JPS63140751A - Manufacture of composite casting article - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to metal matrix composite materials, more specifically,
The present invention relates to a method for manufacturing cast metal matrix composite articles and articles obtained by the method.

[Prior Art] Metal matrix composite materials are composed of segmented solid fillings, i.e.
An article consisting of a metal matrix, for example aluminum or an alloy thereof, in which fibrous or particulate material is distributed. Such solid fillers can be incorporated and distributed into such metal matrices and are incorporated into the metal such that they do not lose their form or identity due to dissolution in the metal or chemical bonding with the metal; at least substantially retains its integrity.

No. 58-20/l 139 describes a method for manufacturing composite materials in which alternating layers of reinforcing fibers and aluminum foil are placed between male and female molds. The foil is placed in a wafer, heated to "melt" the foil, and subjected to relatively low pressure to produce a unitary composite material. However, this method is unsuitable for producing ingots with substantial bulk or thickness, at least when using discontinuous reinforcing fibers. In such cases, a large number of separate foil layers, each with a surface oxide film, are required, and the presence of oxides makes it impossible to achieve the desired properties of the product. Furthermore, when producing bulky composite ingots, it is difficult to determine the proper amount of metal to be delivered; too many or too few metal claws will result in an unacceptable non-uniform product.

Also, for example, U.S. Patent No. 3,970°136
The material consists of a stack of alternating sheets of fibrous reinforcement and (in solid state) matrix metal, which is then heated to melt the metal, applying pressure as the metal melts. It has been proposed to infiltrate the fibrous layer with metal. However, the problem with this type of method known so far is that the resulting composite material tends to have porous regions with poor mechanical properties (especially if the fiber layer has some thickness). occurs. Additionally, these methods have limitations in the structure of the fiber-reinforced region that can be obtained.

SUMMARY OF THE INVENTION The present invention provides a new and improved method of manufacturing composite cast articles comprising a metal matrix and a segmented solid filler incorporated and distributed throughout or at least in desired portions of the matrix. . At least one layer of a preform of split solid filler and a melt of a metal matrix is fed into a die cavity, and pressure is applied thereon parallel to the sleeve of the cavity, driving the molten metal to form the preform. The filler is infiltrated and the resulting cast article is then allowed to solidify. In one embodiment, at least one layer of a preform of segmented solid filler and at least two layers of initially solid matrix metal are stacked side by side in a stack with filler layers between the metal layers. placing in a cavity defined by a surrounding die wall in a direction and having an axis passing through all layers of the stack;
heating the die wall to raise the temperature of the matrix metal of the stack above the liquidus temperature of the metal, thereby completely melting the matrix metal of the stack; applying pressure to the stack in a direction to completely penetrate or impregnate the molten metal into the preformed filler layer while solidifying the infiltrated metal. In another aspect, the preform filler may be impregnated with molten metal by forcing the preform through the molten metal of the die cavity. As used herein, the term "preform" refers to a porous compacted body of segmented solid-filled fibers or granules that is effectively integrated into a compacted body that is subjected to sufficient compaction pressure. It exhibits green strength when exposed, ie, such that the compressed body is self-retaining in shape and size when handled.

In a novel feature of the invention, the solidification step includes a solidification process in which the solidification front is formed by a metal-infiltrated preform layer while the metal before the solidification front within and at least immediately beyond the preform layer remains molten. This is done by adjusting the heat flow within the die cavity in such a way that it travels completely through the die cavity in one direction along the axis of the cavity (relative to the direction of travel of the solidification front described above).
A metal layer disposed beyond the preform layer contains excess claw metal that permeates from that metal layer into the preform during the pressing process. It has been found that with a combination of such features it is possible to produce composite articles in which there are no porous regions and therefore always have fully adequate mechanical properties.

In previously proposed methods for producing fiber-reinforced or similar metal matrix composites by heating and pressing a stack of alternating metal and fiber layers, the solidification fronts approaching each other are It is likely to be encountered within metal-impregnated fiber layers. A porous region is formed at the front joint due to the concentration of solidified metal. Also, since this region is bound to the solidified 011 plane on both sides, a continuous supply of molten metal filling the holes is not possible. As a result, the porous regions remain unfilled and the resulting composite material is weak. However, in the method of the present invention, there is only a single solidification front traveling in one direction through the preformed filler layer, so the pores formed by shrinkage are contained between the convergent solidification fronts of the filler layer. Not possible. This solidification front is also preceded by a continuous supply of molten metal, which fills the voids formed by contraction under continuously applied osmotic pressure.

