EFFECT OF ADDITION OF BETA-PHASE STABILIZING ELEMENTS (NB, MO AND V) ON PLASTIC BEHAVIOR OF TI3AL SINGLE-CRYSTALS WITH THE DO19 STRUCTURE

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 degrees C, (10 ($) over bar 10)(1 ($) over bar 210) prism, (0001)(1 ($) over bar 210) basal and [11 ($) over bar 21)]<($) over bar 1126> pyramidal slip systems were operative at all temperatures depending on crystal orien tation. Activation of the prism slip was most favourable among the thr ee slip systems, while the pyramidal slip was observed only at limited orientations near the [0001] corner because of high CRSS. The CRSS fo r 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. Anomal ous strengthening and peak temperature in the CRSS-temperature curves for the pyramidal slip were very sensitive to the added elements in Ti 3Al. The addition of V, Mo and Nb caused more effectively anomalous st rengthening in this order.