Metal foam production method and metal foam production apparatus

Abstract

The present invention provides a metal foam production method that enables a foaming process to be performed at low cost and enables controlling of the shape of metal foam. According to the present invention, a mold that transmits light and a precursor prepared by mixing a metal with a foaming agent are used, and a metal foam is produced by irradiating the precursor with a light transmitted through the mold to thereby heat and foam the precursor so as to obtain a metal foam, while controlling the shape of the metal foam by the mold.

Claims

1. A metal foam production method comprising steps of: using a mold that transmits light and a precursor made by mixing a metal with a foaming agent, the mold consisting of a net made of metal, the net being formed of a plurality of holes; and irradiating the precursor with a light transmitted through the holes of the net in the mold to thereby heat and foam the precursor to obtain a metal foam, and controlling a shape of the metal foam by the mold.

2. The metal foam production method according to claim 1, wherein the mold is shaped to surround the precursor, and the metal foam is shaped by the mold.

3. The metal foam production method according to claim 1, wherein a plurality of dense metal materials are arranged around the precursor, and the precursor is foamed into the metal foam, so that the plurality of dense metal materials are joined by the metal foam.

4. The metal foam production method according to claim 1, wherein a plurality of additional metal foams are arranged around the precursor, and the precursor is foamed into the metal foam, so that the plurality of additional metal foams are joined by the metal foam.

5. The metal foam production method according to claim 1, wherein the precursor and a dense metal material are used, and the precursor is foamed into the metal foam, so that the dense metal material is joined to the metal foam.

6. The metal foam production method according to claim 1, wherein the precursor, a dense metal material and an additional metal foam are used, and the precursor is foamed into the metal foam, so that the dense metal material is joined to the additional metal foam by the metal foam.

7. The metal foam production method according to claim 1, wherein an irradiation range of light is selected by setting focus of a light source.

8. The metal foam production method according to claim 1, wherein an irradiation range of light is selected by providing a mask having an opening and shielding the light.

9. The metal foam production method according to claim 1, wherein the mold is a cylindrical mold.

10. The metal foam production method according to claim 1, wherein a plurality of the precursors each made of a different metal having a different melting point, two of the plurality of the precursors are arranged so that respective metal foams of the two precursors are joined to each other after foaming, and each precursor is irradiated with a light so as to be heated to thereby produce a functionally graded material whose properties spatially vary.

11. The metal foam production method according to claim 1, wherein the precursor includes a plurality of metals each having different melting points, a foaming agent is mixed with the plurality of metals in the precursor that is irradiated with a light so as to be heated, so that a functionally graded material whose properties spatially vary is produced.

12. A metal foam production method comprising steps of: using a mold that transmits light and a plurality of precursors made by mixing a plurality of metals with a foaming agent, the mold being made of a material with openings, and an aperture ratio of each part of the mold corresponding to each precursor of the plurality of precursors is selected so that the part corresponding to a precursor made from a metal having a lower melting point has a smaller aperture ratio; and irradiating the plurality of precursors with a light transmitted through the mold to thereby heat and foam the plurality of precursors to obtain a metal foam, and controlling a shape of the metal foam by the mold, wherein: the plurality of precursors are each made of a different metal having a different melting point, two of the plurality of the precursors are arranged so that respective metal foams of the two precursors are joined to each other after foaming, and each precursor, when being irradiated and heated with the light, produces a functionally graded material whose properties spatially vary, or the foaming agent is mixed with the plurality of metals in a first precursor of the plurality of precursors when the first precursor is irradiated with the light so as to be heated, so that a functionally graded material whose properties spatially vary is produced.

13. A metal foam production method comprising steps of: using a mold that transmits light and a precursor made by mixing a metal with a foaming agent; and irradiating the precursor with a light transmitted through the mold to thereby heat and foam the precursor to obtain a metal foam, and controlling a shape of the metal foam by the mold, wherein: the foaming agent is mixed with a plurality of metals in the precursor that is irradiated with a light so as to be heated, so that a functionally graded material whose properties spatially vary is produced, and the mold is made of a material with openings, and an aperture ratio of each part of the mold corresponding to each metal is selected so that the part corresponding to a metal having a lower melting point has smaller aperture ratio.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1A and 1B are schematic cross-sectional views showing a first embodiment of the present invention.

(2) FIGS. 2A and 2B are schematic cross-sectional views showing a second embodiment of the present invention.

(3) FIGS. 3A and 3B are schematic cross-sectional views showing a third embodiment of the present invention.

(4) FIGS. 4A and 4B are schematic cross-sectional views showing a fourth embodiment of the present invention.

(5) FIGS. 5A and 5B are schematic cross-sectional views showing a fifth embodiment of the present invention.

(6) FIGS. 6A and 6B are schematic cross-sectional views showing a sixth embodiment of the present invention.

(7) FIGS. 7A and 7B are schematic cross-sectional views showing a seventh embodiment of the present invention.

(8) FIGS. 8A and 8B are schematic cross-sectional views showing an eighth embodiment of the present invention.

(9) FIG. 9 is a graph showing the relationship between aperture ratio of a metal mesh and temperature-rising speed.

