Plastic Properties of Fe 2 B Single Crystals at Temperatures from 20 to 800°C

The plastic properties of body-centred tetragonal Fe₂B single crystals have been studied by Vickers hardness and uniaxial compression tests performed over the temperature range 20–800° C. The crystals were extremely brittle below 400° C and no slip markings were detected. However, they could be deformed above 400° C and slip lines were then observed. Coarse, straight slip lines were characteristics of crystals compressed at temperatures between 400 and 700° C and microcracks were frequently visible, whereas the slip lines were finer and more uniform at temperatures above 700° C and no microcracks were detected. Two slip systems were found to exist. One was identified as {110} 〈001〉; for the other, only the slip plane was identified as {l00}, the possible slip direction being deduced to be 〈010〉. The latter system operated only during Vickers hardness tests. Yield stress increased with temperature from 600° C to ∼ 680° C, where the local maximum value was attained. Large serrations on the stress/strain curves were observed over the range 650–700° C.