High-strength and high-electrical-conductivity hypoeutectic Cu-Zr alloys have been developed. The authors succeeded in balancing characteristics well in a wide range of mechanical strength and electrical conductivity by using dispersion strengthening and fiber reinforcing techniques in nano scale. These have been put to practical use by first processing hypoeutectic Cu-Zr alloy cast-material into ultra-fine wires, and are applied to various cable and wire-electrode applications. In contrast, SPS (Spark Plasma Sintering) material using commercially available powders as a raw material is in practical use as a bulk material. The history of development of hypoeutectic Cu-Zr alloys from their alloy design, their manufacturing process, and the development of eutectic/hypereutectic Cu-Zr alloy SPS material are shown in this paper.

Powders of TiO₂ mixed with TiB₂ of mmol% (m = 0, 1, 2, 3, 4, 5, 10, 12, 20) were prepared, and sintered by using an spark plasma sintering apparatus, the chemical reaction between TiO₂ and TiB₂ in the sintering process was investigated. In the case of m = 2 to 20, it was found TiO₂ was reduced by TiB₂, to form and the Magneli phases (Ti_nO_2n−1 (n = 3, 4, 5, 6)). The maximum value of the dimensionless figure of merit ZT was 0.18 at 800°C for m = 3, and almost the same value as that of the TiO₂-TiN sintered bodies was obtained. The effective carrier concentrations in the TiO₂-TiB₂ sintered bodies were estimated from Heikes’s formula was about 2.4 times larger than those of the TiO₂-TiN, TiO₂-TiC, TiO₂-VC sintered bodies. The electron mobility μ tends to increase as m increases. The thermal conductivity was dominated by the lattice thermal conductivity at m = 0, while the electronic thermal conductivity was suggested at m = 4 and 5. It was confirmed that the formation of the magneli phase contributes to the improvement of ZT.

In accordance with the principles of the cutting phenomenon, following utilizing computational science, we developed an excellent-machinability additive which dramatically improves the machinability of sintered components. We have demonstrated that the developed excellent-machinability additive can reduce the tool wear in each corresponding tool dramatically to 1/6 to 1/12 in outer periphery machining processes assuming outer diameter processing, undercut grooving and so forth, using a cermet, K grade carbide and CBN tools, which are popularly used in machining of sintered parts. This article reports on the details about the above study.

In order to produce ceramic composites having both high Vickers hardness H_v ≥20 GPa and high fracture toughness K_IC ≥10 MPa·m^1/2, dense TiB₂/[ZrO₂-Al₂O₃] composites have been fabricated using pulsed electric-current pressure sintering (PECPS) at 1873 K under 50 MPa for 6.0 × 10² s in Ar. As the former starting materials, two kinds of TiB₂ powders were adopted; i) mono-modal particle size (P_s) distribution with an average particle size <P_s> of 3.24 μm and ii) bi-modal P_s distribution with <P_s> of 3.06 μm, composed of the small P_s of 0.58 and the large P_s of 3.27 μm. On the hand, the latter was the mixed powders composed of ZrO₂(2.5 mol%Y₂O₃) solid solution (ss) and α-Al₂O₃ powders: each primary P_s was 0.1~0.2 μm. Thus fabricated composites consisting of TiB₂, tetragonal/monoclinic ZrO₂ and α-Al₂O₃ with relative densities more than 99.0% showed improved mechanical properties, especially bi-modal TiB₂/[ZrO₂-Al₂O₃] composites revealed high H_v of 22.3 GPa and K_IC of 12.8 MPa·m^1/2. These high-mechanical behaviors might be explained in terms of i) better powder particle configuration, ii) high chemical stability of TiB₂, iii) the most proper composition, with adoption of iv) bi-modal TiB₂ powder and v) the most suitable sintering condition.