(10) FIG. 10 is a schematic cross-sectional view showing a ninth embodiment of the present invention.

(11) FIGS. 11A and 11B are schematic cross-sectional views showing a tenth embodiment of the present invention.

(12) FIGS. 12A to 12C are schematic cross-sectional views showing a modification 1 of the tenth embodiment of the present invention.

(13) FIGS. 13A to 13E are views for explaining each step of a method for producing the precursor according to an example.

(14) FIG. 14 is an X-ray CT image of a metal foam produced using a mold made of sapphire.

(15) FIG. 15 is an X-ray CT image of a metal foam produced using a metal mesh as a mold.

(16) FIG. 16 is a graph comparing the relationship between the elapsed time (foaming time) and the temperature by the presence or absence of a mold.

DESCRIPTION OF EMBODIMENTS

(17) Concrete embodiments of the present invention will be described below with reference to attached drawings.

(18) Note, it is to be understood that the present invention is not limited to the embodiments described above, and any configurations within the scope defined by the claims can be adopted.

First Embodiment

(19) A first embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 1A and 1B.

(20) In the present embodiment, a precursor is surrounded by a mold made of a transparent material, and a metal foam is shaped by the mold.

(21) As shown in FIG. 1A, a precursor 1 made by mixing a metal with a foaming agent is placed on a base (table) 10, and a transparent material 2 is arranged on the base 10 to surround the precursor 1. The transparent material 2 constitutes a mold that molds a metal foam. The base 10 is made of a material having heat-resisting properties, and this definition for base 10 is applied to all embodiments and modifications described below.

(22) Further, the precursor 1 is heated and foamed by being irradiated with a light L transmitted through the transparent material 2 from above.

(23) With such an arrangement, as shown in FIG. 1B, the metal foam 3 which is molded into the shape of the transparent material 2 is formed by filling the inside of the transparent material 2.

(24) In this manner, it is possible to produce the metal foam 3 molded into the shape of the mold made of the transparent material 2.

(25) In the present embodiment, the materials mentioned above can be respectively used for the metal and foaming agent of the precursor 1, and the transparent material 2.

Second Embodiment

(26) A second embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 2A and 2B.

(27) In the present embodiment, the precursor is surrounded by a mold made of a metal mesh, and a metal foam is shaped by the mold.

(28) As shown in FIG. 2A, the precursor 1 made by mixing a metal with a foaming agent is placed on a base 10, and a metal mesh 4 is arranged on the base 10 to surround the precursor 1. The metal mesh 4 constitutes a mold that molds a metal foam.

(29) Further, the precursor 1 is heated and foamed by being irradiated with a light L passing through the opening portions of the metal mesh 4 from above.

(30) With such an arrangement, as shown in FIG. 2B, a metal foam 3 is formed by filling the inside of the metal mesh 4 and molded into the shape of the metal mesh 4.

(31) In this manner, it is possible to produce the metal foam 3 molded into the shape of the mold made of the metal mesh 4.

(32) In the present embodiment, the materials mentioned above can be respectively used for the metal and foaming agent of the precursor 1, and the metal mesh 4.

(33) The thickness of the metal wires of the metal mesh 4 is selected so that the strength of the metal mesh 4 is ensured and the light L is sufficiently transmitted through the metal mesh 4. Further, the width of the opening portions of the metal mesh 4 and the interval between the metal wires are selected so that the metal foam 3 does not protrude from the metal mesh 4.

Third Embodiment

(34) A third embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 3A and 3B.

(35) In the present embodiment, a mold made of a transparent material is placed on a precursor, and the shape of a metal foam is controlled by the mold.

(36) As shown in FIG. 3A, a precursor 1 made by mixing a metal with a foaming agent is placed on a base 10, and a plate-like transparent material 2 is placed on the precursor 1. The transparent material 2 constitutes a mold that controls the shape of the metal foam.

(37) Further, the precursor 1 is heated and foamed by being irradiated with a light L transmitted through the transparent material 2 from above.

(38) With such an arrangement, as shown in FIG. 3B, a metal foam 3 whose upper surface is controlled to be flat by the transparent material 2 is formed.

(39) In this manner, it is possible to produce the metal foam 3 whose shape is controlled by the mold made of the transparent material 2.

(40) In the present embodiment, since no mold is provided in the horizontal direction of the precursor 1, the precursor 1 is freely foamed in the horizontal direction, so that the metal foam 3 spreads in the horizontal direction; however, since a mold is provided on the upper face of the precursor 1, the upper face of the metal foam 3 is controlled to be flat.

(41) In the present embodiment, the materials mentioned above can be respectively used for the metal and foaming agent of the precursor 1, and the transparent material 2.

(42) (Modification)

(43) With respect to the third embodiment, the transparent material 2 may be replaced with a plate-like metal mesh.

(44) In such a case, similarly to the second embodiment, the metal foam whose upper surface is controlled to be approximately flat by the plate-like metal mesh is formed by irradiating the precursor 1 with a light passing through the opening portions of the metal mesh.

