WO2016028229A1

WO2016028229A1 - Metal article forming apparatus and methods for forming metal article

Info

Publication number: WO2016028229A1
Application number: PCT/SG2015/050266
Authority: WO
Inventors: Beng Wah Chua; Meng Kwong Ho
Original assignee: Agency for Science Technology and Research Singapore
Current assignee: Agency for Science Technology and Research Singapore
Priority date: 2014-08-20
Filing date: 2015-08-19
Publication date: 2016-02-25
Anticipated expiration: 2017-02-20
Also published as: CN107405682A

Abstract

According to various embodiments, there is provided a metal article forming apparatus, the apparatus may include: a die having a reservoir cavity recessed into a first part of a surface of the die, and a forming cavity recessed into a second part of the surface of the die adjacent to the first part; and a punch having a protrusion on a surface of the punch facing the surface of the die, wherein the punch is adapted to move relative toward the die to move the surface of the punch relative toward the surface of the die to insert the protrusion of the punch into the reservoir cavity of the die.

Description

METAL ARTICLE FORMING APPARATUS AND METHODS FOR

FORMING METAL ARTICLE

Cross-reference to Related Applications

[0001] The present application claims the benefit of the Singapore patent application No. 10201405077W filed on 20 August 2014, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

[0002] Embodiments relate generally to metal article forming apparatus and methods for forming metal article.

Background

[0003] Wrought alloy parts have been widely used in the commercial applications due to their light weight and excellent mechanical properties. Conventional manufacturing techniques such as forging, stamping, extrusion are employed to produce these metal parts with limited features. For metal parts with complex/intricate features, thin walls, and/or varying thicknesses, multiple steps are usually incorporated in these forging, stamping and extrusion operations. During the operation, intermediate stages of annealing for the parts are required to improve the deformability of the material further. The increase in the number of steps and intermediate stages of annealing translate to a higher production cost for producing these metal parts.

[0004] Alternatively, to avoid the intermediate stages of annealing, forging and stamping may be conducted in warm or elevated temperature to reduce the overall steps and to enhance the formability of the material to achieve the complex features and varying thicknesses. However, there are two major concerns in warm or elevated temperature forming process such as difficulty in maintaining a consistent heating of the material at the desired temperature and the use of suitable lubricant for the necessary lubrication during high temperature forming operation. Improper lubrication during the warm or elevated temperature forming could cause instability of the material plasticity flow and sticking of the material to the die leading to more process stoppages and cleaning operations resulting in higher scrap rate and process cost.

[0005] Recently, semi solid processing of wrought alloy materials, such as thixocasting, thixoforming and rheocasting, has been gaining widespread attention to overcome the limited material formability in the conventional metal forming processes for forming of complex shape features. However, thixocasting or thixoforming processes which are based upon reheating of the semi solid billet feedstock are not attractive as it is not cost effective due to the need of a good preheating station to achieve uniform reheating of the billets. Furthermore, the scrap cannot be recycled through reheating as the semi solid structures are no longer the same as before.

[0006] In rheocasting, fully molten metal is cooled and stirred or agitated until the desired solid fraction/temperature is achieved. In other words, semi-solid is obtained from molten metal. Thus, the scrap can be recycled as it can be returned to the furnace for remelting. The rheocasting technique of wrought alloy is currently developed for the die casting process to produce parts. However, the hot tear defect of the wrought alloys remains a technical challenge in the casting process of using two halves close mould for producing thin parts with multi wall thicknesses. A larger gating is also necessary during the die filling to prevent pre- solidification due to the higher viscosities of the semi solid process. As such, larger and thicker parts can only be produced using this process.

[0007] Liquid forging is an open mould concept and utilizes high direct pressurized solidification during the process. The process for forming high aspect ratio feature parts has been researched on. In essence, the process in which the pre- quantified wrought alloy melt is poured directly into the bottom die cavity and the top punch with the high aspect ratio feature cavity is moved vertically downwards to squeeze upon together with the bottom die cavity. A high direct pressure is applied throughout the solidification process which can overcome hot tear defect in the part and to achieve high aspect ratio features for wrought alloy. The process has also been demonstrated to achieve light weight and higher thermal performance wrought Aluminium (Al) alloy heat sinks for the thermal management applications.

[0008] However, the current liquid forging process of pouring the molten melt directly into the bottom die/part cavity is not suitable to be used to form wrought alloy thin part with varying thicknesses. Due to the fast rate of cooling of the molten metal in the bottom die cavity for large surface area to volume ratio, a pre- solidified layer is formed immediately upon the molten melt contacting the die cavity causing difficulty in achieving desired thin thickness and complete melt filling in the bottom cavity.

