CN1404947A - Preparation for continuous-component gradient material - Google Patents

Abstract

The method for preparing gradient material by using cosettling process includes the following steps: according to the properties of powder for preparing gradient material selecting dispersing agent and defining settling parameters, creating quantitative relationship of component distribution of sediment, settling parameters in the settling process and characteristics of raw material powder; calculating to obtain the mass of sediment group component and grain distribution of unknown powder; according to the calculation result grading the raw material powder to obtain raw material powder with required grain distribution; dispersing the selected raw material powder in the defined dispersing agent to obtain suspension liquid, and making sedimentation to obtain sedimentary body, drying pressing and forming, transferring it into graphite mould, sintering to make densification.

Description

A kind of preparation method of component successive gradient material

Technical field

The present invention relates to the preparation method of gradient material.

Background technology

At present, mostly the structure control of gradient material (Functionally Graded Materials is called for short FGMs) is to adopt the powder metallurgy process of lamination, this stacked system is owing to the internal interface that does not have really to eliminate between material layer and the layer, therefore no matter on preparation technology's operability itself, still be on thermal stresses demulcent degree, all to exist very big shortcoming.Other method such as chemical Vapor deposition process or high-temperature plasma plasma spraying, though can improve the internal interface of material to a certain extent, the existence of " component step " in fact can not get the gradient design result who expects on instability under the high temperature and the random face.From the thinking of out-phase particle cosedimentation, realize the continuous transition of material component by the cosedimentation mode, can eliminate the macroscopic interface of gradient material inside.See FGM ' 94 collections of thesis about the special report that is equipped with gradient material with the cosedimentation legal system the earliest, the human cosedimentation methods such as T.J ü ngling of Germany have been prepared SiC-Cu, Si ₃N ₄-Mo is a gradient material ^[1]Then the people such as Huang Jihua of China University of Science ﹠ Technology, Beijing have also gone out the SUS316/3Y-PSZ gradient material with the cosedimentation prepared ^[2]But these researchs all only rest on checking to be equipped with on the feasibility of gradient material with the cosedimentation legal system, exists very big blindness.In international FGM meeting in 2000, people such as French G.Kapelski have reported the newest research results that they utilize the cosedimentation technology to obtain ^[3], they have discussed and have changed the influence of sedimentation parameter to the settling gradient-structure.But the gradient material with any specified structure is not designed and realize that on this basis autotelic preparation studies, and have only realization the essential advantage of the autotelic design of gradient material with preparation competence exertion cosedimentation method.

In article of delivering and patent, find as yet at present to utilize the cosedimentation technology that gradient material is had purpose design and the report for preparing.

Summary of the invention

The invention provides a kind of cosedimentation method of utilizing and design and prepare novel method that meet design requirement, component successive gradient material, to realize that the gradient material with any specified structure is carried out autotelic design and preparation.Its process is:

Select dispersion agent and definite sedimentation parameter at the raw material powder rerum natura that will prepare gradient material, then the component distribution of lithosomic body is set up quantitative relationship with the sedimentation parameter in the settling process (density of suspension, viscosity and height, the density of clear liquid, viscosity and height) with the powder characteristics (density of powder, granularity and size-grade distribution and powder quality) of raw material.Calculate the quality of lithosomic body constituent element and the size-grade distribution of unknown powder on this basis.According to calculation result, raw material powder is carried out classification and grating, obtain the raw material powder that desired particle size distributes.Raw material powder is dispersed into suspension in selected dispersion agent after, joins and carry out sedimentation experiment in the precipitation apparatus.After the lithosomic body drying that obtains, the compression moulding, be transferred in the mould,, obtain the gradient material of the densification of specified structure through sintering.The particular content division is as follows: 1. the selection of dispersion medium and sedimentation parameter determines

According to the Material Characteristics of the gradient material that will prepare, select suitable dispersion agent, be used for the abundant wetting particle surface of the necessary energy of dispersion liquid of cosedimentation method; Can dissolved particles, and do not have other reaction; Powder particle has suitable settling velocity in dispersion liquid, i.e. the modest viscosity of dispersion liquid.