(45) In FIG. 3A, the mold 2 is placed directly on the precursor 1. Alternatively, it is also possible to shape the metal foam by freely foaming the precursor first, and then, during foaming, perform press working with a mold that transmits light. With such a method, it is possible to produce a metal foam having a complicated shape by performing press working. Further, since press working is performed during foaming, the press working can be performed with a low load.

Fourth Embodiment

(46) A fourth embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 4A and 4B.

(47) The present embodiment is configured by applying the third embodiment. To be specific, in the present embodiment, a mold made of a transparent material is placed on a plurality of precursors, and the shape of metal foam is controlled by the mold so as to produce one metal foam in which the plurality of precursors are joined into one.

(48) As shown in FIG. 4A, three precursors 1 are arranged on the base 10 at a predetermined interval, and one plate-like transparent material 2 is placed on the three precursors 1. The plate-like transparent material 2 constitutes a mold that controls the shape of the metal foam.

(49) Further, the precursors 1 are each heated and foamed by being irradiated with a light L transmitted through the transparent material 2 from above.

(50) With such an arrangement, as shown in FIG. 4B, each precursor 1 is foamed to form a metal foam, and the metal foam such formed is joined and integrated with the adjacent metal foam. Further, the integrated metal foam is controlled by the transparent material 2 so that the upper surface thereof becomes flat.

(51) In this manner, it is possible to produce a larger metal foam 3 from three precursors 1.

(52) The interval between the precursors 1 adjacent to each other is selected in consideration of the degree of foaming so that the precursors 1 are joined to each other after foaming.

(53) In FIG. 4A, three precursors 1 are used; however, the number of precursors 1 is not limited.

(54) The arrangement of the plurality of precursors is not particularly limited. For example, the plurality of precursors can be arranged longitudinally and laterally, concentrically, or the like.

(55) The same integrated metal foam can also be produced even if the plurality of precursors are arranged adjacent to each other (with no interval).

(56) However, if the distance between the precursors is increased, foaming can be performed freely until the precursors join together, so that foaming can be performed quickly, and the outer peripheral portion and the inside of the metal foam can be more uniformly foamed.

(57) (Modification)

(58) With respect to the fourth embodiment, the transparent material 2 may be replaced with a plate-like metal mesh.

(59) In such a case, similarly to the second embodiment, the metal foam whose upper surface is controlled to be approximately flat by the plate-like metal mesh is formed by irradiating the plurality of precursors 1 with a light passing through the opening portions of the metal mesh.

(60) In FIG. 4A, the mold 2 is placed directly on each precursor 1. Alternatively, it is also possible to shape the metal foam by freely foaming the precursor first, and then, during foaming, perform press working with a mold that transmits light. With such a method, it is possible to produce a metal foam having a complicated shape by performing press working to obtain an integrated metal foam. Further, since press working is performed during foaming, the press working can be performed with lower load.

Fifth Embodiment

(61) A fifth embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 5A and 5B.

(62) In the present embodiment, a metal foam is formed between two dense metal materials by applying the aforesaid third embodiment.

(63) As shown in FIG. 5A, a precursor 1 and two dense metal materials 5 are arranged on the base 10 so that the precursor 1 is sandwiched between the two dense metal materials 5, and one plate-like transparent material 2 is placed on the dense metal materials 5 and precursor 1. The plate-like transparent material 2 constitutes a mold that controls the shape of the metal foam. Incidentally, the dense metal material 5 can be moved relative to the base 10 and the transparent material 2, instead of being fixed to the base 10 and the transparent material 2.

(64) Further, a mask 6 that shields light and that has an opening is provided above the transparent material 2. Irradiation range of the light L is regulated by the mask 6.

(65) Further, the precursor 1 is heated and foamed by being irradiated with the light L passing through the opening of the mask 6 and transmitted through the transparent material 2 from above.

(66) With such an arrangement, as shown in FIG. 5B, the precursor 1 is foamed to form a metal foam 3, and the metal foam 3 is joined to the adjacent dense metal materials 5. Further, the metal foam 3 is controlled by the transparent material 2 so that the upper surface thereof becomes flat. The dense metal materials 5 are moved outward by the foamed metal foam 3.

(67) In this manner, it is possible to form the metal foam 3 between the dense metal materials 5, so that the dense metal materials 5 and the metal foam 3 are joined to each other. Further, the dense metal materials 5 also function as lateral molds when the metal foam 3 is being formed from the precursor 1.

(68) The dense metal materials 5 may also be a metal (metal element or alloy) having a higher melting point than the metal constituting the precursor 1 and the metal foam 3.

(69) In FIGS. 5A and 5B, the size of the opening of the mask 6 is set in consideration of the size when the precursor 1 is foamed to become the metal foam 3, so that the size of the opening of the mask 6 is slightly larger than the size of the finally formed metal foam 3. Therefore, heating can be performed until foaming is completed. Further, since the dense metal materials 5 are irradiated with light only in the vicinity of the junction with the precursor 1, heat applied to the dense metal materials 5 can be suppressed. Further, the irradiation range of the light is selected by the mask 6 so that only the precursor 1 and its periphery are locally irradiated with light so as to be heated, and thereby effects of heat on the dense metal materials 5 can be suppressed. Therefore, the dense metal materials 5 can be joined without being damaged.

