Plastic flow of B2-type CoTi single crystals

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Abstract
B2-type CoTi single crystals show a positive temperature dependence of the yield stress at intermediate temperatures, and a negative temperature dependence at low and high temperatures. High yield stress is commonly accompanied by a high work-hardening rate. At temperatures below the peak temperature, single crystals with an orientation close to [001] show marked serrations in the stress-strain curves and corresponding kink bands accompanied with slip. Also, the yield stress of CoTi single crystals is almost independent of strain rate at low temperatures and positively dependent on the strain rate at intermediate and high temperatures. The operative slip system is determined to be {110}〈001〉 in all orientations tested at temperatures below the peak temperature. The CRSS on (T10)[001] is independent of the orientation at low temperatures but is very dependent on the orientation at intermediate temperatures. A possible explanation for the positive temperature dependence of the yield stress based on the experimental results is given.