Microstructural investigation of AA 2195 T81 chips formed during a metal-cutting process

In this study, the microstructure of AA 2195 T81 metal-cutting chips formed during a turning operation were characterized using microscopy and diffraction techniques. At a constant strain of 2, the resulting strain rate imposed on the metal was varied from 0.8 9 104 to 2.6 9 105 s-1. At strain rate of 0.8 9 104 s-1, the resulting microstructure contained regions of 100 nm ultrafine grains. At the highest strain rate of 2.6 9 105 s-1, 150– 200 nm ultrafine grains were observed plus overaged precipitates. The grain size increment and appearance of overaged precipitates with the higher strain rate is conjectured to be a result of temperature increment and not of direct strain rate.