In a preferred embodiment of the invention, one end of the gouer is selectively heated or cooled such that a temperature difference between opposite ends of the die cavity, e.g., heat is preferentially transferred from one end of the gouie to the other end. during the pressurization process by selectively insulating one end of the gouer, or by creating a temperature difference between opposite ends of the die cavity by any suitable combination of these methods. Make necessary heat flow adjustments. Such a temperature difference may cause two opposing solidification fronts to advance toward each other from opposite ends of the cavity along the axis of the cavity, but with different initiation times and/or advancement rates, the solidification fronts may , an area or layer of excess metal is encountered beyond the preform rather than within the preform layer itself, and the only solidification front passes through the preform.

The heating process involves directing an external heat source (melting the matrix metal) from one end of the gouer to the other end of the goo parallel to the sleeve of the die, as osmotic pressure is acting longitudinally on the metal-preform stack within the cavity. It can be carried out simultaneously with the pressing step by gradually moving along the die at the end. In this case, the solidification front advancing in one direction follows the heat source along the axis of the cavity. This is particularly advantageous when manufacturing composite articles from stacks containing multiple filler preforms alternating with matrix metal layers, and when manufacturing articles having a substantially axial length. advantageous to

Each matrix metal layer has a thickness of at least about 2.5 cm.
The preform is also preferably at least about 2°5xx thick.

Further features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

For illustration, aluminum (matrix metal) and SiC or ΔQ, 0. Note consisting of discontinuous reinforcing fibers of fire-resistant materials such as! ! l! The present invention will be described as an embodiment in a method of manufacturing a composite billet. Such composite materials are useful for JM construction and other purposes and are characterized by light grip and high strength.

In FIG. 1, a cylindrical die cavity is defined which is axially perpendicular and open at the top, with the lower end closed by a metal or similar gouly plate 11, made of a suitable thermally conductive material (e.g. steel). The die 11 shown in FIG. The gouy plate is supported on a steel base plate I2 and has a compressible insulation layer 14, such as fiber flux (F
1brerrax, trademark) from plate 12.

Disposed within the die cavity is a matrix metal 16 and a disc-shaped preform 18 of refractory fibrous material that is impregnated with the matrix metal to produce a composite metal-fiber article. Examples of suitable fibrous materials for preforms include alumina, zirconium oxide, silica, silicon carbide,
Includes particles of silicon nitride or titanium diboride, especially alumina in the form of chopped fibers, and silicon carbide or silicon nitride in the form of whiskers or chopped fibers.

When initially placed in the die cavity, the matrix metal consists of two discs of solid metal, preform 1
8 is sandwiched between these disks. The lower one of the two matrix metal discs rests on a layer of insulation 20 on top of the gouly plate 11, while
Another layer 22 of insulation is placed on top of the upper matrix metal disk. Both insulation layers are made of fibrous or such materials (e.g. "fiber flux",
Made from aluminum silicate fibers).

When carrying out the method of the invention in the manner shown in FIG.
4, the die is first heated to melt the matrix metal. Vertically movable ram 2 placed in the die cavity
6 is advanced downward and positioned on the upper insulation layer 22. Once the matrix metal is completely melted, heating is terminated and the ram is activated to apply pressure to the contents of the die cavity in a vertically downward direction (arrow).

FIG. 1 illustrates carrying out the method of the invention when the matrix metal is completely melted, the heating is stopped, and the ram is just in contact with the upper layer of insulation 22. FIG. The pressure from the ram then drives the molten matrix metal into the insulation layers 20 and 22 and the preform [8] and also compresses the insulation layer 14. Preferably, the insulation layer 2
0 and 22 have a tighter weave than preform 18, so that these layers penetrate before the preform. Also preferably, the preform has a compressive strength sufficient to withstand the pressure applied by the ram, and thus
2. A casing that substantially retains its original shape and dimensions.

Since heat is no longer being applied to the system, as pressure is continuously applied, the matrix metal cools and solidifies as the preform impregnates. Finally, the ram is pulled upwards, the formed composite product is removed from the goo, and the trimmed and impregnated insulation T? Remove J20 and 22 and excess metal.

In the present invention, when pressurization is initiated, a temperature difference is created between the upper and lower ends of the contents of the die cavity.

Cooling and resulting solidification proceeds vertically inward from the top and bottom of the die cavity, depending on the temperature difference and the relative initial vertical dimensions of the metal above and below the preform. Because of this, the advancing upper and lower solidification fronts are encountered in the metal below the preform, rather than within the preform itself. For this to occur, the ram must continue to apply sufficient pressure to cause complete infiltration of the preform by the matrix metal before solidification of the metal is complete.

