CN1256209C - Densification method for gradient material with continuously varying constituent - Google Patents

Abstract

The present invention provides a densification method for functional gradient metal system materials with continuously varying components by different phase granule coprecipitation, which is characterized in that aiming for the main components forming the functional gradient metal system materials, sintering aid agents capable of realizing densification for granule homogeneous bodies formed by one or many main components are obtained by a mode of roughing selection. Then, sintering aid agents capable of realizing simultaneous densification for many components under the same conditions are further screened on the basis, and the adding content with which a single substance and composite materials achieve the best density under the conditions is used as a selection standard of a sintering mechanism and the adding content. Finally, the granularity distribution and the adding amount of sintering aid agent powder is calculated according to granularity sizes of each main component forming gradient materials and laminar flow precipitation conditions of granules in suspending liquid. The sintering aid agents are added to the granule precipitation bodies in a precipitation mode, and the granule precipitation bodies with continuous gradient structures are densified by vacuum hot pressing or discharge plasma sintering.

Description

The densifying method of component continually varying functionally gradient material (FGM)

Technical field

The present invention relates to the densifying method of component continually varying functionally gradient material (FGM).

Background technology

Obtaining the continuous gradient composite construction is the inexorable trend of functionally gradient material (FGM), gradient composite theory and technical development, is harsher, the meticulousr requirements of some important applied field to functionally gradient material (FGM).From the angle that thermal stress relaxes, the composition continuous distributed is the key that obtains excellent heat insulation and thermal shock resistance, also is the target that the functionally gradient material (FGM) preparation field is pursued always simultaneously.Utilize out-phase particle cosedimentation to realize that the continuous distributed of functionally gradient material (FGM) component is a kind of novel preparation method who just grew up in recent years, this method has that suitable material system scope is wide, technology controlling and process is comparatively simple, expense is cheap and characteristics such as laboratory facilities are flexible.

The principle that the cosedimentation legal system is equipped with the functionally gradient material (FGM) foundation is the Stokes free settling formula under the laminar condition:

$U=\frac{D^{2}g({\mathrm{\ρ}}_{\mathrm{Particle}}-{\mathrm{\ρ}}_{\mathrm{Liquid}})}{18\mathrm{\η}}---\left(1\right)$

Wherein U represents the sinking speed of particle; D represents particle grain size; η represents the viscosity of suspension; G represents acceleration of gravity.By following formula as can be known: the solid particle of different grain size and density has different sinking speed, so their asynchronism(-nization)s of beginning to pile up at the sedimentation container bottom.By the size distribution of control material powder and the technological parameter in the infall process, just can obtain component continually varying granular deposits.

Lithosomic body for forming by sedimentation need make it densified by some technological means, to satisfy the requirement of using.By the lithosomic body that metal dust forms, adopt the method for sintering to make it densified usually.But because different material there are differences on sintering character, densified under identical conditions for the lithosomic body that different component is formed, the various countries scientist has adopted diverse ways.The people such as T.Jungling of Germany once improved the density of lithosomic body with the method that improves sintering temperature, but effect is unsatisfactory; Behind then earlier that fusing point is the higher material and graphite powder sedimentation of Frenchman, sintering is made perforate pore continually varying porous material, and then the material that fusing point is lower is heated to molten condition, under certain pressure fused mass is pressed in the material of gradient hole.Because the porosity in gradient hole can not reach 100%, Zhi Bei functionally gradient material (FGM) in this way, though material is fine and close in compositional range necessarily, destruction has been suffered in the serialization of functionally gradient material (FGM) overall composition, and this method only is applicable to some specific system.

Summary of the invention

The invention provides a kind of whole densified new method of utilizing out-phase particle cosedimentation to prepare metal functional gradient material, to realize whole densified to metal functional gradient material with any specified structure.Its process is:

Obtain successively and can realize densified sintering aid by the mode of roughly selecting the particle isotropic body that one or more major components metals form.Then on this basis, further filter out and under identical conditions, to realize the sintering aid simultaneously densified multiple major components.At last, according to the granule size of constructing each major components of metal functional gradient material, utilize particle laminar flow setting condition in suspension to calculate the size distribution and the addition of sintering aid powder.With the major constituent sedimentation together of the mode of sedimentation, realize densified to continuous gradient structure particles lithosomic body by vacuum hotpressing or discharge plasma sintering with sintering aid and FGM.

Concrete summary of the invention division is as follows:

1. the screening of sintering aid kind and sintering mechanism determines

The screening of sintering aid is divided into roughly selects and selected two steps; Roughly select is to filter out respectively each major components of metal functional gradient material is had the kind of the sintering aid of densified effect in the scope of broadness.Selected is in roughly selecting the scope of sintering aid, filtering out can be in the same terms (sintering temperature, pressure) realize the sintering aid simultaneously densified down to multiple constituent element, its sintering mechanism and the selection of adding content with simple substance and composite under this temperature the interpolation content when fine and close as standard, that is: the sintering aid of different content and simple substance (or composite) are mixed respectively after, the densified situation of carrying out sintering and testing each sintered specimen under this temperature, the addition of pairing sintering aid is as suitable interpolation content during with simple substance (or composite) densification.

