Deformation mechanism in alpha Cu-Al single crystals and bicrystals under scratching with pyramidal indentor

In order to elucidate the deformation mechanism of materials in abrasive wear process, scratching tests were carried out on the (1 1 1) face of Cu-14.7 at % Al single crystals and Sigma 13 b bicrystals with pyramidal indentor. In the scratching on the single crystals three kinds of scratching directions, [1 1 (2) over bar], [(1) over bar (1) over bar 2] and [(1) over bar 1 0], were chosen. In the case of bicrystals, the [1 (2) over bar 1] and [1 (1) over bar 0] directions were adopted. After scratching the dislocation structure, slip trace patterns and surface profiles across the scratched track were examined. In addition, the dislocation distributions inside the crystals were revealed by successively removing thin layers and developing etch pits on the exposed surface. The slip traces on either side of the scratched track are produced more extensively than those around the indented point. These slip traces are observed only in the surface of about 100 Cim deep, and are not observed in the deeper area. It is found that the microscopic deformations produced due to the scratching consist of three kinds of deformation: formed by indentation, formed by both normal and frictional stresses in the surface layer and formed by stress which is caused in certain limited depth. The swells of the material were produced in the front of the indentor due to the slips on the {1 1 1} crystal faces which are arranged so as to be diverging into the inside. The azimuths of formation of the swells are [1 1 (2) over bar] and [(2) over bar 1 1] in the [1 1 (2) over bar]] and [(1) over bar 1 0] scratching respectively and [1 (2) over bar 1], [(2) over bar 1 1] in the [(1) over bar (1) over bar 2] scratching. In the scratching of the bicrystal, the propagation of dislocation in the surface layer of the one side crystal is obstructed by the grain boundary. The microscopic deformation range on the dislocation order is affected by the distribution density of the grain boundaries.