[0009] Therefore, there is a need to address some of the issues discussed above in relation to the existing methods and apparatus for forming metal articles.

Summary

[0010] According to various embodiments, there is provided a metal article forming apparatus, the apparatus may include: a die having a reservoir cavity recessed into a first part of a surface of the die, and a forming cavity recessed into a second part of the surface of the die adjacent to the first part; and a punch having a protrusion on a surface of the punch facing the surface of the die, wherein the punch is adapted to move relative toward the die to move the surface of the punch relative toward the surface of the die to insert the protrusion of the punch into the reservoir cavity of the die.

[0011] According to various embodiments, there is provided a method of forming metal article, the method may include: introducing molten metal into a reservoir cavity recessed into a first part of a surface of a die; and moving a punch relative toward the die to move a surface of the punch relative toward the surface of the die to insert a protrusion on the surface of the punch into the reservoir cavity to displace molten metal received in the reservoir cavity to flow into a forming cavity recessed into a second part of the surface of the die adjacent to the first part.

Brief description of the drawings

[0012] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings, in which:

FIG. 1 shows a metal article forming apparatus according to various embodiments;

FIG. 2 shows a metal article forming apparatus according to various embodiments; FIG. 3 shows a flow diagram illustrating a method of forming metal article according to various embodiments;

FIG. 4 shows a metal article forming apparatus according to an example embodiment;

FIGs. 5A to 5D show schematic diagrams illustrating a method for forming metal according to various embodiments;

FIG. 6A shows an example of the formed metal piece produced from the method of FIGs. 5 A to 5D; and

FIG. 6B shows an example of the desired formed metal article obtained from the formed metal piece of FIG 6A.

Detailed description

[0013] Embodiments described below in context of the apparatus are analogously valid for the respective methods, and vice versa. Furthermore, it will be understood that the embodiments described below may be combined, for example, a part of one embodiment may be combined with a part of another embodiment.

[0014] It should be understood that the terms "on", "over", "top", "bottom",

"down", "side", "back", "left", "right", "front", "lateral", "side", "up", "down" etc., when used in the following description are used for convenience and to aid understanding of relative positions or directions, and not intended to limit the orientation of any device, or structure or any part of any device or structure.

[0015] According to various embodiments, a metal article forming apparatus and a method for forming metal article may be provided.

[0016] FIG. 1 shows a metal article forming apparatus 100 according to various embodiments. The metal article forming apparatus 100 may include a die 120 having a reservoir cavity 122 recessed into a first part of a surface of the die 120, and a forming cavity 124 recessed into a second part of the surface of the die 120 adjacent to the first part. The metal article forming apparatus 100 may further include a punch 110 having a protrusion 112 on a surface of the punch 110 facing the surface of the die 120. The punch 110 may be adapted to move relative toward the die 120 to move the surface of the punch 110 relative toward the surface of the die 120 to insert the protrusion 122 of the punch 110 into the reservoir cavity 122 of the die 120.

[0017] According to various embodiments, the reservoir cavity 122 may be adapted to contain molten metal.

[0018] According to various embodiments, the forming cavity 124 may be adapted to shape the molten metal.

[0019] According to various embodiments, the protrusion 112 may be adapted to displace the molten metal received in the reservoir cavity 122 to flow into the forming cavity 124.

[0020] In other words, when in use, molten metal may be introduced into the reservoir cavity 122 of the die 120 such that a pool of molten metal may be contained in the reservoir cavity 122. The punch 110 may then be moved toward the die 120 such that the surface of the punch 110 having the protrusion 112 may move relative toward the surface of the die 120 having the reservoir cavity 122 to insert the protrusion 112 into the reservoir cavity 122. As a result, the molten metal may be displaced by the protrusion 112 such that molten metal received in the reservoir cavity 122 may flow into the flowing cavity 124.

[0021] FIG. 2 shows a metal article forming apparatus 200 according to various embodiments. The metal article forming apparatus 200 may include a die 220 having a reservoir cavity 222 recessed into a first part of a surface of the die 220, and a forming cavity 224 recessed into a second part of the surface of the die 220 adjacent to the first part. The metal article forming apparatus 200 may further include a punch 210 having a protrusion 212 on a surface of the punch 210 facing the surface of the die 220. The punch 210 may be adapted to move relative toward the die 220 to move the surface of the punch 210 relative toward the surface of the die 220 to insert the protrusion 222 of the punch 210 into the reservoir cavity 222 of the die 220.

[0022] According to various embodiments, the die 220 may further include an overflow cavity 226 recessed into a third part of the surface of the die adjacent to the second part.