(70) Incidentally, the size of the opening of the mask 6 may also be set different ways. For example, the size of the opening of the mask 6 may also be set to be equal to the size of the metal foam 3 to be finally formed, or to be equal to the initial size of the precursor 1. The size of the opening of the mask 6 is suitably set in consideration of the foaming of the metal foam 3 and the effects of the heat applied to the dense metal materials 5.

(71) In the present embodiment, the mask 6 is provided above the transparent material 2. However, the irradiation range of the light L may also be regulated by other configurations, such as a configuration in which the mask 6 is placed on and in contact with the transparent material 2, a configuration in which a reflection film or an absorption film is formed on the upper surface of the transparent material 2 to shield the light L, a configuration in which the irradiation range of the light L is regulated from the light source side by, for example, setting the focus of the light source, or the like.

(72) Incidentally, the irradiation range of the light L may also be regulated by a configuration in which the mold is configured by two portions: one is a portion made of the transparent material 2, and the other is a portion made of a material that does not transmits light. However, in the case where the mold is configured by two portions, it is likely that the joint between the two portions tends to be weak, and the cost of the mold increases. Therefore, it is preferred that the irradiation range of the light is regulated by a configuration different from the mold.

(73) It is possible to irradiate the precursor 1 with a light to thereby heat the precursor 1 to produce the metal foam 3, and join the dense metal materials 5 and the metal foam 3, even in a state where the dense metal materials 5 and the precursor 1 are arranged apart from each other. However, in such a case, if the distance between the dense metal materials 5 and the precursor 1 is not set within an appropriate range, the foamed metal foam 3 and the dense metal materials 5 will not be brought into close contact with each other at the interface, and therefore there is a possibility that sufficient joining strength may not be obtained.

(74) (Modification 1)

(75) With respect to the fifth embodiment, the transparent material 2 may be replaced with a plate-like metal mesh.

(76) In such a case, as a configuration for regulating the irradiation range of the light (such as setting focus of a light source, providing a mask above the metal mesh, or the like), the precursor 1 is irradiated with a light passing through the opening portions of the metal mesh.

(77) With such an arrangement, a metal foam whose upper surface is controlled by the plate-like metal mesh so as to become substantially flat is formed, and the dense metal materials and the metal foam are joined to each other.

(78) (Modification 2)

(79) With respect to the fifth embodiment, the present invention also includes a configuration in which a precursor and a dense metal material are used, and the dense metal material is arranged only on one side of the precursor, so that a metal foam obtained by foaming the precursor is joined with the dense metal material.

(80) In such a case, as a configuration for regulating the irradiation range of the light (such as setting focus of a light source, providing a mask above the plate-like mold, or the like), the precursor 1 is irradiated with a light passing through the mold.

(81) Thus, a metal foam whose upper surface is controlled by the plate-like mold so as to become substantially flat is formed, and the dense metal material and the metal foam are joined to each other. Further, the irradiation range of the light is selected by a mask or the like so that only the precursor and its surrounding area are irradiated with light locally so as to be heated, and thereby it is possible to reduce the effects of heat on the dense metal material, so that the dense metal material can be joined without being damaged.

Sixth Embodiment

(82) A sixth embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 6A and 6B.

(83) The present embodiment is a configuration in which a metal foam is formed between two other metal foams by applying the third embodiment and the fifth embodiment described above.

(84) As shown in FIG. 6A, a precursor 1 and two other metal foams 7 are arranged on the base 10 so that the precursor 1 is sandwiched between the two other metal foams 7, and one plate-like transparent material 2 is placed on the other metal foams 7 and precursor 1. The plate-like transparent material 2 constitutes a mold that controls the shape of the metal foam. Incidentally, the other metal foams 7 can be moved relative to the base 10 and the transparent material 2, instead of being fixed to the base 10 and the transparent material 2.

(85) Further, a mask 6 that shields light and that has an opening is provided above the transparent material 2. Irradiation range of the light L is regulated by the mask 6.

(86) Further, the precursor 1 is heated and foamed by being irradiated with a light L passing through the opening of the mask 6 and transmitted through the transparent material 2 from above.

(87) With such an arrangement, as shown in FIG. 6B, the precursor 1 is foamed to form a metal foam 3, and the metal foam 3 is joined to the adjacent other metal foams 7. Further, the shape of the upper surface of the metal foam 3 is controlled to be flat by the transparent material 2. The other metal foams 7 are moved outward by the foamed metal foam 3.

(88) In this manner, it is possible to form the metal foam 3 between the other metal foams 7, so that the other metal foams 7 and the metal foam 3 are joined to each other. Further, the other metal foams 7 also function as a lateral mold when the metal foam 3 is being formed from the precursor 1.

(89) As shown in FIGS. 6A and 6B, the irradiation range of the light is selected by the mask 6 so that only the precursor 1 and its periphery are locally irradiated with light so as to be heated, and thereby effects of heat on the other metal foams 7 can be suppressed. Therefore, the other metal foams 7 ca be joined without being damaged.

(90) The other metal foams 7 may also be a metal (metal element or alloy) having a higher melting point than the metal constituting the precursor 1 and the metal foam 3.