Preferably, the first stage is a short pressurization at a relatively low pressure (during which the insulation layers 20 and 22 are impregnated with the matrix metal) and the second stage is a short pressurization at a relatively low pressure (during which the insulation layers 20 and 22 are impregnated with the matrix metal) and a second stage is a pressurization of the preform 1.
It is preferred to employ a two-stage pressure cycle of substantially higher pressures and longer periods of time effective to achieve complete impregnation.

As a result of the above-described features of the invention, while the impregnated matrix metal solidifies within the preform, there is a single solidification front advancing through the preform in one direction, and thus the preform The molten metal is constantly fed to fill the voids created by the shrinkage of the solidifying metal within the object, ie until impregnation and solidification are complete within the preform.

In this way, undesirable porosity in the resulting product can be avoided and satisfactory mechanical properties can be achieved throughout the composite, even with substantially thick composite materials.

To create an initial temperature differential, in the embodiment of FIG. 1, the ram 26 is made of a highly thermally conductive metal such as I or bronze (which may also be the material of the base plate 12) and is supplied to the die cavity. When you do it, it's "cold", i.e.
Not heated. The ram may be internally cooled if it is desired to promote solidification of the matrix metal, but such active cooling may not be necessary in all cases. Furthermore, before positioning the ram, the Goui plate 11 is heated by a resistive or inductive heater 24, the peripheral part of this plate is in direct contact with the heating die, and in order to minimize heat loss, the plate is It should be noted that the base plate +2 is well insulated from the beginning, which is not heated as much by 14. Therefore, as the ram begins to press against the upper end of the die cavity contents, the relative low temperature of the ram and the relative high temperature of the die play (I+) at the lower end of the cavity contents will force the lower end of the cavity against the upper end. It will make it hotter.

Initially, the cold ram absorbs heat from the upper end of the die cavity, solidifying the metal that has penetrated the insulation layer 22 (thereby forming a seal against leakage of molten metal) and moving down the cavity. A first solidification front is created. The pressure exerted by the ram compresses the insulation layer 14 between the gouy plate +1 and the base plate 12, causing the layer 1
4, promoting thermal contact between the initially heated gouy plate and the initially cold base plate, so that heat is absorbed from the lower end of the die cavity. Solidification of the contained metal then begins at that location, sealing off any escape routes for molten metal at the bottom of the die and creating a second assimilation front that moves upward. Due to the initial temperature difference between the top and bottom of the die cavity, the upward advancement speed of the second front surface is slower than the downward advancement speed of the first front surface.

Thus, the front surface will eventually be encountered at a location within the cavity substantially below the midpoint of each starting location.

The relative thicknesses of the metal above the preform, the preform itself, and the metal below the preform are determined by the two solidification fronts advancing from the upper and lower ends of the cavity, respectively, as described above. , are selected to be encountered below the preform, ie at the bottom of the two coats of matrix metal. To this end, generally the initial thickness of the matrix metal below the preform may be selected to be approximately twice the initial thickness of the matrix metal above the preform. More particularly, in the embodiment of FIG. 1, the initial vertical thickness Y of the matrix metal above the preform is determined by the following relationship: The initial vertical thickness of the metal, Q, is a value of about 1.8 to 2.0 (most preferably about 1.9), and I is the thickness of the insulation layer 22. ] and the value of Z is preferably 0.5 times or more the vertical thickness of the preform 18 (Z approximately equal to the thickness of the preform).

To ensure fast heating of the fibers, the thickness of the preform is preferably 25j111 or less.

The lower metal layer thickness Z is sufficient so that when the impregnation of the preform is completed, there is still an excess metal layer below the preform in which the solidification front is encountered. The presence of excess molten metal in the pool below the preform means that as the first solidification front advances downwardly through the preform,
It is important to always ensure a continuous supply of molten metal to perform infiltration of the preform.

In the example of the device shown in FIG. 1, the thickness of the gooey 10 is, for example, 25*x, and the inner diameter is about 7Eryx.

Also, although this is the approximate diameter of the ram 26, the ram can enter the die cavity with some clearance. The vertical thickness of the central part of the Goui plate 11 is about Gxm, the vertical thickness of its thinner end parts is 3 squares, and the vertical thickness of the base plate 12 is 25xm. Both the base plate and the ram are made from gouging steel. The insulation layer is made from "Fiberflux" refractory fibers and the uncompressed vertical thickness of layer 14 is 3RR. The vertical thickness of each layer 20 and 22 is 1.5 am. Heater 24 is a resistance heater.