[0023] According to various embodiments, the overflow cavity 226 may be adapted to collect excess molten metal that overflows from the forming cavity 224. In other words, when there is excess molten metal filling the forming cavity 224, the excess molten metal may overflow into the overflow cavity 226 such that the excess molten may be received in the overflow cavity 226.

[0024] According to various embodiments, the punch 210 may further include a forming insert 214 adapted to pair with the forming cavity 224 of the die 220 to form a mould with a predetermined shape. In other words, when the surface of the punch 210 having the forming insert 214 is in contact with the surface of the die 220 having the forming cavity 224, the forming insert 214 and the forming cavity 224 may form a mould enclosing a space. The mould may have a predetermined shape such that when molten metal fills up the space in the mould, a metal article with a desired shape may be formed as the molten metal solidifies in the mould.

[0025] According to various embodiments, the punch 210 may further include an overflow insert 216. [0026] According to various embodiments, the punch 210 may further include an air vent 218 adapted to allow air to escape. In other words, as molten metal fills up the forming cavity 224 of the die 220, air in the forming cavity 224 may escape via the air vent 218.

[0027] According to various embodiments, the punch 210 may be adapted to pressurize the molten metal in the forming cavity 224 of the die 220. In other words, during solidification of the molten metal in the forming cavity 224, the punch 210 may apply a pressure on the molten metal such that the molten metal solidifies under a pressurized environment.

[0028] According to various embodiments, the die 220 may further include an ejector 228 adapted to eject the formed metal article together with a reservoir biscuit and a solidified overflow. In other words, the metal article formed after the molten metal solidifies may be removed from the die 220 by ejecting the formed metal article via the ejector 228.

[0029] FIG. 3 shows a flow diagram 300 illustrating a method of forming metal article according to various embodiments. In 302, molten metal may be introduced into a reservoir cavity recessed into a first part of a surface of a die. In 304, a punch may be moved relative toward the die to move a surface of the punch relative toward the surface of the die to insert a protrusion on the surface of the punch into the reservoir cavity to displaced molten metal received in the reservoir cavity to flow into the forming cavity recessed into the second part of the surface of the die adjacent to the first part.

[0030] According to various embodiments, the method may further include applying a pressure via the punch to pressurize the molten metal in the forming cavity during solidification. [0031] According to various embodiments, the method may further include removing the formed metal article from the die.

[0032] According to various embodiments, the removing of the formed metal article from the die may include ejecting the formed metal article from the die with an ejector.

[0033] According to various embodiments, the method may further include parting a reservoir biscuit and a solidified overflow material from the formed metal article.

[0034] According to various embodiments, the parting of the reservoir biscuit and the solidified overflow material may include machining away the reservoir biscuit and the solidified overflow material from the formed metal article.

[0035] According to various embodiments, there may be provided a metal article formed by various embodiments of the apparatus as described herein or by various embodiments of the methods as described herein.

[0036] According to various embodiments, forming metal articles or the transfer melt concept devices and methods for liquid forging process as described herein may include or may use an open mould with a direct high pressure solidification process to form metal parts or articles. The materials used for forming the metal parts or articles may be wrought alloy materials. The tool or apparatus used may include a top punch including a plunger (in other words a protrusion), a feature insert (in other words a forming insert), and an overflow insert. The tool or apparatus may further include a die cavity (in other words a die) having a reservoir (in other words a reservoir cavity), a part cavity (in other words a forming cavity) and an overflow cavity. The details of the tool or apparatus are shown in FIG. 4. [0037] According to various embodiments, the method of forming metal article may include introducing a pre quantified melt (or molten metal) into a reservoir within a die cavity when the top punch is moved to a top position with respect to the die cavity. When the top punch is closed or moved toward the die cavity, the longer plunger of the punch may touch the melt in the reservoir first and push the melt from the reservoir horizontally into the part cavity. At the same time, the feature insert of the punch may be closing onto the die cavity and squeezing out the excess melt into the overflow cavity while trapping the desired volume of melt within the part cavity. The closure of the overflow insert may leave a clearance tolerance of about ΙΟΟμιη. As a direct pressure is applied upon the full closure of the punch relative to the die cavity, air is released via the air vent insert (or air vent) in the punch with a holding pressure on the melt while the melt solidifies in the part cavity. After the solidification stage, the liquid forged part connected together with the reservoir biscuit and solidified overflow material is retained in the die cavity and the top punch is moved away relative from the die cavity to separate the liquid forged part from the punch leaving behind the liquid-forged part in the die cavity.