(91) (Modification 1)

(92) With respect to the sixth embodiment, the transparent material 2 may be replaced with a plate-like metal mesh.

(93) In such a case, as a configuration for regulating the irradiation range of the light (such as setting focus of a light source, providing a mask above the metal mesh, or the like), the precursor 1 is irradiated with a light passing through the opening portions of the metal mesh.

(94) With such an arrangement, a metal foam whose upper surface is controlled by the plate-like metal mesh so as to become substantially flat is formed, and the other metal foams and the metal foam are joined to each other.

(95) (Modification 2)

(96) With respect to the sixth embodiment, it is possible to, by combining the configuration of the fifth embodiment with the sixth embodiment described above, use a precursor, a dense metal material and other metal foam and foam the precursor into a metal foam, so that the dense metal material and the other metal foam are joined by the metal foam. In such a case, the precursor is arranged between the dense metal material and the other metal foam, and a plate-like mold is placed above the precursor, the dense metal material and the other metal foam. The precursor is irradiated with a light transmitted through the mold so as to be heated and foamed.

(97) With such an arrangement, the precursor is foamed to form a metal foam, and the metal foam is joined to the adjacent dense metal materials and the adjacent other metal foam respectively. Further, the metal foam is controlled by the mold so that the upper surface thereof becomes flat.

(98) In this manner, it is possible to form a metal foam between a dense metal material and other metal foam, so that the dense metal material and the other metal foam are joined to each other by the metal foam.

(99) At this time, the irradiation range of the light is selected by a mask or the like so that only the precursor and its periphery are locally irradiated with light so as to be heated, and thereby the effects of heat on the dense metal material and the other metal foam can be suppressed. Therefore, the dense metal material and the other metal foam can be joined without being damaged.

Seventh Embodiment

(100) A seventh embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 7A and 7B.

(101) In the present embodiment, two metal foams obtained from different metal are joined to form a metal foam joined body.

(102) As shown in FIG. 7A, On the base 10, two precursors 1A and 1B made of different metals are arranged on the base 10 so that the two precursors 1A and 1B are in contact with each other. Further, a metal mesh 4 is provided so as to surround the precursors 1A and 1B from above and lateral. The metal mesh 4 constitutes a mold that controls the shape of the metal foam.

(103) Further, the precursors 1A and 1B is heated and foamed by being irradiated respectively with a light L1 and a light L2 passing through the opening portions of the metal mesh 4 from above.

(104) With such an arrangement, as shown in FIG. 7B, the precursors 1A and 1B are foamed to form two metal foams 3A and 3B each constituted by different metals, and the two metal foams 3A and 3B are joined to each other. Further, the shapes of the metal foams 3A and 3B are controlled by the metal mesh 4.

(105) In this manner, it is possible to form a metal foam joined body in which the metal foams 3A and 3B constituted by different metals are joined to each other.

(106) Note that, in FIG. 7A, the light L1 and the light L2 may be lights having the same wavelength and/or intensity, or may be lights having different wavelengths and/or intensity.

(107) It is preferred that the intensities of the two lights L1 and L2 are set different according to the melting points of the metals respectively constituting the precursors 1A and 1B.

(108) Here, for example, it is assumed that the metal constituting the precursor 1A arranged on the left side has a lower melting point than the metal constituting the precursor 1B arranged on the right side.

(109) In such a case, it is preferred that the intensity of the light L2 applied to the precursor 1B arranged on the right is set stronger than the light L1 applied to the precursor 1A arranged on the left.

(110) It is further preferred that the intensities of the lights L1 and L2 are selected in accordance with the melting points of the metals constituting the precursors 1A and 1B. Thus, the time required for foaming each of the precursors 1A and 1B becomes the same level, so that the precursors 1A and 1B can be uniformly foamed.

(111) On the other hand, if the two lights L1 and L2 have the same wavelength and intensity, the precursor 1A on the left side with a low melting point will start foaming first, and the precursor 1B on the right side with a high melting point will start foaming later.

(112) According to the present embodiment, it is possible to produce a metal foam joined body (functionally graded material) whose properties spatially vary. Examples of the properties which spatially vary include mechanical characteristics (particularly, crash energy absorption characteristics), noise absorption characteristics, and the like.

(113) (Modification 1)

(114) With respect to the seventh embodiment, the metal mesh 4 can be replaced with a transparent material formed so as to surround the top and sides of the precursors 1A and 1B.

(115) In such a case, the metal foam joined body in which the metal foams 3A and 3B are joined to each other is formed by irradiating the precursors 1A and 1B with a light transmitted through the transparent material.

(116) (Modification 2)

(117) In the seventh embodiment, two precursors 1A and 1B made using different metals are arranged so as to be in contact with each other.

(118) Alternatively, the two precursors 1A and 1B may be arranged slightly apart so that the foamed metals 3A and 3B are joined to each other after their foaming.

Eighth Embodiment

(119) An eighth embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 8A and 8B.

(120) In the present embodiment, two metal foams obtained from different metal are joined to form a metal foam joined body by a method different from the seventh embodiment.

