Crystal Rotation Accompanying the Scratch Deformation of FCC Metal Single Crystals

Abstract

In order to clarify the formation mechanism of work-hardened layer introduced at the time of frictional or abrasive working, (001) planes of pure Al and Cu single crystals are scratch-deformed by diamond cone styli as a simplified model of working. The deformed structures around the end of the scratch-grooves in [100] and [110] directions and also the cross-section of the groove are examined by selected area ECP using SEM, and the results are compared with those by TEM. The following results are obtained:
(1) By the scratch deformation, the regions where crystals are bent and rotated are introduced around the end of scratch groove and under the groove. The form of the region, the amount of crystal rotation and the direction of rotation depend on the scratch direction. The amount of rotation, especially, depends on the cone angle of stylus.
(2) In the case of Cu single crystal, the regions, in which crystal has rotated with respect to ⟨211⟩ axis, can be classified by comperatively clear boundaries between them. Thus the activated region of slip systems contributing to the crystal rotation can be estimated at the time of scratch deformation.
(3) Through the observations around the end of the groove by TEM, the process of variation of dislocation structures during the procession of stylus can be traced. As the result shows, cell walls are formed along the slip planes which are activated at the time of crystal rotation. Also, the increment of dislocation density is recognized in the regions which suffer several different slip processes and at the boundary regions which are formed by the regions of different rotational direction.