In an example of using this exemplary apparatus to carry out the method of the present invention to produce a disc-shaped metal-fiber composite article having a diameter of 7011S vertical thickness of 30xg, a refractory of such dimensions is used within the die cavity. A fibrous preform 18 is placed between lower and upper solid disks of aluminum alloy suitable as the matrix metal. The vertical thickness Z of the matrix metal below the preform is 30zx
, while the vertical thickness Y of the matrix metal above the preform is 17Rj! It is. 21 kg/c
A two-stage ram pressure cycle is employed, operating at x'' for 5 seconds and 211 kg/cm'' for 240 seconds.

The above dimensions and conditions and each are O9!0.0
．． By using preforms with fiber volume fractions (vr) of 15 and 0.20, (a) A Q-12
6% Si alloy as matrix metal
(b) heating to 660°C using A12-2% Si alloy as matrix metal, a satisfactory composite material was obtained. At these temperatures, the base plate temperature is approximately 200°C.

FIG. 2 shows an apparatus similar to FIG. 1 for use in manufacturing disc-shaped metal articles having an annular fiber reinforced region. For this purpose, instead of the disk-shaped preform of FIG. 1, an annular preform 18a of refractory fibrous material is provided. The central hole of the preform is initially filled with a slap of matrix metal. The annular preform, centrally fed with slap, is placed in the cavity of the gouer 10 between solid upper and lower disks 16a and 16b of matrix metal to form a vertical stack. The metal disk has relative vertical thicknesses Y and Z defined with respect to the vertical thickness of the preform. The method of the present invention can also be carried out in the manner described above with reference to FIG. 1 to produce the desired composite article. In this case, when the upper metal disk 16a melts,
The molten metal flows around the outer surface of the preform and penetrates the preform from the sides along with the metal of the sludge 18r. Thus, in the example of the operation shown in FIG. 2, where in the final article there is a central fiber-free metal region surrounded concentrically by a fiber-reinforced metal ring and a peripheral region of fiber-free metal, the preformed ring has a vertical thickness of 451 m, an outer diameter of 60111, and an inner diameter of 30xx. The metal thicknesses Y and Z are 251 m and /15xx, respectively. All other dimensions correspond to the example described above with reference to FIG. The same.vr=o.

15 preforms, AQ-12 as matrix metal
%Si, 5 at die temperature 600°C and 21 kg/am'
Using a pressure cycle of 211 kg/cm'' for 240 seconds):11 composite material was obtained.

Another embodiment of the method of the invention is shown in FIG.

As shown, it is generally preferred that the thickness of the fibrous layers does not exceed about 25 Ivi, so that if it is desired to produce a cast composite material of substantial axial length, multiple fibrous layers 118a, lvi.
18b, I 18c, 118d and 118c (each a single effectively integral preform having a thickness of at least about 2.5 cm) and alternating with and continuous with the fibrous layers. A plurality of metal layers 116a, l
'l 6b, l 16c, I I6d and 1
16e (single effectively integral pieces, each at least about 2,5 ml thick) to form a stack.

Further, with reference to FIG. 3, a stack of multiple layers of metal and fibers is placed in the die 10 of FIGS. 1 and 2, respectively.
The die 10' is placed in a cylindrical cavity perpendicular to the axis (closed at the bottom by a plug lvy) generally similar to the die 10' and subjected to heat and pressure similar to the embodiment of FIGS. 1 and 2. to raise the temperature of the metal layer above the liquidus temperature of the metal, thereby melting the metal and uniting the stack (essentially simultaneously heating the fibers). In the embodiment of FIG. 3, heat is provided to the die by an axially short (illustrated at 24°) heat source that surrounds the die wall and is movable axially relative to the gou wall. During the heating operation, the heat source 24° is gradually moved from the lower end to the upper end of the stack of fiber and metal layers in the die, while being moved in the axial direction (arrow 28°) by the ram 26°.
) a longitudinal pressure is applied to the stack. The movement of the heat source 24' continuously melts the metal layers 116a, 1116b, etc., while also heating the fibers, and the pressure applied by the ram causes the metal, if molten, to penetrate the heated layer of fibers. The unidirectional solidification front follows the heat source up the stack, thereby providing the advantage of the present invention of avoiding the creation of porous regions in the resulting composite material.