For the suspension system that is made of raw material powder and selected dispersion agent, its density and viscosity can be replaced (because the concentration of suspension is very little, general concentration of volume percent is lower than 0.5%) by the density and the viscosity of selected dispersion agent.When the cross-sectional area of precipitation apparatus was determined, the height of suspension was by the concentration decision of suspension.The clear liquid height can freely be selected according to settling process.2. raw material powder particle size distribution and quality determines

In the design process of gradient material, the form of power function commonly used characterizes the composition distribution (supposing that gradient material mainly contains two kinds of elements A, B constitutes) of the gradient material that will prepare: $C_A\left(x\right)=a\×{\left(\frac{x}{l}\right)}^P+b----\left(1\right)$ Wherein, x represents along the position coordinates of gradient layer thickness direction; L is the thickness of gradient layer; P is the component dispersion index; A is 0 coefficient; B is a constant term.Formula (1) is the general expression formula of the gradient material that will prepare, and is objective function.

By the lithosomic body that two kinds of constituent elements of A, B constitute, suppose that component A along the distribution of lithosomic body thickness direction as shown in Figure 1.The floorage of lithosomic body is the floorage S of sedimentation container, and the density of component A, B is respectively ρ _A, ρ _B, then component A along the mass accumulation of lithosomic body thickness direction is: $W_A\left(x\right)={\mathrm{\ρ}}_{A}S{\∫}_0^x(a\×{\left(\frac{x}{l}\right)}^P+b)\mathrm{dx}=\frac{a{\mathrm{\ρ}}_{A}S}{P+1}\frac{x^{P+1}}{l^P}+{\mathrm{\ρ}}_A\mathrm{Sbx}----\left(2\right)$ Equally can be in the hope of the mass accumulation distribution function of constituent element B along the lithosomic body thickness direction: $W_B\left(x\right)={\mathrm{\ρ}}_{B}S(1-b)x-\frac{{\mathrm{a\ρ}}_B{\mathrm{Sx}}^{P+1}}{(P+1)l^P}----\left(3\right)$

In formula (2) and (3), behind the geomery of determining objective function and lithosomic body, parameter ρ _A, ρ _B, P, s, a and b be known quantity, the quality of component A, B is just unique have been determined.

Ask the size-grade distribution of sedimentation powder below again, in the solid particles sediment process, particulate sinkability W is the function of time t: $W\left(t\right)=m\×{\∫}_{D_t}^{D_{\max }}f\left(D\right)\mathrm{dD}+m\×{\∫}_{D_{\min }}^{D_t}\frac{\mathrm{Ut}}{R}f\left(D\right)\mathrm{dD}----\left(4\right)$ Wherein W (t) represents the sinkability of certain powder elapsed time t; M represents the quality of this powder; D _Max, D _MinMaximum and the minimum grain size of representing this powder respectively; F (D) represents that the frequency of this powder distributes (being base with the quality): Ut represents the settling velocity of particle when time t; D is illustrated in the grain diameter that t constantly is deposited on the sedimentation container bottom fully, for particle diameter greater than D _tParticle constantly all deposited to the sedimentation pipe bottom at t, and granularity is less than D _tParticle, have only part to be deposited to the bottom of sedimentation pipe; R represents the elemental height of suspension.

If the size-grade distribution of a kind of powder in two kinds of powder of known A, B is updated to its size-grade distribution in the formula (4), make itself and formula (2) or (3) set up relation of equal quantity, thus can be in the hope of the size-grade distribution of another kind of powder.But obtaining the size-grade distribution of powder B, is very very difficult from the mathematics angle.Below we ask the size-grade distribution of powder B by geometric method.By the curve W that calculates _B(t)-t on (t a bit ₁, W _B(x ₁)) make tangent line, by deriving as can be known: at t ₁Constantly, particle diameter greater than The B powder the cumulative settling quality (also be contain among the powder B particle diameter greater than The particulate quality) equal through (t a bit on the curve ₁, W _B(x ₁)) the intercept of the tangent line of doing on Y-axis.It is particle diameter

Can try to achieve, repeat the mass accumulation distribution curve that above-mentioned solution procedure can obtain powder B.

In the sedimentation experiment of reality, in order to eliminate the uniform bed of lithosomic body bottom in the conventional particles settling process, often need add one section supernatant liquid in the suspension bottom in sedimentation pipe, can calculate with the formula of above-mentioned derivation equally for this settling process.3. the formation of continuous gradient structure and densification

Based on above-mentioned theory calculation result, raw material powder is carried out classification of sedimentation.By the control particulate settling time, choose the raw material powder that the experiment desired particle size distributes.The raw material powder of weighing calculated mass is dispersed into suspension in the dispersion agent of having chosen.After suspension fully disperses by ultrasonic wave, join and carry out sedimentation experiment in the precipitation apparatus.After sedimentation finishes, the liquid medium of granular deposits top is discharged precipitation apparatus.The lithosomic body drying after the compression moulding, moves in the graphite jig, carries out sintering, obtains having the gradient material of the densification of specified structure at last.

