Room temperature deformation of single crystals of Ti5Si3 with the hexagonal D88 structure investigated by micropillar compression tests

Micropillar compression tests of Ti5Si3 single crystals were conducted at room temperature as a function of loading axis orientation and specimen size in order to investigate their room temperature plastic deformation behavior. Plastic flow by the operation of three deformation modes, {1 (1) over bar 00} [0001], {2 (11) over bar2} < 2<(113)over bar> > and {1 (1) over bar 01} < 2<(113)over bar> > slip were observed in [2 (2) over bar 05]-, [0001]- and [4 (31) over bar0]-oriented micropillar specimens deformed at room temperature, respectively. The CRSS values were evaluated to be very high above 2.7 GPa and were confirmed to increase up to about 6 GPa with the decrease in the specimen size. The fracture toughness values are evaluated to be 0.45 MPa m1/2 (notch plane // (0001)) and 0.73 MPa m(1/2) (notch plane //(1 (1) over bar 00)) based on the results of micro-cantilever bend tests of chevron-notched specimens. The fracture toughness values are considerably lower than those for D8(l)Mo(5)SiB(2) and D8(l)-Nb5Si3 evaluated by the same method, indicating the inherent brittleness of binary Ti(5)S(i)3 compared to the other transition-metal silicides of the TM5Si3 type (TM: transition-metal).