(121) As shown in FIG. 8A, two precursors 1A and 1B made using different metals are arranged on the base 10 so that the two precursors 1A and 1B are in contact with each other. Further, a metal mesh 4A is provided so as to surround top and side of the left precursor 1A, and a metal mesh 4B is provided so as to surround the top and side of the right precursor 1B. The metal mesh 4A and the metal mesh 4B are joined to form an integrated metal mesh which constitutes a mold that controls the shape of the metal foam.

(122) Here, it is assumed that the metal constituting the precursor 1A arranged on the left side has a lower melting point than the metal constituting the precursor 1B arranged on the right side. Further, it is assumed that the metal mesh 4A on the left has a small aperture ratio and the metal mesh 4B on the right has a large aperture ratio. In other words, the aperture ratios of the metal meshes 4A and 4B corresponding to the precursors 1A and 1B are selected so that the metal mesh 4A corresponding to the precursor 1A constituted by the metal with lower melting point has smaller aperture ratio.

(123) Further, the precursors 1A and 1B is heated and foamed by being irradiated with a light L passing through the opening portions of the metal meshes 4A and 4B from above.

(124) With such an arrangement, as shown in FIG. 8B, the precursors 1A and 1B are foamed to form two metal foams 3A and 3B each constituted by different metals, and the two metal foams 3A and 3B are joined to each other. Further, the shapes of the metal foams 3A and 3B are respectively controlled by the metal meshes 4A and 4B.

(125) In this manner, it is possible to form a metal foam joined body in which the metal foams 3A and 3B constituted by different metals are joined to each other.

(126) In the present embodiment, it is preferred that the aperture ratio of each of the metal meshes 4A and 4B is selected to be a specific value in accordance with the melting points of the metals constituting the precursors 1A and 1B. Thus, the time required for foaming each of the precursors 1A and 1B becomes the same level, so that the precursors 1A and 1B can be uniformly foamed.

(127) Here, a plurality of metal meshes each having different aperture ratios were prepared, the precursors were respectively irradiated with a plurality of lights of the same intensity passing through the openings of the respective metal meshes, and the temperature-rising speeds of the precursors were measured. Further, as a comparison object, the temperature-rising speeds of the precursors were also measured in the case where the precursor was directly irradiated with the plurality of lights of the same intensity without using metal mesh.

(128) As a measurement result, FIG. 9 shows a relationship between the aperture ratio of the metal mesh and the temperature-rising speed (dT/dt).

(129) As can be known from FIG. 9, the lower the aperture ratio, the slower the temperature-rising speed; and there is a linear relationship between the aperture ratio and the temperature-rising speed. Therefore, the time required for foaming can be controlled by selecting the aperture ratio of the metal mesh.

(130) According to the present embodiment, it is possible to produce a metal foam joined body (functionally graded material) whose properties spatially vary. Examples of the properties which spatially vary include mechanical characteristics (particularly, crash energy absorption characteristics), noise absorption characteristics, and the like.

(131) (Modification 1)

(132) With respect to the eighth embodiment, the two metal meshes 4A and 4B may be replaced with two transparent materials formed to respectively surround the top and side of precursors 1A and 1B.

(133) In such a case, the mold is configured so that the transmittances of the two transparent materials are different from each other; to be specific, the transmittance of the transparent material on the left precursor 1A having a low melting point is smaller than the transmittance of the transparent material on the right precursor 1B having a high melting point.

(134) Further, the metal foam joined body in which the metal foams 3A and 3B are joined to each other is formed by irradiating the precursors 1A and 1B with a light transmitted through the transparent material.

(135) Further, it is also possible to replace the metal meshes 4A, 4B with a material with openings other than a metal mesh (such as a ceramic honeycomb), and the aperture ratio of each part thereof is selected.

(136) (Modification 2)

(137) In the eighth embodiment, two precursors 1A and 1B made using different metals are arranged so as to be in contact with each other.

(138) Alternatively, the two precursors 1A and 1B may also be arranged slightly apart from each other so that the foamed metals 3A and 3B formed are joined to each other after their foaming.

Ninth Embodiment

(139) A ninth embodiment of the present invention is shown in a schematic cross-sectional view of FIG. 10.

(140) In the present embodiment, a mold and a precursor are arranged inside a sealed container (chamber) having a transparent window. The precursor is heated and foamed into a metal foam by being irradiated with a light transmitted through the window and the mold.

(141) As shown in FIG. 10, the upper portion of a chamber 20 (which is a sealed container) is provided with a transparent window 8. A mold made of a transparent material 2 and a precursor 1 are arranged inside the chamber 20. The precursor 1 and the transparent material 2 each have the same configurations as those shown in FIG. 1A.

(142) The transparent materials listed as the material for the mold, such as glass, sapphire, quartz glass, crystal or the like, can be used as the material of the transparent window 8.

(143) Since the window 8 does not come into contact with the foamed metal, the transparent material for the window 8 is not required to have heat resistance as compared with the transparent material for the mold. Therefore, a wider range of transparent materials than those for the mold can be used as the transparent material for the window 8.

(144) Although not shown in the drawings, a light source for irradiating the precursor 1 with light is arranged outside the chamber 20.