[0038] The liquid-forged part connected together with the reservoir biscuit and solidified overflow material are then removed or ejected from the die cavity by relative movement between an ejector and the die until the formed part is clear of the die cavity. The final liquid forged part is trimmed or cut to remove the biscuit and overflow material.

[0039] Advantageously, by utilizing an open mould with transfer melt concept in liquid forging, various embodiments may form wrought alloy preforms or parts of varying thickness and features in a single process operation. [0040] Thin preforms with varying thicknesses and features may be formed using the transfer melt concept with the tool or apparatus according to various embodiments, which includes a plunger (or a protrusion), a feature insert (or a forming insert) and overflow insert in the top punch, and a die cavity (or a die) including a reservoir (or reservoir cavity), a part cavity (or a forming cavity) and an overflow cavity.

[0041] According to various embodiments, the features insert and part cavity may be of either a single or multi cavities design.

[0042] The reservoir may be filled with a pre quantified molten metal by a ladle unit.

[0043] When the top punch is closed or moved toward the die cavity, the longer plunger of the punch may touch the melt in the reservoir first and push the melt in the horizontal direction from the reservoir into the part cavity.

[0044] According to various embodiments, the feature insert, plunger and overflow insert of the punch may close onto the die cavity together and squeeze out the excess melt into the overflow cavity while trapping the desired volume of melt within the part cavity. The closure of the overflow insert may leave a clearance tolerance of about ΙΟΟμιη.

[0045] A vertical direct pressure may be applied onto the punch and the pressure acting perpendicularly onto the full surface area of the part cavity during the melt solidification may provide an evenly distributed pressure in the solidified material to eliminate both the hot tear and porosity defects in the formed part.

[0046] FIG. 4 shows a metal article forming apparatus 400 according to an example embodiment. The apparatus 400 includes a punch 410 and a die 420. The punch 410 and the die 420 may be mounted to a punch press 402 such that the punch 410 may be moved relative to the die 420. In an implementation, the die 420 may be mounted to support 404 of the punch press 402 such that it is fixed in a position on the punch press 402. The punch 410 may be mounted to a ram 406 of the punch press 402 such that the ram 406 of the punch press 402 may be operable to move the punch 410 toward or away from the die 420.

[0047] As shown in FIG. 4, the die 420 includes a reservoir cavity 422 and a forming cavity (or a part cavity) 424. The reservoir cavity 422 may be recessed into a first part of a surface of the die 420. The forming cavity 424 may be recessed into a second part of the surface of the die 420 adjacent to the first part. In FIG. 4, the forming cavity 424 is shown to be located substantially at a centre part on a top surface of the die 420. The forming cavity 424 is shown to be recessed into the die 420. The forming cavity 424 may be adapted to have a predetermined profile suitably shaped to give shape to molten metal for cooling and solidifying into a formed metal with a desired shape. In other words, the forming cavity 424 may function as an open mould to shape molten metal into the desired formed metal article or part. In an implementation, the forming cavity 424 may have a substantially shallow depth for forming thin profiled metal articles or parts. In another implementation, the forming cavity 424 may have varying depths for forming metal articles or parts with varying thickness. In yet another implementation, the forming cavity 424 may have a profile for forming high-aspect ratio features in the formed metal articles or parts.

[0048] The reservoir cavity 422 of the die 420 may be adjacent to the forming cavity 424, and located off-centre on the top surface of the die 420 close to an edge of the die 420. The reservoir cavity 422 may be adapted to hold a substantial amount of liquid, such as molten metal. As shown in FIG. 4, the reservoir cavity 422 may have a profile of a trough which may be suitable for containing a substantial amount of molten metal. The reservoir cavity 422 is also shown to have a depth relatively deeper than that of the forming cavity 424. In various embodiments, the reservoir cavity 422 may have a capacity larger than the capacity of the forming cavity 424.

[0049] The die 420 may be configured such that liquid overflowing from the reservoir cavity 422 may be directed to flow into the forming cavity 424. In other words, the reservoir cavity 422 and the forming cavity 424 may be adapted to direct overflowed liquid from the reservoir cavity 422 into the forming cavity 424.

[0050] In various embodiments, the punch 410 may be adapted to displace liquid (such as molten metal) received in the reservoir cavity 422 of the die 420 to flow into the forming cavity 424 as the punch 410 moves relative toward the die 420. In other words, the punch 410 may cause molten metal contained in the reservoir cavity 422 to be displaced such that, when the molten metal overflows, the molten metal may flow into the forming cavity 424 for filling the forming cavity 424 as the punch 410 is moved relative toward the die 420. In an implementation, the punch 410 may be moved toward the die 420 by operating the punch press 402 such that the ram 406 of the punch press 402 move the punch 410 toward the die 420, which is fixed on the punch press 402.

