Fracture and Deformation on (0001) and (1010) in Sapphire Single Crystals with Vickers Indenter
Shinzo KOBAYASHI, Shinji MASUI and Sei MIURA
Abstract:Abrasive wear on the contacting surface of machine elements proceeds via penetration or scratch of the sharp asoerity tips or wear debris. In order to elusidate the mechanism of wear, it is firstly necessary to have knowledge on the microscopic deformations such as dislocations, minute cracks and slips induced by such penetrations. In the present study, indentation tests using a Vickers indenter were carried out on the (0001) and (1010) crystal faces of Sapphire single crystals. The diagonal of an indenter was oriented in two ways: parallel and 45 @the [1010] direction on the (0001) face, and against the [0001] direction on the (1010) face respectively. The cleaving faces and directions of propagation of the cracks around an indent were estimated. In addition the shape and distributions of etch pits around an indent were estimated. The results obtained are summarized as follows: (1) Radial cracks originate in four directions under compaative lower load of 5.0 N, and in six directions under higer load of 10.0 N on both the (0001) and (1010) faces. Ruptures that form connections with these cracks are also observed. (2) An average length of cracks on the (0001) is longer about 20% in 0indentation than in 45 indentation. (3) Cracks and edges of an indent are formed in a curved pattern due tothe anisotropic crystal deformation. (4) Twinnings are observed on the (1010) in both 0and 45indentations. (5) Noticeable difference in size of indent was not confirmed in 0between 45indentation. An average length of the cracks on the (1010) is about 2.0 times as long as that onthe (0001). (6) The area around an indent on the (1010) is corroded by etching in similar figure to individual etch pit. Key Words:Dislocation, Crack, Indentation, Slip, Anisotropic deformation, Twinning