ON THE ORIENTATION DEPENDENCE OF CRACK-LIKE FAILURE FORMATION NEAR INDENTATIONS ON AN ICOSAHEDRAL AL-PD-MN QUASI-CRYSTAL

Crack propagation near microhardness indentations on surfaces of an ic osahedral Al70Pd23Mn7 Single quasicrystal exhibiting fivefold and twof old symmetry has been studied under ambient conditions at room tempera ture using optical microscopy, atomic force microscopy and laser scan microscopy. Cracks exhibit a shear-like habit and prefer propagation a long planes of symmetry 2, (3) over bar and (5) over bar rather than f ollowing the plane of maximum stress. A fracture toughness of 1.25 MPa m(1/2) has been derived from indentations on a fivefold plane at room temperature.