(145) Further, although not shown in the drawings, a vacuum pump, a gas supply unit (gas cylinder), and/or the like are/is connected to the chamber 20; therefore, the inside of the chamber 20 can be evacuated to vacuum or set to a gas atmosphere.

(146) For example, when the inside of the chamber 20 is evacuated to vacuum or set to an inert gas atmosphere, the foam metal can be prevented from being oxidized.

(147) Further, as shown in FIG. 10, the precursor 1 is heated and foamed by being irradiated with a light L passing through the transparent window 8 and transmitted through the transparent material 2 from above the chamber 20.

(148) With such an arrangement, the precursor 1 is foamed into a metal foam.

(149) In this manner, it is possible to produce a metal foam.

(150) In the present embodiment, since the precursor 1 is foamed into a metal foam within the chamber 20, the inside of the chamber 20 can be evacuated to vacuum or set a predetermined atmosphere. Further, as described above, when the inside of the chamber 20 is evacuated to vacuum or set to an inert gas atmosphere, the foam metal can be prevented from being oxidized.

(151) Further, since the chamber 20 is provided with the transparent window 8, it is possible to irradiate the precursor 1 with the light L from the light source arranged outside the chamber 20 through the transparent window 8.

(152) Further, since the light source is arranged outside the chamber 20, the light source is not affected by the atmosphere inside the chamber 20. Thus, the configuration for heating the precursor 1 can be simplified, compared with a case where a light source is arranged inside the chamber 20 and a case where a heating source is arranged inside the chamber 20.

(153) (Modification)

(154) In comparison with the ninth embodiment, the transparent material 2 may be replaced with a metal mesh.

(155) In such a case, similarly to the second embodiment, the metal foam shaped by the metal mesh is formed by irradiating the precursor 1 with a light passing through the opening portions of the metal mesh.

(156) Further, with respect to the ninth embodiment, the transparent material 2 surrounding the precursor 1 may be replaced with a plate-like transparent material or a plate-like metal mesh.

Tenth Embodiment

(157) A tenth embodiment of the present invention is shown in schematic cross-sectional views of FIGS. 11A and 11B.

(158) In the present embodiment, initially the precursor is heated and caused to foam by being directly irradiated with a light without using a mold, and then, during foaming, the precursor is pressed with a metal mesh so as to be shaped.

(159) One precursor is irradiated with a light L so as to be foamed to form a metal-being-foamed 31 (including metal in soft state immediately after foaming), as shown in FIG. 11A.

(160) Next, as shown in FIG. 11B, the metal-being-foamed 31 is pressed from above using a metal mesh 32 supported by a support 33. Thus, the metal-being-foamed 31 is pressed by the metal mesh 32 into a shape so that the height of metal-being-foamed 31 corresponds to the height of the upper surface of the metal mesh 32.

(161) Thereafter, the metal-being-foamed 31 is irradiated with the light L passing through the opening portions of the metal mesh 32 so as to continue to foam. In this manner, it is possible to produce a metal foam whose shape is controlled to match the inner shape of the metal mesh 32.

(162) According to the present embodiment, the precursor is pressed by the metal mesh 32. Therefore, if the height of the metal mesh 32 is set to be lower than the height of the precursor before foaming, it is possible to produce a metal foam having a height lower than the height of the precursor before foaming.

(163) Further, since the press working is performed during foaming, the press working can be performed with lower load.

(164) Further, since the precursor is pressed by the metal mesh 32, it is possible to produce a metal foam having a complicated shape if the metal mesh 32 is formed to a complicated shape.

(165) (Modification 1)

(166) In the aforesaid tenth embodiment, the metal foam is foamed from one precursor; however, it is also possible to foam a plurality of precursors arranged apart from each other, and perform press working during foaming to give them a shape, so that a plurality of metal foams respectively foamed from the plurality of precursors are joined to each other.

(167) Such case is shown in the schematic cross-sectional views of FIGS. 12A to 12C as a modification 1 of the tenth embodiment of the present invention.

(168) First, as shown in FIG. 12A, two precursors 34, 35 are arranged apart from each other, and the two precursors 34, 35 are irradiated with a light L.

(169) Then, as shown in FIG. 12B, the precursors 34, 35 are respectively foamed to form two metals-being-foamed (including metal in soft state immediately after foaming) 36, 37.

(170) Next, as shown in FIG. 12C, the metals-being-foamed 36, 37 are pressed from above using a metal mesh 32 supported by a support 33. Thus, the metals-being-foamed 36, 37 are pressed by the metal mesh 32 into a shape so that the height of metals-being-foamed 36, 37 corresponds to the height of the upper surface of the metal mesh 32, and the metals-being-foamed 36, 37 are joined to each other.

(171) Thereafter, the metals-being-foamed 36, 37 are irradiated with the light L passing through the opening portions of the metal mesh 32 so as to continue to foam. In this manner, it is possible to produce a metal foam whose shape is controlled to match the inner shape of the metal mesh 32.

(172) (Modification 2)

(173) In the tenth embodiment and the modification 1 thereof, the metals-being-foamed 31, 36, 37 are pressed by the metal mesh 32.

