Hiroshi Kimura and Shin-ichi Kobayashi
National Defence Academy, Department of Mechanical Engineering, Yokosuka
A novel P/M processing of functionally gradient materials is developed, from which one can select the combination of the constituents with greatly different densification rate and then realize full densification. This processing consists of pulse-electric discharge consolidation combined with a temperature slope control technique using a specially designed die in outer shape. For powders of the amorphous TiAl/3 mol%Y2O3-PSZ system, the lowest consolidation temperature necessary to obtain a full density compact increases from 1242 K to approximately 1700 K with increasing molar ratio of PSZ in the case of an applied stress of 49 MPa. We set up a test condition of a temperature profile and a constant sintering rate along a gradient composition, using a die with two different diameters showing a temperature increase of more than 700 K with in a width of 7 mm. Then, we can synthesize a 5-layered functionally gradient material of the intermetallic TiAl/PSZ system, having full densification everywhere in an overall cross-section without any discontinuity. This material shows a high vickers hardness of 650 DPN at a layer of γ-phase TiAl with α2(Ti3Al), synthesized by crystallization from an amorphous phase, and increases up to 1560 DPN at a PSZ layer according to a mixture law.
(Received May 26, 1993)
TiAl/PSZ-functionally gradient material, pulse-electric discharge consolidation, temperature-slope control technique, mechanical alloying, amorphous TiAl powder, nano-scaled structure
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