Also, the localized progressive heating provided in the embodiment of FIG. 3 facilitates removal of air and gases from the fibrous layer as penetration progresses. If gas entrapment is particularly problematic in some cases and/or certain precautions are desirable or necessary to minimize oxidation, the die may be depressurized in a known manner as described above. You can do it.

each supplying multiple layers of fiber and metal;
and directional progressive heating as described above as a method of adjusting the heat flow to form a single solidification front going in one direction across multiple fiber layers. The embodiments of the invention illustrated are generally similar to the embodiments illustrated in FIGS. 1 and 2. By the method shown in Figure 3,
Billets or other cast articles of substantial size can be produced without being constrained by the maximum easily permeable thickness of a single fibrous layer.

It will be appreciated that the invention is not limited to the methods and embodiments particularly described above, but may be implemented in other ways without departing from the inventive concept.

[Brief explanation of the drawing]

1 is a side cross-sectional view of a die implementing the method of the present invention; FIG. 2 is a cross-sectional view similar to FIG. 1 implementing the method of the present invention for manufacturing an annular-shaped composite article; FIG. 1 is a side cross-sectional view of a die including multiple layers; FIG. lO...die, 11...die plate, 1bi...
Plug, 12...Base plate, 14...Insulating material layer, 16...Matrix metal, lGa...Upper disk, +6b...Lower disk, 18...Preform, 18a...Annular Preform, 18r...Stack, 20.22...Insulating material layer, 24...Heater, 24°...Heat source, 2G, 26'...Ram, 1168~"...Matrix metal, 118a-e・
...Preformed product. Patent Applicant: Alcan International Limited

Claims (1)

[Scope of Claims] 1. At least one comprising a preform of segmented solid filler.
The two layers and the metal matrix melt are placed in a die cavity, and pressure is applied in a direction parallel to the axis of the cavity to drive the molten metal to completely penetrate the preform filler, resulting in a cast article. A method of manufacturing a composite cast article comprising a metal matrix and a segmented solid filler incorporated and distributed within the matrix by solidifying a metal infiltrated preform, the solidifying front being along the axis of a cavity. The die passes completely through the material layer in one direction, while the metal in front of this front within the preform layer and at least immediately beyond the preform layer remains molten. A method characterized in that the infiltrated metal is solidified by regulating the heat flow within the cavity. 2. Infiltration of the preformed filler layer comprises (a) at least one layer consisting of a split solid filler preform and at least two layers of initially solid matrix metal, with a filler layer between the metal layers; (b) heating the die wall to form the stack in a cavity defined by a die wall laterally surrounding the stack and having an axis extending through all layers of the stack; raising the temperature of the matrix metal in the stack above the liquidus temperature of the metal, thereby completely melting the matrix metal in the stack; (c) then applying pressure to the stack in a direction parallel to the axis of the cavity; and (d) solidifying the resulting cast article, which is disposed beyond the preform layer. 2. The method of claim 1, wherein the metal layer contains an excess of metal that permeates from the metal layer into the preform during the pressing step. 3. adjusting the heat flow comprises creating a temperature difference between opposite ends of the die cavity such that one end region of the die cavity is hotter than the other region, and the excess metal-containing layer is 3. A method according to claim 1, wherein the preform layer is located between the hot end of the die cavity. 4. The method of claim 3, wherein the step of creating a temperature differential comprises selectively heating one end of the die. 5. The method of claim 3, wherein the step of creating a temperature differential includes selectively cooling one end of the die. 6. The method of claim 3, wherein the step of creating a temperature differential comprises selectively insulating one end of the die to preferentially remove heat from the die cavity at the other end of the die. Method. 7. A patent claim in which the pressurizing step is performed by a ram inserted into the die cavity at the other end of the die, and the ram is made of a material having a lower temperature and greater thermal conductivity than the other end of the die. The method described in item 6. 8. The method of claim 1 or claim 2, wherein the preform is a generally annular structure having a central hole coaxial with the stack, and includes a slug of the matrix metal disposed in the hole. 9. Claim in which the preform has an outer diameter substantially smaller than the diameter of the die cavity, such that during the pressing step, molten metal penetrates the preform both longitudinally and laterally. The method according to item 8. 10. The method of claim 1 or 2, wherein the matrix metal is aluminum and the filler comprises reinforcing refractory fibers. 11. A heating step is carried out simultaneously with the pressing step by gradually and unidirectionally moving an external heat source along the die parallel to the axis, and thereby the solidification front follows the heat source and the die 3. The method of claim 2, wherein heat flow within a die cavity is adjusted to proceed gradually and unidirectionally along said axis within the cavity.