[0051] In various embodiments, the punch 410 may include a protrusion 412. The protrusion 412 may be on a surface of the punch 410 facing the surface of the die 420 having the reservoir cavity 422 and the forming cavity 424. The protrusion 412 may be receivable in the reservoir cavity 422 of the die 420. In other words, the protrusion 412 may be configured such that when the punch 410 moves relative toward the die 420, the surface of the punch 420 having the protrusion 412 may be moved relative toward the surface of the die 410 having the reservoir cavity 422 such that the protrusion 412 may be inserted into the reservoir cavity 422. Accordingly, when molten metal is contained in the reservoir cavity 422 of the die 420, the insertion of the protrusion 412 of the punch 410 into the reservoir cavity 422 of the die 420 may cause the molten metal to be displaced. As the punch 410 moves closer toward the die 420, the protrusion 412 may be inserted deeper into the reservoir cavity 422 to displace more molten metal until the molten metal overflows from the reservoir cavity 422. The overflowed molten metal may then flow into the forming cavity 424 and fill the forming cavity 424.

[0052] In FIG. 4, the protrusion 412 may be protruding from the bottom surface of the punch 410 and may be located off-centre on the bottom surface of the punch 410 close to an edge of the punch 410 such that the protrusion 412 may be directly above the reservoir cavity 422 when the punch 410 is positioned above the die 420, and the protrusion 412 may be inserted into the reservoir cavity 422 when the punch 410 moves relative toward the die 420.

[0053] Further, it is shown in FIG. 4 that the reservoir cavity 422 of the die 420 may be a trough having a slant wall 421 on the side adjacent to the forming cavity 424. The reservoir cavity 422 may have substantially straight vertical walls 423 on the other three sides. As shown in FIG. 4, the protrusion 412 of the punch 410 may have slant wall 411 on one side. The protrusion 412 may further have substantially straight vertical walls 413 on the other three sides. The punch 410 and the die 420 may be positioned such that when the punch 410 moves relative toward the die 420, the three substantially straight vertical walls 413 of the protrusion 412 may come into contact and slide against the three corresponding substantially straight vertical walls 423 of the reservoir cavity 422 as the protrusion 412 is being received into the reservoir cavity 422. At the same time, the slant wall 411 of the protrusion 412 may close in toward the slant wall 421 of the reservoir cavity 422 to form a conduit. When the reservoir cavity 422 contains molten metal, molten metal may be displaced by the protrusion 412 as the protrusion 412 is being inserted into the reservoir cavity 422. The displaced molten metal from the reservoir cavity 422 may flow out of the reservoir cavity 422 via the conduit, which may be formed between the slant wall 411 of the protrusion 412 and the slant wall 421 of the reservoir cavity 422. Since the slant wall 421 of the reservoir cavity 422 is adjacent and slanting towards the forming cavity 424, the molten metal flowing out of the reservoir cavity 422 may flow into the forming cavity 424.

[0054] In various embodiments, the punch 410 may be moved relative toward the die 420 until the punch 410 is in a closed configuration with the die 420. In the closed configuration, the protrusion 412 of the punch 410 may be fully inserted in the reservoir cavity 422 of the die 420, and the punch 410 may fully enclose the forming cavity 424 of the die 420. The bottom surface of the punch 410 may be in contact with the top surface of the die 420. In the closed configuration, molten metal previously contained in the reservoir cavity 422 may have been displaced to fill the forming cavity 424. With the forming cavity 424 filled with molten metal, the punch 410 may be adapted to apply a pressure on the molten metal in the forming cavity 424 when the punch 410 is in the closed configuration relative to the die 420. In this manner, the molten metal may solidify under pressurized condition to form the desired metal article or part. In an implementation, the punch press 402 may be operated so as to translate a required pressure to the punch 410 for applying a direct pressure on the molten metal in the forming cavity 424.

[0055] In FIG. 4, it is shown that the punch 410 may further include a forming insert 414. The forming insert 414 may be adapted to pair with the forming cavity 424 of the die 420 to form a complete mould with a predetermined shape. In other words, the forming cavity 424 of the die 420 may form one part of a mould and the forming insert 414 of the punch 410 may form the other part of the mould. When the forming cavity 424 and the forming insert 414 are joined together, they may form a fully enclosed mould, which encloses a space having a predetermined profile to shape molten metal into the desired shape. In an implementation, the predetermined profile of the fully enclosed mould may include intricate features, high-aspect ration features, thin walls or features with varying thicknesses.

