Abstract
The olivine-spinel transformation experiments in polycrystalline fayalite were conducted at 973 and 1173 K during constant strain rate deformation. Overpressure needed for the transformation was smaller by deformation, suggesting that nucleation process is enhanced. The sample became stiffer with transormation. This is consistent with the microstructural observation that no fine-grained reaction rim is formed. Lower T and larger dP may be needed for the weakeing during the transformation.