Faculty of Engineering, Tohokugakuin University, Tagajo 985-8537
Spark plasma sintering (SPS) is a technique to produce various alloys with low cost. The titanium alloys of Ti-M (M=Co, Ni, Nb, Mo, Ru, Pd, Ta, W and Re) were prepared by SPS and those microstructures and corrosion resistance were examined.
A powder of M was mixed with the powder of titanium at at% of M from 0.1 to 1.0. The mixed powder was sintered by SPS at temperatures of 1073, 1373 and 1773 K to form the Ti-M alloys. Microstructure of the alloys were observed by scanning electron microscopy (SEM) and examined by X-ray diffraction. Corrosion resistance of the alloys were measured by a potentiodynamic polarization in a 5 mass% HCl solution.
The alloys prepared at 1073 K were the particle dispersion type in which the added element phases were dispersed granularly in the Ti matrix. The compound phases of Ti-Ni and Ti-Co generated in SPS were selectively corroded at relatively low potential and the selective dissolution of the added element phases were enhanced by potential cycles. In the alloys prepared at 1373 K, the dispersion of elements and compounds were progressed to increase a ratio of the metastable βTi phase. The alloy structures approached to a solid solution type. Cathodic current densities of the alloys in the polarization curve were similar as those of the solid solution types of the alloys. In the anodic potential region active dissolution of the added element phases disappeared, the anodic current density became low, and a selective corrosion of a specific phase was not observed. The alloys prepared at 1773 K were generally the solid solution type. The polarization curves of the alloys were similar as those of the arc-melted Ti-0.1 Pd alloy and thus the alloys prepared are conceivable to reveal the corrosion resistance almost same 0.5 that of the Ti-Pd alloy.
(Received April 23, 1999; In Final Form August 10, 1999)
powder metallurgy, spark plasma sintering, titanium based alloy, potentiostat, corrosion resistance
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