Renpei Yoda1, Takehiko Itagaki1 and Takeo Hamada2
1National Research Institute for Metals, Tokyo
Tungsten-Rhenium alloys in general continue to attract much attention because of their favorable ductility characteristics. In the present study some properties of 0.5 mm φ wires of doped tungsten containing 0 ∼ 26%Re prepared by powder metallurgy process have been investigated. Both the hardness and the tensile strength of wrought or annealed specimens increase with increasing rhenium content. The elongation of the wrought specimens of both dopod tungsten and tungsten-rhenium alloys is smaller than 4%. However, with increasing annealing temperature, the elongation of dopod tungsten further decreases and that of tungsten-rhenium alloys increases markedly. The elongation of annealed tungsten-rhenium alloys becomes higher with decreasing rhenium content, and the annealing temperature shifts to the higher temperature side. The recrystallization temperature of doped tungsten increases markedly with 3%Re addition, but it decreases with the addition of more than 3% rhenium. The high temperature tensile strength at 1100° ∼ 1600°C is the highest for 10 ∼ 20%Re alloys, but that at 2000°C does not show any large difference between doped tungsten and tungsten-rhenium alloys. The bending transition temperature decreases markedly with the addition up to 10%Re, but the temperature becomes almost constant above its rhenium content. The e.m.f. of a tungsten/tungsten-26 rhenium thermocouple is higher than that of a platinum/platinum-10 rhodium thermocouple, and increases lineally with increasing temperature from about 300° to 2200°C. At temperatures above 2200°C, however, the e.m.f. of the tungsten/tungsten-26 rhenium thermocouple decreases gradually with heating time. Hence, it is desirable that the couple be used in the temperature range below 2200°C.
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