Fig. 6 SEM observations of fractured surfaces: (a) static creep and (b) enlarged inner fibrous zone; (c) second phase particle and (d) its composition; (e) cyclic creep at 12 MPa/s and 39 MPa/s unloading rate with none valley stress duration; (f) cyclic creep with 10 min and (g) 30 min duration under valley stress with an unloading rate of 12 MPa/s.