Adopt this designing technique, overcome traditional pass through trial property means (material preparation-test-refabrication-test again-...) determine the shortcoming of parameter blindness such as raw materials quality, proportioning and size-grade distribution.And this technology combine with computer also have convenience of calculation, quick, economic dispatch characteristics.

Specific embodiments

Introduce specific embodiments of the present invention in detail below in conjunction with accompanying drawing.

Fig. 1: lithosomic body component distribution schematic diagram

Fig. 2: the basic conception figure that is equipped with gradient material with the cosedimentation legal system

Fig. 3: the process flow sheet that is equipped with gradient material with the cosedimentation legal system

Fig. 4: the size-grade distribution of Ti powder

Fig. 5: the size-grade distribution of the Mo powder (granularity of the Mo powder of 1-calculating among the figure; The granularity of Mo powder after 2-grating)

Fig. 6: particles settling synoptic diagram

Fig. 7: the density of suspension and clear liquid and viscosity profile in the Mo-Ti system

Fig. 8: the EPMA of Mo-Ti gradient material longitudinal section figure (1200 ℃, 30MPa, insulation vacuum sintering in 1 hour)

Fig. 9: the comparison of design result and experimental result

Figure 10: the size-grade distribution of known raw material W powder

Figure 11: corresponding to the size-grade distribution of the Mo powder of W

Figure 12: the EPMA of W-Mo gradient material longitudinal section figure (1200 ℃, 30MPa, insulation vacuum sintering in 1 hour)

Figure 13: the design of W-Mo sample and the comparison of measured result

The present invention with the basic ideas of the standby component continually varying functionally gradient material (FGM) of cosedimentation legal system and process chart such as Fig. 2 and Shown in 3. The Mo-Ti functionally gradient material (FGM) that form to distribute with difference respectively below be prepared as example, sketch implementation process of the present invention.

Embodiment 1:

The diameter of the Mo-Ti gradient material that the present invention will prepare is 32mm, and its component is distributed as: $C_{\mathrm{Mo}}\left(x\right)={\left(\frac{x}{1.76}\right)}^2----\left(5\right)$ Wherein, C _Mo(x) the expression elements Mo is along the volumn concentration of prepared gradient material thickness direction, and x represents along the position coordinates of the pure Ti side of Mo-Ti thickness direction distance.The detailed process division is as follows:

(1) quality that calculates Mo, Ti powder according to formula (2) and (3) is respectively 9.52g, 8.41g, and the size-grade distribution of supposing raw material Ti powder is known, as shown in Figure 4.The size-grade distribution of the Mo powder that calculates according to formula (4) as shown in Figure 5.

(2) raw material Mo is carried out classification and grating, the size-grade distribution of the Mo powder that obtains as shown in Figure 5.

(3) to select distilled water for use be dispersion medium in the present invention, the sedimentation device that is adopted as shown in Figure 6, the height of suspension is 50cm, the clear liquid height is 80cm, used clear liquid adopts the mixing solutions of different ratios glycerine and water, and with the gravity of balance upper end suspension, its density distribution as shown in Figure 7.

(4) according to the raw material powder quality of calculating, formulated suspension, the volumn concentration of Mo, Ti solid particulate is 0.36% in the suspension.The suspension for preparing joined through ultrasonication carry out sedimentation in the precipitation apparatus that clear liquid is housed, the sedimentation body carries out vacuum heating-press sintering under the 1473K-30MPa-1h condition.

(5) the gained sample is analyzed through the electronic probe that has energy spectrometer, the result as shown in Figure 8, wherein dark-coloured is the Ti element, light tone be the Mo element.As can be seen from the figure, Mo, Ti have formed the successive gradient-structure.Test result and design result are compared, as shown in Figure 9.Test result and design result are approaching, have realized design process.

