Effect of Addition of β-Phase Stabilizing Elements (Nb, Mo and V) on Plastic Behaviour of Ti₃Al Single Crystals with the D0₁₉ Structure

抄録

Effect of the addition of Nb, Mo and V which are thought to stabilize the bcc structure on plastic behaviour of Ti₃Al based single crystals was investigated in the range from room temperature to 900°C. {1010}<1210> prism, (0001)<1210> basal and {1121}<1126> pyramidal slip systems were operative at all temperatures depending on crystal orientation. Activation of the prism slip was most favourable among the three slip systems, while the pyramidal slip was observed only at limited orientations near the [0001] corner because of high CRSS. The CRSS for the prism and basal slips decreased monotonously as the temperature rose, while that for the pyramidal slip increased rapidly with rising temperature and reached a peak. Addition of V and Mo led to violation of Schmid's law for the prism slip, while the CRSS in binary Ti₃Al and ternary Ti₃Al-Nb crystals exhibited no orientation dependence. Anomalous strengthening and peak temperature in the CRSS-temperature curves for the pyramidal slip were very sensitive to the added elements in Ti₃Al. The addition of V, Mo and Nb caused more effectively anomalous strengthening in this order.