2. the calculating of sintering aid size distribution and content

Because sintering aid is to add in the granular deposits by the mode of particle cosedimentation, therefore the position of sintering aid deposition is corresponding with the position of its densified constituent element deposition, and this need design according to the size distribution of the constituent element size distribution to sintering aid.

Based on particle under laminar condition setting condition (Stokes formula, 1) and suspension in the continuity equation of particles settling

$\frac{\∂C}{\∂t}+\frac{\∂\left(\mathrm{CU}\right)}{\∂h}=0---\left(2\right)$

(wherein, C represents the concentration of particle in suspension, and it is the function of locus and time; H represents the position coordinates along gravity direction; T represents the sedimentation time; U represents the sinking speed of particle), at first according to the size distribution of each major components of functionally gradient material (FGM), calculate the Mass Distribution of each constituent element in lithosomic body after the sedimentation, promptly along the quality of each constituent element of thickness direction at lithosomic body diverse location place; Then, according to determined sintering aid kind of the 1st step with add content, calculate the Mass Distribution (being the quality of sintering aid) of corresponding sintering aid and add and obtain the total content of sintering aid at lithosomic body diverse location place by the Mass Distribution of each constituent element; At last, based on (1) formula and (2) formula, obtain corresponding size distribution by counter the pushing away of the Mass Distribution of sintering aid again.Based on result of calculation, the sintering aid raw material is carried out classification of sedimentation.By the sedimentation time of control particle, choose the particle that desired particle size distributes.On the interpolation content of sintering aid because each components contents is graded in material, the interpolation content that therefore requires sintering aid also with corresponding constituent content graded, so just can obtain sintering effect preferably.

3. the formation of continuous gradient structure and sintering

According to the Material Characteristics of the functionally gradient material (FGM) that will prepare, select suitable dispersant, be used for the necessary abundant wetting functionally gradient principal component of energy of dispersion liquid of cosedimentation method and the particle surface of sintering aid; Can dissolved particles, and do not have other reaction; Powder particle has suitable sinking speed in dispersion liquid, i.e. the modest viscosity of dispersion liquid.

The material powder that the designated size of weighing calculated mass distributes is dispersed into suspension in the dispersant 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, and sintering mechanism and definite identical in the 1st step obtains having the functionally gradient material (FGM) of the densification of specified structure at last by hot pressed sintering or discharge plasma sintering.

Adopt said method, can realize whole densified component continually varying metal functional gradient material.

Description of drawings

Fig. 1: the size distribution of W powder

Fig. 2: the size distribution of Mo powder

Fig. 3: the size distribution of Ni-Cu alloy powder

Fig. 4: the EPMA figure that does not add the W-Mo functionally gradient material (FGM) vertical section of sintering aid: a is rich Mo end, and b is rich W end

Fig. 5: after having added sintering aid Ni-Cu, W-Mo functionally gradient material (FGM) vertical section microstructure a is rich Mo end, and b is rich W end

Fig. 6: the EPMA figure that does not add the Mo-Ti functionally gradient material (FGM) vertical section of sintering aid: a is rich Mo end, and b is an intermediate transition zone, and c is rich Ti end (1200 ℃, 30MPa, insulation vacuum-sintering in 1 hour)

Fig. 7: after having added sintering aid Ni-Cu, the EPMA of Mo-Ti functionally gradient material (FGM) vertical section figure: a is rich Mo end, and b is an intermediate transition zone, and c is rich Ti end (1200 ℃, 30MPa, insulation vacuum-sintering in 1 hour)

Specific embodiments

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

Embodiment 1:

The preparation of component continually varying W-Mo functionally gradient material (FGM), its detailed process division is as follows:

(1) determining of sintering aid kind: in this system functionally gradient material (FGM), its main composition constituent element is W and Mo.The agglutinant system of sintering W alloy mainly contains Ni-Fe, Ni-Cu, Ni-Co, Ni-Cr etc. at present; Preparing with powder metallurgy process in the research of molybdenum alloy, Ti, Zr are usually as sintering aid, and Ni-Cu also has good agglomeration to Mo simultaneously.Therefore with Ni-Cu as W, the common sintering aid of Mo constituent element.By the sintering of W and Mo simple substance and composite thereof being determined its interpolation content is 3Wt.%Ni-2Wt%Cu, and sintering temperature is 1200 ℃.