[0056] The forming insert 414 may be located substantially at a centre part on the bottom surface of the punch 410 and adjacent to the protrusion 412. When the punch 410 is positioned above the die 420, the forming insert 414 may be directly above the forming cavity 424. When the punch 410 and the die 420 are in the closed configuration, the forming insert 414 may be joined with the forming cavity 424 to form a fully enclosed mould.

[0057] When the punch 410 is moved relative toward the die 420 to form the closed configuration, molten metal received in the reservoir cavity 422 may be displaced to flow into the forming cavity 424. As the punch 410 continues to move toward the die 420, the forming insert 414 may close in toward the forming cavity 424. Accordingly, the forming insert 414 may trap desired amount of molten metal to fill the enclosed space within the enclosed mould formed by joining the forming cavity 424 and the forming insert 414. With the enclosed mould filled with molten metal, the punch 410 may be adapted to apply a pressure on the molten metal in the enclosed mould via the forming insert 414. In this manner, the molten metal may solidify under pressurized condition in the enclosed mould to form the desired metal article or part. [0058] FIG. 4 further shows that the die 420 may include an overflow cavity 426. The overflow cavity may be recessed into a third part of the surface of the die adjacent to the second part. The overflow cavity 426 may be adapted to collect excess molten metal that overflows from the forming cavity 424. In other words, when there are excess molten metal flowing into the forming cavity 424 from the reservoir cavity 422, the excess molten metal may overflow into the overflow cavity 426, or may be squeezed out from the forming cavity 424 into the overflow cavity 426 as the punch 410 or the forming insert 414 of the punch 410 close in toward the forming cavity 424.

[0059] The overflow cavity 426 of the die 420 may be adjacent to the forming cavity 424 on the side opposite to the reservoir cavity 422, and located off-centre on the top surface of the die 420 close to an edge of the die 420 opposite the edge where the reservoir cavity 422 is located. The overflow cavity 426 may be adapted to contain liquid such that the excess molten metal may be collected by the overflow cavity 426. As shown in FIG. 4, the overflow cavity 426 may have a profile of a trough, and a depth relatively deeper than that of the forming cavity 424.

[0060] The punch 410 may also include an overflow insert 416. The overflow insert 416 may be adapted to provide a clearance between the overflow insert 416 and the overflow cavity 426 when the punch 410 and the die 420 are in the closed configuration. The clearance provided may be adapted to be sufficient to allow excess molten metal to overflow or be squeezed out from the forming cavity 424 into the overflow cavity 426. In an implementation, the overflow insert 416 and the overflow cavity 426 may be adapted to leave a clearance tolerance of approximately ΙΟΟμιη.

[0061] In FIG. 4, the overflow insert 416 may be a protrusion protruding from a bottom surface of the punch 410 and may be located off-centre on the bottom surface of the punch 410 close to an edge of the punch 410 opposite to the protrusion 412 such that the overflow insert 416 may be directly above the overflow cavity 426 when the punch 410 is positioned above the die 420.

[0062] In various embodiments, the punch 410 may include an air vent (not shown). The air vent may be adapted to allow air to escape when molten metal fills the forming cavity 424 of the die 420. In other words, when molten metal overflows from the reservoir cavity 422 into the forming cavity 424, the air vent may allow air originally in the forming cavity 424 to escape such that the molten metal may fill the space in the forming cavity 424.

[0063] In various embodiments, the die 420 may include an ejector 428 adapted to eject the formed metal article or part from the die 420. The ejector 428 may be in the form of a rod. In FIG. 4, two ejectors 428 are shown to be in a retracted position below the reservoir cavity 422 and the overflow cavity 426. In this position, the ejectors 428 may be retracted within the die 420 and an end of the ejectors 428 is flushed with a respective surface of the reservoir cavity 422 or the overflow cavity 426. After the molten metal has solidified to form the metal article, the punch 410 may be moved away from the die 420 and the ejectors 428 may be operated to push the formed metal piece out of the die 420 such that the formed metal piece may be removed.

[0064] In various embodiments, the reservoir cavity 422, the forming cavity 424 and the overflow cavity 426 may be integrally formed in the die 420. In another embodiment, the reservoir cavity 422, the forming cavity 424 and the overflow cavity 426 may be separate parts which are joined together to form the die 420. Similarly, in various embodiments, the protrusion 412, the forming insert 414 and the overflow insert 416 may be integrally formed in the punch 110. In another embodiment, the plunger 412, the forming insert 414 and the overflow insert 416 may be separate parts which are joined together to form the punch 410.