Embodiment 2:

The diameter of the W-Mo gradient material that the present invention will prepare is 24mm, and its component is distributed as:

C _W＝0.94x (6)

Wherein, C _WExpression element W is along the volumn concentration of prepared gradient material thickness direction, and x represents along the position coordinates of the pure Mo side of W-Mo thickness direction distance.The detailed process division is as follows:

(1) quality of calculating W, Mo powder according to formula (2) and (3) is respectively 4.61g and 2.45g, the size-grade distribution of raw material W powder as shown in figure 10, the size-grade distribution of the Mo powder that calculates according to formula (4) is as shown in figure 11.

(2) select for use dispersion medium, sedimentation and sintering process identical with embodiment 1.

(3) the gained sample is analyzed through the electronic probe that has energy spectrometer, and the result as shown in figure 12.

As can be seen from the figure, W-Mo has formed the successive gradient-structure.Test result and design result are compared, and as shown in figure 13, as can be seen: test result and design result are approaching.

Preparation by the gradient material of above-mentioned different systems and different specified structures shows, the present invention proposes a kind of new approaches that are equipped with gradient material with the cosedimentation legal system, the method of design and the operational path of gradient material have also been proposed to be equipped with simultaneously with the cosedimentation legal system, all can use the present invention to design and prepare at be equipped with component successive gradient material with the cosedimentation legal system, obtain the component successive gradient material that meets design requirement.

Claims (6)

1, a kind of method for preparing component successive gradient material, it is characterized in that selecting dispersion agent and definite sedimentation parameter at the rerum natura of the raw material that will prepare gradient material, component with lithosomic body distributes with the sedimentation parameter (density of suspension in the settling process then, viscosity and height, the density of clear liquid, viscosity and height) with the powder characteristics (density of powder of raw material, granularity and size-grade distribution and powder quality) set up quantitative relationship, calculate the quality of lithosomic body constituent element and the size-grade distribution of unknown powder on this basis, according to calculation result, raw material powder is carried out classification and grating, obtain the raw material powder that desired particle size distributes, raw material powder is dispersed into suspension in selected dispersion agent after, join and carry out sedimentation experiment in the precipitation apparatus, the lithosomic body drying that obtains, after the compression moulding, be transferred in the mould, again through sintering, obtain the gradient material of the densification of specified structure, wherein:

(1) composition of the gradient material that will prepare distribution (supposing that gradient material mainly contains two kinds of elements A, B constitutes): $C_A\left(x\right)=a\×{\left(\frac{x}{l}\right)}^P+b----\left(1\right)$

(2) component A, B along the mass accumulation of lithosomic body thickness direction are: $W_A\left(x\right)={\mathrm{\ρ}}_{A}S{\∫}_0^x(a\×{\left(\frac{x}{l}\right)}^P+b)\mathrm{dx}=\frac{{\mathrm{a\ρ}}_{A}S}{P+1}\frac{x^{P+1}}{l^P}+{\mathrm{\ρ}}_A\mathrm{Sbx}----\left(2\right)$ $W_B\left(x\right)={\mathrm{\ρ}}_{B}S(1-b)x-\frac{{\mathrm{a\ρ}}_B{\mathrm{Sx}}^{P+1}}{{(P+1)l}^P}----\left(3\right)$

(3) quantitative relationship between sedimentation parameter and the powder characteristics: $W\left(t\right)=m\×{\∫}_{D_t}^{D_{\max }}f\left(D\right)\mathrm{dD}+m\×{\∫}_{D_{\min }}^{D_t}\frac{\mathrm{Ut}}{R}f\left(D\right)\mathrm{dD}----\left(4\right)$

2, according to claim 1ly be equipped with the technological method of gradient material, it is characterized in that the solid-liquid volume ratio is less than 1% in the suspension with the cosedimentation legal system.

3, according to claim 1ly be equipped with the technological method of gradient material, it is characterized in that to obtain calculating the raw material powder of gained size-grade distribution by classification with the cosedimentation legal system.

4, according to claim 1ly be equipped with the technological method of gradient material, it is characterized in that adjusting the clear liquid height of sedimentation pipe lower end according to the design needs with the cosedimentation legal system.

5, describedly be equipped with the technological method of gradient material according to claim 1 and 5, it is characterized in that the density according to suspension designs the density and the distribution thereof of clear liquid with the cosedimentation legal system.

6, according to claim 1ly be equipped with the technological method of gradient material, it is characterized in that obtaining the gradient deposition body of specified structure by sedimentation with the cosedimentation legal system.

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