing a liquid under the solid, and then melting the solid A method of producing a functionally gradient material, wherein a functionally gradient material is produced by applying a centrifugal force and utilizing a difference in moving speed of particles in a liquid.