Design and development of functionally graded material by pulse discharge resistance consolidation with temperature gradient control

A novel method of pulse electric discharge resistance consolidation with temperature gradient control has been developed for the design and fabrication of functionally graded materials (FGMs). The powder processing route employed makes it possible to select combinations of constituents with greatly different densification rates, controlling densification up to full density to produce a nanoscaled structure. A die with a specially designed outer shape makes it possible to achieve desired temperature profiles along a graded composition. Using a stepped graphite die with a temperature difference of more than 700 K within a width of 7 mm, a five layered material graded from TiAl intermetallic to partially stabilised zirconia (PSZ) can be fabricated. This structure shows full densification throughout its cross-section without any discontinuity and an increasing hardness from 650 HV at the TiAl nanocrystalline layer to 1560 HV at the PSZ layer, varying according to a mixture rule.