EVALUATION OF SPECIMEN SLIPPAGE UNDER HIGH PRESSURE TORSION USING NOTCHES AND MARKERS

10.25712/ASTU.1811-1416.2025.04.009

Abstract

The paper considers the effect of slippage under high-pressure torsion (HPT) of Grade-4 titanium specimens using conventional marker application techniques and a cutout in the specimen. At the initial stage of HPT (striker rotation angle j_t = 36°), the slippage estimated from the marker shift was L = 35%. A cutout was made in the Ti specimen after preliminary HPT nS»2,5, into j_t = 54°. The shift of the copper insert body was significantly less than expected, and over the main volume of the specimen, the slippage was L = 96%. However, in the upper right corner of the copper insert, a copper “tongue” of about 15 μm thick, captured during torsion, is clearly visible, spreading over the Ti surface. This may indicate that during HPT, the flow occurs predominantly in the local “striker-sample surface” contact zone. It can be assumed that the localization of the slip on the surface distorts the results of the slip assessment by the "method of applying markers to the surface of the samples before HPT". This explains the difference in the slip value recorded by the marker on the surface and by the "method of cutting in the sample" (or "method of joint HPT of two disk halves").