Method for slippage evaluation at various stages of high-pressure torsion and its application to Fe-0.1 %C
For materials such as copper and mild steel Fe-0.1 % C, slippage has been determined at various stages of high-pressure torsion, and a new effective method has been applied. It has been shown that slippage at the initial stages of high-pressure torsion is insignificant, while after high-pressure torsion for n = 5 revolutions, torsional deformation of the steel does not occur due to slippage. Transmission electron microscopy and X-ray diffractometry were performed to reveal the microstructure of Fe-0.1 % C after high-pressure torsion with n = 5, 10 revolutions. It has been shown that irrespective of slippage, the structure of Fe-0.1 % C is still refined during high-pressure torsion for n = 5, and a nanostructured state similar to that observed by other authors is formed after HPT in Fe-0.1 % C. The data of TEM, XRD and HV unambiguously indicate, that the structure after HPT n =10 is more refined and riveted than after HPT n = 5. Hence, despite the slip at HPT when n ≥ 5, the deformation is still carried out. One of the possible explanations for the accumulation of deformation in the sample during HPT, despite the slippage, may be that the planes of the upper and lower anvils are declined from each other by a small angle. This leads to the accumulation of significant deformation during the rotation of the anvils.