THE ANOMALOUS FLOW BEHAVIOR IN SINGLE-PHASE TI44AL56 SINGLE-CRYSTALS - THE EFFECT OF DEFORMATION HISTORY

In this paper we present our studies of effect of deformation temperat ure on the anomalous flow behavior of [001] and [011] oriented Ti44Al5 6 single crystals grown in an ASGAL optical imaging floating zone crys tal growth furnace. The specimens were compression tested at room temp erature (RT), 973 and 1173 K and they displayed anomalous flow behavio r. However, if the sample is deformed at high temperature, at about 97 3 K (below the peak temperature), and then retested at room temperatur e, the high temperature strength is retained, i.e. the flow stress is irreversible. But if the initial deformation at high temperature is pe rformed at about 1173 K (above the peak temperature), and then deforme d at room temperature the room temperature flow strength is observed, i.e. the flow stress is reversible. These results sue est that the rev ersibility of flow stress anomaly is determined by the deformation mec hanism occurring at the elevated temperature. If the deformation mecha nism at the two temperatures is the same, then the flow stress is irre versible, but if they are different, then it is reversible. (C) 1997 E lsevier Science S.A.