DIFFUSION CREEP OF FINE-GRAINED POLYCRYSTALLINE ANORTHITE AT HIGH-TEMPERATURE

We performed creep experiments on synthetic fine-grained polycrystalli ne anorthite (d < 30 mu m) at temperatures from T = 1000 degrees C to 1300 degrees C, oxygen fugacities of f(O2) = 10(-19)-10(-4) MPa, and s tresses of sigma = 5 - 80 MPa at room pressure. Experimental results s how creep with high strain-rate sensitivity for stresses below sigma < 30 MPa. We found the empirical now law:epsilon = (3.8+/-11.5) x 10(10 ) sigma(1.3+/-0.3) d(-2.5+/-0.3) x exp (-420+/-38 kJ/mol/RT) Transmiss ion electron microscopy shows that the material is free of melt. The d islocation density is less than 1 x 10(8) cm(-2). We suggest that the samples deformed in diffusion-controlled grain size sensitive creep.