Toshiyuki Suzuki1 and Katashi Masumoto1
1National Research Institute for Metals, Tokyo
The mechanical properties of intermetallic compound CoZr having a CsCl structure have been measured. Prior to measurements, the composition at which the CoZr phase exists and the condition of heat-treatment to obtain homogeneous CoZr were determined.
The phase exists stably at the stoichiometric composition and has a restricted homogeneity range even at high temperatures. No evidence to occur peritectic decomposition on heating at intermediate temperatures was obtained. The CoZr is, therefore, considered to melt congruently. In the temperature range from room temperature to 900°C, neither order-disorder transformation nor martensitic transformation takes place.
Though it is difficult to obtain completely homogeneous CoZr because of the restricted homogeneity range, CoZr containing a small amount of the second phase is ductile at room temperature and showed tensile elongation up to 7%. Ultimate tensile strength of about 37 kg/mm2 was given in the same specimen. The hardness-temperature relation of the sort H=A \exp BT holds for CoZr. Utilizing the equation, the softening coefficient of 4.95×10-3 °K-1 above the critical temperature was obtained.
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