Tetsuya Takaai1 and Mitsuru Ishii1
1Central Research Laboratory, Hitachi Ltd., Tokyo
The tensile and recrystallization properties of electron beam melted molybdenum wires were studied comparing with those of arc melted and sintered molybdenum. The recrystallization temperature range of electron beam melted molybdenum wires was 930° ∼ 1090°C, while those of arc melted and sintered were 820° ∼ 1070°C and 740° ∼ 1260°C respectively. A linear relationship was observed between yield strength and 1/T for three kinds of molybdenum wires. The temperature range of the linear relationship was 140°∼-70°C for electron beam melted molybdenum wires, 160° ∼ 80°C for arc melted molybdenum wires and 180° ∼ below -110°C for sintered molybdenum wires. The parameters for the yield strength vs 1/T diagrams were 23.5 × 103 kg/mm-2T°K, 27.0 × 103 kg/mm-2T°K and 30.0 × 103 kg/mm-2T°K for the electron beam melted, arc melted and sintered molybdenum wires, respectively.
The ductile-to-brittle transition temperatures in the tensile test (with strain rate of 2.1 × 10-3 s-1) for recrystallized electron beam melted and arc melted molybdenum wires were -70°C and -80°C, but the transition temperatures varied very sensitively with changes in the annealing temperature.
Sharp peaks were observed at about 200°C in strain hardening exponent vs the reverse of test temperature diagrams for 3 molybdenum wires, and the strain hardening exponents of electron beam melted molybdenum wires were the highest at all the test temperatures and those of arc melted were the lowest.
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