(2) size distribution and the content of calculating sintering aid Ni-Cu alloy (Ni, Cu ratio is 3: 2): based on the continuity equation of particle sedimentation in suspension, and laminar flow condition (being the Stokes formula), for the size distribution of the W of given size distribution, Ni-Cu alloy powder that Mo powder (as illustrated in fig. 1 and 2) calculates as shown in Figure 3.And then go out the addition of Ni-Cu alloy powder according to the Mass Calculation of W, Mo powder.To the classification of Ni-Cu alloy raw material, obtain the desired particle size powder based on result of calculation.

(3) formation of W-Mo continuous gradient structure and densified: because absolute ethyl alcohol has good peptizaiton for W, Mo, Ni-Cu alloy, and reactionless generation, it is decentralized medium that the present invention selects absolute ethyl alcohol for use.The quality of raw materials weighing powder is dispersed into suspension in absolute ethyl alcohol.After suspension fully disperses by ultrasonic wave, join and carry out sedimentation experiment in the precipitation apparatus.After sedimentation finishes, the ethanol liquid of granular deposits top is discharged.The lithosomic body drying after the compression moulding, moves in the graphite jig, and the sedimentation body carries out vacuum heating-press sintering under 1200 ℃-30MPa-1h condition.

(4) structured testing: in order being contrasted, W, the Mo particle that does not add sintering aid Ni-Cu to be carried out sedimentation, under similarity condition, to carry out sintering.All samples of gained are analyzed through the electron probe that has energy disperse spectroscopy.Fig. 4 is the microstructure that does not add the W-Mo functionally gradient material (FGM) of sintering aid.Still all there is more hole in tangible as can be seen rich W end at rich Mo end.Fig. 5 is the microstructure of the W-Mo functionally gradient material (FGM) that obtains when being added with sintering aid Ni-Cu alloy.As can be seen, the W-Mo material is densified fully, and the black splotch among the figure is the long-pending place of the richness of sintering aid and Mo powder.

Embodiment 2:

The preparation of component continually varying Mo-Ti functionally gradient material (FGM):

(1) determining of sintering aid kind: its process is identical with embodiment 1, determines that finally Ni-Cu is as Mo, the common sintering aid of Ti constituent element.

(2) size distribution and the content of calculating sintering aid Ni-Cu: its computational process is identical with embodiment 1.

(3) formation of Mo-Ti continuous gradient structure and densified: still select for use absolute ethyl alcohol as decentralized medium.Process is identical with embodiment 1.

(4) structured testing: in order being contrasted, Mo, the Ti particle that is not added with sintering aid Ni-Cu to be carried out sedimentation equally, under similarity condition, to carry out sintering.All samples of gained are analyzed through the electron probe that has energy disperse spectroscopy.Fig. 6 is the microstructure that does not add the Mo-Ti functionally gradient material (FGM) of sintering aid.There is more hole at rich Mo end as can be seen.Fig. 7 is the microstructure of the Mo-Ti functionally gradient material (FGM) that obtains when being added with sintering aid Ni-Cu alloy.As can be seen, the Mo-Ti material is densified fully.

Preparation by above-mentioned different system functionally gradient material (FGM)s shows, the present invention proposes a kind of densified new approaches of the continuous variable gradient material of component that are used for, all can use the present invention at utilizing out-phase particle cosedimentation to prepare the continuous functionally gradient material (FGM) of component, obtain whole fine and close functionally gradient material (FGM).

Claims (3)

1, a kind of densifying method that utilizes out-phase particle cosedimentation to prepare the continuous metal functional gradient material of component, it is characterized in that at each major components of constructing metal functional gradient material, obtain successively and can realize densified sintering aid by the mode of roughly selecting the particle isotropic body that one or more major components form, then on this basis, further filter out the kind that can under identical conditions, realize to the simultaneously densified sintering aid of multiple constituent element, addition and sintering mechanism, at last, according to the granule size of constructing each major components of functionally gradient material (FGM), utilize particle laminar flow setting condition in suspension to calculate the size distribution of sintering aid powder, mode by sedimentation is with the major constituent sedimentation together of sintering aid and FGM, realize densified to continuous gradient structure particles lithosomic body by vacuum hotpressing or discharge plasma sintering, wherein, based on particle under laminar condition setting condition and suspension in the continuity equation of particles settling be:

$\frac{\∂C}{\∂t}+\frac{\∂\left(\mathrm{CU}\right)}{\∂h}=0$

C represents the concentration of particle in suspension in the formula, and it is the function of locus and time; H represents the position coordinates along gravity direction; T represents the sedimentation time; U represents the sinking speed of particle.

2, densifying method according to claim 1, it is characterized in that in the selection of sintering aid, selection can make functionally gradient material (FGM) all components simultaneously fine and close sintering aid under temperature of the same race, the sintering mechanism of sintering aid and the selection of adding content with simple substance and composite under this condition the interpolation content when fine and close as standard.

3, densifying method according to claim 1 is characterized in that the size distribution of agglutinant is corresponding with the size distribution of FGM major constituent, the interpolation content of sintering aid and corresponding constituent content graded.

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