Abstract:

During the metal cutting process, ultrafine-grained chips may form owing to the severe shear deformation, thus resulting in higher hardness and strength for the chips. In this paper, the variations of the shear strain imposed on the chips as well as on the microstrueture and the hardness of chips under the condition of different tool rake angles and various cutting velocities are investigated for different metals and alloys. Experimental results indicate that   with the decrease of the tool rake angle, the microstructure of chips are significantly refined and the hardness of chips is greatly improved;   the effect of the cutting velocity on the microstructure and the hardness is opposite to that of the tool rake angle ;   ultrafine-grained chip materials with high hardness can be obtained by cutting with a negative tool rake angle at a lower cutting velocity; and   the increase in cutting velocity alleviates the improvement of hardness owing to the large shear deformation.

Key words: tool rake angle, cutting velocity, plastic deformation, hardness, microstructure