Fundamental Plastic Behaviors in High-purity BCC Metals (Nb, Mo and Fe)

Abstract

To understand fundamental plastic behaviors of pure bcc transition metals, tensile tests were performed using high-purity Nb, Mo and Fe as the typical metals among Va, VIa and VIII groups, respectively. From various experiments the common and the different features in slip deformation among bcc metals were made clear. In a rough sense there seems no difference when slip is caused by the motion of a single screw dislocation, that is, can be pointed out the common features such as i) the existence of a hump on the Ty - T curve, which corresponds to a peak on the A* - τy curve, ii) the Ty - X curve of concave type at 4.2 K and iii) the normal (101) slip plane for gliding of a primary (single) screw dislocation at 4.2 K. As a thing in difference there is the anomalous slip which appears in Va and VIa groups, but not for Fe in VIII group. Three characteristics and the occurance of the anomalous slip must be discussed from the common and the different natures for the core structure or the interatomic potential. Using the recent theories, in part, the common nature can be explained from the motion of a screw dislocation with the non-degenerate core structure.