The filling density in production becomes stable after it decreases rapidly in the initial stage of the consecutive compacting. Flowability fluctuation caused by history of powder movement was assumed to be one of the causes and experiments were conducted with pre-mixed powder of Fe-2 mass%Cu-0.9 mass%C-0.8 masss%Lubric ant. The experiments of this work verified that filling density is greatly affected by the history of the powder movement right before filling. Based upon the results, a highly precise filling system was developed. The new system enabled to abolish adjustment of compacting condition and to reduce defective compacts.

Porous metals exhibit various unique physical and mechanical properties, such as low bulk density and high strain energy absorbing capability. The optimum shape of the pores (cell morphology and topology) depends on the required properties. In this paper, two processing methods (precursor method and reactive precursor method) and some attempts to control the cell structure are discussed. Porous aluminum alloys are fabricated by the precursor method. In this method, powder compacted precursor consisting of aluminum and titanium hydride powders are prepared. Upon heating the precursor, titanium hydride decomposes and releases hydrogen gas at around the melting point of aluminum. Then the hydrogen gas produces many pores in aluminum. As for the reactive precursor method, the precursors are made by blending at least two kinds of reactive elemental powders (e.g. aluminum and titanium powders). Closed, flat-disc, open, bimodal-sized and high-porosity open pores are currently achieved by the reactive precursor method.

Aiming for an application to the high temperature pressure sensor, semiconductive ceramics foam incorporated with a narrow slit has been fabricated by our innovated superplastically foaming method. We investigated the pressure dependence of resistance on the zinc oxide based foaming body, by changing the fabrication process and composition. The resistance of the sample decreased with an increase in pressure both at room and high temperatures. The performances of this type of sensor such as sensitivity and linearity have been improved by doping ambivalent atoms (Ag and Li) into the matrix.

The evaluation of ejection behavior is important to the final formability of green compact because both the ejection and the compression in the powder die compaction are affected by die wall friction. In other words, there is a hysteretic relationship between the lateral pressure and compacting pressure. In this paper, the effect of powder characteristics on the ejection die wall friction was studied using a powder model that considers the hardness and shape of the powder. The ejection behavior was classified on the basis of the powder’s characteristics coefficient drawn from the model. Next, the influence of the particle size distribution, in addition to that of the hardness and shape of the powder, on the ejection behavior was shown.

The recycling process of the machined chips from the commercial Ti-6%Al-4%V (Ti-64) alloys to raw powders was established through the combination of brittle TiH₂ compounds formation via heat treatment in hydrogen gas atmosphere and fragmentation by ball milling technique. TG-TDA and XRD analysis obviously suggested the hydride and dehydride behavior of pure Ti and TiH₂ powders. The suitable heat treatment temperature at 873 K or more in H₂-Ar mixed gas successfully caused the formation of TiH₂ compounds, and resulted in the fragmentation of Ti-64 machined chips to powders with a median particle size of 120 µm, which were completely consolidated by pressing. In addition, the original machined chips never remained in the ball-milled machined chips after heat treated over 873 K. The green compact after vacuum sintering at 1273 K showed a relative density of about 93%, larger than that of the sintered material in using the commercial Ti-64 powders.