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A systematic investigation is made on the solid solution hardening of binary nickel alloys with additions of B-subgroup and transition metal elements. The 0.2% flow stress at 77 K and the Young's modulus are measured for a variety of binary alloys to evaluate the rate of solution hardening per one available data on the rate of change in lattice constant (da/dc), interpretation of the solution hardening that the hardening is more intense by the additions of transition metal elements than by the additions of B-subgroup elements where the hardening is linearly related with a combined parameter for the interaction between solute atoms and edge dislocations. Then the necessity is raised to carry out the similar type of investigation on the solution hardening of nickel in order to clarify whether the anomalous hardening effect is inherent in the Ll2 crystal structure of Ni3Al or in the majority component of nickel.Technological interest in nickel alloys has often centered on improving the heat resistant properties such as high temperature strength and creep strength by making alloys multicomponent. For this purpose, the additions of transition metals are generally accepted. Prominent examples are the modifications of commercial superalloys, in which the additions of those elements have been properly chosen utilizing regression analyses. As a more fundamental approach, the solid solution hardening has been studied in nickel binary alloys by a number of workers (2)- (9), however, the alloy

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Half-Heusler-type compounds have gained increasing attention as promising thermoelectric materials. In the present work, a focus is placed on TiNiSn with additions of Hf, Zr, Si, or Pt. Nominally stoichiometric TiNiSn alloys were prepared using arc melting and subsequent annealing at 1,073 K for 2 weeks. The thermoelectric properties, such as thermoelectric power, electrical resistivity, and thermal conductivity, were measured in a temperature range from 300 K to 1,000 K. As-cast materials show metallic transport properties, while annealed ones exhibit semiconductor behavior. Microstructures of TiNiSn alloys basically consist of nonequilibrium four-phase; half-Heusler TiNiSn, Heusler TiNi 2 Sn, metallic Ti 6 Sn 5 , and Sn solid solution. The volume fraction of the half-Heusler TiNiSn phase significantly increases by annealing. It is revealed that coexisting metallic phases degrade the thermoelectric properties of halfHeusler TiNiSn. Alloy additions strongly affect not only thermoelectric properties but also phase stability. The thermal conductivity of TiNiSn alloys with alloy additions decreases because of the point-defect phonon scattering.