PROCESSING OF POROUS HIGH MELTING TEMPERATURE METALS USING A REMOVABLE SECOND PHASE

The production of high melting temperature porous metals using a removable second phase has been conducted using two different methods with two different categories of second phase. The first of these is the production of a porous high temperature metal using a nickel copper alloy which has undergone solidification-induced phase separation, followed by phase removal. In this system, the removable phase is an intrinsic part of the alloy (formed as part of the microstructure during solidification) which has been removed using a ferric chloride solution. The alloy has been processed using three different solidification regimes which have in turn resulted in the production of three distinct porous structures, and pore sizes. For comparison with this method (offering different capabilities for pore and sample size, and scale up), the replication process has also been used, in which the removable phase is a secondary material extrinsic to the alloy. Significant modifications to standard processes were needed to overcome the challenges of high melting temperature metals in order for porous samples from titanium alloy (Ti-811) to be produced. An iterative experimental approach to development of replication processing has been trialled. The procedures used comprised three methods for alloy melting and two methods for applying the required infiltration pressure. The porous metal produced using this method has shown that replication casting is a possible manufacturing route, but significant hurdles are still present before a large scale porous component can be produced and tested.