(174) In comparison with the tenth embodiment and the modification 1 thereof, the metal-being-foamed may also be pressed by a transparent material, instead of the metal mesh 32, and then the metal-being-foamed is irradiated with a light transmitted through the transparent material, to thereby form a metal foam.

(175) [Example]

(176) Actually, a metal foam was produced by irradiating light using a mold.

(177) (Preparation of Precursor)

(178) First, as shown in FIG. 13A, a foaming agent and thickening agent 12 were sandwiched between two plates 11 made of ADC12 (Al—Si—Cu-based aluminum alloy). Titanium hydride (TiH.sub.2) was used as the foaming agent, and alumina was used as the thickening agent.

(179) Next, as shown in FIG. 13B, a friction-stirring tool 13 having a probe 14 provided at its tip was used. The friction-stirring tool 13 was rotated at a high speed, pushed into the plates 11, and scanned on the plates 11. The rotation speed was 1000 rpm, and the scanning speed was 100 mm/min.

(180) The friction-stirring tool 13 was scanned four times in the row direction as shown in FIG. 13C, and then scanned four times in the row direction at the same location from the opposite side as shown in FIG. 13D; further, such reciprocating movement of the friction-stirring tool 13 was performed once more.

(181) In such manner, the foaming agent and thickening agent 12 were mixed and dispersed in the plates 11.

(182) Thereafter, as shown in FIG. 13E, the plate 11 was cut into a size of 15 mm×15 mm×6 mm to obtain a precursor 15.

(183) The precursor 15 thus prepared was used to produce a metal foam.

(184) (Production of Metal Foam)

(185) A plate-like mold made of sapphire was used. Instead of placing the mold directly on the precursor as shown in FIG. 3A, the mold was placed above the precursor 15 using a platform, so that, when the precursor was foamed, the metal foam would be brought into contact with the mold.

(186) Further, the precursor 15 is heated and foamed by being irradiated with a light transmitted through the mold, so that the precursor 15 is foamed into a metal foam.

(187) Light irradiation is performed using four halogen lamps, and the total output of the four halogen lamps is 2 kW.

(188) The produced metal foam was observed by X-ray CT. An X-ray CT image of the produced metal foam is shown in FIG. 14. As shown in FIG. 14, a metal foam 22 having pores 21 therein is formed.

(189) (In a Case where a Metal Mesh was Used as Mold)

(190) A metal foam is produced by performing light irradiation under the same condition except that a metal mesh made of steel is used as the mold. Three metal meshes were used. The thickness of the metal wire of the three metal meshes was about 0.5 mm, and the interval between metal wires of the three metal meshes were 0.67 mm, 1 mm, and 2 mm respectively.

(191) The metal foam produced using the metal mesh as the mold was observed by X-ray CT. An X-ray CT image of the produced metal foam is shown in FIG. 15. As shown in FIG. 15, a metal foam 22 having pores 21 therein is formed.

(192) In the cases where the interval between metal wires was 0.67 mm and 1 mm, the surface of the metal foam was substantially flat. In the case where the interval between metal wires was 2 mm, the portions of the metal foam corresponding to the openings of the metal mesh swelled slightly outward, and slight unevenness was observed on the surface of the metal foam.

(193) (Effects of Presence or Absence of Mold on Temperature Behavior)

(194) The difference in temperature behavior between the following two cases was examined: one is a case where the precursor 15 was irradiated with a light transmitted through a plate-like mold made of sapphire, and the other is a case where the precursor 15 was directly irradiated with a light without using a mold.

(195) In each of above two cases, the precursor 15 is heated by being irradiated with a light in a state where the precursor 15 is in contact with a thermocouple; the light irradiation was stopped when the measurement temperature reached about 650° C., and then the precursor 15 was naturally cooled.

(196) The relationship between elapsed time (foaming time) and temperature is compared between the above two cases, and the results are shown in FIG. 16, in which the case where mold is used is indicated by a solid line, and the case where mold is not used is indicated by a broken line.

(197) It is known from FIG. 16 that, between 0 to 200 seconds, the temperature behavior is the same regardless of whether or not the mold is used; and therefore, even if the mold made of sapphire is arranged between the light source and the precursor, there is almost no energy loss. The reason why the temperature behavior changes after 200 seconds have passed is that the foamed precursor comes into contact with sapphire, and thereby the heat of the precursor is taken away by sapphire, so that more heat energy is required. Thus, it is considered that, between 0 and 200 seconds, the sapphire is hardly warmed by light irradiation, and almost all of the light energy was given to the precursor.

(198) Thus, when a mold made of sapphire that transmits light is used, loss of thermal energy caused by the mold can be suppressed, and therefore energy is saved.

REFERENCE SIGNS LIST

(199) 1, 1A, 1B Precursor, 2 Transparent material 3, 3A, 3B Metal foam 4, 4A, 4B, 32 Metal mesh 5 Dense metal material 6 Mask 7 Other metal foam 8 Window 10 Base 11 Plate 12 Foaming agent and thickening agent 13 Friction-stirring tool 14 Probe 15 Precursor 20 Chamber 21 Pores 22 Metal foam 31, 36, 37 Metal-being-foamed 33 Support L, L1, L2 Light