In the Selective Laser Melting method, metallic powders are successively melted in a microscopic zone and clad to the already formed base to produce 3D models. It is shown that the SLM enables fabrication of titanium models directly from pure titanium powders. The mechanical properties (tensile strength, density and fatigue strength) are determined for various working conditions. It is found that titanium models made under the optimum condition has a relative density of about 95% with the strength same of level as the solid metal. Porous models seem to have certain merits for medical purposes, but the fatigue strength has yet to be improved.

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  Bending test of an annealed Ti-47 at. % Al intermetallic compound with a duplex structure consisting of γ-α₂ two-phases lamellar and eqiaxed γ-phase grains was carried out at 973 K. Fracture surfaces and internal deformation structure were observed under a scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. SEM observations revealed grain boundary fracture of the equiaxed γ-phase grains. TEM observations of the internal microstructure revealed comparatively long deformation twins in the initial stage of plastic deformation, and these twins were observed along the direction of about 45 degrees to the loading axis. New deformation twins, which were short and formed among the initially formed long deformation twins, were observed in the final stage of the plastic deformation. Based on the SEM and TEM observations, the bending fracture mechanism of the annealed Ti-Al compound at 973 K was reviewed.

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  A new welding method was proposed based on the self-propagating high-temperature synthesis (SHS) reaction between droplets and powder of elemental metals, and its feasibility was investigated in a simple experiment. In the experiment, an aluminum droplet was dropped onto nickel powder heaped up in a groove at the interface between two NiAl substrates. The aluminum and nickel exothermically reacted and produced intermetallic compounds in Al-Ni system, and the NiAl substrates near the interface were melted by the heat from the reaction. The microstructure of the reaction products varied depending on the initial temperatures of the aluminum droplet and nickel powder and also the groove spacing. Increase in initial temperatures of the aluminum droplet and nickel powder and the groove spacing promoted both the exothermic reaction to synthesize NiAl in the groove and the melting of the joint surface of the substrates.

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  Cu-Be alloy castings revealed an anomalous phenomenon of spontaneous deformation by aging under stress and restoration of the deformation by solution treatment. Three kinds of Cu-Be cast alloys containing beryllium of 1.5 mass %, 2.0 mass % and 2.5 mass % respectively were prepared. The alloy containing beryllium of 1.5 % is mainly composed of the α phase and the alloys containing beryllium of 2.0 % and 2.5 % are composed of the α and β phases. The cast alloys were cut into plate-like specimens of 2.5 mm thickness. The plate was fixed to a cantilever jig and loaded at the free end of the cantilever up to the elastic limit of the alloy. The loaded specimen was aged to measure deflection following spontaneous deformation. The Cu-1.5 % Be alloy composed of uniform α phase exhibited the highest warping deflection and the longest incubation time to start the spontaneous warping among the alloys. The spontaneous warping has a close correlation to the hardening and contraction behaviors during aging and therefore to the precipitation of the metastable γ” and γ’ phases in the α phase of Cu-Be alloy. These experimental results indicate that the warping deflection and the incubation time are dependent upon the volume fraction and beryllium content of the α phase, respectively. Homogenizing treatment was found to be effective in enhancing the warping deflection and shortening the incubation time even in cast alloy with higher beryllium content due to the dissolution of β phase.

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