The Positron Probe Microanalyser Studies of Defect Distribution Induced by Machining of Copper, Iron and Titanium

Abstract

We demonstrate the application of the new experimental technique: positron probe microanalyser for studies of the defect profiles induced by milling. Metal foils of Cu, Fe and Ti were subjected to machining in a milling machine with different cutting speed. This technique revealed well-defined profiles of defects below the machined surface which was extended up to hundreds of micrometres. The extent of the profile depended on the metal and the cutting speed. The positron probe microanalyser allowed us to trace the evolution of the profile after annealing in different temperatures. Surprisingly, the high thermal stability of a few tens of micrometres thick layer adjacent to the machined surface was detected.

Positron Annihilation and Complementary Studies of Copper Sandblasted with Alumina Particles at Different Pressures

“…The maximum, at the depth of about 50 µm ( Figure 7 ), is a new interesting feature which was not observed in distributions registered for copper exposed to other treatment processes [ 16 , 17 ]. For analysis of the near surface region the depth up to 100 µm was additionally presented in Figure 9 .…”

“…In turn, the exponential character can be assigned to the rest of profiles. The former tendency was registered in machined copper [ 16 ], while the latter was noted in copper samples exposed to sliding and cutting [ 17 ]. Various types of S parameter distributions from one treatment process were also obtained for austenitic stainless steel exposed to sliding under varied dry load conditions [ 39 ].…”

“…It has been proved in many experiments that sequential removal of layers by chemical etching and measurements of annihilation characteristics make it possible to detect the depth profile in an accurate way. Chemical etching does not produce any defects which could disturb the initial defect depth distribution [ 15 , 16 ]. In our studies the samples were etched in a 25% solution of nitride acid and distilled water.…”

“…It allows us to recognize the type of introduced structural defects and their depth profile. The successful application of PAS in studies of defects in materials treated in different ways is well documented in the literature [ 15 , 16 , 17 , 18 ].…”

Destructive and non-destructive testing methods for characterization and detection of machining-induced white layer: A review paper

“…It has been shown that PAS can be used for the detection of machining damage in Ti-6Al-4V (Patton et al), copper (Dryzek et al, 2015) and stainless steel (Horodek et al, 2012). The ability to distinguish between damaged an undamaged samples was attributed to the increased number of dislocations in the near-surface, caused by deformation during machining.…”