DISCUSSION OF A LIQUID-METAL PRESSURE INFILTRATION PROCESS TO PRODUCE METAL MATRIX COMPOSITES

The two major processes presently used to manufacture metal matrix composites are solid-state diffusion bonding and squeeze casting. The former has shape limitations; it is suitable to produce only flat plates or sheets, and the manufacturing rate is low and expensive. The latter, although suitable for quantity production of complex shapes, requires heavy and expensive tooling. The described pressure infiltration process was developed at Massachusetts Institute of Technology, With this process, fiber, whisker or particulate pre-forms are placed in inexpensive throw-away containers, into which the molten matrix material is forced by gas pressure. Because the gas pressure on the pre-form container is quasi hydrostatic, its strength requirement is minimal, consequently pre-form containers, even those with complicated shapes, are easy to prepare. By virtue of the simplicity of the containers and the absence of the requirement of a heavy mechanical system to effect the infiltration of the liquid metal into the pre-forms, the process is suitable to produce bulk or final-shape composite parts inexpensively. As the processing parameters such as pre-form temperature, infiltrating metal temperature, infiltrating pressure and cooling rate, can be accurately controlled, the process is particularly suitable for research and limited production.