[0065] In use, the metal article forming apparatus 400 in FIG. 4 may be operated in accordance with the following steps. The punch 410 may be moved away from the die 420 so that the punch 410 and the die 420 are in an opened configuration. This may be achieved via operating the punch press 402. In the opened configuration, a predetermined quantity of molten metal may be introduced into the reservoir cavity 422 of the die 420. The punch 410 may then be moved relative toward the die 420 until the punch 410 and the die 420 are in a closed configuration.

[0066] When the punch 410 is moving relative toward the die 420, the protrusion 412 of the punch 410 may first contact the molten metal in the reservoir cavity 422. As the punch 410 continues to move toward the die 420, the protrusion 412 may push into the molten metal and displace the molten metal in the reservoir cavity 422. The molten metal in the reservoir cavity 422 may continue to be displaced until the molten metal overflows from the reservoir cavity 422. The overflowed molten metal may flow into the forming cavity 424. At the same time, the forming insert 414 of the punch 110 may close in on the forming cavity 424. The forming insert 414 may squeeze out excess molten metal from the forming cavity 424 while trapping the desired amount of molten metal in the forming cavity 424. The excess molten metal may be directed into the overflow cavity 426. As molten metal fills the forming cavity 424, air may be released via an air vent (not shown) in the punch 420.

[0067] In the closed configuration, with molten metal filled in the forming cavity 424, a pressure may be applied on the molten metal trapped in the forming cavity 424 via the punch 410 and the forming insert 414. The pressure may be applied continuously to pressurize the molten metal in the forming cavity 424 such that the molten metal solidifies under pressurized conditions. After solidification, the formed metal piece in the die 420 may include the desired formed metal article or part connected to a reservoir biscuit and an overflow solidified material. In order to remove the formed metal piece from the die 420, the punch 410 may be moved away from the die 420 such that they are in the opened configuration. In the opened configuration, the formed metal piece may be removed or ejected from the die 420. Ejection of the formed metal piece may be via the ejector 428. The relative movement between the ejector 428 and the die 420 may push the formed metal piece out of the die 420. The formed metal piece may be trimmed or cut to remove the reservoir biscuit and the overflow solidified material to obtain the desired formed metal article or part.

[0068] FIGs. 5A to 5D show schematic diagrams illustrating a method for forming metal according to various embodiments. In FIG. 5 A, a predetermined quantity of molten melt including molten wrought alloy material may be introduced into a reservoir cavity 522 of a die cavity (or a die 520) via a ladle unit 508 with protective gas. The melt temperature may range from 680 °C to 720°C, depending on the type of wrought alloy material chosen. In FIG. 5B, a punch 510 may be heated to about 130 °C and above, and may be moved relative to the die 520 which may also be heated to about 140 °C and above. The punch 510 may be moved downwards to contact the melt in the reservoir cavity 522 at a speed between the range of 30 to 200 mm/s. In another embodiment, the speed may be between the range of 150 to 200 mm/s. The melt may be forced to flow (or displace) in a substantially horizontal direction and enter the part cavity (or forming cavity) 524 of the die 520 in a laminar flow behaviour. During the filling, as the melt enters and fills the part cavity 524, air may be released or allowed to escape via air vent inserts (not shown) provided in the punch. Simultaneously, a high pressure may be applied onto the melt during filling and solidification. A holding pressure between the range of 60 to 140 MPa may be applied throughout the solidification. In another embodiment, the holding pressure may be between the range of 60 to 100 MPa. By exerting a direct forming pressure during solidification on the full surface area of the part cavity 524, stress is evenly distributed in the solidified material to eliminate both the hot tear and porosity defects in the formed part 530 in FIG. 5C. In FIG. 5D, after the melt has solidified, the punch 510 may be moved away relative to the die cavity 520 to separate the liquid-forged parts 530 from the punch 510 leaving behind the liquid-forged parts 530 in the die cavity 520. The liquid-forged parts 530 may then be removed or ejected from the die cavity 520 by the ejector 528 movement until the formed parts 530 are clear of the die cavity 520. The parts may be finished by machining or cutting off the reservoir biscuit 534 and the overflow material 536 to obtain the final part (or the desired formed metal article) 532 .

[0069] In other words, according to various embodiments, a method of forming metal article may include the following steps:

Step 1: Introducing of pre quantified melt into the melt reservoir (See FIG.

