A method for forming a metal matrix composite within a mold of investment material. The method comprises the steps of forming a preform mixture of liquid flow medium, binding agent and reinforcement into the desired shape of a metal matrix composite. Then, allowing the preform mixture to solidify into desired shape. Next, encasing the preform mixture within a container of investment material. Then, heating the preform mixture at a controlled rate which first allows any fluid, such as water, to evaporate, then allows removal of the flow medium. Next, sintering the remaining reinforcement material and binder to form a solid preform. Then, disposing molten metal on top of the solid preform within the container such that the molten metal forms a seal with the container. Next, pressurizing the molten metal such that it is forced into said preform. Next, solidifying the molten metal to form a metal matrix composite in the shape of this preform; and removing the investment material from metal matrix composite. Additionally, there is a method comprising the steps of connecting a preform, which has been previously prepared for infiltration of molten material and having a binding agent, to a sprue system. Next, encasing the preform and sprue system within a container of investment material. Then, melting out the sprue system to form piping which allows the metal to flow to the preform. Next, sintering said preform with said binding agent therein to form a solid preform. Then, disposing molten metal on top of the preform within the container such that molten metal form a seal with the container. Next, pressurizing the molten metal such that it is found through the sprue system and into the preform. Then, solidifying the molten metal to form a metal matrix composite in the shape of the preform; and removing the investment material from metal matrix composite.

A method for forming a metal matrix composite within a mold of investment material. The method comprises the steps of forming a preform mixture of liquid flow medium, binding agent and reinforcement into the desired shape of a metal matrix composite. Then, allowing the preform mixture to solidify into desired shape. Next, encasing the preform mixture within investment material. Then, heating the preform mixture at a controlled rate which first allows any fluid, such as water, to evaporate, then allows removal of the flow medium. Next, sintering the remaining reinforcement material and binder to form a solid preform. Then, forcing molten metal under pressure into said preform. Next, solidifying the molten metal to form a metal matrix composite in the shape of this preform; and removing the investment material from metal matrix composite. Additionally, there is a method comprising the steps of connecting a preform, which has been previously prepared for infiltration of molten metal, to a sprue system. Next, encasing the preform and sprue system within investment material. Then, melting out the sprue system to form piping which allows the metal to flow to the preform. Next, forcing molten metal under pressure through the sprue system and into the preform. Then, solidifying the molten metal to form a metal matrix composite in the shape of the preform; and removing the investment material from metal matrix composite.

The conventional investment casting technique is modified to cast metal products where the product has one or more support portons and at least one feeding tube for feeding molten metal into the cast of the product comprising providing a source of molten metal, connecting at least one metal feed tube to the mold of the metal product to be cast, of forming a hole in each support portion wherein the hole in each support portion is much larger than the volume of metal that can be non turbulently transmitted in a deflected manner into the mold by the feed tube so that the metal poured nto the generally uniform cross section mold cools gradually so that the support portions of the cast metal products will have a generally homogenous composition without air bubbles or cracks which could weaken the product.

An apparatus is disclosed for an evaporative pattern assembly for metal castings and associated cast metal feeding, the assembly comprising: (a) a central upright sprue; (b) a plurality of sprue branches integral with and extending radially away from said central sprue at each of at least two axial locations of the central sprue; (c) at least two gating rails, each integrally connected with the extremities of at least two sprue branches extending from different axial locations of the central sprue, each rail being connected to different and independent sprue branches so as to be supported in circumferentially-spaced positions relative to each other about said sprue; and (d) at least one pattern body integrally connected across two of said gating rails. Preferably, the body is complex in configuration having a plurality of projections connected to said rails by gates. The radially extending sprue branches are advantageously layered in different planes with the angular spacing between branches being in the range of 45.degree.-90.degree.. Also disclosed is a method of making and a method of using such evaporative pattern assembly.

Gate is a wax structure for forming part of a wax master in investment casting of a dental prosthesis. The gate has a square feeder with a circular disc on each end. The square feeder reduces the cracking stresses between adjacent feeders to reduce unwanted fins, and the square shape aids in final cutoff of the cast prosthetic. In the wax master, one of the discs is secured to the prosthetic form and the other disc to the conventional reservoir bar. The disc shape aids in filleting to the form and bar.