High- temperature creep of forsterite single crystals.

Abstract

Creep of forsterite single crystals has been studied with respect to the orientation of the differential stress. Three orientations have been investigated: (110),(101) and (011). Specimens were deformed at high temperature (T = or > 1400oC) and moderate stresses (15 < sigma < 110 MPa) in a dead load creep apparatus at room pressure and under controlled atmosphere. Assuming that the creep law has the general form epsilon - Asigma n - Aon exp -(Q/RT), two different tests were performed. Stress step and temperature step experiments gave the stress exponent n and the activation energy Q, respectively. A thorough analysis of the dislocation microstructures was carried out in the potential glide planes using the optical microscope (decorated thin sections) and transmission electron microscope. -Authors