Positron Annihilation Spectroscopy Study of Metallic Materials after High-Speed Cutting

Abstract

During high-speed cutting, a white layer is often produced on the machined surfaces after mechanical machining, seriously affecting the mechanical properties. These properties are related to the material structure and the defects induced by cutting. However, there is a lack of research on the atomic-scale defects of the white layer. This paper studied the influence of cutting parameters, namely the feed rate, cutting speed and cutting depth, on atomic-scale defects induced by high-speed cutting in GCr15 steel. Positron annihilation studies showed typical plastically deformed or tempered carbon steel defects with additional vacancy cluster components. The quantity of these clusters changed with cutting parameters. Furthermore, significant changes were observed in the subsurface region up to 1 µm, occurring as a result of simultaneous phase transformations, deformation and thermal impacts. The predominant accumulation of only one type of atomic-scale defect was not observed.

Positron Annihilation Lifetime Spectroscopy as a Special Technique for the Solid-State Characterization of Pharmaceutical Excipients, Drug Delivery Systems, and Medical Devices—A Systematic Review

“…The method is based on the lifetime and intensity of ortho-positronium (o-Ps) atoms in free volumes of given structures; positronium (Ps) trapping in vacancies has a characteristic lifetime and, therefore, allows one to measure the size of a vacancy cluster, providing information about the structural characteristics of solids, liquids, and semi-solid materials [ 1 , 3 , 4 ]. PALS is utilized in several sectors for the examination of energy carriers [ 5 , 6 , 7 , 8 ], catalysts [ 9 , 10 , 11 ], and packaging materials [ 12 , 13 ] and for interrogating defects and pores in metals [ 14 , 15 ], ceramics [ 16 , 17 ], and polymers [ 3 ]. The principles of positron annihilation in condensed matter have been extensively discussed [ 18 , 19 ].…”