5A)

Step 2: Transferring of melt horizontally into the cavity upon the punch closing upon the die cavity (See FIG. 5B)

Step 3: Pressurizing the melt in the die cavity till part is fully solidified (See FIG. 5C)

Step 4: Opening of the top punch with the liquid forged parts retained at the die cavity, and ejecting liquid forged parts away from the die cavity via the bottom ejector (See FIG. 5D) [0070] FIG. 6A shows an example of the formed metal piece 630 produced from the method of FIGs. 5A to 5D. As shown in FIG. 6A, the formed metal piece 630 includes a reservoir biscuit 634 and a solidified overflow material 636 connected to a desired formed metal article 632.

[0071] FIG. 6B shows an example of the desired formed metal article 632 obtained from the formed metal piece 630 of FIG 6A. The desired formed metal article shown in FIG. 6B is a wrought alloy thin prototype of size 100mm x 100mm with varying thickness. The thinnest is about 0.9mm and the thickest section is at 6mm indicating the process capability of the transfer melt concept in liquid forging process.

[0072] Embodiments of the method and apparatus for forming metal article may be used for forming wrought alloy materials (Al 1000, Al 2000, Al 5000, Al 6000, AZ31, AZ61 AZ80) for near net shape preforms or parts with complex features, such as intricate features, thin walls or features with varying thickness. The complex features formed may be pore-free structures. The metal article may be formed through the transfer melt concept in liquid forging in a single or multi cavities mode. In particular, embodiments of the method and apparatus as described herein may provide thin preforms or parts for subsequent forming operations to further minimize operation cost and material wastage.

[0073] Embodiments of the method and apparatus as described herein may be of interest in precision engineering sector where complex shape and intricate features thin preforms and parts are required. For example, the transfer melt concept in liquid forging process may complement with existing forming processes to provide thin preforms that will lead to greater reduction in process cost and material saving. Embodiments may also be of great interest in areas where high volume production of near net shape wrought alloy parts with varying thicknesses and intricate features are desired to be formed in one processing step with minimal machining.

[0074] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

1. A metal article forming apparatus, the apparatus comprising:

a die having

a reservoir cavity recessed into a first part of a surface of the die, and

a forming cavity recessed into a second part of the surface of the die adjacent to the first part; and

a punch having a protrusion on a surface of the punch facing the surface of the die,

wherein the punch is adapted to move relative toward the die to move the surface of the punch relative toward the surface of the die to insert the protrusion of the punch into the reservoir cavity of the die.

2. The apparatus as claimed in claim 1, wherein the die further comprises an overflow cavity recessed into a third part of the surface of the die adjacent to the second part.

3. The apparatus as claimed in claim 1 or 2, wherein the punch further comprises a forming insert adapted to pair with the forming cavity of the die to form a mould with a predetermined shape.

4. The apparatus as claimed in any of the preceding claims, wherein the reservoir cavity is adapted to contain molten metal.

5. The apparatus as claimed in claim 4, wherein the forming cavity is adapted to shape the molten metal.

6. The apparatus as claimed in claim 4 or 5, wherein the protrusion is adapted to displace the molten metal received in the reservoir cavity to flow into the forming cavity.

7. The apparatus as claimed in claim 7, wherein the overflow cavity is adapted to collect excess molten metal that overflows from the forming cavity.

8. The apparatus as claimed in any of the preceding claims, wherein the punch further comprises an air vent adapted to allow air to escape.

9. The apparatus as claimed in any of the preceding claims, wherein the punch is further adapted to pressurize the molten metal in the forming cavity of the die.

10. The apparatus as claimed in any of the preceding claims, wherein the die further comprises an ejector adapted to eject the formed metal article.

11. The apparatus as claimed in any of the claims 2 to 10, wherein the punch further comprises an overflow insert.

12. A method of forming metal article, the method comprising:

introducing molten metal into a reservoir cavity recessed into a first part of a surface of a die; and

moving a punch relative toward the die to move a surface of the punch relative toward the surface of the die to insert a protrusion on the surface of the punch into the reservoir cavity to displace molten metal received in the reservoir cavity to flow into a forming cavity recessed into a second part of the surface of the die adjacent to the first part.

13. The method as claimed in claim 12, further comprising applying a pressure via the punch to pressurize the molten metal in the forming cavity during solidification.

14. The method as claimed in claim 12 or 13, further comprising removing the formed metal article from the die.

15. The method as claimed in claim 14, wherein the removing comprises ejecting the formed metal article from the die with an ejector.

16. The method as claimed in claim 14 or 15, further comprising parting a reservoir biscuit and a solidified overflow material from the formed metal article.

17. The method as claimed in claim 16, wherein the parting comprises machining away the reservoir biscuit and the solidified overflow material from the formed metal article.

18. A metal article formed by the apparatus as claimed in any of claims 1 to 11 or by the method as claimed in any of claims 12 to 17.